modules/libbz2/src/huffman.c@129ffea94266 (annotated)
modules/libbz2/src/huffman.c
Sat, 03 Jan 2015 20:18:00 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Sat, 03 Jan 2015 20:18:00 +0100
- branch
- TOR_BUG_3246
- changeset 7
- 129ffea94266
- permissions
- -rw-r--r--
Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.
| michael@0 | 1 | |
| michael@0 | 2 | /*-------------------------------------------------------------*/ |
| michael@0 | 3 | /*--- Huffman coding low-level stuff ---*/ |
| michael@0 | 4 | /*--- huffman.c ---*/ |
| michael@0 | 5 | /*-------------------------------------------------------------*/ |
| michael@0 | 6 | |
| michael@0 | 7 | /* ------------------------------------------------------------------ |
| michael@0 | 8 | This file is part of bzip2/libbzip2, a program and library for |
| michael@0 | 9 | lossless, block-sorting data compression. |
| michael@0 | 10 | |
| michael@0 | 11 | bzip2/libbzip2 version 1.0.4 of 20 December 2006 |
| michael@0 | 12 | Copyright (C) 1996-2006 Julian Seward <jseward@bzip.org> |
| michael@0 | 13 | |
| michael@0 | 14 | Please read the WARNING, DISCLAIMER and PATENTS sections in the |
| michael@0 | 15 | README file. |
| michael@0 | 16 | |
| michael@0 | 17 | This program is released under the terms of the license contained |
| michael@0 | 18 | in the file LICENSE. |
| michael@0 | 19 | ------------------------------------------------------------------ */ |
| michael@0 | 20 | |
| michael@0 | 21 | |
| michael@0 | 22 | #include "bzlib_private.h" |
| michael@0 | 23 | |
| michael@0 | 24 | /*---------------------------------------------------*/ |
| michael@0 | 25 | #define WEIGHTOF(zz0) ((zz0) & 0xffffff00) |
| michael@0 | 26 | #define DEPTHOF(zz1) ((zz1) & 0x000000ff) |
| michael@0 | 27 | #define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3)) |
| michael@0 | 28 | |
| michael@0 | 29 | #define ADDWEIGHTS(zw1,zw2) \ |
| michael@0 | 30 | (WEIGHTOF(zw1)+WEIGHTOF(zw2)) | \ |
| michael@0 | 31 | (1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2))) |
| michael@0 | 32 | |
| michael@0 | 33 | #define UPHEAP(z) \ |
| michael@0 | 34 | { \ |
| michael@0 | 35 | Int32 zz, tmp; \ |
| michael@0 | 36 | zz = z; tmp = heap[zz]; \ |
| michael@0 | 37 | while (weight[tmp] < weight[heap[zz >> 1]]) { \ |
| michael@0 | 38 | heap[zz] = heap[zz >> 1]; \ |
| michael@0 | 39 | zz >>= 1; \ |
| michael@0 | 40 | } \ |
| michael@0 | 41 | heap[zz] = tmp; \ |
| michael@0 | 42 | } |
| michael@0 | 43 | |
| michael@0 | 44 | #define DOWNHEAP(z) \ |
| michael@0 | 45 | { \ |
| michael@0 | 46 | Int32 zz, yy, tmp; \ |
| michael@0 | 47 | zz = z; tmp = heap[zz]; \ |
| michael@0 | 48 | while (True) { \ |
| michael@0 | 49 | yy = zz << 1; \ |
| michael@0 | 50 | if (yy > nHeap) break; \ |
| michael@0 | 51 | if (yy < nHeap && \ |
| michael@0 | 52 | weight[heap[yy+1]] < weight[heap[yy]]) \ |
| michael@0 | 53 | yy++; \ |
| michael@0 | 54 | if (weight[tmp] < weight[heap[yy]]) break; \ |
| michael@0 | 55 | heap[zz] = heap[yy]; \ |
| michael@0 | 56 | zz = yy; \ |
| michael@0 | 57 | } \ |
| michael@0 | 58 | heap[zz] = tmp; \ |
| michael@0 | 59 | } |
| michael@0 | 60 | |
| michael@0 | 61 | |
| michael@0 | 62 | /*---------------------------------------------------*/ |
