net/spdy/hpack_output_stream.h

   1 // Copyright 2014 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_SPDY_HPACK_OUTPUT_STREAM_H_
   6 #define NET_SPDY_HPACK_OUTPUT_STREAM_H_
   7
   8 #include <map>
   9 #include <string>
  10
  11 #include "base/basictypes.h"
  12 #include "base/macros.h"
  13 #include "base/strings/string_piece.h"
  14 #include "net/base/net_export.h"
  15 #include "net/spdy/hpack_constants.h"
  16
  17 // All section references below are to
  18 // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08
  19
  20 namespace net {
  21
  22 // An HpackOutputStream handles all the low-level details of encoding
  23 // header fields.
  24 class NET_EXPORT_PRIVATE HpackOutputStream {
  25  public:
  26   explicit HpackOutputStream();
  27   ~HpackOutputStream();
  28
  29   // Appends the lower |bit_size| bits of |bits| to the internal buffer.
  30   //
  31   // |bit_size| must be > 0 and <= 8. |bits| must not have any bits
  32   // set other than the lower |bit_size| bits.
  33   void AppendBits(uint8 bits, size_t bit_size);
  34
  35   // Simply forwards to AppendBits(prefix.bits, prefix.bit-size).
  36   void AppendPrefix(HpackPrefix prefix);
  37
  38   // Directly appends |buffer|.
  39   void AppendBytes(base::StringPiece buffer);
  40
  41   // Appends the given integer using the representation described in
  42   // 6.1. If the internal buffer ends on a byte boundary, the prefix
  43   // length N is taken to be 8; otherwise, it is taken to be the
  44   // number of bits to the next byte boundary.
  45   //
  46   // It is guaranteed that the internal buffer will end on a byte
  47   // boundary after this function is called.
  48   void AppendUint32(uint32 I);
  49
  50   // Swaps the interal buffer with |output|.
  51   void TakeString(std::string* output);
  52
  53  private:
  54   // The internal bit buffer.
  55   std::string buffer_;
  56
  57   // If 0, the buffer ends on a byte boundary. If non-zero, the buffer
  58   // ends on the most significant nth bit. Guaranteed to be < 8.
  59   size_t bit_offset_;
  60
  61   DISALLOW_COPY_AND_ASSIGN(HpackOutputStream);
  62 };
  63
  64 }  // namespace net
  65
  66 #endif  // NET_SPDY_HPACK_OUTPUT_STREAM_H_