net/quic/quic_data_writer.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_QUIC_QUIC_DATA_WRITER_H_
   6 #define NET_QUIC_QUIC_DATA_WRITER_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "base/logging.h"
  12 #include "base/port.h"
  13 #include "base/strings/string_piece.h"
  14 #include "net/base/int128.h"
  15 #include "net/base/net_export.h"
  16 #include "net/quic/quic_protocol.h"
  17
  18 namespace net {
  19
  20 // This class provides facilities for packing QUIC data.
  21 //
  22 // The QuicDataWriter supports appending primitive values (int, string, etc)
  23 // to a frame instance.  The QuicDataWriter grows its internal memory buffer
  24 // dynamically to hold the sequence of primitive values.   The internal memory
  25 // buffer is exposed as the "data" of the QuicDataWriter.
  26 class NET_EXPORT_PRIVATE QuicDataWriter {
  27  public:
  28   explicit QuicDataWriter(size_t length);
  29
  30   ~QuicDataWriter();
  31
  32   // Returns the size of the QuicDataWriter's data.
  33   size_t length() const { return length_; }
  34
  35   // Takes the buffer from the QuicDataWriter.
  36   char* take();
  37
  38   // Methods for adding to the payload.  These values are appended to the end
  39   // of the QuicDataWriter payload. Note - binary integers are written in
  40   // host byte order (little endian) not network byte order (big endian).
  41   bool WriteUInt8(uint8 value);
  42   bool WriteUInt16(uint16 value);
  43   bool WriteUInt32(uint32 value);
  44   bool WriteUInt48(uint64 value);
  45   bool WriteUInt64(uint64 value);
  46   // Write unsigned floating point corresponding to the value. Large values are
  47   // clamped to the maximum representable (kUFloat16MaxValue). Values that can
  48   // not be represented directly are rounded down.
  49   bool WriteUFloat16(uint64 value);
  50   bool WriteStringPiece16(base::StringPiece val);
  51   bool WriteIOVector(const IOVector& data);
  52   bool WriteBytes(const void* data, size_t data_len);
  53   bool WriteRepeatedByte(uint8 byte, size_t count);
  54   // Fills the remaining buffer with null characters.
  55   void WritePadding();
  56
  57   // Methods for editing the payload at a specific offset, where the
  58   // offset must be within the writer's capacity.
  59   // Return true if there is enough space at that offset, false otherwise.
  60   bool WriteUInt8ToOffset(uint8 value, size_t offset);
  61   bool WriteUInt32ToOffset(uint32 value, size_t offset);
  62   bool WriteUInt48ToOffset(uint64 value, size_t offset);
  63
  64   size_t capacity() const {
  65     return capacity_;
  66   }
  67
  68  private:
  69   // Returns the location that the data should be written at, or NULL if there
  70   // is not enough room. Call EndWrite with the returned offset and the given
  71   // length to pad out for the next write.
  72   char* BeginWrite(size_t length);
  73
  74   char* buffer_;
  75   size_t capacity_;  // Allocation size of payload (or -1 if buffer is const).
  76   size_t length_;    // Current length of the buffer.
  77
  78   DISALLOW_COPY_AND_ASSIGN(QuicDataWriter);
  79 };
  80
  81 }  // namespace net
  82
  83 #endif  // NET_QUIC_QUIC_DATA_WRITER_H_