other-licenses/7zstub/src/7zip/Compress/RangeCoder/RangeCoderBit.cpp@97036ab72558
other-licenses/7zstub/src/7zip/Compress/RangeCoder/RangeCoderBit.cpp
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 // Compress/RangeCoder/RangeCoderBit.cpp
3 #include "StdAfx.h"
5 #include "RangeCoderBit.h"
7 namespace NCompress {
8 namespace NRangeCoder {
10 UInt32 CPriceTables::ProbPrices[kBitModelTotal >> kNumMoveReducingBits];
11 static CPriceTables g_PriceTables;
13 CPriceTables::CPriceTables() { Init(); }
15 void CPriceTables::Init()
16 {
17 const int kNumBits = (kNumBitModelTotalBits - kNumMoveReducingBits);
18 for(int i = kNumBits - 1; i >= 0; i--)
19 {
20 UInt32 start = 1 << (kNumBits - i - 1);
21 UInt32 end = 1 << (kNumBits - i);
22 for (UInt32 j = start; j < end; j++)
23 ProbPrices[j] = (i << kNumBitPriceShiftBits) +
24 (((end - j) << kNumBitPriceShiftBits) >> (kNumBits - i - 1));
25 }
27 /*
28 // simplest: bad solution
29 for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
30 ProbPrices[i] = kBitPrice;
31 */
33 /*
34 const double kDummyMultMid = (1.0 / kBitPrice) / 2;
35 const double kDummyMultMid = 0;
36 // float solution
37 double ln2 = log(double(2));
38 double lnAll = log(double(kBitModelTotal >> kNumMoveReducingBits));
39 for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
40 ProbPrices[i] = UInt32((fabs(lnAll - log(double(i))) / ln2 + kDummyMultMid) * kBitPrice);
41 */
43 /*
44 // experimental, slow, solution:
45 for(UInt32 i = 1; i < (kBitModelTotal >> kNumMoveReducingBits) - 1; i++)
46 {
47 const int kCyclesBits = 5;
48 const UInt32 kCycles = (1 << kCyclesBits);
50 UInt32 range = UInt32(-1);
51 UInt32 bitCount = 0;
52 for (UInt32 j = 0; j < kCycles; j++)
53 {
54 range >>= (kNumBitModelTotalBits - kNumMoveReducingBits);
55 range *= i;
56 while(range < (1 << 31))
57 {
58 range <<= 1;
59 bitCount++;
60 }
61 }
62 bitCount <<= kNumBitPriceShiftBits;
63 range -= (1 << 31);
64 for (int k = kNumBitPriceShiftBits - 1; k >= 0; k--)
65 {
66 range <<= 1;
67 if (range > (1 << 31))
68 {
69 bitCount += (1 << k);
70 range -= (1 << 31);
71 }
72 }
73 ProbPrices[i] = (bitCount
74 // + (1 << (kCyclesBits - 1))
75 ) >> kCyclesBits;
76 }
77 */
78 }
80 }}
