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 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
 //
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 
 // Author: kenton@google.com (Kenton Varda)
 //  Based on original Protocol Buffers design by
 //  Sanjay Ghemawat, Jeff Dean, and others.
 //
 // This file contains classes which describe a type of protocol message.
 // You can use a message's descriptor to learn at runtime what fields
 // it contains and what the types of those fields are.  The Message
 // interface also allows you to dynamically access and modify individual
 // fields by passing the FieldDescriptor of the field you are interested
 // in.
 //
 // Most users will not care about descriptors, because they will write
 // code specific to certain protocol types and will simply use the classes
 // generated by the protocol compiler directly.  Advanced users who want
 // to operate on arbitrary types (not known at compile time) may want to
 // read descriptors in order to learn about the contents of a message.
 // A very small number of users will want to construct their own
 // Descriptors, either because they are implementing Message manually or
 // because they are writing something like the protocol compiler.
 //
 // For an example of how you might use descriptors, see the code example
 // at the top of message.h.
 
 #ifndef GOOGLE_PROTOBUF_DESCRIPTOR_H__
 #define GOOGLE_PROTOBUF_DESCRIPTOR_H__
 
 #include <atomic>
 #include <cstdint>
 #include <iterator>
 #include <memory>
 #include <string>
 #include <type_traits>
 #include <utility>
 #include <vector>
 
 #include "absl/base/attributes.h"
 #include "absl/base/call_once.h"
 #include "absl/base/macros.h"
 #include "absl/base/optimization.h"
 #include "absl/container/flat_hash_map.h"
 #include "absl/functional/any_invocable.h"
 #include "absl/functional/function_ref.h"
 #include "absl/log/absl_check.h"
 #include "absl/log/absl_log.h"
 #include "absl/strings/str_format.h"
 #include "absl/strings/string_view.h"
 #include "absl/synchronization/mutex.h"
 #include "google/protobuf/descriptor_lite.h"
 #include "google/protobuf/extension_set.h"
 #include "google/protobuf/port.h"
 
 // Must be included last.
 #include "google/protobuf/port_def.inc"
 
 #ifdef SWIG
 #define PROTOBUF_EXPORT
 #define PROTOBUF_IGNORE_DEPRECATION_START
 #define PROTOBUF_IGNORE_DEPRECATION_STOP
 #endif
 
 
 namespace google {
 namespace protobuf {
 // Defined in this file.
 class Descriptor;
 class FieldDescriptor;
 class OneofDescriptor;
 class EnumDescriptor;
 class EnumValueDescriptor;
 class ServiceDescriptor;
 class MethodDescriptor;
 class FileDescriptor;
 class DescriptorDatabase;
 class DescriptorPool;
 
 // Defined in descriptor.proto
 #ifndef SWIG
 enum Edition : int;
 enum SymbolVisibility : int;
 #else   // !SWIG
 typedef int Edition;
 typedef int SymbolVisibility;
 #endif  // !SWIG
 class DescriptorProto;
 class DescriptorProto_ExtensionRange;
 class FieldDescriptorProto;
 class OneofDescriptorProto;
 class EnumDescriptorProto;
 class EnumValueDescriptorProto;
 class ServiceDescriptorProto;
 class MethodDescriptorProto;
 class FileDescriptorProto;
 class MessageOptions;
 class FieldOptions;
 class OneofOptions;
 class EnumOptions;
 class EnumValueOptions;
 class ExtensionRangeOptions;
 class ServiceOptions;
 class MethodOptions;
 class FileOptions;
 class UninterpretedOption;
 class FeatureSet;
 class FeatureSetDefaults;
 class SourceCodeInfo;
 
 // Defined in message_lite.h
 class MessageLite;
 
 // Defined in message.h
 class Message;
 class Reflection;
 
 // Defined in descriptor.cc
 class DescriptorBuilder;
 class FileDescriptorTables;
 class Symbol;
 
 // Defined in unknown_field_set.h.
 class UnknownField;
 
 // Defined in command_line_interface.cc
 namespace compiler {
 class CodeGenerator;
 class CommandLineInterface;
 namespace cpp {
 class CppGenerator;
 // Defined in helpers.h
 class Formatter;
 }  // namespace cpp
 namespace java {
 class MemoizeProjection;
 }  // namespace java
 }  // namespace compiler
 
 namespace descriptor_unittest {
 class DescriptorPoolMemoizationTest;
 class DescriptorTest;
 class ValidationErrorTest;
 }  // namespace descriptor_unittest
 
 // Defined in printer.h
 namespace io {
 class Printer;
 }  // namespace io
 
 namespace internal {
 class InternalFeatureHelper;
 }  // namespace internal
 
 // NB, all indices are zero-based.
 struct SourceLocation {
   int start_line;
   int end_line;
   int start_column;
   int end_column;
 
   // Doc comments found at the source location.
   // See the comments in SourceCodeInfo.Location (descriptor.proto) for details.
   std::string leading_comments;
   std::string trailing_comments;
   std::vector<std::string> leading_detached_comments;
 };
 
 // Options when generating machine-parsable output from a descriptor with
 // DebugString().
 struct DebugStringOptions {
   // include original user comments as recorded in SourceLocation entries. N.B.
   // that this must be |false| by default: several other pieces of code (for
   // example, the C++ code generation for fields in the proto compiler) rely on
   // DebugString() output being unobstructed by user comments.
   bool include_comments;
   // If true, elide the braced body in the debug string.
   bool elide_group_body;
   bool elide_oneof_body;
 
   DebugStringOptions()
       : include_comments(false),
         elide_group_body(false),
         elide_oneof_body(false) {
   }
 };
 
 // A class to handle the simplest cases of a lazily linked descriptor
 // for a message type that isn't built at the time of cross linking,
 // which is needed when a pool has lazily_build_dependencies_ set.
 // Must be instantiated as mutable in a descriptor.
 namespace internal {
 
 // The classes in this file represent a significant memory footprint for the
 // library. We make sure we are not accidentally making them larger by
 // hardcoding the struct size for a specific platform. Use as:
 //
 //   PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(type, expected_size_in_x84-64);
 //
 
 #if !defined(PROTOBUF_INTERNAL_CHECK_CLASS_SIZE)
 #define PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(t, expected)
 #endif
 
 // This class is used to index into the memory it is pointing at.
 // The layout is as follows:
 //  [ chars .... ] [ data0 (uint16_t) ] [ ... ] [ dataN (uint16_t) ]
 //                ^
 //       payload_ points here
 //
 // The offsets are relative to payload_.
 //
 // The offsets are as follows:
 //  (0) `name` size. `name` ends at `payload_`
 //  (1) `full_name` size. `full_name` ends at `payload_` and shares bytes with
 //      `name`.
 //    .. the following offsets only available for `FieldDescriptor` ..
 //  (2)/(3) `lowercase` offset/size. The data bytes could be shared.
 //  (4)/(5) `camelcase` offset/size. The data bytes could be shared.
 //  (6)/(7) `json_name` offset/size. The data bytes could be shared.
 //
 //  NOTE ABOUT NULL TERMINATION:
 //  The name accessors were migrated from `std::string` to `absl::string_view`,
 //  which caused valid code to break. In particular, there are previously
 //  correct callers calling `foo.name().data()` and using it as a NULL
 //  terminated C-string.
 //  To prevent further breakage we are adding null termination on all these
 //  names even though it is outside the contract for `absl::string_view`.
 //  This might change in the future.
 class DescriptorNames {
  public:
   // Uninitialized, to support `= default` of descriptor types.
   DescriptorNames() = default;
   explicit DescriptorNames(const char* payload) : payload_(payload) {}
 
   // The full name is just before `payload_`, and the name is the suffix of it.
   // We don't need a special offset for them.
   // NOTE: the sizes don't include the null terminator, so add +1 to the offset.
   absl::string_view name() const { return get(get_size(0) + 1, get_size(0)); }
   absl::string_view full_name() const {
     return get(get_size(1) + 1, get_size(1));
   }
 
   // Only available for `FieldDescriptor`. This is not checked at runtime.
   // NOTE: The offsets here already take into account the null terminator.
   absl::string_view lowercase_name() const {
     return get(get_size(2), get_size(3));
   }
   absl::string_view camelcase_name() const {
     return get(get_size(4), get_size(5));
   }
   absl::string_view json_name() const { return get(get_size(6), get_size(7)); }
 
   static constexpr size_t AllocationSizeForSimpleNames(size_t full_name_size) {
     return full_name_size + /* \0 */ 1 + 2 * sizeof(uint16_t);
   }
 
  private:
   size_t get_size(int index) const {
     // We don't use `uint16_t` in the payload type to avoid having to align it.
     // Instead, we read via memcpy.
     uint16_t size;
     memcpy(&size, payload_ + index * sizeof(size), sizeof(size));
     return size;
   }
 
   absl::string_view get(size_t offset, size_t size) const {
     return absl::string_view(payload_ - offset, size);
   }
 
   const char* payload_;
 };
 
 class FlatAllocator;
 
 class PROTOBUF_EXPORT LazyDescriptor {
  public:
   // Init function to be called at init time of a descriptor containing
   // a LazyDescriptor.
   void Init() {
     descriptor_ = nullptr;
     once_ = nullptr;
   }
 
   // Sets the value of the descriptor if it is known during the descriptor
   // building process. Not thread safe, should only be called during the
   // descriptor build process. Should not be called after SetLazy has been
   // called.
   void Set(const Descriptor* descriptor);
 
   // Sets the information needed to lazily cross link the descriptor at a later
   // time, SetLazy is not thread safe, should be called only once at descriptor
   // build time if the symbol wasn't found and building of the file containing
   // that type is delayed because lazily_build_dependencies_ is set on the pool.
   // Should not be called after Set() has been called.
   void SetLazy(absl::string_view name, const FileDescriptor* file);
 
   // Returns the current value of the descriptor, thread-safe. If SetLazy(...)
   // has been called, will do a one-time cross link of the type specified,
   // building the descriptor file that contains the type if necessary.
   inline const Descriptor* Get(const ServiceDescriptor* service) {
     Once(service);
     return descriptor_;
   }
 
  private:
   void Once(const ServiceDescriptor* service);
 
   const Descriptor* descriptor_;
   // The once_ flag is followed by a NUL terminated string for the type name.
   absl::once_flag* once_;
 };
 
 class PROTOBUF_EXPORT SymbolBase {
  private:
   friend class google::protobuf::Symbol;
   uint8_t symbol_type_;
 };
 
 // Some types have more than one SymbolBase because they have multiple
 // identities in the table. We can't have duplicate direct bases, so we use this
 // intermediate base to do so.
 // See BuildEnumValue for details.
 template <int N>
 class PROTOBUF_EXPORT SymbolBaseN : public SymbolBase {};
 
 PROTOBUF_EXPORT absl::string_view ShortEditionName(Edition edition);
 
 bool IsEnumFullySequential(const EnumDescriptor* enum_desc);
 
 const std::string& DefaultValueStringAsString(const FieldDescriptor* field);
 const std::string& NameOfEnumAsString(const EnumValueDescriptor* descriptor);
 
 }  // namespace internal
 
 // Provide an Abseil formatter for edition names.
 template <typename Sink>
 void AbslStringify(Sink& sink, Edition edition) {
   absl::Format(&sink, "%v", internal::ShortEditionName(edition));
 }
 
 // Describes a type of protocol message, or a particular group within a
 // message.  To obtain the Descriptor for a given message object, call
 // Message::GetDescriptor().  Generated message classes also have a
 // static method called descriptor() which returns the type's descriptor.
 // Use DescriptorPool to construct your own descriptors.
 class PROTOBUF_EXPORT Descriptor : private internal::SymbolBase {
  public:
   typedef DescriptorProto Proto;
 #ifndef SWIG
   Descriptor(const Descriptor&) = delete;
   Descriptor& operator=(const Descriptor&) = delete;
 #endif
 
   // The name of the message type, not including its scope.
   absl::string_view name() const;
 
   // The fully-qualified name of the message type, scope delimited by
   // periods.  For example, message type "Foo" which is declared in package
   // "bar" has full name "bar.Foo".  If a type "Baz" is nested within
   // Foo, Baz's full_name is "bar.Foo.Baz".  To get only the part that
   // comes after the last '.', use name().
   absl::string_view full_name() const;
 
   // Index of this descriptor within the file or containing type's message
   // type array.
   int index() const;
 
   // The .proto file in which this message type was defined.  Never nullptr.
   const FileDescriptor* file() const;
 
   // If this Descriptor describes a nested type, this returns the type
   // in which it is nested.  Otherwise, returns nullptr.
   const Descriptor* containing_type() const;
 
   // Get options for this message type.  These are specified in the .proto file
   // by placing lines like "option foo = 1234;" in the message definition.
   // Allowed options are defined by MessageOptions in descriptor.proto, and any
   // available extensions of that message.
   const MessageOptions& options() const;
 
   // Write the contents of this Descriptor into the given DescriptorProto.
   // The target DescriptorProto must be clear before calling this; if it
   // isn't, the result may be garbage.
   void CopyTo(DescriptorProto* proto) const;
 
   // Fills in the message-level settings of this message (e.g. name, reserved
   // fields, message options) to `proto`.  This is essentially all of the
   // metadata owned exclusively by this descriptor, and not any nested
   // descriptors.
   void CopyHeadingTo(DescriptorProto* proto) const;
 
   // Write the contents of this descriptor in a human-readable form. Output
   // will be suitable for re-parsing.
   std::string DebugString() const;
 
   // Similar to DebugString(), but additionally takes options (e.g.,
   // include original user comments in output).
   std::string DebugStringWithOptions(const DebugStringOptions& options) const;
 
   // Allows formatting with absl and gtest.
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const Descriptor& d) {
     absl::Format(&sink, "%s", d.DebugString());
   }
 
   // Returns true if this is a placeholder for an unknown type. This will
   // only be the case if this descriptor comes from a DescriptorPool
   // with AllowUnknownDependencies() set.
   bool is_placeholder() const;
 
   enum WellKnownType {
     WELLKNOWNTYPE_UNSPECIFIED,  // Not a well-known type.
 
