OLD | NEW |
(Empty) | |
| 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 "chrome/browser/net/bit_stream_reader.h" |
| 6 |
| 7 #include "base/big_endian.h" |
| 8 #include "base/logging.h" |
| 9 #include "base/numerics/safe_conversions.h" |
| 10 |
| 11 namespace internal { |
| 12 |
| 13 BitStreamReader::BitStreamReader(const base::StringPiece& source) |
| 14 : source_(source), current_byte_(0), current_bit_(7) { |
| 15 DCHECK_LT(source_.length(), UINT32_MAX); |
| 16 } |
| 17 |
| 18 bool BitStreamReader::ReadUnaryEncoding(uint64_t* out) { |
| 19 if (BitsLeft() == 0) |
| 20 return false; |
| 21 |
| 22 *out = 0; |
| 23 while ((BitsLeft() > 0) && ReadBit()) |
| 24 ++(*out); |
| 25 |
| 26 return true; |
| 27 } |
| 28 |
| 29 bool BitStreamReader::ReadBits(uint8_t num_bits, uint64_t* out) { |
| 30 DCHECK_LE(num_bits, 64); |
| 31 |
| 32 if (BitsLeft() < num_bits) |
| 33 return false; |
| 34 |
| 35 *out = 0; |
| 36 for (uint8_t i = 0; i < num_bits; ++i) |
| 37 (*out) |= (static_cast<uint64_t>(ReadBit()) << (num_bits - (i + 1))); |
| 38 |
| 39 return true; |
| 40 } |
| 41 |
| 42 uint64_t BitStreamReader::BitsLeft() const { |
| 43 if (current_byte_ == source_.length()) |
| 44 return 0; |
| 45 DCHECK_GT(source_.length(), current_byte_); |
| 46 return (source_.length() - (current_byte_ + 1)) * 8 + current_bit_ + 1; |
| 47 } |
| 48 |
| 49 uint8_t BitStreamReader::ReadBit() { |
| 50 DCHECK_GT(BitsLeft(), 0u); |
| 51 DCHECK(current_bit_ < 8 && current_bit_ >= 0); |
| 52 uint8_t res = |
| 53 (source_.data()[current_byte_] & (1 << current_bit_)) >> current_bit_; |
| 54 current_bit_--; |
| 55 if (current_bit_ < 0) { |
| 56 current_byte_++; |
| 57 current_bit_ = 7; |
| 58 } |
| 59 |
| 60 return res; |
| 61 } |
| 62 |
| 63 } // namespace internal |
OLD | NEW |