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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