     // Wrapper types.
     WELLKNOWNTYPE_DOUBLEVALUE,  // google.protobuf.DoubleValue
     WELLKNOWNTYPE_FLOATVALUE,   // google.protobuf.FloatValue
     WELLKNOWNTYPE_INT64VALUE,   // google.protobuf.Int64Value
     WELLKNOWNTYPE_UINT64VALUE,  // google.protobuf.UInt64Value
     WELLKNOWNTYPE_INT32VALUE,   // google.protobuf.Int32Value
     WELLKNOWNTYPE_UINT32VALUE,  // google.protobuf.UInt32Value
     WELLKNOWNTYPE_STRINGVALUE,  // google.protobuf.StringValue
     WELLKNOWNTYPE_BYTESVALUE,   // google.protobuf.BytesValue
     WELLKNOWNTYPE_BOOLVALUE,    // google.protobuf.BoolValue
 
     // Other well known types.
     WELLKNOWNTYPE_ANY,        // google.protobuf.Any
     WELLKNOWNTYPE_FIELDMASK,  // google.protobuf.FieldMask
     WELLKNOWNTYPE_DURATION,   // google.protobuf.Duration
     WELLKNOWNTYPE_TIMESTAMP,  // google.protobuf.Timestamp
     WELLKNOWNTYPE_VALUE,      // google.protobuf.Value
     WELLKNOWNTYPE_LISTVALUE,  // google.protobuf.ListValue
     WELLKNOWNTYPE_STRUCT,     // google.protobuf.Struct
 
     // New well-known types may be added in the future.
     // Please make sure any switch() statements have a 'default' case.
     __WELLKNOWNTYPE__DO_NOT_USE__ADD_DEFAULT_INSTEAD__,
   };
 
   WellKnownType well_known_type() const;
 
   // Field stuff -----------------------------------------------------
 
   // The number of fields in this message type.
   int field_count() const;
   // Gets a field by index, where 0 <= index < field_count().
   // These are returned in the order they were defined in the .proto file, not
   // the field number order. (Use `FindFieldByNumber()` for
   // tag number -> value lookup).
   const FieldDescriptor* field(int index) const;
 
   // Looks up a field by declared tag number.  Returns nullptr if no such field
   // exists.
   const FieldDescriptor* FindFieldByNumber(int number) const;
   // Looks up a field by name.  Returns nullptr if no such field exists.
   const FieldDescriptor* FindFieldByName(absl::string_view name) const;
 
   // Looks up a field by lowercased name (as returned by lowercase_name()).
   // This lookup may be ambiguous if multiple field names differ only by case,
   // in which case the field returned is chosen arbitrarily from the matches.
   const FieldDescriptor* FindFieldByLowercaseName(
       absl::string_view lowercase_name) const;
 
   // Looks up a field by camel-case name (as returned by camelcase_name()).
   // This lookup may be ambiguous if multiple field names differ in a way that
   // leads them to have identical camel-case names, in which case the field
   // returned is chosen arbitrarily from the matches.
   const FieldDescriptor* FindFieldByCamelcaseName(
       absl::string_view camelcase_name) const;
 
   // The number of oneofs in this message type.
   int oneof_decl_count() const;
   // The number of oneofs in this message type, excluding synthetic oneofs.
   // Real oneofs always come first, so iterating up to real_oneof_decl_cout()
   // will yield all real oneofs.
   int real_oneof_decl_count() const;
   // Get a oneof by index, where 0 <= index < oneof_decl_count().
   // These are returned in the order they were defined in the .proto file.
   const OneofDescriptor* oneof_decl(int index) const;
   // Get a oneof by index, excluding synthetic oneofs, where 0 <= index <
   // real_oneof_decl_count(). These are returned in the order they were defined
   // in the .proto file.
   const OneofDescriptor* real_oneof_decl(int index) const;
 
   // Looks up a oneof by name.  Returns nullptr if no such oneof exists.
   const OneofDescriptor* FindOneofByName(absl::string_view name) const;
 
   // Nested type stuff -----------------------------------------------
 
   // The number of nested types in this message type.
   int nested_type_count() const;
   // Gets a nested type by index, where 0 <= index < nested_type_count().
   // These are returned in the order they were defined in the .proto file.
   const Descriptor* nested_type(int index) const;
 
   // Looks up a nested type by name.  Returns nullptr if no such nested type
   // exists.
   const Descriptor* FindNestedTypeByName(absl::string_view name) const;
 
   // Enum stuff ------------------------------------------------------
 
   // The number of enum types in this message type.
   int enum_type_count() const;
   // Gets an enum type by index, where 0 <= index < enum_type_count().
   // These are returned in the order they were defined in the .proto file.
   const EnumDescriptor* enum_type(int index) const;
 
   // Looks up an enum type by name.  Returns nullptr if no such enum type
   // exists.
   const EnumDescriptor* FindEnumTypeByName(absl::string_view name) const;
 
   // Looks up an enum value by name, among all enum types in this message.
   // Returns nullptr if no such value exists.
   const EnumValueDescriptor* FindEnumValueByName(absl::string_view name) const;
 
   // Extensions ------------------------------------------------------
 
   // A range of field numbers which are designated for third-party
   // extensions.
   class PROTOBUF_EXPORT ExtensionRange {
    public:
     typedef DescriptorProto_ExtensionRange Proto;
 
     typedef ExtensionRangeOptions OptionsType;
 
     // See Descriptor::CopyTo().
     void CopyTo(DescriptorProto_ExtensionRange* proto) const;
 
     // Returns the start field number of this range (inclusive).
     int start_number() const { return start_; }
 
     // Returns the end field number of this range (exclusive).
     int end_number() const { return end_; }
 
     // Returns the index of this extension range within the message's extension
     // range array.
     int index() const;
 
     // Returns the ExtensionRangeOptions for this range.
     const ExtensionRangeOptions& options() const { return *options_; }
 
     // Returns the name of the containing type.
     absl::string_view name() const { return containing_type_->name(); }
 
     // Returns the full name of the containing type.
     absl::string_view full_name() const {
       return containing_type_->full_name();
     }
 
     // Returns the .proto file in which this range was defined.
     // Never nullptr.
     const FileDescriptor* file() const { return containing_type_->file(); }
 
     // Returns the Descriptor for the message containing this range.
     // Never nullptr.
     const Descriptor* containing_type() const { return containing_type_; }
 
    private:
     int start_;
     int end_;
     const ExtensionRangeOptions* options_;
 
    private:
     const Descriptor* containing_type_;
     const FeatureSet* proto_features_;
     const FeatureSet* merged_features_;
 
     // Get the merged features that apply to this extension range.  These are
     // specified in the .proto file through the feature options in the message
     // definition. Allowed features are defined by Features in descriptor.proto,
     // along with any backend-specific extensions to it.
     const FeatureSet& features() const { return *merged_features_; }
     friend class internal::InternalFeatureHelper;
 
     // Walks up the descriptor tree to generate the source location path
     // to this descriptor from the file root.
     void GetLocationPath(std::vector<int>* output) const;
 
     friend class Descriptor;
     friend class DescriptorPool;
     friend class DescriptorBuilder;
   };
 
   // The number of extension ranges in this message type.
   int extension_range_count() const;
   // Gets an extension range by index, where 0 <= index <
   // extension_range_count(). These are returned in the order they were defined
   // in the .proto file.
   const ExtensionRange* extension_range(int index) const;
 
   // Returns true if the number is in one of the extension ranges.
   bool IsExtensionNumber(int number) const;
 
   // Returns nullptr if no extension range contains the given number.
   const ExtensionRange* FindExtensionRangeContainingNumber(int number) const;
 
   // The number of extensions defined nested within this message type's scope.
   // See doc:
   // https://developers.google.com/protocol-buffers/docs/proto#nested-extensions
   //
   // Note that the extensions may be extending *other* messages.
   //
   // For example:
   // message M1 {
   //   extensions 1 to max;
   // }
   //
   // message M2 {
   //   extend M1 {
   //     optional int32 foo = 1;
   //   }
   // }
   //
   // In this case,
   // DescriptorPool::generated_pool()
   //     ->FindMessageTypeByName("M2")
   //     ->extension(0)
   // will return "foo", even though "foo" is an extension of M1.
   // To find all known extensions of a given message, instead use
   // DescriptorPool::FindAllExtensions.
   int extension_count() const;
   // Get an extension by index, where 0 <= index < extension_count().
   // These are returned in the order they were defined in the .proto file.
   const FieldDescriptor* extension(int index) const;
 
   // Looks up a named extension (which extends some *other* message type)
   // defined within this message type's scope.
   const FieldDescriptor* FindExtensionByName(absl::string_view name) const;
 
   // Similar to FindFieldByLowercaseName(), but finds extensions defined within
   // this message type's scope.
   const FieldDescriptor* FindExtensionByLowercaseName(
       absl::string_view name) const;
 
   // Similar to FindFieldByCamelcaseName(), but finds extensions defined within
   // this message type's scope.
   const FieldDescriptor* FindExtensionByCamelcaseName(
       absl::string_view name) const;
 
   // Reserved fields -------------------------------------------------
 
   // A range of reserved field numbers.
   struct ReservedRange {
     int start;  // inclusive
     int end;    // exclusive
   };
 
   // The number of reserved ranges in this message type.
   int reserved_range_count() const;
   // Gets an reserved range by index, where 0 <= index <
   // reserved_range_count(). These are returned in the order they were defined
   // in the .proto file.
   const ReservedRange* reserved_range(int index) const;
 
   // Returns true if the number is in one of the reserved ranges.
   bool IsReservedNumber(int number) const;
 
   // Returns nullptr if no reserved range contains the given number.
   const ReservedRange* FindReservedRangeContainingNumber(int number) const;
 
   // The number of reserved field names in this message type.
   int reserved_name_count() const;
 
   // Gets a reserved name by index, where 0 <= index < reserved_name_count().
   absl::string_view reserved_name(int index) const;
 
   // Returns true if the field name is reserved.
   bool IsReservedName(absl::string_view name) const;
 
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
   // extent of this message declaration.  Returns false and leaves
   // |*out_location| unchanged iff location information was not available.
   bool GetSourceLocation(SourceLocation* out_location) const;
 
   // Maps --------------------------------------------------------------
 
   // Returns the FieldDescriptor for the "key" field. If this isn't a map entry
   // field, returns nullptr.
   const FieldDescriptor* map_key() const;
 
   // Returns the FieldDescriptor for the "value" field. If this isn't a map
   // entry field, returns nullptr.
   const FieldDescriptor* map_value() const;
 
  private:
   friend class Symbol;
   typedef MessageOptions OptionsType;
 
   // Allows tests to test CopyTo(proto, true).
   friend class descriptor_unittest::DescriptorTest;
 
   // Allows access to GetLocationPath for annotations.
   friend class io::Printer;
   friend class compiler::cpp::Formatter;
 
   // Get the merged features that apply to this message type.  These are
   // specified in the .proto file through the feature options in the message
   // definition.  Allowed features are defined by Features in descriptor.proto,
   // along with any backend-specific extensions to it.
   const FeatureSet& features() const { return *merged_features_; }
   friend class internal::InternalFeatureHelper;
 
   // Fill the json_name field of FieldDescriptorProto.
   void CopyJsonNameTo(DescriptorProto* proto) const;
 
   // Internal version of DebugString; controls the level of indenting for
   // correct depth. Takes |options| to control debug-string options, and
   // |include_opening_clause| to indicate whether the "message ... " part of the
   // clause has already been generated (this varies depending on context).
   void DebugString(int depth, std::string* contents,
                    const DebugStringOptions& options,
                    bool include_opening_clause) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
   void GetLocationPath(std::vector<int>* output) const;
 
   // visibility declared on the message
   SymbolVisibility visibility_keyword() const;
 
   // True if this is a placeholder for an unknown type.
   bool is_placeholder_ : 1;
   // True if this is a placeholder and the type name wasn't fully-qualified.
   bool is_unqualified_placeholder_ : 1;
   // Well known type.  Stored like this to conserve space.
   uint8_t well_known_type_ : 5;
   // bitfield representation of SymbolVisibility, which only requires 2 bits
   uint8_t visibility_ : 2;
 
   // This points to the last field _number_ that is part of the sequence
   // starting at 1, where
   //     `desc->field(i)->number() == i + 1`
   // A value of `0` means no field matches. That is, there are no fields or the
   // first field is not field `1`.
   // Uses 16-bit to avoid extra padding. Unlikely to have more than 2^16
   // sequentially numbered fields in a message.
   uint16_t sequential_field_limit_;
 
   int field_count_;
 
   internal::DescriptorNames all_names_;
   const FileDescriptor* file_;
   const Descriptor* containing_type_;
   const MessageOptions* options_;
   const FeatureSet* proto_features_;
   const FeatureSet* merged_features_;
 
   // These arrays are separated from their sizes to minimize padding on 64-bit.
   FieldDescriptor* fields_;
   OneofDescriptor* oneof_decls_;
   Descriptor* nested_types_;
   EnumDescriptor* enum_types_;
   ExtensionRange* extension_ranges_;
   FieldDescriptor* extensions_;
   ReservedRange* reserved_ranges_;
   const std::string** reserved_names_;
 
   int oneof_decl_count_;
   int real_oneof_decl_count_;
   int nested_type_count_;
   int enum_type_count_;
   int extension_range_count_;
   int extension_count_;
   int reserved_range_count_;
   int reserved_name_count_;
 
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<Descriptor>() and AllocateArray<Descriptor>() in descriptor.cc
   // and update them to initialize the field.
 
   // Must be constructed using DescriptorPool.
   Descriptor();
   friend class DescriptorBuilder;
   friend class DescriptorPool;
   friend class EnumDescriptor;
   friend class FieldDescriptor;
   friend class FileDescriptorTables;
   friend class OneofDescriptor;
   friend class MethodDescriptor;
   friend class FileDescriptor;
 };
 
 PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(Descriptor, 160);
 
 // Describes a single field of a message.  To get the descriptor for a given
 // field, first get the Descriptor for the message in which it is defined,
 // then call Descriptor::FindFieldByName().  To get a FieldDescriptor for
 // an extension, do one of the following:
 // - Get the Descriptor or FileDescriptor for its containing scope, then
 //   call Descriptor::FindExtensionByName() or
 //   FileDescriptor::FindExtensionByName().
 // - Given a DescriptorPool, call DescriptorPool::FindExtensionByNumber() or
 //   DescriptorPool::FindExtensionByPrintableName().
 // Use DescriptorPool to construct your own descriptors.
 class PROTOBUF_EXPORT FieldDescriptor : private internal::SymbolBase,
                                         public internal::FieldDescriptorLite {
  public:
   typedef FieldDescriptorProto Proto;
 
 #ifndef SWIG
   FieldDescriptor(const FieldDescriptor&) = delete;
   FieldDescriptor& operator=(const FieldDescriptor&) = delete;
 #endif
 
   // Identifies a field type.  0 is reserved for errors.  The order is weird
   // for historical reasons.  Types 12 and up are new in proto2.
   // Inherited from FieldDescriptorLite:
   // enum Type {
   //   TYPE_DOUBLE = 1,    // double, exactly eight bytes on the wire.
   //   TYPE_FLOAT = 2,     // float, exactly four bytes on the wire.
   //   TYPE_INT64 = 3,     // int64, varint on the wire.  Negative numbers
   //                       // take 10 bytes.  Use TYPE_SINT64 if negative
   //                       // values are likely.
   //   TYPE_UINT64 = 4,    // uint64, varint on the wire.
   //   TYPE_INT32 = 5,     // int32, varint on the wire.  Negative numbers
   //                       // take 10 bytes.  Use TYPE_SINT32 if negative
   //                       // values are likely.
   //   TYPE_FIXED64 = 6,   // uint64, exactly eight bytes on the wire.
   //   TYPE_FIXED32 = 7,   // uint32, exactly four bytes on the wire.
   //   TYPE_BOOL = 8,      // bool, varint on the wire.
   //   TYPE_STRING = 9,    // UTF-8 text.
   //   TYPE_GROUP = 10,    // Tag-delimited message.  Deprecated.
   //   TYPE_MESSAGE = 11,  // Length-delimited message.
 
