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 // Copyright 2021 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef INCLUDE_V8_INITIALIZATION_H_
 #define INCLUDE_V8_INITIALIZATION_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "v8-callbacks.h"  // NOLINT(build/include_directory)
 #include "v8-internal.h"   // NOLINT(build/include_directory)
 #include "v8-isolate.h"    // NOLINT(build/include_directory)
 #include "v8-platform.h"   // NOLINT(build/include_directory)
 #include "v8config.h"      // NOLINT(build/include_directory)
 
 // We reserve the V8_* prefix for macros defined in V8 public API and
 // assume there are no name conflicts with the embedder's code.
 
 /**
  * The v8 JavaScript engine.
  */
 namespace v8 {
 
 class PageAllocator;
 class Platform;
 template <class K, class V, class T>
 class PersistentValueMapBase;
 
 /**
  * EntropySource is used as a callback function when v8 needs a source
  * of entropy.
  */
 using EntropySource = bool (*)(unsigned char* buffer, size_t length);
 
 /**
  * ReturnAddressLocationResolver is used as a callback function when v8 is
  * resolving the location of a return address on the stack. Profilers that
  * change the return address on the stack can use this to resolve the stack
  * location to wherever the profiler stashed the original return address.
  *
  * \param return_addr_location A location on stack where a machine
  *    return address resides.
  * \returns Either return_addr_location, or else a pointer to the profiler's
  *    copy of the original return address.
  *
  * \note The resolver function must not cause garbage collection.
  */
 using ReturnAddressLocationResolver =
     uintptr_t (*)(uintptr_t return_addr_location);
 
 using DcheckErrorCallback = void (*)(const char* file, int line,
                                      const char* message);
 
 /**
  * Container class for static utility functions.
  */
 class V8_EXPORT V8 {
  public:
   /**
    * Hand startup data to V8, in case the embedder has chosen to build
    * V8 with external startup data.
    *
    * Note:
    * - By default the startup data is linked into the V8 library, in which
    *   case this function is not meaningful.
    * - If this needs to be called, it needs to be called before V8
    *   tries to make use of its built-ins.
    * - To avoid unnecessary copies of data, V8 will point directly into the
    *   given data blob, so pretty please keep it around until V8 exit.
    * - Compression of the startup blob might be useful, but needs to
    *   handled entirely on the embedders' side.
    * - The call will abort if the data is invalid.
    */
   static void SetSnapshotDataBlob(StartupData* startup_blob);
 
   /** Set the callback to invoke in case of Dcheck failures. */
   static void SetDcheckErrorHandler(DcheckErrorCallback that);
 
   /**
    * Sets V8 flags from a string.
    */
   static void SetFlagsFromString(const char* str);
   static void SetFlagsFromString(const char* str, size_t length);
 
   /**
    * Sets V8 flags from the command line.
    */
   static void SetFlagsFromCommandLine(int* argc, char** argv,
                                       bool remove_flags);
 
   /** Get the version string. */
   static const char* GetVersion();
 
   /**
    * Initializes V8. This function needs to be called before the first Isolate
    * is created. It always returns true.
    */
   V8_INLINE static bool Initialize() {
     const int kBuildConfiguration =
         (internal::PointerCompressionIsEnabled() ? kPointerCompression : 0) |
         (internal::SmiValuesAre31Bits() ? k31BitSmis : 0) |
         (internal::SandboxIsEnabled() ? kSandbox : 0);
     return Initialize(kBuildConfiguration);
   }
 
   /**
    * Allows the host application to provide a callback which can be used
    * as a source of entropy for random number generators.
    */
   static void SetEntropySource(EntropySource source);
 
   /**
    * Allows the host application to provide a callback that allows v8 to
    * cooperate with a profiler that rewrites return addresses on stack.
    */
   static void SetReturnAddressLocationResolver(
       ReturnAddressLocationResolver return_address_resolver);
 
   /**
    * Releases any resources used by v8 and stops any utility threads
    * that may be running.  Note that disposing v8 is permanent, it
    * cannot be reinitialized.
    *
    * It should generally not be necessary to dispose v8 before exiting
    * a process, this should happen automatically.  It is only necessary
    * to use if the process needs the resources taken up by v8.
    */
   static bool Dispose();
 
   /**
    * Initialize the ICU library bundled with V8. The embedder should only
    * invoke this method when using the bundled ICU. Returns true on success.
    *
    * If V8 was compiled with the ICU data in an external file, the location
    * of the data file has to be provided.
    */
   static bool InitializeICU(const char* icu_data_file = nullptr);
 
   /**
    * Initialize the ICU library bundled with V8. The embedder should only
    * invoke this method when using the bundled ICU. If V8 was compiled with
    * the ICU data in an external file and when the default location of that
    * file should be used, a path to the executable must be provided.
    * Returns true on success.
    *
    * The default is a file called icudtl.dat side-by-side with the executable.
    *
    * Optionally, the location of the data file can be provided to override the
    * default.
    */
   static bool InitializeICUDefaultLocation(const char* exec_path,
                                            const char* icu_data_file = nullptr);
 
