text: // Copyright (c) 2012 The Chromium 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 NET_QUIC_CORE_QUIC_DATA_WRITER_H_
  #define NET_QUIC_CORE_QUIC_DATA_WRITER_H_
  
  #include <cstddef>
  #include <cstdint>
  #include <string>
  
  #include "base/macros.h"
  #include "base/strings/string_piece.h"
  #include "net/base/int128.h"
  #include "net/quic/core/quic_packets.h"
  #include "net/quic/platform/api/quic_export.h"
  
  namespace net {
  
  // This class provides facilities for packing QUIC data.
  //
  // The QuicDataWriter supports appending primitive values (int, string, etc)
  // to a frame instance.  The internal memory buffer is exposed as the "data"
  // of the QuicDataWriter.
  class QUIC_EXPORT_PRIVATE QuicDataWriter {
   public:
    // Creates a QuicDataWriter where |buffer| is not owned.
    QuicDataWriter(size_t size, char* buffer);
  
    ~QuicDataWriter();
  
    // Returns the size of the QuicDataWriter's data.
    size_t length() const { return length_; }
  
    // Retrieves the buffer from the QuicDataWriter without changing ownership.
    char* data();
  
    // Methods for adding to the payload.  These values are appended to the end
    // of the QuicDataWriter payload. Note - binary integers are written in
    // host byte order (little endian) not network byte order (big endian).
    bool WriteUInt8(uint8_t value);
    bool WriteUInt16(uint16_t value);
    bool WriteUInt32(uint32_t value);
    bool WriteUInt48(uint64_t value);
    bool WriteUInt64(uint64_t value);
    // Write unsigned floating point corresponding to the value. Large values are
    // clamped to the maximum representable (kUFloat16MaxValue). Values that can
    // not be represented directly are rounded down.
    bool WriteUFloat16(uint64_t value);
    bool WriteStringPiece16(base::StringPiece val);
    bool WriteBytes(const void* data, size_t data_len);
    bool WriteRepeatedByte(uint8_t byte, size_t count);
    // Fills the remaining buffer with null characters.
    void WritePadding();
  
    size_t capacity() const { return capacity_; }
  
   private:
    // Returns the location that the data should be written at, or nullptr if
    // there is not enough room. Call EndWrite with the returned offset and the
    // given length to pad out for the next write.
    char* BeginWrite(size_t length);
  
    char* buffer_;
    size_t capacity_;  // Allocation size of payload (or -1 if buffer is const).
    size_t length_;    // Current length of the buffer.
  
    DISALLOW_COPY_AND_ASSIGN(QuicDataWriter);
  };
  
  }  // namespace net
  
  #endif  // NET_QUIC_CORE_QUIC_DATA_WRITER_H_
  