[3320] | 1 | /*
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| 2 | * bzip2 is written by Julian Seward <jseward@bzip.org>.
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| 3 | * Adapted for busybox by Denys Vlasenko <vda.linux@googlemail.com>.
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| 4 | * See README and LICENSE files in this directory for more information.
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| 5 | */
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| 6 |
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| 7 | /*-------------------------------------------------------------*/
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| 8 | /*--- Huffman coding low-level stuff ---*/
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| 9 | /*--- huffman.c ---*/
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| 10 | /*-------------------------------------------------------------*/
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| 11 |
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| 12 | /* ------------------------------------------------------------------
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| 13 | This file is part of bzip2/libbzip2, a program and library for
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| 14 | lossless, block-sorting data compression.
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| 15 |
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| 16 | bzip2/libbzip2 version 1.0.4 of 20 December 2006
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| 17 | Copyright (C) 1996-2006 Julian Seward <jseward@bzip.org>
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| 18 |
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| 19 | Please read the WARNING, DISCLAIMER and PATENTS sections in the
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| 20 | README file.
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| 21 |
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| 22 | This program is released under the terms of the license contained
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| 23 | in the file LICENSE.
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| 24 | ------------------------------------------------------------------ */
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| 25 |
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| 26 | /* #include "bzlib_private.h" */
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| 27 |
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| 28 | /*---------------------------------------------------*/
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| 29 | #define WEIGHTOF(zz0) ((zz0) & 0xffffff00)
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| 30 | #define DEPTHOF(zz1) ((zz1) & 0x000000ff)
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| 31 | #define MYMAX(zz2,zz3) ((zz2) > (zz3) ? (zz2) : (zz3))
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| 32 |
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| 33 | #define ADDWEIGHTS(zw1,zw2) \
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| 34 | (WEIGHTOF(zw1)+WEIGHTOF(zw2)) | \
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| 35 | (1 + MYMAX(DEPTHOF(zw1),DEPTHOF(zw2)))
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| 36 |
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| 37 | #define UPHEAP(z) \
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| 38 | { \
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| 39 | int32_t zz, tmp; \
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| 40 | zz = z; \
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| 41 | tmp = heap[zz]; \
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| 42 | while (weight[tmp] < weight[heap[zz >> 1]]) { \
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| 43 | heap[zz] = heap[zz >> 1]; \
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| 44 | zz >>= 1; \
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| 45 | } \
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| 46 | heap[zz] = tmp; \
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| 47 | }
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| 48 |
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| 49 |
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| 50 | /* 90 bytes, 0.3% of overall compress speed */
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| 51 | #if CONFIG_BZIP2_FEATURE_SPEED >= 1
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| 52 |
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| 53 | /* macro works better than inline (gcc 4.2.1) */
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| 54 | #define DOWNHEAP1(heap, weight, Heap) \
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| 55 | { \
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| 56 | int32_t zz, yy, tmp; \
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| 57 | zz = 1; \
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| 58 | tmp = heap[zz]; \
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| 59 | while (1) { \
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| 60 | yy = zz << 1; \
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| 61 | if (yy > nHeap) \
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| 62 | break; \
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| 63 | if (yy < nHeap \
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| 64 | && weight[heap[yy+1]] < weight[heap[yy]]) \
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| 65 | yy++; \
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| 66 | if (weight[tmp] < weight[heap[yy]]) \
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| 67 | break; \
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| 68 | heap[zz] = heap[yy]; \
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| 69 | zz = yy; \
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| 70 | } \
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| 71 | heap[zz] = tmp; \
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| 72 | }
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| 73 |
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| 74 | #else
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| 75 |
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| 76 | static
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| 77 | void DOWNHEAP1(int32_t *heap, int32_t *weight, int32_t nHeap)
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| 78 | {
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| 79 | int32_t zz, yy, tmp;
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| 80 | zz = 1;
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| 81 | tmp = heap[zz];
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| 82 | while (1) {
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| 83 | yy = zz << 1;
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| 84 | if (yy > nHeap)
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| 85 | break;
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| 86 | if (yy < nHeap
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| 87 | && weight[heap[yy + 1]] < weight[heap[yy]])
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| 88 | yy++;
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| 89 | if (weight[tmp] < weight[heap[yy]])
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| 90 | break;
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| 91 | heap[zz] = heap[yy];
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| 92 | zz = yy;
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| 93 | }
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| 94 | heap[zz] = tmp;
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| 95 | }
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| 96 |
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| 97 | #endif
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| 98 |
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| 99 | /*---------------------------------------------------*/
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| 100 | static
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| 101 | void BZ2_hbMakeCodeLengths(EState *s,
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| 102 | uint8_t *len,
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| 103 | int32_t *freq,
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| 104 | int32_t alphaSize,
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| 105 | int32_t maxLen)
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| 106 | {
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| 107 | /*
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| 108 | * Nodes and heap entries run from 1. Entry 0
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| 109 | * for both the heap and nodes is a sentinel.
