1 | /* |
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2 | * puff.c |
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3 | * Copyright (C) 2002-2010 Mark Adler |
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4 | * For conditions of distribution and use, see copyright notice in puff.h |
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5 | * version 2.1, 4 Apr 2010 |
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6 | * |
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7 | * puff.c is a simple inflate written to be an unambiguous way to specify the |
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8 | * deflate format. It is not written for speed but rather simplicity. As a |
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9 | * side benefit, this code might actually be useful when small code is more |
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10 | * important than speed, such as bootstrap applications. For typical deflate |
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11 | * data, zlib's inflate() is about four times as fast as puff(). zlib's |
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12 | * inflate compiles to around 20K on my machine, whereas puff.c compiles to |
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13 | * around 4K on my machine (a PowerPC using GNU cc). If the faster decode() |
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14 | * function here is used, then puff() is only twice as slow as zlib's |
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15 | * inflate(). |
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16 | * |
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17 | * All dynamically allocated memory comes from the stack. The stack required |
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18 | * is less than 2K bytes. This code is compatible with 16-bit int's and |
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19 | * assumes that long's are at least 32 bits. puff.c uses the short data type, |
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20 | * assumed to be 16 bits, for arrays in order to to conserve memory. The code |
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21 | * works whether integers are stored big endian or little endian. |
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22 | * |
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23 | * In the comments below are "Format notes" that describe the inflate process |
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24 | * and document some of the less obvious aspects of the format. This source |
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25 | * code is meant to supplement RFC 1951, which formally describes the deflate |
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26 | * format: |
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27 | * |
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28 | * http://www.zlib.org/rfc-deflate.html |
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29 | */ |
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30 | |
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31 | /* |
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32 | * Change history: |
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33 | * |
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34 | * 1.0 10 Feb 2002 - First version |
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35 | * 1.1 17 Feb 2002 - Clarifications of some comments and notes |
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36 | * - Update puff() dest and source pointers on negative |
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37 | * errors to facilitate debugging deflators |
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38 | * - Remove longest from struct huffman -- not needed |
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39 | * - Simplify offs[] index in construct() |
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40 | * - Add input size and checking, using longjmp() to |
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41 | * maintain easy readability |
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42 | * - Use short data type for large arrays |
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43 | * - Use pointers instead of long to specify source and |
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44 | * destination sizes to avoid arbitrary 4 GB limits |
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45 | * 1.2 17 Mar 2002 - Add faster version of decode(), doubles speed (!), |
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46 | * but leave simple version for readabilty |
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47 | * - Make sure invalid distances detected if pointers |
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48 | * are 16 bits |
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49 | * - Fix fixed codes table error |
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50 | * - Provide a scanning mode for determining size of |
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51 | * uncompressed data |
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52 | * 1.3 20 Mar 2002 - Go back to lengths for puff() parameters [Jean-loup] |
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53 | * - Add a puff.h file for the interface |
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54 | * - Add braces in puff() for else do [Jean-loup] |
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55 | * - Use indexes instead of pointers for readability |
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56 | * 1.4 31 Mar 2002 - Simplify construct() code set check |
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57 | * - Fix some comments |
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58 | * - Add FIXLCODES #define |
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59 | * 1.5 6 Apr 2002 - Minor comment fixes |
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60 | * 1.6 7 Aug 2002 - Minor format changes |
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61 | * 1.7 3 Mar 2003 - Added test code for distribution |
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62 | * - Added zlib-like license |
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63 | * 1.8 9 Jan 2004 - Added some comments on no distance codes case |
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64 | * 1.9 21 Feb 2008 - Fix bug on 16-bit integer architectures [Pohland] |
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65 | * - Catch missing end-of-block symbol error |
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66 | * 2.0 25 Jul 2008 - Add #define to permit distance too far back |
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67 | * - Add option in TEST code for puff to write the data |
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68 | * - Add option in TEST code to skip input bytes |
