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      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_
     84