   //   TYPE_BYTES = 12,     // Arbitrary byte array.
   //   TYPE_UINT32 = 13,    // uint32, varint on the wire
   //   TYPE_ENUM = 14,      // Enum, varint on the wire
   //   TYPE_SFIXED32 = 15,  // int32, exactly four bytes on the wire
   //   TYPE_SFIXED64 = 16,  // int64, exactly eight bytes on the wire
   //   TYPE_SINT32 = 17,    // int32, ZigZag-encoded varint on the wire
   //   TYPE_SINT64 = 18,    // int64, ZigZag-encoded varint on the wire
 
   //   MAX_TYPE = 18,  // Constant useful for defining lookup tables
   //                   // indexed by Type.
   // };
 
   // Specifies the C++ data type used to represent the field.  There is a
   // fixed mapping from Type to CppType where each Type maps to exactly one
   // CppType.  0 is reserved for errors.
   // Inherited from FieldDescriptorLite:
   // enum CppType {
   //   CPPTYPE_INT32 = 1,     // TYPE_INT32, TYPE_SINT32, TYPE_SFIXED32
   //   CPPTYPE_INT64 = 2,     // TYPE_INT64, TYPE_SINT64, TYPE_SFIXED64
   //   CPPTYPE_UINT32 = 3,    // TYPE_UINT32, TYPE_FIXED32
   //   CPPTYPE_UINT64 = 4,    // TYPE_UINT64, TYPE_FIXED64
   //   CPPTYPE_DOUBLE = 5,    // TYPE_DOUBLE
   //   CPPTYPE_FLOAT = 6,     // TYPE_FLOAT
   //   CPPTYPE_BOOL = 7,      // TYPE_BOOL
   //   CPPTYPE_ENUM = 8,      // TYPE_ENUM
   //   CPPTYPE_STRING = 9,    // TYPE_STRING, TYPE_BYTES
   //   CPPTYPE_MESSAGE = 10,  // TYPE_MESSAGE, TYPE_GROUP
 
   //   MAX_CPPTYPE = 10,  // Constant useful for defining lookup tables
   //                      // indexed by CppType.
   // };
 
   // Identifies whether the field is optional, required, or repeated.  0 is
   // reserved for errors.
   // Inherited from FieldDescriptorLite:
   // enum Label {
   //   LABEL_OPTIONAL = 1,  // optional
   //   LABEL_REQUIRED = 2,  // required
   //   LABEL_REPEATED = 3,  // repeated
 
   //   MAX_LABEL = 3,  // Constant useful for defining lookup tables
   //                   // indexed by Label.
   // };
 
   // Valid field numbers are positive integers up to kMaxNumber.
   static const int kMaxNumber = (1 << 29) - 1;
 
   // First field number reserved for the protocol buffer library implementation.
   // Users may not declare fields that use reserved numbers.
   static const int kFirstReservedNumber = 19000;
   // Last field number reserved for the protocol buffer library implementation.
   // Users may not declare fields that use reserved numbers.
   static const int kLastReservedNumber = 19999;
 
   // Name of this field within the message.
   absl::string_view name() const;
   // Fully-qualified name of the field.
   absl::string_view full_name() const;
   // JSON name of this field.
   absl::string_view json_name() const;
 
   const FileDescriptor* file() const;  // File in which this field was defined.
   bool is_extension() const;           // Is this an extension field?
   int number() const;                  // Declared tag number.
 
   // Same as name() except converted to lower-case.  This (and especially the
   // FindFieldByLowercaseName() method) can be useful when parsing formats
   // which prefer to use lowercase naming style.  (Although, technically
   // field names should be lowercased anyway according to the protobuf style
   // guide, so this only makes a difference when dealing with old .proto files
   // which do not follow the guide.)
   absl::string_view lowercase_name() const;
 
   // Same as name() except converted to camel-case.  In this conversion, any
   // time an underscore appears in the name, it is removed and the next
   // letter is capitalized.  Furthermore, the first letter of the name is
   // lower-cased.  Examples:
   //   FooBar -> fooBar
   //   foo_bar -> fooBar
   //   fooBar -> fooBar
   // This (and especially the FindFieldByCamelcaseName() method) can be useful
   // when parsing formats which prefer to use camel-case naming style.
   absl::string_view camelcase_name() const;
 
   Type type() const;  // Declared type of this field.
   // Name of the declared type.
   absl::string_view type_name() const;
   CppType cpp_type() const;  // C++ type of this field.
   // Name of the C++ type.
   absl::string_view cpp_type_name() const;
 
   // This should never be called directly. Use is_required() and is_repeated()
   // helper methods instead.
   ABSL_DEPRECATED("Use is_required() or is_repeated() instead.")
   Label label() const;  // optional/required/repeated
 
 #ifndef SWIG
   CppStringType cpp_string_type() const;  // The C++ string type of this field.
 #endif
 
   // Whether or not the field is required. For proto2 required fields and
   // Editions LEGACY_REQUIRED fields.
   bool is_required() const;
   bool is_repeated() const;  // Whether or not the field is repeated/map field.
 
   ABSL_DEPRECATE_AND_INLINE()
   bool is_optional() const;  // Use !is_required() && !is_repeated() instead.
 
   bool is_packable() const;  // shorthand for is_repeated() &&
                              //               IsTypePackable(type())
   bool is_map() const;       // shorthand for type() == TYPE_MESSAGE &&
                              // message_type()->options().map_entry()
 
   // Whether or not this field is packable and packed.  In proto2, packable
   // fields must have `packed = true` specified.  In proto3, all packable fields
   // are packed by default unless `packed = false` is specified.
   bool is_packed() const;
 
   // Returns true if this field tracks presence, ie. does the field
   // distinguish between "unset" and "present with default value."
   // This includes required, optional, and oneof fields. It excludes maps,
   // repeated fields, and singular proto3 fields without "optional".
   //
   // For fields where has_presence() == true, the return value of
   // Reflection::HasField() is semantically meaningful.
   bool has_presence() const;
 
   // Returns true if this TYPE_STRING-typed field requires UTF-8 validation on
   // parse.
   bool requires_utf8_validation() const;
 
   // Determines if the given enum field is treated as closed based on legacy
   // non-conformant behavior.
   //
   // Conformant behavior determines closedness based on the enum and
   // can be queried using EnumDescriptor::is_closed().
   //
   // Some runtimes currently have a quirk where non-closed enums are
   // treated as closed when used as the type of fields defined in a
   // `syntax = proto2;` file. This quirk is not present in all runtimes; as of
   // writing, we know that:
   //
   // - C++, Java, and C++-based Python share this quirk.
   // - UPB and UPB-based Python do not.
   // - PHP and Ruby treat all enums as open regardless of declaration.
   //
   // Care should be taken when using this function to respect the target
   // runtime's enum handling quirks.
   bool legacy_enum_field_treated_as_closed() const;
 
   // Index of this field within the message's field array, or the file or
   // extension scope's extensions array.
   int index() const;
 
   // Does this field have an explicitly-declared default value?
   bool has_default_value() const;
 
   // Whether the user has specified the json_name field option in the .proto
   // file.
   bool has_json_name() const;
 
   // Get the field default value if cpp_type() == CPPTYPE_INT32.  If no
   // explicit default was defined, the default is 0.
   int32_t default_value_int32_t() const;
   int32_t default_value_int32() const { return default_value_int32_t(); }
   // Get the field default value if cpp_type() == CPPTYPE_INT64.  If no
   // explicit default was defined, the default is 0.
   int64_t default_value_int64_t() const;
   int64_t default_value_int64() const { return default_value_int64_t(); }
   // Get the field default value if cpp_type() == CPPTYPE_UINT32.  If no
   // explicit default was defined, the default is 0.
   uint32_t default_value_uint32_t() const;
   uint32_t default_value_uint32() const { return default_value_uint32_t(); }
   // Get the field default value if cpp_type() == CPPTYPE_UINT64.  If no
   // explicit default was defined, the default is 0.
   uint64_t default_value_uint64_t() const;
   uint64_t default_value_uint64() const { return default_value_uint64_t(); }
   // Get the field default value if cpp_type() == CPPTYPE_FLOAT.  If no
   // explicit default was defined, the default is 0.0.
   float default_value_float() const;
   // Get the field default value if cpp_type() == CPPTYPE_DOUBLE.  If no
   // explicit default was defined, the default is 0.0.
   double default_value_double() const;
   // Get the field default value if cpp_type() == CPPTYPE_BOOL.  If no
   // explicit default was defined, the default is false.
   bool default_value_bool() const;
   // Get the field default value if cpp_type() == CPPTYPE_ENUM.  If no
   // explicit default was defined, the default is the first value defined
   // in the enum type (all enum types are required to have at least one value).
   // This never returns nullptr.
   const EnumValueDescriptor* default_value_enum() const;
   // Get the field default value if cpp_type() == CPPTYPE_STRING.  If no
   // explicit default was defined, the default is the empty string.
   absl::string_view default_value_string() const;
 
   // The Descriptor for the message of which this is a field.  For extensions,
   // this is the extended type.  Never nullptr.
   const Descriptor* containing_type() const;
 
   // If the field is a member of a oneof, this is the one, otherwise this is
   // nullptr.
   const OneofDescriptor* containing_oneof() const;
 
   // If the field is a member of a non-synthetic oneof, returns the descriptor
   // for the oneof, otherwise returns nullptr.
   const OneofDescriptor* real_containing_oneof() const;
 
   // If the field is a member of a oneof, returns the index in that oneof.
   int index_in_oneof() const;
 
   // An extension may be declared within the scope of another message.  If this
   // field is an extension (is_extension() is true), then extension_scope()
   // returns that message, or nullptr if the extension was declared at global
   // scope.  If this is not an extension, extension_scope() is undefined (may
   // assert-fail).
   const Descriptor* extension_scope() const;
 
   // If type is TYPE_MESSAGE or TYPE_GROUP, returns a descriptor for the
   // message or the group type.  Otherwise, returns null.
   const Descriptor* message_type() const;
   // If type is TYPE_ENUM, returns a descriptor for the enum.  Otherwise,
   // returns null.
   const EnumDescriptor* enum_type() const;
 
   // Get the FieldOptions for this field.  This includes things listed in
   // square brackets after the field definition.  E.g., the field:
   //   optional string text = 1 [ctype=CORD];
   // has the "ctype" option set.  Allowed options are defined by FieldOptions in
   // descriptor.proto, and any available extensions of that message.
   const FieldOptions& options() const;
 
   // See Descriptor::CopyTo().
   void CopyTo(FieldDescriptorProto* proto) const;
 
   // See Descriptor::DebugString().
   std::string DebugString() const;
 
   // See Descriptor::DebugStringWithOptions().
   std::string DebugStringWithOptions(const DebugStringOptions& options) const;
 
   // Allows formatting with absl and gtest.
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const FieldDescriptor& d) {
     absl::Format(&sink, "%s", d.DebugString());
   }
 
   // Helper method to get the CppType for a particular Type.
   static CppType TypeToCppType(Type type);
 
   // Helper method to get the name of a Type.
   static absl::string_view TypeName(Type type);
 
   // Helper method to get the name of a CppType.
   static absl::string_view CppTypeName(CppType cpp_type);
 
   // Return true iff [packed = true] is valid for fields of this type.
   static inline bool IsTypePackable(Type field_type);
 
   // Returns full_name() except if the field is a MessageSet extension,
   // in which case it returns the full_name() of the containing message type
   // for backwards compatibility with proto1.
   //
   // A MessageSet extension is defined as an optional message extension
   // whose containing type has the message_set_wire_format option set.
   // This should be true of extensions of google.protobuf.bridge.MessageSet;
   // by convention, such extensions are named "message_set_extension".
   //
   // The opposite operation (looking up an extension's FieldDescriptor given
   // its printable name) can be accomplished with
   //     message->file()->pool()->FindExtensionByPrintableName(message, name)
   // where the extension extends "message".
   absl::string_view PrintableNameForExtension() const;
 
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
   // extent of this field declaration.  Returns false and leaves
   // |*out_location| unchanged iff location information was not available.
   bool GetSourceLocation(SourceLocation* out_location) const;
 
  private:
   friend class Symbol;
   typedef FieldOptions OptionsType;
 
   // Allows access to GetLocationPath for annotations.
   friend class io::Printer;
   friend class compiler::cpp::Formatter;
   friend class Reflection;
   friend class FieldDescriptorLegacy;
   friend const std::string& internal::DefaultValueStringAsString(
       const FieldDescriptor* field);
 
   // Returns the original ctype specified in the .proto file.  This should not
   // be relied on, as it no longer uniquely determines behavior.  The
   // cpp_string_type() method should be used instead, which takes feature
   // settings into account.  Needed by CppGenerator for validation only.
   friend class compiler::cpp::CppGenerator;
   int legacy_proto_ctype() const { return legacy_proto_ctype_; }
   bool has_legacy_proto_ctype() const;
 
   // Returns true if this field was syntactically written with "optional" in the
   // .proto file. Excludes singular proto3 fields that do not have a label.
   ABSL_DEPRECATED("Use has_presence() instead.")
   bool has_optional_keyword() const;
 
   // Get the merged features that apply to this field.  These are specified in
   // the .proto file through the feature options in the message definition.
   // Allowed features are defined by Features in descriptor.proto, along with
   // any backend-specific extensions to it.
   const FeatureSet& features() const { return *merged_features_; }
   friend class internal::InternalFeatureHelper;
 
   // Fill the json_name field of FieldDescriptorProto.
   void CopyJsonNameTo(FieldDescriptorProto* proto) const;
 
   // See Descriptor::DebugString().
   void DebugString(int depth, std::string* contents,
                    const DebugStringOptions& options) const;
 
   // formats the default value appropriately and returns it as a string.
   // Must have a default value to call this. If quote_string_type is true, then
   // types of CPPTYPE_STRING will be surrounded by quotes and CEscaped.
   std::string DefaultValueAsString(bool quote_string_type) const;
 
   // Helper function that returns the field type name for DebugString.
   std::string FieldTypeNameDebugString() const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
   void GetLocationPath(std::vector<int>* output) const;
 
   // Returns true if this is a map message type.
   bool is_map_message_type() const;
 
   CppStringType CalculateCppStringType() const;
 
   bool has_default_value_ : 1;
   bool proto3_optional_ : 1;
   // Whether the user has specified the json_name field option in the .proto
   // file.
   bool has_json_name_ : 1;
   bool is_extension_ : 1;
   bool is_oneof_ : 1;
   bool is_repeated_ : 1;  // Redundant with label_, but it is queried a lot.
 
   // Actually a `Label` but stored as uint8_t to save space.
   uint8_t label_ : 2;
 
   // Actually a `Type`, but stored as uint8_t to save space.
   uint8_t type_;
 
   // Actually a `CppStringType`, but stored as uint8_t to save space.
   // We cache it because it's expensive to calculate.
   uint8_t cpp_string_type_ : 3;
 
   // Can be calculated from containing_oneof(), but we cache it for performance.
   // Located here for bitpacking.
   bool in_real_oneof_ : 1;
 
   // We could calculate as `message_type()->options().map_entry()`, but that is
   // way more expensive and can potentially force load extra lazy files.
   bool is_map_ : 1;
 
   // Actually an optional `CType`, but stored as uint8_t to save space.  This
   // contains the original ctype option specified in the .proto file.
   uint8_t legacy_proto_ctype_ : 2;
 
   // Sadly, `number_` located here to reduce padding. Unrelated to all_names_
   // and its indices above.
   int number_;
   internal::DescriptorNames all_names_;
   const FileDescriptor* file_;
 
   // The once_flag is followed by a NUL terminated string for the type name and
   // enum default value (or empty string if no default enum).
   absl::once_flag* type_once_;
   static void TypeOnceInit(const FieldDescriptor* to_init);
   void InternalTypeOnceInit() const;
   const Descriptor* containing_type_;
   union {
     const OneofDescriptor* containing_oneof;
     const Descriptor* extension_scope;
   } scope_;
   union {
     mutable const Descriptor* message_type;
     mutable const EnumDescriptor* enum_type;
   } type_descriptor_;
   const FieldOptions* options_;
   const FeatureSet* proto_features_;
   const FeatureSet* merged_features_;
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<FieldDescriptor>() and AllocateArray<FieldDescriptor>() in
   // descriptor.cc and update them to initialize the field.
 
   union {
     int32_t default_value_int32_t_;
     int64_t default_value_int64_t_;
     uint32_t default_value_uint32_t_;
     uint64_t default_value_uint64_t_;
     float default_value_float_;
     double default_value_double_;
     bool default_value_bool_;
 
     mutable const EnumValueDescriptor* default_value_enum_;
     const std::string* default_value_string_;
     mutable std::atomic<const Message*> default_generated_instance_;
   };
 
   static const CppType kTypeToCppTypeMap[MAX_TYPE + 1];
 
   static const char* const kTypeToName[MAX_TYPE + 1];
 
   static const char* const kCppTypeToName[MAX_CPPTYPE + 1];
 
   static const char* const kLabelToName[MAX_LABEL + 1];
 