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69 | * - Allow TEST code to read from piped stdin |
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70 | * 2.1 4 Apr 2010 - Avoid variable initialization for happier compilers |
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71 | * - Avoid unsigned comparisons for even happier compilers |
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72 | */ |
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73 | |
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74 | #include <setjmp.h> /* for setjmp(), longjmp(), and jmp_buf */ |
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75 | #include "puff.h" /* prototype for puff() */ |
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76 | |
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77 | #define local static /* for local function definitions */ |
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78 | #define NIL ((unsigned char *)0) /* for no output option */ |
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79 | |
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80 | /* |
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81 | * Maximums for allocations and loops. It is not useful to change these -- |
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82 | * they are fixed by the deflate format. |
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83 | */ |
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84 | #define MAXBITS 15 /* maximum bits in a code */ |
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85 | #define MAXLCODES 286 /* maximum number of literal/length codes */ |
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86 | #define MAXDCODES 30 /* maximum number of distance codes */ |
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87 | #define MAXCODES (MAXLCODES+MAXDCODES) /* maximum codes lengths to read */ |
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88 | #define FIXLCODES 288 /* number of fixed literal/length codes */ |
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89 | |
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90 | /* input and output state */ |
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91 | struct state { |
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92 | /* output state */ |
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93 | unsigned char *out; /* output buffer */ |
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94 | unsigned long outlen; /* available space at out */ |
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95 | unsigned long outcnt; /* bytes written to out so far */ |
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96 | |
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97 | /* input state */ |
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98 | unsigned char *in; /* input buffer */ |
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99 | unsigned long inlen; /* available input at in */ |
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100 | unsigned long incnt; /* bytes read so far */ |
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101 | int bitbuf; /* bit buffer */ |
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102 | int bitcnt; /* number of bits in bit buffer */ |
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103 | |
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104 | /* input limit error return state for bits() and decode() */ |
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105 | jmp_buf env; |
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106 | }; |
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107 | |
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108 | /* |
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109 | * Return need bits from the input stream. This always leaves less than |
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110 | * eight bits in the buffer. bits() works properly for need == 0. |
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111 | * |
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112 | * Format notes: |
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113 | * |
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114 | * - Bits are stored in bytes from the least significant bit to the most |
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115 | * significant bit. Therefore bits are dropped from the bottom of the bit |
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116 | * buffer, using shift right, and new bytes are appended to the top of the |
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117 | * bit buffer, using shift left. |
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118 | */ |
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119 | local int bits(struct state *s, int need) |
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120 | { |
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121 | long val; /* bit accumulator (can use up to 20 bits) */ |
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122 | |
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123 | /* load at least need bits into val */ |
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124 | val = s->bitbuf; |
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125 | while (s->bitcnt < need) { |
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126 | if (s->incnt == s->inlen) longjmp(s->env, 1); /* out of input */ |
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127 | val |= (long)(s->in[s->incnt++]) << s->bitcnt; /* load eight bits */ |
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128 | s->bitcnt += 8; |
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129 | } |
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130 | |
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131 | /* drop need bits and update buffer, always zero to seven bits left */ |
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132 | s->bitbuf = (int)(val >> need); |
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133 | s->bitcnt -= need; |
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134 | |
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135 | /* return need bits, zeroing the bits above that */ |
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136 | return (int)(val & ((1L << need) - 1)); |
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137 | } |
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138 | |
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139 | /* |
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140 | * Process a stored block. |
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141 | * |
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142 | * Format notes: |
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143 | * |
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144 | * - After the two-bit stored block type (00), the stored block length and |
