Index: chrome/browser/net/bit_stream_reader.cc |
diff --git a/chrome/browser/net/bit_stream_reader.cc b/chrome/browser/net/bit_stream_reader.cc |
new file mode 100644 |
index 0000000000000000000000000000000000000000..ad92470394f368f7c727ca9f0db1166335defc03 |
--- /dev/null |
+++ b/chrome/browser/net/bit_stream_reader.cc |
@@ -0,0 +1,63 @@ |
+// Copyright 2014 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+#include "chrome/browser/net/bit_stream_reader.h" |
+ |
+#include "base/big_endian.h" |
+#include "base/logging.h" |
+ |
+namespace internal { |
+ |
+BitStreamReader::BitStreamReader(const base::StringPiece& source) |
+ : source_(source), current_byte_(0), current_bit_(7) { |
+} |
+ |
+bool BitStreamReader::ReadUnaryEncoding(uint64_t* out) { |
+ uint64_t res = 0; |
+ if (BitsLeft() == 0) |
+ return false; |
+ |
+ while ((BitsLeft() > 0) && ReadBit()) |
+ res++; |
Ryan Sleevi
2014/10/20 19:18:24
Why keep the temporary?
You could change line 20
Eran Messeri
2014/10/21 14:59:59
Done.
|
+ |
+ *out = res; |
+ return true; |
+} |
+ |
+bool BitStreamReader::ReadBits(uint8_t num_bits, uint64_t* out) { |
+ if (num_bits > 64) |
+ return false; |
Ryan Sleevi
2014/10/20 19:18:24
API: Your API contract says they shouldn't call wi
Eran Messeri
2014/10/21 14:59:59
Done. In practice I always read a fixed amount so
|
+ |
+ if (BitsLeft() < num_bits) |
+ return false; |
+ |
+ uint64_t res = 0; |
+ for (uint8_t i = 0; i < num_bits; ++i) |
+ res |= (static_cast<uint64_t>(ReadBit()) << (num_bits - (i + 1))); |
+ |
+ *out = res; |
Ryan Sleevi
2014/10/20 19:18:24
ditto the temporary again
Eran Messeri
2014/10/21 14:59:59
Done.
|
+ return true; |
+} |
+ |
+uint64_t BitStreamReader::BitsLeft() const { |
+ if (current_byte_ == source_.length()) |
+ return 0; |
+ return (source_.length() - (current_byte_ + 1)) * 8 + current_bit_ + 1; |
Ryan Sleevi
2014/10/20 19:18:24
BUG: integer overflow issues here. Should you use
Eran Messeri
2014/10/21 14:59:59
Added a DCHECK that source_.length() is greater th
|
+} |
+ |
+uint8_t BitStreamReader::ReadBit() { |
+ DCHECK_GT(BitsLeft(), 0u); |
+ DCHECK(current_bit_ < 8 && current_bit_ >= 0); |
+ uint8_t res = |
+ (source_.data()[current_byte_] & (1 << current_bit_)) >> current_bit_; |
+ current_bit_--; |
+ if (current_bit_ < 0) { |
+ current_byte_++; |
+ current_bit_ = 7; |
+ } |
+ |
+ return res; |
+} |
+ |
+} // namespace internal |