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 // © 2016 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 // Copyright (C) 2009-2012, International Business Machines
 // Corporation and others. All Rights Reserved.
 //
 // Copyright 2007 Google Inc. All Rights Reserved.
 // Author: sanjay@google.com (Sanjay Ghemawat)
 //
 // Abstract interface that consumes a sequence of bytes (ByteSink).
 //
 // Used so that we can write a single piece of code that can operate
 // on a variety of output string types.
 //
 // Various implementations of this interface are provided:
 //   ByteSink:
 //      CheckedArrayByteSink    Write to a flat array, with bounds checking
 //      StringByteSink          Write to an STL string
 
 // This code is a contribution of Google code, and the style used here is
 // a compromise between the original Google code and the ICU coding guidelines.
 // For example, data types are ICU-ified (size_t,int->int32_t),
 // and API comments doxygen-ified, but function names and behavior are
 // as in the original, if possible.
 // Assertion-style error handling, not available in ICU, was changed to
 // parameter "pinning" similar to UnicodeString.
 //
 // In addition, this is only a partial port of the original Google code,
 // limited to what was needed so far. The (nearly) complete original code
 // is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
 // (see ICU ticket 6765, r25517).
 
 #ifndef __BYTESTREAM_H__
 #define __BYTESTREAM_H__
 
 /**
  * \file
  * \brief C++ API: Interface for writing bytes, and implementation classes.
  */
 
 #include "unicode/utypes.h"
 
 #if U_SHOW_CPLUSPLUS_API
 
 #include "unicode/uobject.h"
 #include "unicode/std_string.h"
 
 U_NAMESPACE_BEGIN
 
 /**
  * A ByteSink can be filled with bytes.
  * @stable ICU 4.2
  */
 class U_COMMON_API ByteSink : public UMemory {
 public:
   /**
    * Default constructor.
    * @stable ICU 4.2
    */
   ByteSink() { }
   /**
    * Virtual destructor.
    * @stable ICU 4.2
    */
   virtual ~ByteSink();
 
   /**
    * Append "bytes[0,n-1]" to this.
    * @param bytes the pointer to the bytes
    * @param n the number of bytes; must be non-negative
    * @stable ICU 4.2
    */
   virtual void Append(const char* bytes, int32_t n) = 0;
 
   /**
    * Appends n bytes to this. Same as Append().
    * Call AppendU8() with u8"string literals" which are const char * in C++11
    * but const char8_t * in C++20.
    * If the compiler does support char8_t as a distinct type,
    * then an AppendU8() overload for that is defined and will be chosen.
    *
    * @param bytes the pointer to the bytes
    * @param n the number of bytes; must be non-negative
    * @stable ICU 67
    */
   inline void AppendU8(const char* bytes, int32_t n) {
     Append(bytes, n);
   }
 
 #if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
   /**
    * Appends n bytes to this. Same as Append() but for a const char8_t * pointer.
    * Call AppendU8() with u8"string literals" which are const char * in C++11
    * but const char8_t * in C++20.
    * If the compiler does support char8_t as a distinct type,
    * then this AppendU8() overload for that is defined and will be chosen.
    *
    * @param bytes the pointer to the bytes
    * @param n the number of bytes; must be non-negative
    * @stable ICU 67
    */
   inline void AppendU8(const char8_t* bytes, int32_t n) {
     Append(reinterpret_cast<const char*>(bytes), n);
   }
 #endif
 
   /**
    * Returns a writable buffer for appending and writes the buffer's capacity to
    * *result_capacity. Guarantees *result_capacity>=min_capacity.
    * May return a pointer to the caller-owned scratch buffer which must have
    * scratch_capacity>=min_capacity.
    * The returned buffer is only valid until the next operation
    * on this ByteSink.
    *
    * After writing at most *result_capacity bytes, call Append() with the
    * pointer returned from this function and the number of bytes written.
    * Many Append() implementations will avoid copying bytes if this function
    * returned an internal buffer.
    *
    * Partial usage example:
    *  int32_t capacity;
    *  char* buffer = sink->GetAppendBuffer(..., &capacity);
    *  ... Write n bytes into buffer, with n <= capacity.
    *  sink->Append(buffer, n);
    * In many implementations, that call to Append will avoid copying bytes.
    *
    * If the ByteSink allocates or reallocates an internal buffer, it should use
    * the desired_capacity_hint if appropriate.
    * If a caller cannot provide a reasonable guess at the desired capacity,
    * it should pass desired_capacity_hint=0.
    *
    * If a non-scratch buffer is returned, the caller may only pass
    * a prefix to it to Append().
    * That is, it is not correct to pass an interior pointer to Append().
    *
    * The default implementation always returns the scratch buffer.
    *
    * @param min_capacity required minimum capacity of the returned buffer;
    *                     must be non-negative
    * @param desired_capacity_hint desired capacity of the returned buffer;
    *                              must be non-negative
    * @param scratch default caller-owned buffer
    * @param scratch_capacity capacity of the scratch buffer
    * @param result_capacity pointer to an integer which will be set to the
    *                        capacity of the returned buffer
    * @return a buffer with *result_capacity>=min_capacity
    * @stable ICU 4.2
    */
   virtual char* GetAppendBuffer(int32_t min_capacity,
                                 int32_t desired_capacity_hint,
                                 char* scratch, int32_t scratch_capacity,
                                 int32_t* result_capacity);
 