| michael@0 | 63 | void BZ2_hbMakeCodeLengths ( UChar *len, |
| michael@0 | 64 | Int32 *freq, |
| michael@0 | 65 | Int32 alphaSize, |
| michael@0 | 66 | Int32 maxLen ) |
| michael@0 | 67 | { |
| michael@0 | 68 | /*-- |
| michael@0 | 69 | Nodes and heap entries run from 1. Entry 0 |
| michael@0 | 70 | for both the heap and nodes is a sentinel. |
| michael@0 | 71 | --*/ |
| michael@0 | 72 | Int32 nNodes, nHeap, n1, n2, i, j, k; |
| michael@0 | 73 | Bool tooLong; |
| michael@0 | 74 | |
| michael@0 | 75 | Int32 heap [ BZ_MAX_ALPHA_SIZE + 2 ]; |
| michael@0 | 76 | Int32 weight [ BZ_MAX_ALPHA_SIZE * 2 ]; |
| michael@0 | 77 | Int32 parent [ BZ_MAX_ALPHA_SIZE * 2 ]; |
| michael@0 | 78 | |
| michael@0 | 79 | for (i = 0; i < alphaSize; i++) |
| michael@0 | 80 | weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8; |
| michael@0 | 81 | |
| michael@0 | 82 | while (True) { |
| michael@0 | 83 | |
| michael@0 | 84 | nNodes = alphaSize; |
| michael@0 | 85 | nHeap = 0; |
| michael@0 | 86 | |
| michael@0 | 87 | heap[0] = 0; |
| michael@0 | 88 | weight[0] = 0; |
| michael@0 | 89 | parent[0] = -2; |
| michael@0 | 90 | |
| michael@0 | 91 | for (i = 1; i <= alphaSize; i++) { |
| michael@0 | 92 | parent[i] = -1; |
| michael@0 | 93 | nHeap++; |
| michael@0 | 94 | heap[nHeap] = i; |
| michael@0 | 95 | UPHEAP(nHeap); |
| michael@0 | 96 | } |
| michael@0 | 97 | |
| michael@0 | 98 | AssertH( nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001 ); |
| michael@0 | 99 | |
| michael@0 | 100 | while (nHeap > 1) { |
| michael@0 | 101 | n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); |
| michael@0 | 102 | n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP(1); |
| michael@0 | 103 | nNodes++; |
| michael@0 | 104 | parent[n1] = parent[n2] = nNodes; |
| michael@0 | 105 | weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]); |
| michael@0 | 106 | parent[nNodes] = -1; |
| michael@0 | 107 | nHeap++; |
| michael@0 | 108 | heap[nHeap] = nNodes; |
| michael@0 | 109 | UPHEAP(nHeap); |
| michael@0 | 110 | } |
| michael@0 | 111 | |
| michael@0 | 112 | AssertH( nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002 ); |
| michael@0 | 113 | |
| michael@0 | 114 | tooLong = False; |
| michael@0 | 115 | for (i = 1; i <= alphaSize; i++) { |
| michael@0 | 116 | j = 0; |
| michael@0 | 117 | k = i; |
| michael@0 | 118 | while (parent[k] >= 0) { k = parent[k]; j++; } |
| michael@0 | 119 | len[i-1] = j; |
| michael@0 | 120 | if (j > maxLen) tooLong = True; |
| michael@0 | 121 | } |
| michael@0 | 122 | |
| michael@0 | 123 | if (! tooLong) break; |
| michael@0 | 124 | |
| michael@0 | 125 | /* 17 Oct 04: keep-going condition for the following loop used |
| michael@0 | 126 | to be 'i < alphaSize', which missed the last element, |
| michael@0 | 127 | theoretically leading to the possibility of the compressor |
| michael@0 | 128 | looping. However, this count-scaling step is only needed if |
| michael@0 | 129 | one of the generated Huffman code words is longer than |
| michael@0 | 130 | maxLen, which up to and including version 1.0.2 was 20 bits, |
| michael@0 | 131 | which is extremely unlikely. In version 1.0.3 maxLen was |
| michael@0 | 132 | changed to 17 bits, which has minimal effect on compression |
