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1 // Copyright 2013 The Chromium Authors. All rights reserved. | 1 // Copyright 2013 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "net/websockets/websocket_deflater.h" | 5 #include "net/websockets/websocket_deflater.h" |
6 | 6 |
7 #include <string.h> | 7 #include <string.h> |
8 #include <algorithm> | 8 #include <algorithm> |
9 #include <deque> | 9 #include <deque> |
10 #include <vector> | 10 #include <vector> |
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24 stream_.reset(NULL); | 24 stream_.reset(NULL); |
25 } | 25 } |
26 } | 26 } |
27 | 27 |
28 bool WebSocketDeflater::Initialize(int window_bits) { | 28 bool WebSocketDeflater::Initialize(int window_bits) { |
29 DCHECK(!stream_); | 29 DCHECK(!stream_); |
30 stream_.reset(new z_stream); | 30 stream_.reset(new z_stream); |
31 | 31 |
32 DCHECK_LE(8, window_bits); | 32 DCHECK_LE(8, window_bits); |
33 DCHECK_GE(15, window_bits); | 33 DCHECK_GE(15, window_bits); |
| 34 |
| 35 // Use a negative value to compress a raw deflate stream. |
| 36 // |
| 37 // Upgrade window_bits = 8 to 9 because zlib is unable to compress at |
| 38 // window_bits = 8. Historically, zlib has silently increased the window size |
| 39 // during compression in this case, although this is no longer done for raw |
| 40 // deflate streams since zlib 1.2.9. |
| 41 // |
| 42 // Because of a zlib deflate quirk, back-references will not use the entire |
| 43 // range of 1 << window_bits, but will instead use a restricted range of (1 << |
| 44 // window_bits) - 262. With an increased window_bits = 9, back-references will |
| 45 // be within a range of 250. These can still be decompressed with window_bits |
| 46 // = 8 and the 256-byte window used there. |
| 47 // |
| 48 // Both the requirement to do this upgrade and the ability to compress with |
| 49 // window_bits = 9 while expecting a decompressor to function with window_bits |
| 50 // = 8 are quite specific to zlib's particular deflate implementation, but not |
| 51 // specific to any particular inflate implementation. |
| 52 // |
| 53 // See https://crbug.com/691074 |
| 54 window_bits = -std::max(window_bits, 9); |
| 55 |
34 memset(stream_.get(), 0, sizeof(*stream_)); | 56 memset(stream_.get(), 0, sizeof(*stream_)); |
35 int result = deflateInit2(stream_.get(), | 57 int result = deflateInit2(stream_.get(), |
36 Z_DEFAULT_COMPRESSION, | 58 Z_DEFAULT_COMPRESSION, |
37 Z_DEFLATED, | 59 Z_DEFLATED, |
38 -window_bits, // Negative value for raw deflate | 60 window_bits, |
39 8, // default mem level | 61 8, // default mem level |
40 Z_DEFAULT_STRATEGY); | 62 Z_DEFAULT_STRATEGY); |
41 if (result != Z_OK) { | 63 if (result != Z_OK) { |
42 deflateEnd(stream_.get()); | 64 deflateEnd(stream_.get()); |
43 stream_.reset(); | 65 stream_.reset(); |
44 return false; | 66 return false; |
45 } | 67 } |
46 const size_t kFixedBufferSize = 4096; | 68 const size_t kFixedBufferSize = 4096; |
47 fixed_buffer_.resize(kFixedBufferSize); | 69 fixed_buffer_.resize(kFixedBufferSize); |
48 return true; | 70 return true; |
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119 stream_->next_out = reinterpret_cast<Bytef*>(&fixed_buffer_[0]); | 141 stream_->next_out = reinterpret_cast<Bytef*>(&fixed_buffer_[0]); |
120 stream_->avail_out = fixed_buffer_.size(); | 142 stream_->avail_out = fixed_buffer_.size(); |
121 result = deflate(stream_.get(), flush); | 143 result = deflate(stream_.get(), flush); |
122 size_t size = fixed_buffer_.size() - stream_->avail_out; | 144 size_t size = fixed_buffer_.size() - stream_->avail_out; |
123 buffer_.insert(buffer_.end(), &fixed_buffer_[0], &fixed_buffer_[0] + size); | 145 buffer_.insert(buffer_.end(), &fixed_buffer_[0], &fixed_buffer_[0] + size); |
124 } while (result == Z_OK); | 146 } while (result == Z_OK); |
125 return result; | 147 return result; |
126 } | 148 } |
127 | 149 |
128 } // namespace net | 150 } // namespace net |
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