other-licenses/7zstub/src/7zip/Common/LSBFDecoder.h@97036ab72558 (annotated)
other-licenses/7zstub/src/7zip/Common/LSBFDecoder.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 | // LSBFDecoder.h |
| michael@0 | 2 | |
| michael@0 | 3 | #ifndef __STREAM_LSBFDECODER_H |
| michael@0 | 4 | #define __STREAM_LSBFDECODER_H |
| michael@0 | 5 | |
| michael@0 | 6 | #include "../IStream.h" |
| michael@0 | 7 | |
| michael@0 | 8 | namespace NStream { |
| michael@0 | 9 | namespace NLSBF { |
| michael@0 | 10 | |
| michael@0 | 11 | const int kNumBigValueBits = 8 * 4; |
| michael@0 | 12 | |
| michael@0 | 13 | const int kNumValueBytes = 3; |
| michael@0 | 14 | const int kNumValueBits = 8 * kNumValueBytes; |
| michael@0 | 15 | |
| michael@0 | 16 | const UInt32 kMask = (1 << kNumValueBits) - 1; |
| michael@0 | 17 | |
| michael@0 | 18 | extern Byte kInvertTable[256]; |
| michael@0 | 19 | // the Least Significant Bit of byte is First |
| michael@0 | 20 | |
| michael@0 | 21 | template<class TInByte> |
| michael@0 | 22 | class CBaseDecoder |
| michael@0 | 23 | { |
| michael@0 | 24 | protected: |
| michael@0 | 25 | int m_BitPos; |
| michael@0 | 26 | UInt32 m_Value; |
| michael@0 | 27 | TInByte m_Stream; |
| michael@0 | 28 | public: |
| michael@0 | 29 | UInt32 NumExtraBytes; |
| michael@0 | 30 | bool Create(UInt32 bufferSize) { return m_Stream.Create(bufferSize); } |
| michael@0 | 31 | void SetStream(ISequentialInStream *inStream) { m_Stream.SetStream(inStream); } |
| michael@0 | 32 | void ReleaseStream() { m_Stream.ReleaseStream(); } |
| michael@0 | 33 | void Init() |
| michael@0 | 34 | { |
| michael@0 | 35 | m_Stream.Init(); |
| michael@0 | 36 | m_BitPos = kNumBigValueBits; |
| michael@0 | 37 | m_Value = 0; |
| michael@0 | 38 | NumExtraBytes = 0; |
| michael@0 | 39 | } |
| michael@0 | 40 | UInt64 GetProcessedSize() const |
| michael@0 | 41 | { return m_Stream.GetProcessedSize() - (kNumBigValueBits - m_BitPos) / 8; } |
| michael@0 | 42 | UInt64 GetProcessedBitsSize() const |
| michael@0 | 43 | { return (m_Stream.GetProcessedSize() << 3) - (kNumBigValueBits - m_BitPos); } |
| michael@0 | 44 | int GetBitPosition() const { return (m_BitPos & 7); } |
| michael@0 | 45 | |
| michael@0 | 46 | void Normalize() |
| michael@0 | 47 | { |
| michael@0 | 48 | for (;m_BitPos >= 8; m_BitPos -= 8) |
| michael@0 | 49 | { |
| michael@0 | 50 | Byte b; |
| michael@0 | 51 | if (!m_Stream.ReadByte(b)) |
| michael@0 | 52 | { |
| michael@0 | 53 | b = 0xFF; // check it |
| michael@0 | 54 | NumExtraBytes++; |
| michael@0 | 55 | } |
| michael@0 | 56 | m_Value = (b << (kNumBigValueBits - m_BitPos)) | m_Value; |
| michael@0 | 57 | } |
| michael@0 | 58 | } |
| michael@0 | 59 | |
| michael@0 | 60 | UInt32 ReadBits(int numBits) |
| michael@0 | 61 | { |
| michael@0 | 62 | Normalize(); |
| michael@0 | 63 | UInt32 res = m_Value & ((1 << numBits) - 1); |
| michael@0 | 64 | m_BitPos += numBits; |
| michael@0 | 65 | m_Value >>= numBits; |
| michael@0 | 66 | return res; |
| michael@0 | 67 | } |
| michael@0 | 68 | |
| michael@0 | 69 | bool ExtraBitsWereRead() const |
| michael@0 | 70 | { |
| michael@0 | 71 | if (NumExtraBytes == 0) |
| michael@0 | 72 | return false; |
| michael@0 | 73 | return ((UInt32)(kNumBigValueBits - m_BitPos) < (NumExtraBytes << 3)); |
| michael@0 | 74 | } |
| michael@0 | 75 | }; |
| michael@0 | 76 | |
| michael@0 | 77 | template<class TInByte> |
| michael@0 | 78 | class CDecoder: public CBaseDecoder<TInByte> |
| michael@0 | 79 | { |
| michael@0 | 80 | UInt32 m_NormalValue; |
| michael@0 | 81 | |
| michael@0 | 82 | public: |
| michael@0 | 83 | void Init() |
| michael@0 | 84 | { |
| michael@0 | 85 | CBaseDecoder<TInByte>::Init(); |
| michael@0 | 86 | m_NormalValue = 0; |
| michael@0 | 87 | } |
| michael@0 | 88 | |
| michael@0 | 89 | void Normalize() |
| michael@0 | 90 | { |
| michael@0 | 91 | for (;this->m_BitPos >= 8; this->m_BitPos -= 8) |
| michael@0 | 92 | { |
| michael@0 | 93 | Byte b; |
| michael@0 | 94 | if (!this->m_Stream.ReadByte(b)) |
| michael@0 | 95 | { |
| michael@0 | 96 | b = 0xFF; // check it |
| michael@0 | 97 | this->NumExtraBytes++; |
| michael@0 | 98 | } |
| michael@0 | 99 | m_NormalValue = (b << (kNumBigValueBits - this->m_BitPos)) | m_NormalValue; |
| michael@0 | 100 | this->m_Value = (this->m_Value << 8) | kInvertTable[b]; |
| michael@0 | 101 | } |
| michael@0 | 102 | } |
| michael@0 | 103 | |
| michael@0 | 104 | UInt32 GetValue(int numBits) |
| michael@0 | 105 | { |
| michael@0 | 106 | Normalize(); |
| michael@0 | 107 | return ((this->m_Value >> (8 - this->m_BitPos)) & kMask) >> (kNumValueBits - numBits); |
| michael@0 | 108 | } |
| michael@0 | 109 | |
| michael@0 | 110 | void MovePos(int numBits) |
| michael@0 | 111 | { |
| michael@0 | 112 | this->m_BitPos += numBits; |
| michael@0 | 113 | m_NormalValue >>= numBits; |
| michael@0 | 114 | } |
| michael@0 | 115 | |
| michael@0 | 116 | UInt32 ReadBits(int numBits) |
| michael@0 | 117 | { |
| michael@0 | 118 | Normalize(); |
| michael@0 | 119 | UInt32 res = m_NormalValue & ( (1 << numBits) - 1); |
| michael@0 | 120 | MovePos(numBits); |
| michael@0 | 121 | return res; |
| michael@0 | 122 | } |
| michael@0 | 123 | }; |
| michael@0 | 124 | |
| michael@0 | 125 | }} |
| michael@0 | 126 | |
| michael@0 | 127 | #endif |
