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