   // Must be constructed using DescriptorPool.
   FieldDescriptor();
   friend class DescriptorBuilder;
   friend class FileDescriptor;
   friend class Descriptor;
   friend class OneofDescriptor;
 };
 
 PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(FieldDescriptor, 88);
 
 // Describes a oneof defined in a message type.
 class PROTOBUF_EXPORT OneofDescriptor : private internal::SymbolBase {
  public:
   typedef OneofDescriptorProto Proto;
 
 #ifndef SWIG
   OneofDescriptor(const OneofDescriptor&) = delete;
   OneofDescriptor& operator=(const OneofDescriptor&) = delete;
 #endif
 
   // Name of this oneof.
   absl::string_view name() const;
   // Fully-qualified name of the oneof.
   absl::string_view full_name() const;
 
   // Index of this oneof within the message's oneof array.
   int index() const;
 
   // The .proto file in which this oneof was defined.  Never nullptr.
   const FileDescriptor* file() const;
   // The Descriptor for the message containing this oneof.
   const Descriptor* containing_type() const;
 
   // The number of (non-extension) fields which are members of this oneof.
   int field_count() const;
   // Get a member of this oneof, in the order in which they were declared in the
   // .proto file.  Does not include extensions.
   const FieldDescriptor* field(int index) const;
 
   const OneofOptions& options() const;
 
   // See Descriptor::CopyTo().
   void CopyTo(OneofDescriptorProto* proto) const;
 
   // See Descriptor::DebugString().
   std::string DebugString() const;
 
   // See Descriptor::DebugStringWithOptions().
   std::string DebugStringWithOptions(const DebugStringOptions& options) const;
 
   // Allows formatting with absl and gtest.
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const OneofDescriptor& d) {
     absl::Format(&sink, "%s", d.DebugString());
   }
 
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
   // extent of this oneof declaration.  Returns false and leaves
   // |*out_location| unchanged iff location information was not available.
   bool GetSourceLocation(SourceLocation* out_location) const;
 
  private:
   friend class Symbol;
   typedef OneofOptions OptionsType;
 
   // Allows access to GetLocationPath for annotations.
   friend class io::Printer;
   friend class compiler::cpp::Formatter;
   friend class OneofDescriptorLegacy;
 
   // Returns whether this oneof was inserted by the compiler to wrap a proto3
   // optional field. If this returns true, code generators should *not* emit it.
   bool is_synthetic() const;
 
   // Get the merged features that apply to this oneof.  These are specified in
   // the .proto file through the feature options in the oneof definition.
   // Allowed features are defined by Features in descriptor.proto, along with
   // any backend-specific extensions to it.
   const FeatureSet& features() const { return *merged_features_; }
   friend class internal::InternalFeatureHelper;
 
   // See Descriptor::DebugString().
   void DebugString(int depth, std::string* contents,
                    const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
   void GetLocationPath(std::vector<int>* output) const;
 
   int field_count_;
 
   internal::DescriptorNames all_names_;
   const Descriptor* containing_type_;
   const OneofOptions* options_;
   const FeatureSet* proto_features_;
   const FeatureSet* merged_features_;
   const FieldDescriptor* fields_;
 
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<OneofDescriptor>() and AllocateArray<OneofDescriptor>()
   // in descriptor.cc and update them to initialize the field.
 
   // Must be constructed using DescriptorPool.
   OneofDescriptor();
   friend class DescriptorBuilder;
   friend class Descriptor;
   friend class FieldDescriptor;
   friend class Reflection;
 };
 
 PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(OneofDescriptor, 56);
 
 // Describes an enum type defined in a .proto file.  To get the EnumDescriptor
 // for a generated enum type, call TypeName_descriptor().  Use DescriptorPool
 // to construct your own descriptors.
 class PROTOBUF_EXPORT EnumDescriptor : private internal::SymbolBase {
  public:
   typedef EnumDescriptorProto Proto;
 
 #ifndef SWIG
   EnumDescriptor(const EnumDescriptor&) = delete;
   EnumDescriptor& operator=(const EnumDescriptor&) = delete;
 #endif
 
   // The name of this enum type in the containing scope.
   absl::string_view name() const;
 
   // The fully-qualified name of the enum type, scope delimited by periods.
   absl::string_view full_name() const;
 
   // Index of this enum within the file or containing message's enum array.
   int index() const;
 
   // The .proto file in which this enum type was defined.  Never nullptr.
   const FileDescriptor* file() const;
 
   // The number of values for this EnumDescriptor.  Guaranteed to be greater
   // than zero.
   int value_count() const;
   // Gets a value by index, where 0 <= index < value_count().
   // These are returned in the order they were defined in the .proto file, not
   // the enum value order. (Use `FindValueByNumber()` for enum -> value lookup).
   const EnumValueDescriptor* value(int index) const;
 
   // Looks up a value by name.  Returns nullptr if no such value exists.
   const EnumValueDescriptor* FindValueByName(absl::string_view name) const;
   // Looks up a value by number.  Returns nullptr if no such value exists.  If
   // multiple values have this number, the first one defined is returned.
   const EnumValueDescriptor* FindValueByNumber(int number) const;
 
   // If this enum type is nested in a message type, this is that message type.
   // Otherwise, nullptr.
   const Descriptor* containing_type() const;
 
   // Get options for this enum type.  These are specified in the .proto file by
   // placing lines like "option foo = 1234;" in the enum definition.  Allowed
   // options are defined by EnumOptions in descriptor.proto, and any available
   // extensions of that message.
   const EnumOptions& options() const;
 
   // See Descriptor::CopyTo().
   void CopyTo(EnumDescriptorProto* proto) const;
 
   // See Descriptor::DebugString().
   std::string DebugString() const;
 
   // See Descriptor::DebugStringWithOptions().
   std::string DebugStringWithOptions(const DebugStringOptions& options) const;
 
   // Allows formatting with absl and gtest.
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const EnumDescriptor& d) {
     absl::Format(&sink, "%s", d.DebugString());
   }
 
   // Returns true if this is a placeholder for an unknown enum. This will
   // only be the case if this descriptor comes from a DescriptorPool
   // with AllowUnknownDependencies() set.
   bool is_placeholder() const;
 
   // Returns true whether this is a "closed" enum, meaning that it:
   // - Has a fixed set of values, rather than being equivalent to an int32.
   // - Encountering values not in this set causes them to be treated as unknown
   //   fields.
   // - The first value (i.e., the default) may be nonzero.
   //
   // WARNING: Some runtimes currently have a quirk where non-closed enums are
   // treated as closed when used as the type of fields defined in a
   // `syntax = proto2;` file. This quirk is not present in all runtimes; as of
   // writing, we know that:
   //
   // - C++, Java, and C++-based Python share this quirk.
   // - UPB and UPB-based Python do not.
   // - PHP and Ruby treat all enums as open regardless of declaration.
   //
   // Care should be taken when using this function to respect the target
   // runtime's enum handling quirks.
   bool is_closed() const;
 
   // Reserved fields -------------------------------------------------
 
   // A range of reserved field numbers.
   struct ReservedRange {
     int start;  // inclusive
     int end;    // inclusive
   };
 
   // The number of reserved ranges in this message type.
   int reserved_range_count() const;
   // Gets an reserved range by index, where 0 <= index <
   // reserved_range_count(). These are returned in the order they were defined
   // in the .proto file.
   const EnumDescriptor::ReservedRange* reserved_range(int index) const;
 
   // Returns true if the number is in one of the reserved ranges.
   bool IsReservedNumber(int number) const;
 
   // Returns nullptr if no reserved range contains the given number.
   const EnumDescriptor::ReservedRange* FindReservedRangeContainingNumber(
       int number) const;
 
   // The number of reserved field names in this message type.
   int reserved_name_count() const;
 
   // Gets a reserved name by index, where 0 <= index < reserved_name_count().
   absl::string_view reserved_name(int index) const;
 
   // Returns true if the field name is reserved.
   bool IsReservedName(absl::string_view name) const;
 
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
   // extent of this enum declaration.  Returns false and leaves
   // |*out_location| unchanged iff location information was not available.
   bool GetSourceLocation(SourceLocation* out_location) const;
 
  private:
   friend class Symbol;
   friend bool internal::IsEnumFullySequential(const EnumDescriptor* enum_desc);
   typedef EnumOptions OptionsType;
 
   // Allows access to GetLocationPath for annotations.
   friend class io::Printer;
   friend class compiler::cpp::Formatter;
 
   // Allow access to FindValueByNumberCreatingIfUnknown.
   friend class descriptor_unittest::DescriptorTest;
 
   // Get the merged features that apply to this enum type.  These are specified
   // in the .proto file through the feature options in the message definition.
   // Allowed features are defined by Features in descriptor.proto, along with
   // any backend-specific extensions to it.
   const FeatureSet& features() const { return *merged_features_; }
   friend class internal::InternalFeatureHelper;
 
   // Looks up a value by number.  If the value does not exist, dynamically
   // creates a new EnumValueDescriptor for that value, assuming that it was
   // unknown. If a new descriptor is created, this is done in a thread-safe way,
   // and future calls will return the same value descriptor pointer.
   //
   // This is private but is used by Reflection (which is friended below) to
   // return a valid EnumValueDescriptor from GetEnum() when this feature is
   // enabled.
   const EnumValueDescriptor* FindValueByNumberCreatingIfUnknown(
       int number) const;
 
   // See Descriptor::DebugString().
   void DebugString(int depth, std::string* contents,
                    const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
   void GetLocationPath(std::vector<int>* output) const;
 
   // visibility declared on the enum
   SymbolVisibility visibility_keyword() const;
 
   // True if this is a placeholder for an unknown type.
   bool is_placeholder_ : 1;
   // True if this is a placeholder and the type name wasn't fully-qualified.
   bool is_unqualified_placeholder_ : 1;
 
   // bitfield representation of SymbolVisibility, which only requires 2 bits
   uint8_t visibility_ : 2;
 
   // This points to the last value _index_ that is part of the sequence starting
   // with the first label, where
   //   `enum->value(i)->number() == enum->value(0)->number() + i`
   // We measure relative to the first label to adapt to enum labels starting at
   // 0 or 1.
   // Uses 16-bit to avoid extra padding. Unlikely to have more than 2^15
   // sequentially numbered labels in an enum.
   int16_t sequential_value_limit_;
 
   int value_count_;
 
   internal::DescriptorNames all_names_;
   const FileDescriptor* file_;
   const Descriptor* containing_type_;
   const EnumOptions* options_;
   const FeatureSet* proto_features_;
   const FeatureSet* merged_features_;
   EnumValueDescriptor* values_;
 
   int reserved_range_count_;
   int reserved_name_count_;
   EnumDescriptor::ReservedRange* reserved_ranges_;
   const std::string** reserved_names_;
 
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<EnumDescriptor>() and AllocateArray<EnumDescriptor>() in
   // descriptor.cc and update them to initialize the field.
 
   // Must be constructed using DescriptorPool.
   EnumDescriptor();
   friend class DescriptorBuilder;
   friend class Descriptor;
   friend class FieldDescriptor;
   friend class FileDescriptorTables;
   friend class EnumValueDescriptor;
   friend class FileDescriptor;
   friend class DescriptorPool;
   friend class Reflection;
 };
 
 PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(EnumDescriptor, 88);
 
 // Describes an individual enum constant of a particular type.  To get the
 // EnumValueDescriptor for a given enum value, first get the EnumDescriptor
 // for its type, then use EnumDescriptor::FindValueByName() or
 // EnumDescriptor::FindValueByNumber().  Use DescriptorPool to construct
 // your own descriptors.
 class PROTOBUF_EXPORT EnumValueDescriptor : private internal::SymbolBaseN<0>,
                                             private internal::SymbolBaseN<1> {
  public:
   typedef EnumValueDescriptorProto Proto;
 
 #ifndef SWIG
   EnumValueDescriptor(const EnumValueDescriptor&) = delete;
   EnumValueDescriptor& operator=(const EnumValueDescriptor&) = delete;
 #endif
 
   absl::string_view name() const;   // Name of this enum constant.
   int index() const;                // Index within the enums's Descriptor.
   int number() const;               // Numeric value of this enum constant.
 
   // The full_name of an enum value is a sibling symbol of the enum type.
   // e.g. the full name of FieldDescriptorProto::TYPE_INT32 is actually
   // "google.protobuf.FieldDescriptorProto.TYPE_INT32", NOT
   // "google.protobuf.FieldDescriptorProto.Type.TYPE_INT32".  This is to conform
   // with C++ scoping rules for enums.
   absl::string_view full_name() const;
 
   // The .proto file in which this value was defined.  Never nullptr.
   const FileDescriptor* file() const;
   // The type of this value.  Never nullptr.
   const EnumDescriptor* type() const;
 
   // Get options for this enum value.  These are specified in the .proto file by
   // adding text like "[foo = 1234]" after an enum value definition.  Allowed
   // options are defined by EnumValueOptions in descriptor.proto, and any
   // available extensions of that message.
   const EnumValueOptions& options() const;
 
   // See Descriptor::CopyTo().
   void CopyTo(EnumValueDescriptorProto* proto) const;
 
   // See Descriptor::DebugString().
   std::string DebugString() const;
 
   // See Descriptor::DebugStringWithOptions().
   std::string DebugStringWithOptions(const DebugStringOptions& options) const;
 
   // Allows formatting with absl and gtest.
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const EnumValueDescriptor& d) {
     absl::Format(&sink, "%s", d.DebugString());
   }
 
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
   // extent of this enum value declaration.  Returns false and leaves
   // |*out_location| unchanged iff location information was not available.
   bool GetSourceLocation(SourceLocation* out_location) const;
 
  private:
   friend class Symbol;
   typedef EnumValueOptions OptionsType;
 
   // Allows access to GetLocationPath for annotations.
   friend class io::Printer;
   friend class compiler::cpp::Formatter;
   friend const std::string& internal::NameOfEnumAsString(
       const EnumValueDescriptor* descriptor);
 
   // Get the merged features that apply to this enum value.  These are specified
   // in the .proto file through the feature options in the message definition.
   // Allowed features are defined by Features in descriptor.proto, along with
   // any backend-specific extensions to it.
   const FeatureSet& features() const { return *merged_features_; }
   friend class internal::InternalFeatureHelper;
 
   // See Descriptor::DebugString().
   void DebugString(int depth, std::string* contents,
                    const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
   void GetLocationPath(std::vector<int>* output) const;
 
   int number_;
   // We keep the old-style std::string payload to support `NameOfEnumAsString`
   // Once we start migrating Enum_Name functions to string_view we can switch
   // this too.
   const std::string* all_names_;
   const EnumDescriptor* type_;
   const EnumValueOptions* options_;
   const FeatureSet* proto_features_;
   const FeatureSet* merged_features_;
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<EnumValueDescriptor>() and AllocateArray<EnumValueDescriptor>()
   // in descriptor.cc and update them to initialize the field.
 