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145 | * stored bytes are byte-aligned for fast copying. Therefore any leftover |
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146 | * bits in the byte that has the last bit of the type, as many as seven, are |
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147 | * discarded. The value of the discarded bits are not defined and should not |
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148 | * be checked against any expectation. |
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149 | * |
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150 | * - The second inverted copy of the stored block length does not have to be |
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151 | * checked, but it's probably a good idea to do so anyway. |
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152 | * |
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153 | * - A stored block can have zero length. This is sometimes used to byte-align |
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154 | * subsets of the compressed data for random access or partial recovery. |
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155 | */ |
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156 | local int stored(struct state *s) |
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157 | { |
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158 | unsigned len; /* length of stored block */ |
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159 | |
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160 | /* discard leftover bits from current byte (assumes s->bitcnt < 8) */ |
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161 | s->bitbuf = 0; |
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162 | s->bitcnt = 0; |
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163 | |
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164 | /* get length and check against its one's complement */ |
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165 | if (s->incnt + 4 > s->inlen) return 2; /* not enough input */ |
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166 | len = s->in[s->incnt++]; |
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167 | len |= s->in[s->incnt++] << 8; |
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168 | if (s->in[s->incnt++] != (~len & 0xff) || |
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169 | s->in[s->incnt++] != ((~len >> 8) & 0xff)) |
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170 | return -2; /* didn't match complement! */ |
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171 | |
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172 | /* copy len bytes from in to out */ |
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173 | if (s->incnt + len > s->inlen) return 2; /* not enough input */ |
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174 | if (s->out != NIL) { |
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175 | if (s->outcnt + len > s->outlen) |
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176 | return 1; /* not enough output space */ |
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177 | while (len--) |
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178 | s->out[s->outcnt++] = s->in[s->incnt++]; |
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179 | } |
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180 | else { /* just scanning */ |
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181 | s->outcnt += len; |
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182 | s->incnt += len; |
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183 | } |
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184 | |
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185 | /* done with a valid stored block */ |
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186 | return 0; |
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187 | } |
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188 | |
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189 | /* |
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190 | * Huffman code decoding tables. count[1..MAXBITS] is the number of symbols of |
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191 | * each length, which for a canonical code are stepped through in order. |
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192 | * symbol[] are the symbol values in canonical order, where the number of |
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193 | * entries is the sum of the counts in count[]. The decoding process can be |
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194 | * seen in the function decode() below. |
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195 | */ |
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196 | struct huffman { |
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197 | short *count; /* number of symbols of each length */ |
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198 | short *symbol; /* canonically ordered symbols */ |
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199 | }; |
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200 | |
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201 | /* |
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202 | * Decode a code from the stream s using huffman table h. Return the symbol or |
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203 | * a negative value if there is an error. If all of the lengths are zero, i.e. |
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204 | * an empty code, or if the code is incomplete and an invalid code is received, |
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205 | * then -10 is returned after reading MAXBITS bits. |
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206 | * |
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207 | * Format notes: |
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208 | * |
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209 | * - The codes as stored in the compressed data are bit-reversed relative to |
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210 | * a simple integer ordering of codes of the same lengths. Hence below the |
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211 | * bits are pulled from the compressed data one at a time and used to |
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212 | * build the code value reversed from what is in the stream in order to |
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213 | * permit simple integer comparisons for decoding. A table-based decoding |
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214 | * scheme (as used in zlib) does not need to do this reversal. |
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215 | * |
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216 | * - The first code for the shortest length is all zeros. Subsequent codes of |