   /**
    * Flush internal buffers.
    * Some byte sinks use internal buffers or provide buffering
    * and require calling Flush() at the end of the stream.
    * The ByteSink should be ready for further Append() calls after Flush().
    * The default implementation of Flush() does nothing.
    * @stable ICU 4.2
    */
   virtual void Flush();
 
 private:
   ByteSink(const ByteSink &) = delete;
   ByteSink &operator=(const ByteSink &) = delete;
 };
 
 // -------------------------------------------------------------
 // Some standard implementations
 
 /** 
  * Implementation of ByteSink that writes to a flat byte array,
  * with bounds-checking:
  * This sink will not write more than capacity bytes to outbuf.
  * If more than capacity bytes are Append()ed, then excess bytes are ignored,
  * and Overflowed() will return true.
  * Overflow does not cause a runtime error.
  * @stable ICU 4.2
  */
 class U_COMMON_API CheckedArrayByteSink : public ByteSink {
 public:
   /**
    * Constructs a ByteSink that will write to outbuf[0..capacity-1].
    * @param outbuf buffer to write to
    * @param capacity size of the buffer
    * @stable ICU 4.2
    */
   CheckedArrayByteSink(char* outbuf, int32_t capacity);
   /**
    * Destructor.
    * @stable ICU 4.2
    */
   virtual ~CheckedArrayByteSink();
   /**
    * Returns the sink to its original state, without modifying the buffer.
    * Useful for reusing both the buffer and the sink for multiple streams.
    * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0
    * and Overflowed()=false.
    * @return *this
    * @stable ICU 4.6
    */
   virtual CheckedArrayByteSink& Reset();
   /**
    * Append "bytes[0,n-1]" to this.
    * @param bytes the pointer to the bytes
    * @param n the number of bytes; must be non-negative
    * @stable ICU 4.2
    */
   virtual void Append(const char* bytes, int32_t n) override;
   /**
    * Returns a writable buffer for appending and writes the buffer's capacity to
    * *result_capacity. For details see the base class documentation.
    * @param min_capacity required minimum capacity of the returned buffer;
    *                     must be non-negative
    * @param desired_capacity_hint desired capacity of the returned buffer;
    *                              must be non-negative
    * @param scratch default caller-owned buffer
    * @param scratch_capacity capacity of the scratch buffer
    * @param result_capacity pointer to an integer which will be set to the
    *                        capacity of the returned buffer
    * @return a buffer with *result_capacity>=min_capacity
    * @stable ICU 4.2
    */
   virtual char* GetAppendBuffer(int32_t min_capacity,
                                 int32_t desired_capacity_hint,
                                 char* scratch, int32_t scratch_capacity,
                                 int32_t* result_capacity) override;
   /**
    * Returns the number of bytes actually written to the sink.
    * @return number of bytes written to the buffer
    * @stable ICU 4.2
    */
   int32_t NumberOfBytesWritten() const { return size_; }
   /**
    * Returns true if any bytes were discarded, i.e., if there was an
    * attempt to write more than 'capacity' bytes.
    * @return true if more than 'capacity' bytes were Append()ed
    * @stable ICU 4.2
    */
   UBool Overflowed() const { return overflowed_; }
   /**
    * Returns the number of bytes appended to the sink.
    * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten()
    * else they return the same number.
    * @return number of bytes written to the buffer
    * @stable ICU 4.6
    */
   int32_t NumberOfBytesAppended() const { return appended_; }
 private:
   char* outbuf_;
   const int32_t capacity_;
   int32_t size_;
   int32_t appended_;
   UBool overflowed_;
 
   CheckedArrayByteSink() = delete;
   CheckedArrayByteSink(const CheckedArrayByteSink &) = delete;
   CheckedArrayByteSink &operator=(const CheckedArrayByteSink &) = delete;
 };
 
 /** 
  * Implementation of ByteSink that writes to a "string".
  * The StringClass is usually instantiated with a std::string.
  * @stable ICU 4.2
  */
 template<typename StringClass>
 class StringByteSink : public ByteSink {
  public:
   /**
    * Constructs a ByteSink that will append bytes to the dest string.
    * @param dest pointer to string object to append to
    * @stable ICU 4.2
    */
   StringByteSink(StringClass* dest) : dest_(dest) { }
   /**
    * Constructs a ByteSink that reserves append capacity and will append bytes to the dest string.
    * 
    * @param dest pointer to string object to append to
    * @param initialAppendCapacity capacity beyond dest->length() to be reserve()d
    * @stable ICU 60
    */
   StringByteSink(StringClass* dest, int32_t initialAppendCapacity) : dest_(dest) {
     if (initialAppendCapacity > 0 &&
         (uint32_t)initialAppendCapacity > (dest->capacity() - dest->length())) {
       dest->reserve(dest->length() + initialAppendCapacity);
     }
   }
   /**
    * Append "bytes[0,n-1]" to this.
    * @param data the pointer to the bytes
    * @param n the number of bytes; must be non-negative
    * @stable ICU 4.2
    */
   virtual void Append(const char* data, int32_t n) override { dest_->append(data, n); }
  private:
   StringClass* dest_;
 
   StringByteSink() = delete;
   StringByteSink(const StringByteSink &) = delete;
   StringByteSink &operator=(const StringByteSink &) = delete;
 };
 
 U_NAMESPACE_END
 
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif  // __BYTESTREAM_H__

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