   /**
    * Initialize the external startup data. The embedder only needs to
    * invoke this method when external startup data was enabled in a build.
    *
    * If V8 was compiled with the startup data in an external file, then
    * V8 needs to be given those external files during startup. There are
    * three ways to do this:
    * - InitializeExternalStartupData(const char*)
    *   This will look in the given directory for the file "snapshot_blob.bin".
    * - InitializeExternalStartupDataFromFile(const char*)
    *   As above, but will directly use the given file name.
    * - Call SetSnapshotDataBlob.
    *   This will read the blobs from the given data structure and will
    *   not perform any file IO.
    */
   static void InitializeExternalStartupData(const char* directory_path);
   static void InitializeExternalStartupDataFromFile(const char* snapshot_blob);
 
   /**
    * Sets the v8::Platform to use. This should be invoked before V8 is
    * initialized.
    */
   static void InitializePlatform(Platform* platform);
 
   /**
    * Clears all references to the v8::Platform. This should be invoked after
    * V8 was disposed.
    */
   static void DisposePlatform();
 
 #if defined(V8_ENABLE_SANDBOX)
   /**
    * Returns true if the sandbox is configured securely.
    *
    * If V8 cannot create a regular sandbox during initialization, for example
    * because not enough virtual address space can be reserved, it will instead
    * create a fallback sandbox that still allows it to function normally but
    * does not have the same security properties as a regular sandbox. This API
    * can be used to determine if such a fallback sandbox is being used, in
    * which case it will return false.
    */
   static bool IsSandboxConfiguredSecurely();
 
   /**
    * Provides access to the virtual address subspace backing the sandbox.
    *
    * This can be used to allocate pages inside the sandbox, for example to
    * obtain virtual memory for ArrayBuffer backing stores, which must be
    * located inside the sandbox.
    *
    * It should be assumed that an attacker can corrupt data inside the sandbox,
    * and so in particular the contents of pages allocagted in this virtual
    * address space, arbitrarily and concurrently. Due to this, it is
    * recommended to to only place pure data buffers in them.
    */
   static VirtualAddressSpace* GetSandboxAddressSpace();
 
   /**
    * Returns the size of the sandbox in bytes.
    *
    * This represents the size of the address space that V8 can directly address
    * and in which it allocates its objects.
    */
   static size_t GetSandboxSizeInBytes();
 
   /**
    * Returns the size of the address space reservation backing the sandbox.
    *
    * This may be larger than the sandbox (i.e. |GetSandboxSizeInBytes()|) due
    * to surrounding guard regions, or may be smaller than the sandbox in case a
    * fallback sandbox is being used, which will use a smaller virtual address
    * space reservation. In the latter case this will also be different from
    * |GetSandboxAddressSpace()->size()| as that will cover a larger part of the
    * address space than what has actually been reserved.
    */
   static size_t GetSandboxReservationSizeInBytes();
 #endif  // V8_ENABLE_SANDBOX
 
   /**
    * Activate trap-based bounds checking for WebAssembly.
    *
    * \param use_v8_signal_handler Whether V8 should install its own signal
    * handler or rely on the embedder's.
    */
   static bool EnableWebAssemblyTrapHandler(bool use_v8_signal_handler);
 
 #if defined(V8_OS_WIN)
   /**
    * On Win64, by default V8 does not emit unwinding data for jitted code,
    * which means the OS cannot walk the stack frames and the system Structured
    * Exception Handling (SEH) cannot unwind through V8-generated code:
    * https://code.google.com/p/v8/issues/detail?id=3598.
    *
    * This function allows embedders to register a custom exception handler for
    * exceptions in V8-generated code.
    */
   static void SetUnhandledExceptionCallback(
       UnhandledExceptionCallback callback);
 #endif
 
   /**
    * Allows the host application to provide a callback that will be called when
    * v8 has encountered a fatal failure to allocate memory and is about to
    * terminate.
    */
   static void SetFatalMemoryErrorCallback(OOMErrorCallback callback);
 
   /**
    * Get statistics about the shared memory usage.
    */
   static void GetSharedMemoryStatistics(SharedMemoryStatistics* statistics);
 
  private:
   V8();
 
   enum BuildConfigurationFeatures {
     kPointerCompression = 1 << 0,
     k31BitSmis = 1 << 1,
     kSandbox = 1 << 2,
   };
 
   /**
    * Checks that the embedder build configuration is compatible with
    * the V8 binary and if so initializes V8.
    */
   static bool Initialize(int build_config);
 
   friend class Context;
   template <class K, class V, class T>
   friend class PersistentValueMapBase;
 };
 
 }  // namespace v8
 
 #endif  // INCLUDE_V8_INITIALIZATION_H_

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