| michael@0 | 133 | ratio, but does mean this scaling step is used from time to |
| michael@0 | 134 | time, enough to verify that it works. |
| michael@0 | 135 | |
| michael@0 | 136 | This means that bzip2-1.0.3 and later will only produce |
| michael@0 | 137 | Huffman codes with a maximum length of 17 bits. However, in |
| michael@0 | 138 | order to preserve backwards compatibility with bitstreams |
| michael@0 | 139 | produced by versions pre-1.0.3, the decompressor must still |
| michael@0 | 140 | handle lengths of up to 20. */ |
| michael@0 | 141 | |
| michael@0 | 142 | for (i = 1; i <= alphaSize; i++) { |
| michael@0 | 143 | j = weight[i] >> 8; |
| michael@0 | 144 | j = 1 + (j / 2); |
| michael@0 | 145 | weight[i] = j << 8; |
| michael@0 | 146 | } |
| michael@0 | 147 | } |
| michael@0 | 148 | } |
| michael@0 | 149 | |
| michael@0 | 150 | |
| michael@0 | 151 | /*---------------------------------------------------*/ |
| michael@0 | 152 | void BZ2_hbAssignCodes ( Int32 *code, |
| michael@0 | 153 | UChar *length, |
| michael@0 | 154 | Int32 minLen, |
| michael@0 | 155 | Int32 maxLen, |
| michael@0 | 156 | Int32 alphaSize ) |
| michael@0 | 157 | { |
| michael@0 | 158 | Int32 n, vec, i; |
| michael@0 | 159 | |
| michael@0 | 160 | vec = 0; |
| michael@0 | 161 | for (n = minLen; n <= maxLen; n++) { |
| michael@0 | 162 | for (i = 0; i < alphaSize; i++) |
| michael@0 | 163 | if (length[i] == n) { code[i] = vec; vec++; }; |
| michael@0 | 164 | vec <<= 1; |
| michael@0 | 165 | } |
| michael@0 | 166 | } |
| michael@0 | 167 | |
| michael@0 | 168 | |
| michael@0 | 169 | /*---------------------------------------------------*/ |
| michael@0 | 170 | void BZ2_hbCreateDecodeTables ( Int32 *limit, |
| michael@0 | 171 | Int32 *base, |
| michael@0 | 172 | Int32 *perm, |
| michael@0 | 173 | UChar *length, |
| michael@0 | 174 | Int32 minLen, |
| michael@0 | 175 | Int32 maxLen, |
| michael@0 | 176 | Int32 alphaSize ) |
| michael@0 | 177 | { |
| michael@0 | 178 | Int32 pp, i, j, vec; |
| michael@0 | 179 | |
| michael@0 | 180 | pp = 0; |
| michael@0 | 181 | for (i = minLen; i <= maxLen; i++) |
| michael@0 | 182 | for (j = 0; j < alphaSize; j++) |
| michael@0 | 183 | if (length[j] == i) { perm[pp] = j; pp++; }; |
| michael@0 | 184 | |
| michael@0 | 185 | for (i = 0; i < BZ_MAX_CODE_LEN; i++) base[i] = 0; |
| michael@0 | 186 | for (i = 0; i < alphaSize; i++) base[length[i]+1]++; |
| michael@0 | 187 | |
| michael@0 | 188 | for (i = 1; i < BZ_MAX_CODE_LEN; i++) base[i] += base[i-1]; |
| michael@0 | 189 | |
| michael@0 | 190 | for (i = 0; i < BZ_MAX_CODE_LEN; i++) limit[i] = 0; |
| michael@0 | 191 | vec = 0; |
| michael@0 | 192 | |
| michael@0 | 193 | for (i = minLen; i <= maxLen; i++) { |
| michael@0 | 194 | vec += (base[i+1] - base[i]); |
| michael@0 | 195 | limit[i] = vec-1; |
| michael@0 | 196 | vec <<= 1; |
| michael@0 | 197 | } |
| michael@0 | 198 | for (i = minLen + 1; i <= maxLen; i++) |
| michael@0 | 199 | base[i] = ((limit[i-1] + 1) << 1) - base[i]; |
| michael@0 | 200 | } |
| michael@0 | 201 | |
| michael@0 | 202 | |
| michael@0 | 203 | /*-------------------------------------------------------------*/ |
| michael@0 | 204 | /*--- end huffman.c ---*/ |
| michael@0 | 205 | /*-------------------------------------------------------------*/ |
