other-licenses/7zstub/src/7zip/Common/MSBFDecoder.h@97036ab72558 (annotated)
other-licenses/7zstub/src/7zip/Common/MSBFDecoder.h
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
| michael@0 | 1 | // MSBFDecoder.h |
| michael@0 | 2 | // the Most Significant Bit of byte is First |
| michael@0 | 3 | |
| michael@0 | 4 | #ifndef __STREAM_MSBFDECODER_H |
| michael@0 | 5 | #define __STREAM_MSBFDECODER_H |
| michael@0 | 6 | |
| michael@0 | 7 | #include "../../Common/Types.h" |
| michael@0 | 8 | #include "../IStream.h" |
| michael@0 | 9 | |
| michael@0 | 10 | namespace NStream { |
| michael@0 | 11 | namespace NMSBF { |
| michael@0 | 12 | |
| michael@0 | 13 | const int kNumBigValueBits = 8 * 4; |
| michael@0 | 14 | const int kNumValueBytes = 3; |
| michael@0 | 15 | const int kNumValueBits = 8 * kNumValueBytes; |
| michael@0 | 16 | |
| michael@0 | 17 | const UInt32 kMask = (1 << kNumValueBits) - 1; |
| michael@0 | 18 | |
| michael@0 | 19 | template<class TInByte> |
| michael@0 | 20 | class CDecoder |
| michael@0 | 21 | { |
| michael@0 | 22 | UInt32 m_BitPos; |
| michael@0 | 23 | UInt32 m_Value; |
| michael@0 | 24 | public: |
| michael@0 | 25 | TInByte m_Stream; |
| michael@0 | 26 | bool Create(UInt32 bufferSize) { return m_Stream.Create(bufferSize); } |
| michael@0 | 27 | void SetStream(ISequentialInStream *inStream) { m_Stream.SetStream(inStream);} |
| michael@0 | 28 | void ReleaseStream() { m_Stream.ReleaseStream();} |
| michael@0 | 29 | |
| michael@0 | 30 | void Init() |
| michael@0 | 31 | { |
| michael@0 | 32 | m_Stream.Init(); |
| michael@0 | 33 | m_BitPos = kNumBigValueBits; |
| michael@0 | 34 | Normalize(); |
| michael@0 | 35 | } |
| michael@0 | 36 | |
| michael@0 | 37 | UInt64 GetProcessedSize() const |
| michael@0 | 38 | { return m_Stream.GetProcessedSize() - (kNumBigValueBits - m_BitPos) / 8; } |
| michael@0 | 39 | UInt32 GetBitPosition() const { return (m_BitPos & 7); } |
| michael@0 | 40 | |
| michael@0 | 41 | void Normalize() |
| michael@0 | 42 | { |
| michael@0 | 43 | for (;m_BitPos >= 8; m_BitPos -= 8) |
| michael@0 | 44 | m_Value = (m_Value << 8) | m_Stream.ReadByte(); |
| michael@0 | 45 | } |
| michael@0 | 46 | |
| michael@0 | 47 | UInt32 GetValue(UInt32 numBits) const |
| michael@0 | 48 | { |
| michael@0 | 49 | // return (m_Value << m_BitPos) >> (kNumBigValueBits - numBits); |
| michael@0 | 50 | return ((m_Value >> (8 - m_BitPos)) & kMask) >> (kNumValueBits - numBits); |
| michael@0 | 51 | } |
| michael@0 | 52 | |
| michael@0 | 53 | void MovePos(UInt32 numBits) |
| michael@0 | 54 | { |
| michael@0 | 55 | m_BitPos += numBits; |
| michael@0 | 56 | Normalize(); |
| michael@0 | 57 | } |
| michael@0 | 58 | |
| michael@0 | 59 | UInt32 ReadBits(UInt32 numBits) |
| michael@0 | 60 | { |
| michael@0 | 61 | UInt32 res = GetValue(numBits); |
| michael@0 | 62 | MovePos(numBits); |
| michael@0 | 63 | return res; |
| michael@0 | 64 | } |
| michael@0 | 65 | }; |
| michael@0 | 66 | |
| michael@0 | 67 | }} |
| michael@0 | 68 | |
| michael@0 | 69 | #endif |
