spdy_frame_builder.h revision 4e180b6a0b4720a9b8e9e959a882386f690f08ff 
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
17namespace net {
18
19class 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.
28class NET_EXPORT_PRIVATE SpdyFrameBuilder {
29 public:
30  // Initializes a SpdyFrameBuilder with a buffer of given size
31  explicit SpdyFrameBuilder(size_t size);
32
33  ~SpdyFrameBuilder();
34
35  // Returns the size of the SpdyFrameBuilder's data.
36  size_t length() const { return length_; }
37
38  // Returns a writeable buffer of given size in bytes, to be appended to the
39  // currently written frame. Does bounds checking on length but does not
40  // increment the underlying iterator. To do so, consumers should subsequently
41  // call Seek().
42  // In general, consumers should use Write*() calls instead of this.
43  // Returns NULL on failure.
44  char* GetWritableBuffer(size_t length);
45
46  // Seeks forward by the given number of bytes. Useful in conjunction with
47  // GetWriteableBuffer() above.
48  bool Seek(size_t length);
49
50  // Populates this frame with a SPDY control frame header using
51  // version-specific information from the |framer| and length information from
52  // capacity_. The given type must be a control frame type.
53  // Used only for SPDY versions <4.
54  bool WriteControlFrameHeader(const SpdyFramer& framer,
55                               SpdyFrameType type,
56                               uint8 flags);
57
58  // Populates this frame with a SPDY data frame header using version-specific
59  // information from the |framer| and length information from capacity_.
60  bool WriteDataFrameHeader(const SpdyFramer& framer,
61                            SpdyStreamId stream_id,
62                            SpdyDataFlags flags);
63
64  // Populates this frame with a SPDY4/HTTP2 frame prefix using
65  // version-specific information from the |framer| and length information from
66  // capacity_. The given type must be a control frame type.
67  // Used only for SPDY versions >=4.
68  bool WriteFramePrefix(const SpdyFramer& framer,
69                        SpdyFrameType type,
70                        uint8 flags,
71                        SpdyStreamId stream_id);
72
73  // Takes the buffer from the SpdyFrameBuilder.
74  SpdyFrame* take() {
75    SpdyFrame* rv = new SpdyFrame(buffer_.release(), length_, true);
76    capacity_ = 0;
77    length_ = 0;
78    return rv;
79  }
80
81  // Methods for adding to the payload.  These values are appended to the end
82  // of the SpdyFrameBuilder payload. Note - binary integers are converted from
83  // host to network form.
84  bool WriteUInt8(uint8 value) {
85    return WriteBytes(&value, sizeof(value));
86  }
87  bool WriteUInt16(uint16 value) {
88    value = htons(value);
89    return WriteBytes(&value, sizeof(value));
90  }
91  bool WriteUInt32(uint32 value) {
92    value = htonl(value);
93    return WriteBytes(&value, sizeof(value));
94  }
95  // TODO(hkhalil) Rename to WriteStringPiece16().
96  bool WriteString(const std::string& value);
97  bool WriteStringPiece32(const base::StringPiece& value);
98  bool WriteBytes(const void* data, uint32 data_len);
99
100  // Update (in-place) the length field in the frame being built to reflect the
101  // current actual length of bytes written to said frame through this builder.
102  // The framer parameter is used to determine version-specific location and
103  // size information of the length field to be written, and must be initialized
104  // with the correct version for the frame being written.
105  bool RewriteLength(const SpdyFramer& framer);
106
107  // Update (in-place) the length field in the frame being built to reflect the
108  // given length.
109  // The framer parameter is used to determine version-specific location and
110  // size information of the length field to be written, and must be initialized
111  // with the correct version for the frame being written.
112  bool OverwriteLength(const SpdyFramer& framer, size_t length);
113
114 private:
115  // Checks to make sure that there is an appropriate amount of space for a
116  // write of given size, in bytes.
117  bool CanWrite(size_t length) const;
118
119  scoped_ptr<char[]> buffer_;
120  size_t capacity_;  // Allocation size of payload, set by constructor.
121  size_t length_;    // Current length of the buffer.
122};
123
124}  // namespace net
125
126#endif  // NET_SPDY_SPDY_FRAME_BUILDER_H_
127