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| 110 | */
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| 111 | int32_t nNodes, nHeap, n1, n2, i, j, k;
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| 112 | Bool tooLong;
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| 113 |
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| 114 | /* bbox: moved to EState to save stack
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| 115 | int32_t heap [BZ_MAX_ALPHA_SIZE + 2];
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| 116 | int32_t weight[BZ_MAX_ALPHA_SIZE * 2];
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| 117 | int32_t parent[BZ_MAX_ALPHA_SIZE * 2];
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| 118 | */
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| 119 | #define heap (s->BZ2_hbMakeCodeLengths__heap)
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| 120 | #define weight (s->BZ2_hbMakeCodeLengths__weight)
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| 121 | #define parent (s->BZ2_hbMakeCodeLengths__parent)
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| 122 |
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| 123 | for (i = 0; i < alphaSize; i++)
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| 124 | weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8;
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| 125 |
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| 126 | while (1) {
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| 127 | nNodes = alphaSize;
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| 128 | nHeap = 0;
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| 129 |
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| 130 | heap[0] = 0;
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| 131 | weight[0] = 0;
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| 132 | parent[0] = -2;
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| 133 |
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| 134 | for (i = 1; i <= alphaSize; i++) {
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| 135 | parent[i] = -1;
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| 136 | nHeap++;
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| 137 | heap[nHeap] = i;
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| 138 | UPHEAP(nHeap);
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| 139 | }
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| 140 |
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| 141 | AssertH(nHeap < (BZ_MAX_ALPHA_SIZE+2), 2001);
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| 142 |
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| 143 | while (nHeap > 1) {
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| 144 | n1 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP1(heap, weight, nHeap);
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| 145 | n2 = heap[1]; heap[1] = heap[nHeap]; nHeap--; DOWNHEAP1(heap, weight, nHeap);
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| 146 | nNodes++;
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| 147 | parent[n1] = parent[n2] = nNodes;
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| 148 | weight[nNodes] = ADDWEIGHTS(weight[n1], weight[n2]);
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| 149 | parent[nNodes] = -1;
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| 150 | nHeap++;
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| 151 | heap[nHeap] = nNodes;
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| 152 | UPHEAP(nHeap);
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| 153 | }
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| 154 |
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| 155 | AssertH(nNodes < (BZ_MAX_ALPHA_SIZE * 2), 2002);
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| 156 |
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| 157 | tooLong = False;
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| 158 | for (i = 1; i <= alphaSize; i++) {
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| 159 | j = 0;
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| 160 | k = i;
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| 161 | while (parent[k] >= 0) {
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| 162 | k = parent[k];
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| 163 | j++;
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| 164 | }
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| 165 | len[i-1] = j;
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| 166 | if (j > maxLen)
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| 167 | tooLong = True;
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| 168 | }
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| 169 |
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| 170 | if (!tooLong)
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| 171 | break;
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| 172 |
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| 173 | /* 17 Oct 04: keep-going condition for the following loop used
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| 174 | to be 'i < alphaSize', which missed the last element,
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| 175 | theoretically leading to the possibility of the compressor
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| 176 | looping. However, this count-scaling step is only needed if
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| 177 | one of the generated Huffman code words is longer than
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| 178 | maxLen, which up to and including version 1.0.2 was 20 bits,
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| 179 | which is extremely unlikely. In version 1.0.3 maxLen was
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| 180 | changed to 17 bits, which has minimal effect on compression
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| 181 | ratio, but does mean this scaling step is used from time to
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| 182 | time, enough to verify that it works.
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| 183 |
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| 184 | This means that bzip2-1.0.3 and later will only produce
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| 185 | Huffman codes with a maximum length of 17 bits. However, in
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| 186 | order to preserve backwards compatibility with bitstreams
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| 187 | produced by versions pre-1.0.3, the decompressor must still
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| 188 | handle lengths of up to 20. */
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| 189 |
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| 190 | for (i = 1; i <= alphaSize; i++) {
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| 191 | j = weight[i] >> 8;
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| 192 | /* bbox: yes, it is a signed division.
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| 193 | * don't replace with shift! */
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| 194 | j = 1 + (j / 2);
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| 195 | weight[i] = j << 8;
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| 196 | }
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| 197 | }
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| 198 | #undef heap
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| 199 | #undef weight
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| 200 | #undef parent
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| 201 | }
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| 202 |
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| 203 |
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| 204 | /*---------------------------------------------------*/
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| 205 | static
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| 206 | void BZ2_hbAssignCodes(int32_t *code,
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| 207 | uint8_t *length,
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| 208 | int32_t minLen,
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| 209 | int32_t maxLen,
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| 210 | int32_t alphaSize)
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| 211 | {
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| 212 | int32_t n, vec, i;
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| 213 |
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| 214 | vec = 0;
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| 215 | for (n = minLen; n <= maxLen; n++) {
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| 216 | for (i = 0; i < alphaSize; i++) {
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| 217 | if (length[i] == n) {
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| 218 | code[i] = vec;
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| 219 | vec++;
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| 220 | };
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| 221 | }
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| 222 | vec <<= 1;
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| 223 | }
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| 224 | }
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| 225 |
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| 226 |
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| 227 | /*-------------------------------------------------------------*/
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| 228 | /*--- end huffman.c ---*/
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| 229 | /*-------------------------------------------------------------*/
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