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217 | * the same length are simply integer increments of the previous code. When |
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218 | * moving up a length, a zero bit is appended to the code. For a complete |
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219 | * code, the last code of the longest length will be all ones. |
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220 | * |
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221 | * - Incomplete codes are handled by this decoder, since they are permitted |
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222 | * in the deflate format. See the format notes for fixed() and dynamic(). |
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223 | */ |
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224 | #ifdef SLOW |
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225 | local int decode(struct state *s, struct huffman *h) |
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226 | { |
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227 | int len; /* current number of bits in code */ |
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228 | int code; /* len bits being decoded */ |
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229 | int first; /* first code of length len */ |
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230 | int count; /* number of codes of length len */ |
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231 | int index; /* index of first code of length len in symbol table */ |
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232 | |
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233 | code = first = index = 0; |
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234 | for (len = 1; len <= MAXBITS; len++) { |
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235 | code |= bits(s, 1); /* get next bit */ |
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236 | count = h->count[len]; |
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237 | if (code - count < first) /* if length len, return symbol */ |
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238 | return h->symbol[index + (code - first)]; |
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239 | index += count; /* else update for next length */ |
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240 | first += count; |
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241 | first <<= 1; |
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242 | code <<= 1; |
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243 | } |
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244 | return -10; /* ran out of codes */ |
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245 | } |
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246 | |
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247 | /* |
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248 | * A faster version of decode() for real applications of this code. It's not |
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249 | * as readable, but it makes puff() twice as fast. And it only makes the code |
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250 | * a few percent larger. |
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251 | */ |
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252 | #else /* !SLOW */ |
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253 | local int decode(struct state *s, struct huffman *h) |
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254 | { |
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255 | int len; /* current number of bits in code */ |
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256 | int code; /* len bits being decoded */ |
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257 | int first; /* first code of length len */ |
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258 | int count; /* number of codes of length len */ |
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259 | int index; /* index of first code of length len in symbol table */ |
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260 | int bitbuf; /* bits from stream */ |
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261 | int left; /* bits left in next or left to process */ |
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262 | short *next; /* next number of codes */ |
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263 | |
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264 | bitbuf = s->bitbuf; |
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265 | left = s->bitcnt; |
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266 | code = first = index = 0; |
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267 | len = 1; |
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268 | next = h->count + 1; |
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269 | while (1) { |
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270 | while (left--) { |
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271 | code |= bitbuf & 1; |
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272 | bitbuf >>= 1; |
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273 | count = *next++; |
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274 | if (code - count < first) { /* if length len, return symbol */ |
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275 | s->bitbuf = bitbuf; |
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276 | s->bitcnt = (s->bitcnt - len) & 7; |
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277 | return h->symbol[index + (code - first)]; |
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278 | } |
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279 | index += count; /* else update for next length */ |
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280 | first += count; |
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281 | first <<= 1; |
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282 | code <<= 1; |
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283 | len++; |
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284 | } |
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285 | left = (MAXBITS+1) - len; |
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286 | if (left == 0) break; |
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287 | if (s->incnt == s->inlen) longjmp(s->env, 1); /* out of input */ |
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288 | bitbuf = s->in[s->incnt++]; |
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289 | if (left > 8) left = 8; |
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290 | } |
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291 | return -10; /* ran out of codes */ |
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292 | } |
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293 | #endif /* SLOW */ |
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294 | |
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295 | /* |