   // Must be constructed using DescriptorPool.
   EnumValueDescriptor();
   friend class DescriptorBuilder;
   friend class EnumDescriptor;
   friend class DescriptorPool;
   friend class FileDescriptorTables;
   friend class Reflection;
 };
 
 PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(EnumValueDescriptor, 48);
 
 // Describes an RPC service. Use DescriptorPool to construct your own
 // descriptors.
 class PROTOBUF_EXPORT ServiceDescriptor : private internal::SymbolBase {
  public:
   typedef ServiceDescriptorProto Proto;
 
 #ifndef SWIG
   ServiceDescriptor(const ServiceDescriptor&) = delete;
   ServiceDescriptor& operator=(const ServiceDescriptor&) = delete;
 #endif
 
   // The name of the service, not including its containing scope.
   absl::string_view name() const;
   // The fully-qualified name of the service, scope delimited by periods.
   absl::string_view full_name() const;
   // Index of this service within the file's services array.
   int index() const;
 
   // The .proto file in which this service was defined.  Never nullptr.
   const FileDescriptor* file() const;
 
   // Get options for this service type.  These are specified in the .proto file
   // by placing lines like "option foo = 1234;" in the service definition.
   // Allowed options are defined by ServiceOptions in descriptor.proto, and any
   // available extensions of that message.
   const ServiceOptions& options() const;
 
   // The number of methods this service defines.
   int method_count() const;
   // Gets a MethodDescriptor by index, where 0 <= index < method_count().
   // These are returned in the order they were defined in the .proto file.
   const MethodDescriptor* method(int index) const;
 
   // Look up a MethodDescriptor by name.
   const MethodDescriptor* FindMethodByName(absl::string_view name) const;
 
   // See Descriptor::CopyTo().
   void CopyTo(ServiceDescriptorProto* proto) const;
 
   // See Descriptor::DebugString().
   std::string DebugString() const;
 
   // See Descriptor::DebugStringWithOptions().
   std::string DebugStringWithOptions(const DebugStringOptions& options) const;
 
   // Allows formatting with absl and gtest.
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const ServiceDescriptor& d) {
     absl::Format(&sink, "%s", d.DebugString());
   }
 
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
   // extent of this service declaration.  Returns false and leaves
   // |*out_location| unchanged iff location information was not available.
   bool GetSourceLocation(SourceLocation* out_location) const;
 
  private:
   friend class Symbol;
   typedef ServiceOptions OptionsType;
 
   // Allows access to GetLocationPath for annotations.
   friend class io::Printer;
   friend class compiler::cpp::Formatter;
 
   // Get the merged features that apply to this service type.  These are
   // specified in the .proto file through the feature options in the service
   // definition. Allowed features are defined by Features in descriptor.proto,
   // along with any backend-specific extensions to it.
   const FeatureSet& features() const { return *merged_features_; }
   friend class internal::InternalFeatureHelper;
 
   // See Descriptor::DebugString().
   void DebugString(std::string* contents,
                    const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
   void GetLocationPath(std::vector<int>* output) const;
 
   internal::DescriptorNames all_names_;
   const FileDescriptor* file_;
   const ServiceOptions* options_;
   const FeatureSet* proto_features_;
   const FeatureSet* merged_features_;
   MethodDescriptor* methods_;
   int method_count_;
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<ServiceDescriptor>() and AllocateArray<ServiceDescriptor>() in
   // descriptor.cc and update them to initialize the field.
 
   // Must be constructed using DescriptorPool.
   ServiceDescriptor();
   friend class DescriptorBuilder;
   friend class FileDescriptor;
   friend class MethodDescriptor;
 };
 
 PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(ServiceDescriptor, 64);
 
 // Describes an individual service method.  To obtain a MethodDescriptor given
 // a service, first get its ServiceDescriptor, then call
 // ServiceDescriptor::FindMethodByName().  Use DescriptorPool to construct your
 // own descriptors.
 class PROTOBUF_EXPORT MethodDescriptor : private internal::SymbolBase {
  public:
   typedef MethodDescriptorProto Proto;
 
 #ifndef SWIG
   MethodDescriptor(const MethodDescriptor&) = delete;
   MethodDescriptor& operator=(const MethodDescriptor&) = delete;
 #endif
 
   // Name of this method, not including containing scope.
   absl::string_view name() const;
   // The fully-qualified name of the method, scope delimited by periods.
   absl::string_view full_name() const;
   // Index within the service's Descriptor.
   int index() const;
 
   // The .proto file in which this method was defined.  Never nullptr.
   const FileDescriptor* file() const;
   // Gets the service to which this method belongs.  Never nullptr.
   const ServiceDescriptor* service() const;
 
   // Gets the type of protocol message which this method accepts as input.
   const Descriptor* input_type() const;
   // Gets the type of protocol message which this message produces as output.
   const Descriptor* output_type() const;
 
   // Gets whether the client streams multiple requests.
   bool client_streaming() const;
   // Gets whether the server streams multiple responses.
   bool server_streaming() const;
 
   // Get options for this method.  These are specified in the .proto file by
   // placing lines like "option foo = 1234;" in curly-braces after a method
   // declaration.  Allowed options are defined by MethodOptions in
   // descriptor.proto, and any available extensions of that message.
   const MethodOptions& options() const;
 
   // See Descriptor::CopyTo().
   void CopyTo(MethodDescriptorProto* proto) const;
 
   // See Descriptor::DebugString().
   std::string DebugString() const;
 
   // See Descriptor::DebugStringWithOptions().
   std::string DebugStringWithOptions(const DebugStringOptions& options) const;
 
   // Allows formatting with absl and gtest.
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const MethodDescriptor& d) {
     absl::Format(&sink, "%s", d.DebugString());
   }
 
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
   // extent of this method declaration.  Returns false and leaves
   // |*out_location| unchanged iff location information was not available.
   bool GetSourceLocation(SourceLocation* out_location) const;
 
  private:
   friend class Symbol;
   typedef MethodOptions OptionsType;
 
   // Allows access to GetLocationPath for annotations.
   friend class io::Printer;
   friend class compiler::cpp::Formatter;
 
   // Get the merged features that apply to this method.  These are specified in
   // the .proto file through the feature options in the method definition.
   // Allowed features are defined by Features in descriptor.proto, along with
   // any backend-specific extensions to it.
   const FeatureSet& features() const { return *merged_features_; }
   friend class internal::InternalFeatureHelper;
 
   // See Descriptor::DebugString().
   void DebugString(int depth, std::string* contents,
                    const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
   void GetLocationPath(std::vector<int>* output) const;
 
   bool client_streaming_;
   bool server_streaming_;
   internal::DescriptorNames all_names_;
   const ServiceDescriptor* service_;
   mutable internal::LazyDescriptor input_type_;
   mutable internal::LazyDescriptor output_type_;
   const MethodOptions* options_;
   const FeatureSet* proto_features_;
   const FeatureSet* merged_features_;
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<MethodDescriptor>() and AllocateArray<MethodDescriptor>() in
   // descriptor.cc and update them to initialize the field.
 
   // Must be constructed using DescriptorPool.
   MethodDescriptor();
   friend class DescriptorBuilder;
   friend class ServiceDescriptor;
 };
 
 PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(MethodDescriptor, 80);
 
 // Describes a whole .proto file.  To get the FileDescriptor for a compiled-in
 // file, get the descriptor for something defined in that file and call
 // descriptor->file().  Use DescriptorPool to construct your own descriptors.
 class PROTOBUF_EXPORT FileDescriptor : private internal::SymbolBase {
  public:
   typedef FileDescriptorProto Proto;
 
 #ifndef SWIG
   FileDescriptor(const FileDescriptor&) = delete;
   FileDescriptor& operator=(const FileDescriptor&) = delete;
 #endif
 
   // The filename, relative to the source tree.
   // e.g. "foo/bar/baz.proto"
   absl::string_view name() const;
 
   // The package, e.g. "google.protobuf.compiler".
   absl::string_view package() const;
 
   // The DescriptorPool in which this FileDescriptor and all its contents were
   // allocated.  Never nullptr.
   const DescriptorPool* pool() const;
 
   // The number of files imported by this one.
   int dependency_count() const;
   // Gets an imported file by index, where 0 <= index < dependency_count().
   // These are returned in the order they were defined in the .proto file.
   const FileDescriptor* dependency(int index) const;
 
   // The number of files public imported by this one.
   // The public dependency list is a subset of the dependency list.
   int public_dependency_count() const;
   // Gets a public imported file by index, where 0 <= index <
   // public_dependency_count().
   // These are returned in the order they were defined in the .proto file.
   const FileDescriptor* public_dependency(int index) const;
 
   // The number of files that are imported for weak fields.
   // The weak dependency list is a subset of the dependency list.
   int weak_dependency_count() const;
   // Gets a weak imported file by index, where 0 <= index <
   // weak_dependency_count().
   // These are returned in the order they were defined in the .proto file.
   const FileDescriptor* weak_dependency(int index) const;
 
   // The number of files that are imported for options.
   // The option dependency list is separate from the dependency list.
   int option_dependency_count() const;
   // Gets name of an option imported file by index, where
   //     0 <= index < option_dependency_count()
   // These are returned in the relative order they were defined in the .proto
   // file.
   absl::string_view option_dependency_name(int index) const;
 
   // Number of top-level message types defined in this file.  (This does not
   // include nested types.)
   int message_type_count() const;
   // Gets a top-level message type, where 0 <= index < message_type_count().
   // These are returned in the order they were defined in the .proto file.
   const Descriptor* message_type(int index) const;
 
   // Number of top-level enum types defined in this file.  (This does not
   // include nested types.)
   int enum_type_count() const;
   // Gets a top-level enum type, where 0 <= index < enum_type_count().
   // These are returned in the order they were defined in the .proto file.
   const EnumDescriptor* enum_type(int index) const;
 
   // Number of services defined in this file.
   int service_count() const;
   // Gets a service, where 0 <= index < service_count().
   // These are returned in the order they were defined in the .proto file.
   const ServiceDescriptor* service(int index) const;
 
   // Number of extensions defined at file scope.  (This does not include
   // extensions nested within message types.)
   int extension_count() const;
   // Gets an extension's descriptor, where 0 <= index < extension_count().
   // These are returned in the order they were defined in the .proto file.
   const FieldDescriptor* extension(int index) const;
 
   // Get options for this file.  These are specified in the .proto file by
   // placing lines like "option foo = 1234;" at the top level, outside of any
   // other definitions.  Allowed options are defined by FileOptions in
   // descriptor.proto, and any available extensions of that message.
   const FileOptions& options() const;
 
   // Find a top-level message type by name (not full_name).  Returns nullptr if
   // not found.
   const Descriptor* FindMessageTypeByName(absl::string_view name) const;
   // Find a top-level enum type by name.  Returns nullptr if not found.
   const EnumDescriptor* FindEnumTypeByName(absl::string_view name) const;
   // Find an enum value defined in any top-level enum by name.  Returns nullptr
   // if not found.
   const EnumValueDescriptor* FindEnumValueByName(absl::string_view name) const;
   // Find a service definition by name.  Returns nullptr if not found.
   const ServiceDescriptor* FindServiceByName(absl::string_view name) const;
   // Find a top-level extension definition by name.  Returns nullptr if not
   // found.
   const FieldDescriptor* FindExtensionByName(absl::string_view name) const;
   // Similar to FindExtensionByName(), but searches by lowercased-name.  See
   // Descriptor::FindFieldByLowercaseName().
   const FieldDescriptor* FindExtensionByLowercaseName(
       absl::string_view name) const;
   // Similar to FindExtensionByName(), but searches by camelcased-name.  See
   // Descriptor::FindFieldByCamelcaseName().
   const FieldDescriptor* FindExtensionByCamelcaseName(
       absl::string_view name) const;
 
   // See Descriptor::CopyTo().
   // Notes:
   // - This method does NOT copy source code information since it is relatively
   //   large and rarely needed.  See CopySourceCodeInfoTo() below.
   void CopyTo(FileDescriptorProto* proto) const;
   // Write the source code information of this FileDescriptor into the given
   // FileDescriptorProto.  See CopyTo() above.
   void CopySourceCodeInfoTo(FileDescriptorProto* proto) const;
   // Fill the json_name field of FieldDescriptorProto for all fields. Can only
   // be called after CopyTo().
   void CopyJsonNameTo(FileDescriptorProto* proto) const;
   // Fills in the file-level settings of this file (e.g. edition, package,
   // file options) to `proto`.
   void CopyHeadingTo(FileDescriptorProto* proto) const;
 
   // See Descriptor::DebugString().
   std::string DebugString() const;
 
   // See Descriptor::DebugStringWithOptions().
   std::string DebugStringWithOptions(const DebugStringOptions& options) const;
 
   // Allows formatting with absl and gtest.
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const FileDescriptor& d) {
     absl::Format(&sink, "%s", d.DebugString());
   }
 
   // Returns true if this is a placeholder for an unknown file. This will
   // only be the case if this descriptor comes from a DescriptorPool
   // with AllowUnknownDependencies() set.
   bool is_placeholder() const;
 
   // Updates |*out_location| to the source location of the complete extent of
   // this file declaration (namely, the empty path).
   bool GetSourceLocation(SourceLocation* out_location) const;
 
   // Updates |*out_location| to the source location of the complete
   // extent of the declaration or declaration-part denoted by |path|.
   // Returns false and leaves |*out_location| unchanged iff location
   // information was not available.  (See SourceCodeInfo for
   // description of path encoding.)
   bool GetSourceLocation(const std::vector<int>& path,
                          SourceLocation* out_location) const;
 
  private:
   friend class Symbol;
   friend class FileDescriptorLegacy;
   typedef FileOptions OptionsType;
 
   bool is_placeholder_;
   // Indicates the FileDescriptor is completed building. Used to verify
   // that type accessor functions that can possibly build a dependent file
   // aren't called during the process of building the file.
   bool finished_building_;
   // This one is here to fill the padding.
   int extension_count_;
 
   const std::string* name_;
   const std::string* package_;
   const DescriptorPool* pool_;
   Edition edition_;
 
   // Returns edition of this file.  For legacy proto2/proto3 files, special
   // EDITION_PROTO2 and EDITION_PROTO3 values are used.
   Edition edition() const;
 
   // Get the merged features that apply to this file.  These are specified in
   // the .proto file through the feature options in the message definition.
   // Allowed features are defined by FeatureSet in descriptor.proto, along with
   // any backend-specific extensions to it.
   const FeatureSet& features() const { return *merged_features_; }
   friend class internal::InternalFeatureHelper;
 
   // dependencies_once_ contain a once_flag followed by N NUL terminated
   // strings. Dependencies that do not need to be loaded will be empty. ie just
   // {'\0'}
   absl::once_flag* dependencies_once_;
   static void DependenciesOnceInit(const FileDescriptor* to_init);
   void InternalDependenciesOnceInit() const;
 
   // These are arranged to minimize padding on 64-bit.
   int dependency_count_;
   int public_dependency_count_;
   int weak_dependency_count_;
   int option_dependency_count_;
   int message_type_count_;
   int enum_type_count_;
   int service_count_;
 
   mutable const FileDescriptor** dependencies_;
   int* public_dependencies_;
   int* weak_dependencies_;
   absl::string_view* option_dependencies_;
 
   Descriptor* message_types_;
   EnumDescriptor* enum_types_;
   ServiceDescriptor* services_;
   FieldDescriptor* extensions_;
   const FileOptions* options_;
   const FeatureSet* proto_features_;
   const FeatureSet* merged_features_;
 
   const FileDescriptorTables* tables_;
   const SourceCodeInfo* source_code_info_;
 
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<FileDescriptor>() and AllocateArray<FileDescriptor>() in
   // descriptor.cc and update them to initialize the field.
 
