net/spdy/spdy_frame_builder.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_SPDY_SPDY_FRAME_BUILDER_H_
   6 #define NET_SPDY_SPDY_FRAME_BUILDER_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/strings/string_piece.h"
  13 #include "base/sys_byteorder.h"
  14 #include "net/base/net_export.h"
  15 #include "net/spdy/spdy_protocol.h"
  16
  17 namespace net {
  18
  19 class SpdyFramer;
  20
  21 // This class provides facilities for basic binary value packing
  22 // into Spdy frames.
  23 //
  24 // The SpdyFrameBuilder supports appending primitive values (int, string, etc)
  25 // to a frame instance.  The SpdyFrameBuilder grows its internal memory buffer
  26 // dynamically to hold the sequence of primitive values.   The internal memory
  27 // buffer is exposed as the "data" of the SpdyFrameBuilder.
  28 class NET_EXPORT_PRIVATE SpdyFrameBuilder {
  29  public:
  30   // Initializes a SpdyFrameBuilder with a buffer of given size
  31   SpdyFrameBuilder(size_t size, SpdyMajorVersion version);
  32
  33   ~SpdyFrameBuilder();
  34
  35   // Returns the total size of the SpdyFrameBuilder's data, which may include
  36   // multiple frames.
  37   size_t length() const { return offset_ + length_; }
  38
  39   // Returns a writeable buffer of given size in bytes, to be appended to the
  40   // currently written frame. Does bounds checking on length but does not
  41   // increment the underlying iterator. To do so, consumers should subsequently
  42   // call Seek().
  43   // In general, consumers should use Write*() calls instead of this.
  44   // Returns NULL on failure.
  45   char* GetWritableBuffer(size_t length);
  46
  47   // Seeks forward by the given number of bytes. Useful in conjunction with
  48   // GetWriteableBuffer() above.
  49   bool Seek(size_t length);
  50
  51   // Populates this frame with a SPDY control frame header using
  52   // version-specific information from the |framer| and length information from
  53   // capacity_. The given type must be a control frame type.
  54   // Used only for SPDY versions <4.
  55   bool WriteControlFrameHeader(const SpdyFramer& framer,
  56                                SpdyFrameType type,
  57                                uint8 flags);
  58
  59   // Populates this frame with a SPDY data frame header using version-specific
  60   // information from the |framer| and length information from capacity_.
  61   bool WriteDataFrameHeader(const SpdyFramer& framer,
  62                             SpdyStreamId stream_id,
  63                             uint8 flags);
  64
  65   // Populates this frame with a SPDY4/HTTP2 frame prefix using
  66   // version-specific information from the |framer| and length information from
  67   // capacity_. The given type must be a control frame type.
  68   // Used only for SPDY versions >=4.
  69   bool BeginNewFrame(const SpdyFramer& framer,
  70                      SpdyFrameType type,
  71                      uint8 flags,
  72                      SpdyStreamId stream_id);
  73
  74   // Takes the buffer from the SpdyFrameBuilder.
  75   SpdyFrame* take() {
  76     if (version_ > SPDY3) {
  77       DLOG_IF(DFATAL, SpdyConstants::GetFrameMaximumSize(version_) < length_)
  78           << "Frame length " << length_
  79           << " is longer than the maximum allowed length.";
  80     }
  81     SpdyFrame* rv = new SpdyFrame(buffer_.release(), length(), true);
  82     capacity_ = 0;
  83     length_ = 0;
  84     offset_ = 0;
  85     return rv;
  86   }
  87
  88   // Methods for adding to the payload.  These values are appended to the end
  89   // of the SpdyFrameBuilder payload. Note - binary integers are converted from
  90   // host to network form.
  91   bool WriteUInt8(uint8 value) {
  92     return WriteBytes(&value, sizeof(value));
  93   }
  94   bool WriteUInt16(uint16 value) {
  95     value = htons(value);
  96     return WriteBytes(&value, sizeof(value));
  97   }
  98   bool WriteUInt24(uint32 value) {
  99     value = htonl(value);
 100     return WriteBytes(reinterpret_cast<char*>(&value) + 1,
 101                       sizeof(value) - 1);
 102   }
 103   bool WriteUInt32(uint32 value) {
 104     value = htonl(value);
 105     return WriteBytes(&value, sizeof(value));
 106   }
 107   bool WriteUInt64(uint64 value) {
 108     uint32 upper = htonl(value >> 32);
 109     uint32 lower = htonl(static_cast<uint32>(value));
 110     return (WriteBytes(&upper, sizeof(upper)) &&
 111             WriteBytes(&lower, sizeof(lower)));
 112   }
 113   bool WriteStringPiece16(const base::StringPiece& value);
 114   bool WriteStringPiece32(const base::StringPiece& value);
 115   bool WriteBytes(const void* data, uint32 data_len);
 116
 117   // Update (in-place) the length field in the frame being built to reflect the
 118   // current actual length of bytes written to said frame through this builder.
 119   // The framer parameter is used to determine version-specific location and
 120   // size information of the length field to be written, and must be initialized
 121   // with the correct version for the frame being written.
 122   bool RewriteLength(const SpdyFramer& framer);
 123
 124   // Update (in-place) the length field in the frame being built to reflect the
 125   // given length.
 126   // The framer parameter is used to determine version-specific location and
 127   // size information of the length field to be written, and must be initialized
 128   // with the correct version for the frame being written.
 129   bool OverwriteLength(const SpdyFramer& framer, size_t length);
 130
 131   // Update (in-place) the flags field in the frame being built to reflect the
 132   // given flags value.
 133   // Used only for SPDY versions >=4.
 134   bool OverwriteFlags(const SpdyFramer& framer, uint8 flags);
 135
 136  private:
 137   // Checks to make sure that there is an appropriate amount of space for a
 138   // write of given size, in bytes.
 139   bool CanWrite(size_t length) const;
 140
 141   scoped_ptr<char[]> buffer_;
 142   size_t capacity_;  // Allocation size of payload, set by constructor.
 143   size_t length_;    // Length of the latest frame in the buffer.
 144   size_t offset_;    // Position at which the latest frame begins.
 145
 146   const SpdyMajorVersion version_;
 147 };
 148
 149 }  // namespace net
 150
 151 #endif  // NET_SPDY_SPDY_FRAME_BUILDER_H_