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296 | * Given the list of code lengths length[0..n-1] representing a canonical |
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297 | * Huffman code for n symbols, construct the tables required to decode those |
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298 | * codes. Those tables are the number of codes of each length, and the symbols |
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299 | * sorted by length, retaining their original order within each length. The |
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300 | * return value is zero for a complete code set, negative for an over- |
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301 | * subscribed code set, and positive for an incomplete code set. The tables |
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302 | * can be used if the return value is zero or positive, but they cannot be used |
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303 | * if the return value is negative. If the return value is zero, it is not |
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304 | * possible for decode() using that table to return an error--any stream of |
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305 | * enough bits will resolve to a symbol. If the return value is positive, then |
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306 | * it is possible for decode() using that table to return an error for received |
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307 | * codes past the end of the incomplete lengths. |
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308 | * |
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309 | * Not used by decode(), but used for error checking, h->count[0] is the number |
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310 | * of the n symbols not in the code. So n - h->count[0] is the number of |
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311 | * codes. This is useful for checking for incomplete codes that have more than |
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312 | * one symbol, which is an error in a dynamic block. |
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313 | * |
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314 | * Assumption: for all i in 0..n-1, 0 <= length[i] <= MAXBITS |
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315 | * This is assured by the construction of the length arrays in dynamic() and |
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316 | * fixed() and is not verified by construct(). |
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317 | * |
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318 | * Format notes: |
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319 | * |
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320 | * - Permitted and expected examples of incomplete codes are one of the fixed |
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321 | * codes and any code with a single symbol which in deflate is coded as one |
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322 | * bit instead of zero bits. See the format notes for fixed() and dynamic(). |
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323 | * |
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324 | * - Within a given code length, the symbols are kept in ascending order for |
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325 | * the code bits definition. |
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326 | */ |
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327 | local int construct(struct huffman *h, short *length, int n) |
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328 | { |
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329 | int symbol; /* current symbol when stepping through length[] */ |
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330 | int len; /* current length when stepping through h->count[] */ |
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331 | int left; /* number of possible codes left of current length */ |
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332 | short offs[MAXBITS+1]; /* offsets in symbol table for each length */ |
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333 | |
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334 | /* count number of codes of each length */ |
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335 | for (len = 0; len <= MAXBITS; len++) |
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336 | h->count[len] = 0; |
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337 | for (symbol = 0; symbol < n; symbol++) |
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338 | (h->count[length[symbol]])++; /* assumes lengths are within bounds */ |
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339 | if (h->count[0] == n) /* no codes! */ |
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340 | return 0; /* complete, but decode() will fail */ |
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341 | |
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342 | /* check for an over-subscribed or incomplete set of lengths */ |
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343 | left = 1; /* one possible code of zero length */ |
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344 | for (len = 1; len <= MAXBITS; len++) { |
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345 | left <<= 1; /* one more bit, double codes left */ |
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346 | left -= h->count[len]; /* deduct count from possible codes */ |
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347 | if (left < 0) return left; /* over-subscribed--return negative */ |
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348 | } /* left > 0 means incomplete */ |
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349 | |
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350 | /* generate offsets into symbol table for each length for sorting */ |
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351 | offs[1] = 0; |
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352 | for (len = 1; len < MAXBITS; len++) |
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353 | offs[len + 1] = offs[len] + h->count[len]; |
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354 | |
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355 | /* |
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356 | * put symbols in table sorted by length, by symbol order within each |
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357 | * length |
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358 | */ |
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359 | for (symbol = 0; symbol < n; symbol++) |
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360 | if (length[symbol] != 0) |
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361 | h->symbol[offs[length[symbol]]++] = symbol; |