   FileDescriptor();
   friend class DescriptorBuilder;
   friend class DescriptorPool;
   friend class Descriptor;
   friend class FieldDescriptor;
   friend class internal::LazyDescriptor;
   friend class OneofDescriptor;
   friend class EnumDescriptor;
   friend class EnumValueDescriptor;
   friend class MethodDescriptor;
   friend class ServiceDescriptor;
 };
 
 PROTOBUF_INTERNAL_CHECK_CLASS_SIZE(FileDescriptor, 184);
 
 #ifndef SWIG
 enum class ExtDeclEnforcementLevel : uint8_t {
   // No enforcement.
   kNoEnforcement = 0,
   // All extensions excluding descriptor.proto extensions
   // (go/extension-declarations#descriptor-proto)
   kCustomExtensions = 1,
   // All extensions including descriptor.proto extensions.
   kAllExtensions = 2,
 };
 #endif  // !SWIG
 
 // ===================================================================
 
 // Used to construct descriptors.
 //
 // Normally you won't want to build your own descriptors.  Message classes
 // constructed by the protocol compiler will provide them for you.  However,
 // if you are implementing Message on your own, or if you are writing a
 // program which can operate on totally arbitrary types and needs to load
 // them from some sort of database, you might need to.
 //
 // Since Descriptors are composed of a whole lot of cross-linked bits of
 // data that would be a pain to put together manually, the
 // DescriptorPool class is provided to make the process easier.  It can
 // take a FileDescriptorProto (defined in descriptor.proto), validate it,
 // and convert it to a set of nicely cross-linked Descriptors.
 //
 // DescriptorPool also helps with memory management.  Descriptors are
 // composed of many objects containing static data and pointers to each
 // other.  In all likelihood, when it comes time to delete this data,
 // you'll want to delete it all at once.  In fact, it is not uncommon to
 // have a whole pool of descriptors all cross-linked with each other which
 // you wish to delete all at once.  This class represents such a pool, and
 // handles the memory management for you.
 //
 // You can also search for descriptors within a DescriptorPool by name, and
 // extensions by number.
 class PROTOBUF_EXPORT DescriptorPool {
  public:
   // Create a normal, empty DescriptorPool.
   DescriptorPool();
 
   // Constructs a DescriptorPool that, when it can't find something among the
   // descriptors already in the pool, looks for it in the given
   // DescriptorDatabase.
   // Notes:
   // - If a DescriptorPool is constructed this way, its BuildFile*() methods
   //   must not be called (they will assert-fail).  The only way to populate
   //   the pool with descriptors is to call the Find*By*() methods.
   // - The Find*By*() methods may block the calling thread if the
   //   DescriptorDatabase blocks.  This in turn means that parsing messages
   //   may block if they need to look up extensions.
   // - The Find*By*() methods will use mutexes for thread-safety, thus making
   //   them slower even when they don't have to fall back to the database.
   //   In fact, even the Find*By*() methods of descriptor objects owned by
   //   this pool will be slower, since they will have to obtain locks too.
   // - An ErrorCollector may optionally be given to collect validation errors
   //   in files loaded from the database.  If not given, errors will be printed
   //   to ABSL_LOG(ERROR).  Remember that files are built on-demand, so this
   //   ErrorCollector may be called from any thread that calls one of the
   //   Find*By*() methods.
   // - The DescriptorDatabase must not be mutated during the lifetime of
   //   the DescriptorPool. Even if the client takes care to avoid data races,
   //   changes to the content of the DescriptorDatabase may not be reflected
   //   in subsequent lookups in the DescriptorPool.
   class ErrorCollector;
   explicit DescriptorPool(DescriptorDatabase* fallback_database,
                           ErrorCollector* error_collector = nullptr);
 
 #ifndef SWIG
   DescriptorPool(const DescriptorPool&) = delete;
   DescriptorPool& operator=(const DescriptorPool&) = delete;
 #endif
   ~DescriptorPool();
 
   // Get a pointer to the generated pool.  Generated protocol message classes
   // which are compiled into the binary will allocate their descriptors in
   // this pool.  Do not add your own descriptors to this pool.
   static const DescriptorPool* generated_pool();
 
 
   // Find a FileDescriptor in the pool by file name.  Returns nullptr if not
   // found.
   const FileDescriptor* FindFileByName(absl::string_view name) const;
 
   // Find the FileDescriptor in the pool which defines the given symbol.
   // If any of the Find*ByName() methods below would succeed, then this is
   // equivalent to calling that method and calling the result's file() method.
   // Otherwise this returns nullptr.
   const FileDescriptor* FindFileContainingSymbol(
       absl::string_view symbol_name) const;
 
   // Looking up descriptors ------------------------------------------
   // These find descriptors by fully-qualified name.  These will find both
   // top-level descriptors and nested descriptors.  They return nullptr if not
   // found.
 
   const Descriptor* FindMessageTypeByName(absl::string_view name) const;
   const FieldDescriptor* FindFieldByName(absl::string_view name) const;
   const FieldDescriptor* FindExtensionByName(absl::string_view name) const;
   const OneofDescriptor* FindOneofByName(absl::string_view name) const;
   const EnumDescriptor* FindEnumTypeByName(absl::string_view name) const;
   const EnumValueDescriptor* FindEnumValueByName(absl::string_view name) const;
   const ServiceDescriptor* FindServiceByName(absl::string_view name) const;
   const MethodDescriptor* FindMethodByName(absl::string_view name) const;
 
   // Finds an extension of the given type by number.  The extendee must be
   // a member of this DescriptorPool or one of its underlays.
   const FieldDescriptor* FindExtensionByNumber(const Descriptor* extendee,
                                                int number) const;
 
   // Finds an extension of the given type by its printable name.
   // See comments above PrintableNameForExtension() for the definition of
   // "printable name".  The extendee must be a member of this DescriptorPool
   // or one of its underlays.  Returns nullptr if there is no known message
   // extension with the given printable name.
   const FieldDescriptor* FindExtensionByPrintableName(
       const Descriptor* extendee, absl::string_view printable_name) const;
 
   // Finds extensions of extendee. The extensions will be appended to
   // out in an undefined order. Only extensions defined directly in
   // this DescriptorPool or one of its underlays are guaranteed to be
   // found: extensions defined in the fallback database might not be found
   // depending on the database implementation.
   void FindAllExtensions(const Descriptor* extendee,
                          std::vector<const FieldDescriptor*>* out) const;
 
   // Building descriptors --------------------------------------------
 
   // When converting a FileDescriptorProto to a FileDescriptor, various
   // errors might be detected in the input.  The caller may handle these
   // programmatically by implementing an ErrorCollector.
   class PROTOBUF_EXPORT ErrorCollector {
    public:
     inline ErrorCollector() {}
 #ifndef SWIG
     ErrorCollector(const ErrorCollector&) = delete;
     ErrorCollector& operator=(const ErrorCollector&) = delete;
 #endif
     virtual ~ErrorCollector();
 
     // These constants specify what exact part of the construct is broken.
     // This is useful e.g. for mapping the error back to an exact location
     // in a .proto file.
     enum ErrorLocation {
       NAME,           // the symbol name, or the package name for files
       NUMBER,         // field, extension range or extension decl number
       TYPE,           // field type
       EXTENDEE,       // field extendee
       DEFAULT_VALUE,  // field default value
       INPUT_TYPE,     // method input type
       OUTPUT_TYPE,    // method output type
       OPTION_NAME,    // name in assignment
       OPTION_VALUE,   // value in option assignment
       IMPORT,         // import error
       EDITIONS,       // editions-related error
       OTHER           // some other problem
     };
     static absl::string_view ErrorLocationName(ErrorLocation location);
 
     // Reports an error in the FileDescriptorProto. Use this function if the
     // problem occurred should interrupt building the FileDescriptorProto.
     // Provided the following arguments:
     // filename - File name in which the error occurred.
     // element_name - Full name of the erroneous element.
     // descriptor - Descriptor of the erroneous element.
     // location - One of the location constants, above.
     // message - Human-readable error message.
     virtual void RecordError(absl::string_view filename,
                              absl::string_view element_name,
                              const Message* descriptor, ErrorLocation location,
                              absl::string_view message)
         = 0;
 
     // Reports a warning in the FileDescriptorProto. Use this function if the
     // problem occurred should NOT interrupt building the FileDescriptorProto.
     // Provided the following arguments:
     // filename - File name in which the error occurred.
     // element_name - Full name of the erroneous element.
     // descriptor - Descriptor of the erroneous element.
     // location - One of the location constants, above.
     // message - Human-readable error message.
     virtual void RecordWarning([[maybe_unused]] absl::string_view filename,
                                [[maybe_unused]] absl::string_view element_name,
                                [[maybe_unused]] const Message* descriptor,
                                [[maybe_unused]] ErrorLocation location,
                                [[maybe_unused]] absl::string_view message) {
     }
 
   };
 
   // Convert the FileDescriptorProto to real descriptors and place them in
   // this DescriptorPool.  All dependencies of the file must already be in
   // the pool.  Returns the resulting FileDescriptor, or nullptr if there were
   // problems with the input (e.g. the message was invalid, or dependencies
   // were missing).  Details about the errors are written to ABSL_LOG(ERROR).
   const FileDescriptor* BuildFile(const FileDescriptorProto& proto);
 
   // Same as BuildFile() except errors are sent to the given ErrorCollector.
   const FileDescriptor* BuildFileCollectingErrors(
       const FileDescriptorProto& proto, ErrorCollector* error_collector);
 
   // By default, it is an error if a FileDescriptorProto contains references
   // to types or other files that are not found in the DescriptorPool (or its
   // backing DescriptorDatabase, if any).  If you call
   // AllowUnknownDependencies(), however, then unknown types and files
   // will be replaced by placeholder descriptors (which can be identified by
   // the is_placeholder() method).  This can allow you to
   // perform some useful operations with a .proto file even if you do not
   // have access to other .proto files on which it depends.  However, some
   // heuristics must be used to fill in the gaps in information, and these
   // can lead to descriptors which are inaccurate.  For example, the
   // DescriptorPool may be forced to guess whether an unknown type is a message
   // or an enum, as well as what package it resides in.  Furthermore,
   // placeholder types will not be discoverable via FindMessageTypeByName()
   // and similar methods, which could confuse some descriptor-based algorithms.
   // Generally, the results of this option should be handled with extreme care.
   void AllowUnknownDependencies() { allow_unknown_ = true; }
 
   // By default, weak imports are allowed to be missing, in which case we will
   // use a placeholder for the dependency and convert the field to be an Empty
   // message field. If you call EnforceWeakDependencies(true), however, the
   // DescriptorPool will report a import not found error.
   void EnforceWeakDependencies(bool enforce) { enforce_weak_ = enforce; }
 
   // Enforce the naming style rules. This applies the intended style rules
   // corresponding to the edition of the file, and was first introduced
   // with Edition 2024. Proto2, Proto3 and Edition 2023 are never considered
   // to be in violation and so are unaffected by this.
   //
   // In Edition 2024+, the 'enforce_naming_style` feature can be used to opt out
   // of this enforcement.
   void EnforceNamingStyle(bool enforce) { enforce_naming_style_ = enforce; }
 
   // Enforce symbol visibility rules.  This will enable enforcement of the
   // `export` and `local` keywords added in edition 2024, honoring the behavior
   // of the `default_symbol_visibility` feature.
   void EnforceSymbolVisibility(bool enforce) {
     enforce_symbol_visibility_ = enforce;
   }
 
   // By default, option imports are allowed to be missing.
   // If you call EnforceOptionDependencies(true), however, the DescriptorPool
   // will report a import not found error.
   void EnforceOptionDependencies(bool enforce) { enforce_option_ = enforce; }
 
   // Sets the default feature mappings used during the build. If this function
   // isn't called, the C++ feature set defaults are used.  If this function is
   // called, these defaults will be used instead.
   // FeatureSetDefaults includes a minimum/maximum supported edition, which will
   // be enforced while building proto files.
   absl::Status SetFeatureSetDefaults(FeatureSetDefaults spec);
 
   // Returns true if the descriptor pool resolves features for the given
   // extension.
   template <typename TypeTraitsT, uint8_t field_type, bool is_packed>
   bool ResolvesFeaturesFor(
       const google::protobuf::internal::ExtensionIdentifier<
           FeatureSet, TypeTraitsT, field_type, is_packed>& extension) const {
     return ResolvesFeaturesForImpl(extension.number());
   }
 
   // Toggles enforcement of extension declarations.
   // This enforcement is disabled by default because it requires full
   // descriptors with source-retention options, which are generally not
   // available at runtime.
   void EnforceExtensionDeclarations(google::protobuf::ExtDeclEnforcementLevel enforce) {
     enforce_extension_declarations_ = enforce;
   }
 
   bool ShouldEnforceDescriptorExtensionDeclarations() const {
     return enforce_extension_declarations_ ==
            ExtDeclEnforcementLevel::kAllExtensions;
   }
 
   bool ShouldEnforceExtensionDeclaration(const FieldDescriptor& field) const;
 
 #ifndef SWIG
   // Dispatch recursive builds to a callback that may stick them onto a separate
   // thread.  This is primarily to avoid stack overflows on untrusted inputs.
   // The dispatcher must always synchronously execute the provided callback.
   // Asynchronous execution is undefined behavior.
   void SetRecursiveBuildDispatcher(
       absl::AnyInvocable<void(absl::FunctionRef<void()>) const> dispatcher) {
     if (dispatcher != nullptr) {
       dispatcher_ = std::make_unique<
           absl::AnyInvocable<void(absl::FunctionRef<void()>) const>>(
           std::move(dispatcher));
     } else {
       dispatcher_.reset(nullptr);
     }
   }
 #endif  // SWIG
 
   // Internal stuff --------------------------------------------------
   // These methods MUST NOT be called from outside the proto2 library.
   // These methods may contain hidden pitfalls and may be removed in a
   // future library version.
 
   // Create a DescriptorPool which is overlaid on top of some other pool.
   // If you search for a descriptor in the overlay and it is not found, the
   // underlay will be searched as a backup.  If the underlay has its own
   // underlay, that will be searched next, and so on.  This also means that
   // files built in the overlay will be cross-linked with the underlay's
   // descriptors if necessary.  The underlay remains property of the caller;
   // it must remain valid for the lifetime of the newly-constructed pool.
   //
   // Example:  Say you want to parse a .proto file at runtime in order to use
   // its type with a DynamicMessage.  Say this .proto file has dependencies,
   // but you know that all the dependencies will be things that are already
   // compiled into the binary.  For ease of use, you'd like to load the types
   // right out of generated_pool() rather than have to parse redundant copies
   // of all these .protos and runtime.  But, you don't want to add the parsed
   // types directly into generated_pool(): this is not allowed, and would be
   // bad design anyway.  So, instead, you could use generated_pool() as an
   // underlay for a new DescriptorPool in which you add only the new file.
   //
   // WARNING:  Use of underlays can lead to many subtle gotchas.  Instead,
   //   try to formulate what you want to do in terms of DescriptorDatabases.
   explicit DescriptorPool(const DescriptorPool* underlay);
 
   // Called by generated classes at init time to add their descriptors to
   // generated_pool.  Do NOT call this in your own code!  filename must be a
   // permanent string (e.g. a string literal).
   static void InternalAddGeneratedFile(const void* encoded_file_descriptor,
                                        int size);
 
   // Disallow [enforce_utf8 = false] in .proto files.
   void DisallowEnforceUtf8() { disallow_enforce_utf8_ = true; }
 
   // Use the deprecated legacy behavior for handling JSON field name conflicts.
   ABSL_DEPRECATED("Deprecated treatment of field name conflicts is enabled.")
   void UseDeprecatedLegacyJsonFieldConflicts() {
     deprecated_legacy_json_field_conflicts_ = true;
   }
 
 
   // For internal use only:  Gets a non-const pointer to the generated pool.
   // This is called at static-initialization time only, so thread-safety is
   // not a concern.  If both an underlay and a fallback database are present,
   // the underlay takes precedence.
   static DescriptorPool* internal_generated_pool();
 
   // For internal use only:  Gets a non-const pointer to the generated
   // descriptor database.
   // Only used for testing.
   static DescriptorDatabase* internal_generated_database();
 
   // For internal use only:  Changes the behavior of BuildFile() such that it
   // allows the file to make reference to message types declared in other files
   // which it did not officially declare as dependencies.
   void InternalDontEnforceDependencies();
 
