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| 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 #include "net/spdy/hpack_output_stream.h" | |
| 6 | |
| 7 #include "base/logging.h" | |
| 8 | |
| 9 | |
| 10 namespace net { | |
| 11 | |
| 12 using base::StringPiece; | |
| 13 using std::string; | |
| 14 | |
| 15 HpackOutputStream::HpackOutputStream() | |
| 16 : bit_offset_(0) {} | |
| 17 | |
| 18 HpackOutputStream::~HpackOutputStream() {} | |
| 19 | |
| 20 void HpackOutputStream::AppendBits(uint8 bits, size_t bit_size) { | |
| 21 DCHECK_GT(bit_size, 0u); | |
| 22 DCHECK_LE(bit_size, 8u); | |
| 23 DCHECK_EQ(bits >> bit_size, 0); | |
| 24 size_t new_bit_offset = bit_offset_ + bit_size; | |
| 25 if (bit_offset_ == 0) { | |
| 26 // Buffer ends on a byte boundary. | |
| 27 DCHECK_LE(bit_size, 8u); | |
| 28 buffer_.append(1, bits << (8 - bit_size)); | |
| 29 } else if (new_bit_offset <= 8) { | |
| 30 // Buffer does not end on a byte boundary but the given bits fit | |
| 31 // in the remainder of the last byte. | |
| 32 *buffer_.rbegin() |= bits << (8 - new_bit_offset); | |
| 33 } else { | |
| 34 // Buffer does not end on a byte boundary and the given bits do | |
| 35 // not fit in the remainder of the last byte. | |
| 36 *buffer_.rbegin() |= bits >> (new_bit_offset - 8); | |
| 37 buffer_.append(1, bits << (16 - new_bit_offset)); | |
| 38 } | |
| 39 bit_offset_ = new_bit_offset % 8; | |
| 40 } | |
| 41 | |
| 42 void HpackOutputStream::AppendPrefix(HpackPrefix prefix) { | |
| 43 AppendBits(prefix.bits, prefix.bit_size); | |
| 44 } | |
| 45 | |
| 46 void HpackOutputStream::AppendBytes(StringPiece buffer) { | |
| 47 DCHECK_EQ(bit_offset_, 0u); | |
| 48 buffer_.append(buffer.data(), buffer.size()); | |
| 49 } | |
| 50 | |
| 51 void HpackOutputStream::AppendUint32(uint32 I) { | |
| 52 // The algorithm below is adapted from the pseudocode in 6.1. | |
| 53 size_t N = 8 - bit_offset_; | |
| 54 uint8 max_first_byte = static_cast<uint8>((1 << N) - 1); | |
| 55 if (I < max_first_byte) { | |
| 56 AppendBits(static_cast<uint8>(I), N); | |
| 57 } else { | |
| 58 AppendBits(max_first_byte, N); | |
| 59 I -= max_first_byte; | |
| 60 while ((I & ~0x7f) != 0) { | |
| 61 buffer_.append(1, (I & 0x7f) | 0x80); | |
| 62 I >>= 7; | |
| 63 } | |
| 64 AppendBits(static_cast<uint8>(I), 8); | |
| 65 } | |
| 66 } | |
| 67 | |
| 68 void HpackOutputStream::TakeString(string* output) { | |
| 69 // This must hold, since all public functions cause the buffer to | |
| 70 // end on a byte boundary. | |
| 71 DCHECK_EQ(bit_offset_, 0u); | |
| 72 buffer_.swap(*output); | |
| 73 buffer_.clear(); | |
| 74 bit_offset_ = 0; | |
| 75 } | |
| 76 | |
| 77 } // namespace net | |
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