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362 | |
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363 | /* return zero for complete set, positive for incomplete set */ |
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364 | return left; |
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365 | } |
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366 | |
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367 | /* |
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368 | * Decode literal/length and distance codes until an end-of-block code. |
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369 | * |
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370 | * Format notes: |
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371 | * |
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372 | * - Compressed data that is after the block type if fixed or after the code |
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373 | * description if dynamic is a combination of literals and length/distance |
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374 | * pairs terminated by and end-of-block code. Literals are simply Huffman |
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375 | * coded bytes. A length/distance pair is a coded length followed by a |
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376 | * coded distance to represent a string that occurs earlier in the |
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377 | * uncompressed data that occurs again at the current location. |
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378 | * |
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379 | * - Literals, lengths, and the end-of-block code are combined into a single |
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380 | * code of up to 286 symbols. They are 256 literals (0..255), 29 length |
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381 | * symbols (257..285), and the end-of-block symbol (256). |
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382 | * |
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383 | * - There are 256 possible lengths (3..258), and so 29 symbols are not enough |
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384 | * to represent all of those. Lengths 3..10 and 258 are in fact represented |
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385 | * by just a length symbol. Lengths 11..257 are represented as a symbol and |
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386 | * some number of extra bits that are added as an integer to the base length |
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387 | * of the length symbol. The number of extra bits is determined by the base |
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388 | * length symbol. These are in the static arrays below, lens[] for the base |
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389 | * lengths and lext[] for the corresponding number of extra bits. |
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390 | * |
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391 | * - The reason that 258 gets its own symbol is that the longest length is used |
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392 | * often in highly redundant files. Note that 258 can also be coded as the |
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393 | * base value 227 plus the maximum extra value of 31. While a good deflate |
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394 | * should never do this, it is not an error, and should be decoded properly. |
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395 | * |
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396 | * - If a length is decoded, including its extra bits if any, then it is |
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397 | * followed a distance code. There are up to 30 distance symbols. Again |
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398 | * there are many more possible distances (1..32768), so extra bits are added |
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399 | * to a base value represented by the symbol. The distances 1..4 get their |
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400 | * own symbol, but the rest require extra bits. The base distances and |
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401 | * corresponding number of extra bits are below in the static arrays dist[] |
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402 | * and dext[]. |
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403 | * |
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404 | * - Literal bytes are simply written to the output. A length/distance pair is |
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405 | * an instruction to copy previously uncompressed bytes to the output. The |
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406 | * copy is from distance bytes back in the output stream, copying for length |
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407 | * bytes. |
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408 | * |
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409 | * - Distances pointing before the beginning of the output data are not |
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410 | * permitted. |
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411 | * |
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412 | * - Overlapped copies, where the length is greater than the distance, are |
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413 | * allowed and common. For example, a distance of one and a length of 258 |
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414 | * simply copies the last byte 258 times. A distance of four and a length of |
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415 | * twelve copies the last four bytes three times. A simple forward copy |
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416 | * ignoring whether the length is greater than the distance or not implements |
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417 | * this correctly. You should not use memcpy() since its behavior is not |
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418 | * defined for overlapped arrays. You should not use memmove() or bcopy() |
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419 | * since though their behavior -is- defined for overlapping arrays, it is |
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420 | * defined to do the wrong thing in this case. |
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421 | */ |
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422 | local int codes(struct state *s, |
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423 | struct huffman *lencode, |
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424 | struct huffman *distcode) |
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425 | { |