   // For internal use only: Enables lazy building of dependencies of a file.
   // Delay the building of dependencies of a file descriptor until absolutely
   // necessary, like when message_type() is called on a field that is defined
   // in that dependency's file. This will cause functional issues if a proto
   // or one of its dependencies has errors. Should only be enabled for the
   // generated_pool_ (because no descriptor build errors are guaranteed by
   // the compilation generation process), testing, or if a lack of descriptor
   // build errors can be guaranteed for a pool.
   void InternalSetLazilyBuildDependencies() {
     lazily_build_dependencies_ = true;
     // This needs to be set when lazily building dependencies, as it breaks
     // dependency checking.
     InternalDontEnforceDependencies();
   }
 
   // For internal use only.
   void internal_set_underlay(const DescriptorPool* underlay) {
     underlay_ = underlay;
   }
 
   // For internal (unit test) use only:  Returns true if a FileDescriptor has
   // been constructed for the given file, false otherwise.  Useful for testing
   // lazy descriptor initialization behavior.
   bool InternalIsFileLoaded(absl::string_view filename) const;
 
   // Add a file to to apply more strict checks to.
   // - unused imports will log either warnings or errors.
   // - deprecated features will log warnings.
   void AddDirectInputFile(absl::string_view file_name,
                           bool unused_import_is_error = false);
   void ClearDirectInputFiles();
 
 #if !defined(PROTOBUF_FUTURE_RENAME_ADD_UNUSED_IMPORT) && !defined(SWIG)
   ABSL_DEPRECATED("Use AddDirectInputFile")
   void AddUnusedImportTrackFile(absl::string_view file_name,
                                 bool is_error = false) {
     AddDirectInputFile(file_name, is_error);
   }
   ABSL_DEPRECATED("Use AddDirectInputFile")
   void ClearUnusedImportTrackFiles() { ClearDirectInputFiles(); }
 #endif  // !PROTOBUF_FUTURE_RENAME_ADD_UNUSED_IMPORT && !SWIG
 
 
  private:
   friend class Descriptor;
   friend class internal::LazyDescriptor;
   friend class FieldDescriptor;
   friend class EnumDescriptor;
   friend class ServiceDescriptor;
   friend class MethodDescriptor;
   friend class FileDescriptor;
   friend class DescriptorBuilder;
   friend class FileDescriptorTables;
   friend class google::protobuf::descriptor_unittest::DescriptorPoolMemoizationTest;
   friend class google::protobuf::descriptor_unittest::ValidationErrorTest;
   friend class ::google::protobuf::compiler::CommandLineInterface;
   friend class TextFormat;
   friend Reflection;
   friend class ::google::protobuf::compiler::java::MemoizeProjection;
 
   struct MemoBase {
     virtual ~MemoBase() = default;
   };
   template <typename T>
   struct MemoData : MemoBase {
     T value;
   };
 
   template <typename Desc>
   static const DescriptorPool* GetPool(const Desc* descriptor) {
     return descriptor->file()->pool();
   }
 
   static const DescriptorPool* GetPool(const FileDescriptor* descriptor) {
     return descriptor->pool();
   }
 
   // Memoize a projection of a descriptor. This is used to cache the results of
   // calling a function on a descriptor, used for expensive descriptor
   // calculations.
   template <typename Desc, typename Func>
   static const auto& MemoizeProjection(const Desc* descriptor, Func func) {
     using ResultT = std::decay_t<decltype(func(descriptor))>;
     auto* pool = GetPool(descriptor);
     static_assert(std::is_empty_v<Func> ||
                   std::is_function_v<std::remove_pointer_t<Func>>);
     // This static bool is unique per-Func, so its address can be used as a key.
     static bool type_key;
     auto key = std::pair<const void*, const void*>(descriptor, &type_key);
     {
       absl::ReaderMutexLock lock(&pool->field_memo_table_mutex_);
       auto it = pool->field_memo_table_->find(key);
       if (it != pool->field_memo_table_->end()) {
         return internal::DownCast<const MemoData<ResultT>&>(*it->second).value;
       }
     }
     auto result = std::make_unique<MemoData<ResultT>>();
     result->value = func(descriptor);
     {
       absl::MutexLock lock(&pool->field_memo_table_mutex_);
       auto insert_result =
           pool->field_memo_table_->insert({key, std::move(result)});
       auto it = insert_result.first;
       return internal::DownCast<const MemoData<ResultT>&>(*it->second).value;
     }
   }
   // Return true if the given name is a sub-symbol of any non-package
   // descriptor that already exists in the descriptor pool.  (The full
   // definition of such types is already known.)
   bool IsSubSymbolOfBuiltType(absl::string_view name) const;
 
   // Tries to find something in the fallback database and link in the
   // corresponding proto file.  Returns true if successful, in which case
   // the caller should search for the thing again.  These are declared
   // const because they are called by (semantically) const methods.
   // DeferredValidation stores temporary information necessary to run validation
   // checks that can't be done inside the database lock.  This is generally
   // reflective operations that also require the lock to do safely.
   class DeferredValidation;
   bool TryFindFileInFallbackDatabase(
       absl::string_view name, DeferredValidation& deferred_validation) const;
   bool TryFindSymbolInFallbackDatabase(
       absl::string_view name, DeferredValidation& deferred_validation) const;
   bool TryFindExtensionInFallbackDatabase(
       const Descriptor* containing_type, int field_number,
       DeferredValidation& deferred_validation) const;
 
   // This internal find extension method only check with its table and underlay
   // descriptor_pool's table. It does not check with fallback DB and no
   // additional proto file will be build in this method.
   const FieldDescriptor* InternalFindExtensionByNumberNoLock(
       const Descriptor* extendee, int number) const;
 
   // Like BuildFile() but called internally when the file has been loaded from
   // fallback_database_.  Declared const because it is called by (semantically)
   // const methods.
   const FileDescriptor* BuildFileFromDatabase(
       const FileDescriptorProto& proto,
       DeferredValidation& deferred_validation) const;
 
   // Helper for when lazily_build_dependencies_ is set, can look up a symbol
   // after the file's descriptor is built, and can build the file where that
   // symbol is defined if necessary. Will create a placeholder if the type
   // doesn't exist in the fallback database, or the file doesn't build
   // successfully.
   Symbol CrossLinkOnDemandHelper(absl::string_view name,
                                  bool expecting_enum) const;
 
   // Create a placeholder FileDescriptor of the specified name
   FileDescriptor* NewPlaceholderFile(absl::string_view name) const;
   FileDescriptor* NewPlaceholderFileWithMutexHeld(
       absl::string_view name, internal::FlatAllocator& alloc) const;
 
   enum PlaceholderType {
     PLACEHOLDER_MESSAGE,
     PLACEHOLDER_ENUM,
     PLACEHOLDER_EXTENDABLE_MESSAGE
   };
   // Create a placeholder Descriptor of the specified name
   Symbol NewPlaceholder(absl::string_view name,
                         PlaceholderType placeholder_type) const;
   Symbol NewPlaceholderWithMutexHeld(absl::string_view name,
                                      PlaceholderType placeholder_type) const;
 
 #ifndef SWIG
   mutable absl::Mutex field_memo_table_mutex_;
   mutable std::unique_ptr<absl::flat_hash_map<
       std::pair<const void*, const void*>, std::unique_ptr<MemoBase>>>
       field_memo_table_ ABSL_GUARDED_BY(field_memo_table_mutex_) =
           std::make_unique<
               absl::flat_hash_map<std::pair<const void*, const void*>,
                                   std::unique_ptr<MemoBase>>>();
 #endif  // SWIG
 
   // If fallback_database_ is nullptr, this is nullptr.  Otherwise, this is a
   // mutex which must be locked while accessing tables_.
   absl::Mutex* mutex_;
 
   // See constructor.
   DescriptorDatabase* fallback_database_;
   ErrorCollector* default_error_collector_;
   const DescriptorPool* underlay_;
 
 #ifndef SWIG
   // Dispatcher for recursive calls during builds.
   std::unique_ptr<absl::AnyInvocable<void(absl::FunctionRef<void()>) const>>
       dispatcher_;
 #endif  // SWIG
 
   // This class contains a lot of hash maps with complicated types that
   // we'd like to keep out of the header.
   class Tables;
   std::unique_ptr<Tables> tables_;
 
   bool enforce_dependencies_;
   bool lazily_build_dependencies_;
   bool allow_unknown_;
   bool enforce_weak_;
   bool enforce_option_ = false;
   ExtDeclEnforcementLevel enforce_extension_declarations_;
   bool disallow_enforce_utf8_;
   bool deprecated_legacy_json_field_conflicts_;
   bool enforce_naming_style_;
   bool enforce_symbol_visibility_ = false;
   mutable bool build_started_ = false;
 
   // Set of files to track for additional validation. The bool value when true
   // means unused imports are treated as errors (and as warnings when false).
   absl::flat_hash_map<std::string, bool> direct_input_files_;
 
   // Specification of defaults to use for feature resolution.  This defaults to
   // just the global and C++ features, but can be overridden for other runtimes.
   std::unique_ptr<FeatureSetDefaults> feature_set_defaults_spec_;
 
   // Returns true if the field extends an option message of descriptor.proto.
   bool IsReadyForCheckingDescriptorExtDecl(
       absl::string_view message_name) const;
 
 
   bool ResolvesFeaturesForImpl(int extension_number) const;
 
   const FeatureSetDefaults& GetFeatureSetDefaults() const;
 };
 
 
 // inline methods ====================================================
 
 // These macros makes this repetitive code more readable.
 #define PROTOBUF_DEFINE_ACCESSOR(CLASS, FIELD, TYPE) \
   inline TYPE CLASS::FIELD() const { return FIELD##_; }
 
 // Strings fields are stored as pointers but returned as const references.
 #define PROTOBUF_DEFINE_STRING_ACCESSOR(CLASS, FIELD) \
   inline absl::string_view CLASS::FIELD() const { return *FIELD##_; }
 
 // Name and full name are stored in a single array to save space.
 #define PROTOBUF_DEFINE_NAME_ACCESSOR(CLASS)                                 \
   inline absl::string_view CLASS::name() const { return all_names_.name(); } \
   inline absl::string_view CLASS::full_name() const {                        \
     return all_names_.full_name();                                           \
   }
 
 // Arrays take an index parameter, obviously.
 #define PROTOBUF_DEFINE_ARRAY_ACCESSOR(CLASS, FIELD, TYPE) \
   inline TYPE CLASS::FIELD(int index) const {              \
     ABSL_DCHECK_LE(0, index);                              \
     ABSL_DCHECK_LT(index, FIELD##_count());                \
     return FIELD##s_ + index;                              \
   }
 
 #define PROTOBUF_DEFINE_OPTIONS_ACCESSOR(CLASS, TYPE) \
   inline const TYPE& CLASS::options() const { return *options_; }
 
 PROTOBUF_DEFINE_NAME_ACCESSOR(Descriptor)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, file, const FileDescriptor*)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, containing_type, const Descriptor*)
 
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, field_count, int)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, oneof_decl_count, int)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, real_oneof_decl_count, int)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, nested_type_count, int)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, enum_type_count, int)
 
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(Descriptor, field, const FieldDescriptor*)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(Descriptor, oneof_decl, const OneofDescriptor*)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(Descriptor, nested_type, const Descriptor*)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(Descriptor, enum_type, const EnumDescriptor*)
 inline const OneofDescriptor* Descriptor::real_oneof_decl(int index) const {
   ABSL_DCHECK(index < real_oneof_decl_count());
   return oneof_decl(index);
 }
 
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, extension_range_count, int)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, extension_count, int)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(Descriptor, extension_range,
                                const Descriptor::ExtensionRange*)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(Descriptor, extension, const FieldDescriptor*)
 
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, reserved_range_count, int)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(Descriptor, reserved_range,
                                const Descriptor::ReservedRange*)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, reserved_name_count, int)
 
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(Descriptor, MessageOptions)
 PROTOBUF_DEFINE_ACCESSOR(Descriptor, is_placeholder, bool)
 
 PROTOBUF_DEFINE_NAME_ACCESSOR(FieldDescriptor)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, file, const FileDescriptor*)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, number, int)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, is_extension, bool)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, containing_type, const Descriptor*)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(FieldDescriptor, FieldOptions)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, has_default_value, bool)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, has_json_name, bool)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, default_value_int32_t, int32_t)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, default_value_int64_t, int64_t)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, default_value_uint32_t, uint32_t)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, default_value_uint64_t, uint64_t)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, default_value_float, float)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, default_value_double, double)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, default_value_bool, bool)
 PROTOBUF_DEFINE_STRING_ACCESSOR(FieldDescriptor, default_value_string)
 
 PROTOBUF_DEFINE_NAME_ACCESSOR(OneofDescriptor)
 PROTOBUF_DEFINE_ACCESSOR(OneofDescriptor, containing_type, const Descriptor*)
 PROTOBUF_DEFINE_ACCESSOR(OneofDescriptor, field_count, int)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(OneofDescriptor, field, const FieldDescriptor*)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(OneofDescriptor, OneofOptions)
 
 PROTOBUF_DEFINE_NAME_ACCESSOR(EnumDescriptor)
 PROTOBUF_DEFINE_ACCESSOR(EnumDescriptor, file, const FileDescriptor*)
 PROTOBUF_DEFINE_ACCESSOR(EnumDescriptor, containing_type, const Descriptor*)
 PROTOBUF_DEFINE_ACCESSOR(EnumDescriptor, value_count, int)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(EnumDescriptor, value,
                                const EnumValueDescriptor*)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(EnumDescriptor, EnumOptions)
 PROTOBUF_DEFINE_ACCESSOR(EnumDescriptor, is_placeholder, bool)
 PROTOBUF_DEFINE_ACCESSOR(EnumDescriptor, reserved_range_count, int)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(EnumDescriptor, reserved_range,
                                const EnumDescriptor::ReservedRange*)
 PROTOBUF_DEFINE_ACCESSOR(EnumDescriptor, reserved_name_count, int)
 
 inline absl::string_view EnumValueDescriptor::name() const {
   return all_names_[0];
 }
 inline absl::string_view EnumValueDescriptor::full_name() const {
   return all_names_[1];
 }
 PROTOBUF_DEFINE_ACCESSOR(EnumValueDescriptor, number, int)
 PROTOBUF_DEFINE_ACCESSOR(EnumValueDescriptor, type, const EnumDescriptor*)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(EnumValueDescriptor, EnumValueOptions)
 
 PROTOBUF_DEFINE_NAME_ACCESSOR(ServiceDescriptor)
 PROTOBUF_DEFINE_ACCESSOR(ServiceDescriptor, file, const FileDescriptor*)
 PROTOBUF_DEFINE_ACCESSOR(ServiceDescriptor, method_count, int)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(ServiceDescriptor, method,
                                const MethodDescriptor*)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(ServiceDescriptor, ServiceOptions)
 
 PROTOBUF_DEFINE_NAME_ACCESSOR(MethodDescriptor)
 PROTOBUF_DEFINE_ACCESSOR(MethodDescriptor, service, const ServiceDescriptor*)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(MethodDescriptor, MethodOptions)
 PROTOBUF_DEFINE_ACCESSOR(MethodDescriptor, client_streaming, bool)
 PROTOBUF_DEFINE_ACCESSOR(MethodDescriptor, server_streaming, bool)
 
 PROTOBUF_DEFINE_STRING_ACCESSOR(FileDescriptor, name)
 PROTOBUF_DEFINE_STRING_ACCESSOR(FileDescriptor, package)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, pool, const DescriptorPool*)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, dependency_count, int)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, public_dependency_count, int)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, weak_dependency_count, int)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, option_dependency_count, int)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, message_type_count, int)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, enum_type_count, int)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, service_count, int)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, extension_count, int)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(FileDescriptor, FileOptions)
 PROTOBUF_DEFINE_ACCESSOR(FileDescriptor, is_placeholder, bool)
 
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(FileDescriptor, message_type, const Descriptor*)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(FileDescriptor, enum_type, const EnumDescriptor*)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(FileDescriptor, service,
                                const ServiceDescriptor*)
 PROTOBUF_DEFINE_ARRAY_ACCESSOR(FileDescriptor, extension,
                                const FieldDescriptor*)
 
