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  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(value);
110    return (WriteBytes(&upper, sizeof(upper)) &&
111            WriteBytes(&lower, sizeof(lower)));
112  }
113  // TODO(hkhalil) Rename to WriteStringPiece16().
114  bool WriteString(const std::string& value);
115  bool WriteStringPiece32(const base::StringPiece& value);
116  bool WriteBytes(const void* data, uint32 data_len);
117
118  // Update (in-place) the length field in the frame being built to reflect the
119  // current actual length of bytes written to said frame through this builder.
120  // The framer parameter is used to determine version-specific location and
121  // size information of the length field to be written, and must be initialized
122  // with the correct version for the frame being written.
123  bool RewriteLength(const SpdyFramer& framer);
124
125  // Update (in-place) the length field in the frame being built to reflect the
126  // given length.
127  // The framer parameter is used to determine version-specific location and
128  // size information of the length field to be written, and must be initialized
129  // with the correct version for the frame being written.
130  bool OverwriteLength(const SpdyFramer& framer, size_t length);
131
132  // Update (in-place) the flags field in the frame being built to reflect the
133  // given flags value.
134  // Used only for SPDY versions >=4.
135  bool OverwriteFlags(const SpdyFramer& framer, uint8 flags);
136
137 private:
138  // Checks to make sure that there is an appropriate amount of space for a
139  // write of given size, in bytes.
140  bool CanWrite(size_t length) const;
141
142  scoped_ptr<char[]> buffer_;
143  size_t capacity_;  // Allocation size of payload, set by constructor.
144  size_t length_;    // Length of the latest frame in the buffer.
145  size_t offset_;    // Position at which the latest frame begins.
146
147  const SpdyMajorVersion version_;
148};
149
150}  // namespace net
151
152#endif  // NET_SPDY_SPDY_FRAME_BUILDER_H_
153