 #undef PROTOBUF_DEFINE_ACCESSOR
 #undef PROTOBUF_DEFINE_STRING_ACCESSOR
 #undef PROTOBUF_DEFINE_ARRAY_ACCESSOR
 
 // A few accessors differ from the macros...
 
 inline Descriptor::WellKnownType Descriptor::well_known_type() const {
   return static_cast<Descriptor::WellKnownType>(well_known_type_);
 }
 
 inline bool Descriptor::IsExtensionNumber(int number) const {
   return FindExtensionRangeContainingNumber(number) != nullptr;
 }
 
 inline bool Descriptor::IsReservedNumber(int number) const {
   return FindReservedRangeContainingNumber(number) != nullptr;
 }
 
 inline bool Descriptor::IsReservedName(absl::string_view name) const {
   for (int i = 0; i < reserved_name_count(); i++) {
     if (name == static_cast<absl::string_view>(reserved_name(i))) {
       return true;
     }
   }
   return false;
 }
 
 // Can't use PROTOBUF_DEFINE_ARRAY_ACCESSOR because reserved_names_ is actually
 // an array of pointers rather than the usual array of objects.
 inline absl::string_view Descriptor::reserved_name(int index) const {
   return *reserved_names_[index];
 }
 
 inline bool EnumDescriptor::IsReservedNumber(int number) const {
   return FindReservedRangeContainingNumber(number) != nullptr;
 }
 
 inline bool EnumDescriptor::IsReservedName(absl::string_view name) const {
   for (int i = 0; i < reserved_name_count(); i++) {
     if (name == static_cast<absl::string_view>(reserved_name(i))) {
       return true;
     }
   }
   return false;
 }
 
 // Can't use PROTOBUF_DEFINE_ARRAY_ACCESSOR because reserved_names_ is actually
 // an array of pointers rather than the usual array of objects.
 inline absl::string_view EnumDescriptor::reserved_name(int index) const {
   return *reserved_names_[index];
 }
 
 inline absl::string_view FieldDescriptor::lowercase_name() const {
   return all_names_.lowercase_name();
 }
 
 inline absl::string_view FieldDescriptor::camelcase_name() const {
   return all_names_.camelcase_name();
 }
 
 inline absl::string_view FieldDescriptor::json_name() const {
   return all_names_.json_name();
 }
 
 inline const OneofDescriptor* FieldDescriptor::containing_oneof() const {
   if (is_oneof_) {
     auto* res = scope_.containing_oneof;
     PROTOBUF_ASSUME(res != nullptr);
     return res;
   }
   return nullptr;
 }
 
 inline int FieldDescriptor::index_in_oneof() const {
   ABSL_DCHECK(is_oneof_);
   return static_cast<int>(this - scope_.containing_oneof->field(0));
 }
 
 inline const Descriptor* FieldDescriptor::extension_scope() const {
   ABSL_CHECK(is_extension_);
   return scope_.extension_scope;
 }
 
 inline FieldDescriptor::Label FieldDescriptor::label() const {
   if (is_required()) {
     return LABEL_REQUIRED;
   } else if (is_repeated()) {
     return LABEL_REPEATED;
   } else {
     return LABEL_OPTIONAL;
   }
 }
 
 inline FieldDescriptor::Type FieldDescriptor::type() const {
   return static_cast<Type>(type_);
 }
 
 inline FieldDescriptor::CppStringType FieldDescriptor::cpp_string_type() const {
   ABSL_DCHECK_EQ(cpp_string_type_,
                  static_cast<uint8_t>(CalculateCppStringType()));
   return static_cast<FieldDescriptor::CppStringType>(cpp_string_type_);
 }
 
 inline bool FieldDescriptor::is_optional() const {
   return !is_repeated() && !is_required();
 }
 
 inline bool FieldDescriptor::is_repeated() const {
   ABSL_DCHECK_EQ(is_repeated_, static_cast<Label>(label_) == LABEL_REPEATED);
   return is_repeated_;
 }
 
 inline bool FieldDescriptor::is_packable() const {
   return is_repeated() && IsTypePackable(type());
 }
 
 inline bool FieldDescriptor::is_map() const {
   ABSL_DCHECK_EQ(is_map_, type() == TYPE_MESSAGE && is_map_message_type());
   return is_map_;
 }
 
 inline const OneofDescriptor* FieldDescriptor::real_containing_oneof() const {
   if (in_real_oneof_) {
     auto* res = containing_oneof();
     PROTOBUF_ASSUME(res != nullptr);
     ABSL_DCHECK(!res->is_synthetic());
     return res;
   }
   return nullptr;
 }
 
 // To save space, index() is computed by looking at the descriptor's position
 // in the parent's array of children.
 inline int FieldDescriptor::index() const {
   if (!is_extension_) {
     return static_cast<int>(this - containing_type()->fields_);
   } else if (extension_scope() != nullptr) {
     return static_cast<int>(this - extension_scope()->extensions_);
   } else {
     return static_cast<int>(this - file_->extensions_);
   }
 }
 
 inline int Descriptor::index() const {
   if (containing_type_ == nullptr) {
     return static_cast<int>(this - file_->message_types_);
   } else {
     return static_cast<int>(this - containing_type_->nested_types_);
   }
 }
 
 inline int Descriptor::ExtensionRange::index() const {
   return static_cast<int>(this - containing_type_->extension_ranges_);
 }
 
 inline const FileDescriptor* OneofDescriptor::file() const {
   return containing_type()->file();
 }
 
 inline int OneofDescriptor::index() const {
   return static_cast<int>(this - containing_type_->oneof_decls_);
 }
 
 inline bool OneofDescriptor::is_synthetic() const {
   return field_count() == 1 && field(0)->proto3_optional_;
 }
 
 inline int EnumDescriptor::index() const {
   if (containing_type_ == nullptr) {
     return static_cast<int>(this - file_->enum_types_);
   } else {
     return static_cast<int>(this - containing_type_->enum_types_);
   }
 }
 
 inline const FileDescriptor* EnumValueDescriptor::file() const {
   return type()->file();
 }
 
 inline int EnumValueDescriptor::index() const {
   return static_cast<int>(this - type_->values_);
 }
 
 inline int ServiceDescriptor::index() const {
   return static_cast<int>(this - file_->services_);
 }
 
 inline const FileDescriptor* MethodDescriptor::file() const {
   return service()->file();
 }
 
 inline int MethodDescriptor::index() const {
   return static_cast<int>(this - service_->methods_);
 }
 
 inline absl::string_view FieldDescriptor::type_name() const {
   return kTypeToName[type()];
 }
 
 inline FieldDescriptor::CppType FieldDescriptor::cpp_type() const {
   return kTypeToCppTypeMap[type()];
 }
 
 inline absl::string_view FieldDescriptor::cpp_type_name() const {
   return kCppTypeToName[kTypeToCppTypeMap[type()]];
 }
 
 inline FieldDescriptor::CppType FieldDescriptor::TypeToCppType(Type type) {
   return kTypeToCppTypeMap[type];
 }
 
 inline absl::string_view FieldDescriptor::TypeName(Type type) {
   return kTypeToName[type];
 }
 
 inline absl::string_view FieldDescriptor::CppTypeName(CppType cpp_type) {
   return kCppTypeToName[cpp_type];
 }
 
 inline bool FieldDescriptor::IsTypePackable(Type field_type) {
   return (field_type != FieldDescriptor::TYPE_STRING &&
           field_type != FieldDescriptor::TYPE_GROUP &&
           field_type != FieldDescriptor::TYPE_MESSAGE &&
           field_type != FieldDescriptor::TYPE_BYTES);
 }
 
 inline const FileDescriptor* FileDescriptor::public_dependency(
     int index) const {
   return dependency(public_dependencies_[index]);
 }
 
 inline const FileDescriptor* FileDescriptor::weak_dependency(int index) const {
   return dependency(weak_dependencies_[index]);
 }
 
 // BitField handling of SymbolVisibility in message/enum
 inline SymbolVisibility Descriptor::visibility_keyword() const {
   return static_cast<SymbolVisibility>(visibility_);
 }
 
 inline SymbolVisibility EnumDescriptor::visibility_keyword() const {
   return static_cast<SymbolVisibility>(visibility_);
 }
 
 namespace internal {
 
 inline const std::string& DefaultValueStringAsString(
     const FieldDescriptor* field) {
   return *field->default_value_string_;
 }
 
 inline const std::string& NameOfEnumAsString(
     const EnumValueDescriptor* descriptor) {
   return descriptor->all_names_[0];
 }
 
 inline bool IsEnumFullySequential(const EnumDescriptor* enum_desc) {
   return enum_desc->sequential_value_limit_ == enum_desc->value_count() - 1;
 }
 
 // FieldRange(desc) provides an iterable range for the fields of a
 // descriptor type, appropriate for range-for loops.
 
 template <typename T>
 struct FieldRangeImpl;
 
 template <typename T>
 FieldRangeImpl<T> FieldRange(const T* desc) {
   return {desc};
 }
 
 template <typename T>
 struct FieldRangeImpl {
   struct Iterator {
     using iterator_category = std::forward_iterator_tag;
     using value_type = const FieldDescriptor*;
     using difference_type = int;
 
     value_type operator*() { return descriptor->field(idx); }
 
     friend bool operator==(const Iterator& a, const Iterator& b) {
       ABSL_DCHECK(a.descriptor == b.descriptor);
       return a.idx == b.idx;
     }
     friend bool operator!=(const Iterator& a, const Iterator& b) {
       return !(a == b);
     }
 
     Iterator& operator++() {
       idx++;
       return *this;
     }
 
     int idx;
     const T* descriptor;
   };
 
   Iterator begin() const { return {0, descriptor}; }
   Iterator end() const { return {descriptor->field_count(), descriptor}; }
 
   const T* descriptor;
 };
 
 // While building descriptors, we need to avoid using MergeFrom()/CopyFrom() to
 // be -fno-rtti friendly. Without RTTI, MergeFrom() and CopyFrom() will fallback
 // to the reflection based method, which requires the Descriptor. However, while
 // building the descriptors, this causes deadlock. We also must disable lazy
 // parsing because that uses reflection to verify consistency.
 bool ParseNoReflection(absl::string_view from, google::protobuf::MessageLite& to);
 
 // The context for these functions under `cpp` is "for the C++ implementation".
 // In particular, questions like "does this field have a has bit?" have a
 // different answer depending on the language.
 namespace cpp {
 
 // The maximum allowed nesting for message declarations.
 // Going over this limit will make the proto definition invalid.
 constexpr int MaxMessageDeclarationNestingDepth() { return 32; }
 
 // Returns true if 'enum' semantics are such that unknown values are preserved
 // in the enum field itself, rather than going to the UnknownFieldSet.
 PROTOBUF_EXPORT bool HasPreservingUnknownEnumSemantics(
     const FieldDescriptor* field);
 
 #ifndef SWIG
 enum class HasbitMode : uint8_t {
   // Hasbits do not exist for the field.
   kNoHasbit,
   // Hasbits exist and indicate field presence.
   // Hasbit is set if and only if field is present.
   kTrueHasbit,
   // Hasbits exist and "hint at" field presence.
   // When hasbit is set, field is 'probably' present, but field accessors must
   // still check for field presence (i.e. false positives are possible).
   // When hasbit is unset, field is guaranteed to be not present.
   kHintHasbit,
 };
 
 // Returns the "hasbit mode" of the field. Depending on the implementation, a
 // field can:
 //   - have no hasbits in its internal object (kNoHasbit);
 //   - have hasbits where hasbit == 1 indicates field presence and hasbit == 0
 //     indicates an unset field (kTrueHasbit);
 //   - have hasbits where hasbit == 1 indicates "field is possibly modified" and
 //     hasbit == 0 indicates "field is definitely missing" (kHintHasbit).
 //
 // Note that this may not match the hasbit mode chosen by the compiler, which
 // may be influenced by other factors like PDProto profiles.
 PROTOBUF_EXPORT HasbitMode
 GetFieldHasbitModeWithoutProfile(const FieldDescriptor* field);
 
 // Returns true if there are hasbits for the field.
 // Note that this does not correlate with "hazzer"s, i.e., whether has_foo APIs
 // are emitted.
 //
 // Note that this may not match the hasbit mode chosen by the compiler, which
 // may be influenced by other factors like PDProto profiles.
 PROTOBUF_EXPORT bool HasHasbitWithoutProfile(const FieldDescriptor* field);
 
 enum class Utf8CheckMode : uint8_t {
   kStrict = 0,  // Parsing will fail if non UTF-8 data is in string fields.
   kVerify = 1,  // Only log an error but parsing will succeed.
   kNone = 2,    // No UTF-8 check.
 };
 PROTOBUF_EXPORT Utf8CheckMode GetUtf8CheckMode(const FieldDescriptor* field,
                                                bool is_lite);
 
 // Returns true if the field is a "group-like field" consistent with a proto2
 // group:
 //  - Message encoding is DELIMITED (synonymous with type TYPE_GROUP)
 //  - Field name is exactly the message name lowercased
 //  - Message is defined within the same scope as the field
 PROTOBUF_EXPORT bool IsGroupLike(const FieldDescriptor& field);
 
 // Returns whether or not this file is lazily initialized rather than
 // pre-main via static initialization.  This has to be done for our bootstrapped
 // protos to avoid linker bloat in lite runtimes.
 PROTOBUF_EXPORT bool IsLazilyInitializedFile(absl::string_view filename);
 
 // Returns true during internal calls that should avoid calling trackers.  These
 // calls can be particularly dangerous during build steps like feature
 // resolution, where a MergeFrom call can wind up in a deadlock.
 PROTOBUF_EXPORT inline bool& IsTrackingEnabledVar() {
   static PROTOBUF_THREAD_LOCAL bool is_tracking_enabled = true;
   return is_tracking_enabled;
 }
 PROTOBUF_EXPORT inline bool IsTrackingEnabled() {
   return ABSL_PREDICT_TRUE(IsTrackingEnabledVar());
 }
 
 template <typename F>
 auto VisitDescriptorsInFileOrder(const Descriptor* desc,
                                  F& f) -> decltype(f(desc)) {
   for (int i = 0; i < desc->nested_type_count(); i++) {
     if (auto res = VisitDescriptorsInFileOrder(desc->nested_type(i), f)) {
       return res;
     }
   }
   if (auto res = f(desc)) return res;
   return {};
 }
 
 // Visit the messages in post-order traversal.
 // We need several pieces of code to follow the same order because we use the
 // index of types during array lookups.
 // If any call returns a "truthy" value, it stops visitation and returns that
 // value right away. Otherwise returns `{}` after visiting all types.
 template <typename F>
 auto VisitDescriptorsInFileOrder(const FileDescriptor* file,
                                  F f) -> decltype(f(file->message_type(0))) {
   for (int i = 0; i < file->message_type_count(); i++) {
     if (auto res = VisitDescriptorsInFileOrder(file->message_type(i), f)) {
       return res;
     }
   }
   return {};
 }
 #endif  // !SWIG
 
 // Whether the given string field should have the accessors be privatized due
 // to it being an unsupported type. If this returns true, cpp_string_type()
 // returns kString for the storage, the C++ Generator will not generate
 // public accessors for the type, but the field will sill be accessible via
 // reflection.
 PROTOBUF_EXPORT bool IsStringFieldWithPrivatizedAccessors(
     const FieldDescriptor& field);
 
 }  // namespace cpp
 }  // namespace internal
 
 }  // namespace protobuf
 }  // namespace google
 
 #undef PROTOBUF_INTERNAL_CHECK_CLASS_SIZE
 #include "google/protobuf/port_undef.inc"
 
 #endif  // GOOGLE_PROTOBUF_DESCRIPTOR_H__