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426 | int symbol; /* decoded symbol */ |
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427 | int len; /* length for copy */ |
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428 | unsigned dist; /* distance for copy */ |
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429 | static const short lens[29] = { /* Size base for length codes 257..285 */ |
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430 | 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, |
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431 | 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258}; |
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432 | static const short lext[29] = { /* Extra bits for length codes 257..285 */ |
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433 | 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, |
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434 | 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0}; |
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435 | static const short dists[30] = { /* Offset base for distance codes 0..29 */ |
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436 | 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, |
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437 | 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, |
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438 | 8193, 12289, 16385, 24577}; |
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439 | static const short dext[30] = { /* Extra bits for distance codes 0..29 */ |
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440 | 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, |
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441 | 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, |
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442 | 12, 12, 13, 13}; |
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443 | |
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444 | /* decode literals and length/distance pairs */ |
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445 | do { |
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446 | symbol = decode(s, lencode); |
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447 | if (symbol < 0) return symbol; /* invalid symbol */ |
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448 | if (symbol < 256) { /* literal: symbol is the byte */ |
---|
449 | /* write out the literal */ |
---|
450 | if (s->out != NIL) { |
---|
451 | if (s->outcnt == s->outlen) return 1; |
---|
452 | s->out[s->outcnt] = symbol; |
---|
453 | } |
---|
454 | s->outcnt++; |
---|
455 | } |
---|
456 | else if (symbol > 256) { /* length */ |
---|
457 | /* get and compute length */ |
---|
458 | symbol -= 257; |
---|
459 | if (symbol >= 29) return -10; /* invalid fixed code */ |
---|
460 | len = lens[symbol] + bits(s, lext[symbol]); |
---|
461 | |
---|
462 | /* get and check distance */ |
---|
463 | symbol = decode(s, distcode); |
---|
464 | if (symbol < 0) return symbol; /* invalid symbol */ |
---|
465 | dist = dists[symbol] + bits(s, dext[symbol]); |
---|
466 | #ifndef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR |
---|
467 | if (dist > s->outcnt) |
---|
468 | return -11; /* distance too far back */ |
---|
469 | #endif |
---|
470 | |
---|
471 | /* copy length bytes from distance bytes back */ |
---|
472 | if (s->out != NIL) { |
---|
473 | if (s->outcnt + len > s->outlen) return 1; |
---|
474 | while (len--) { |
---|
475 | s->out[s->outcnt] = |
---|
476 | #ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR |
---|
477 | dist > s->outcnt ? 0 : |
---|
478 | #endif |
---|
479 | s->out[s->outcnt - dist]; |
---|
480 | s->outcnt++; |
---|
481 | } |
---|
482 | } |
---|
483 | else |
---|
484 | s->outcnt += len; |
---|
485 | } |
---|
486 | } while (symbol != 256); /* end of block symbol */ |
---|
487 | |
---|
488 | /* done with a valid fixed or dynamic block */ |
---|
489 | return 0; |
---|
490 | } |
---|
491 | |
---|
492 | /* |
---|
493 | * Process a fixed codes block. |
---|
494 | * |
---|
495 | * Format notes: |
---|
496 | * |
---|
497 | * - This block type can be useful for compressing small amounts of data for |
---|
498 | * which the size of the code descriptions in a dynamic block exceeds the |
---|
499 | * benefit of custom codes for that block. For fixed codes, no bits are |
---|
500 | * spent on code descriptions. Instead the code lengths for literal/length |
---|
501 | * codes and distance codes are fixed. The specific lengths for each symbol |
---|
502 | * can be seen in the "for" loops below. |
---|
503 | * |
---|
504 | * - The literal/length code is complete, but has two symbols that are invalid |
---|
505 | * and should result in an error if received. This cannot be implemented |
---|
506 | * simply as an incomplete code since those two symbols are in the "middle" |
---|
507 | * of the code. They are eight bits long and the longest literal/length\ |
---|
508 | * code is nine bits. Therefore the code must be constructed with those |
---|
509 | * symbols, and the invalid symbols must be detected after decoding. |
---|
510 | * |
---|
511 | * - The fixed distance codes also have two invalid symbols that should result |
---|
512 | * in an error if received. Since all of the distance codes are the same |
---|
513 | * length, this can be implemented as an incomplete code. Then the invalid |
---|
514 | * codes are detected while decoding. |
---|
515 | */ |
---|
516 | local int fixed(struct state *s) |
---|
517 | { |
---|
518 | static int virgin = 1; |
---|
519 | static short lencnt[MAXBITS+1], lensym[FIXLCODES]; |
---|
520 | static short distcnt[MAXBITS+1], distsym[MAXDCODES]; |
---|
521 | static struct huffman lencode, distcode; |
---|
522 | |
---|
523 | /* build fixed huffman tables if first call (may not be thread safe) */ |
---|
524 | if (virgin) { |
---|
525 | int symbol; |
---|
526 | short lengths[FIXLCODES]; |
---|
527 | |
---|
528 | /* literal/length table */ |
---|
529 | for (symbol = 0; symbol < 144; symbol++) |
---|
530 | lengths[symbol] = 8; |
---|
531 | for (; symbol < 256; symbol++) |
---|
532 | lengths[symbol] = 9; |
---|
533 | for (; symbol < 280; symbol++) |
---|
534 | lengths[symbol] = 7; |
---|
535 | for (; symbol < FIXLCODES; symbol++) |
---|
536 | lengths[symbol] = 8; |
---|
537 | construct(&lencode, lengths, FIXLCODES); |
---|
538 | |
---|
539 | /* distance table */ |
---|
540 | for (symbol = 0; symbol < MAXDCODES; symbol++) |
---|
541 | lengths[symbol] = 5; |
---|
542 | construct(&distcode, lengths, MAXDCODES); |
---|
543 | |
---|
544 | /* construct lencode and distcode */ |
---|
545 | lencode.count = lencnt; |
---|
546 | lencode.symbol = lensym; |
---|
547 | distcode.count = distcnt; |
---|
548 | distcode.symbol = distsym; |
---|
549 | |
---|
550 | /* do this just once */ |
---|
551 | virgin = 0; |
---|
552 | } |
---|
553 | |
---|
554 | /* decode data until end-of-block code */ |
---|
555 | return codes(s, &lencode, &distcode); |
---|
556 | } |
---|
557 | |
---|
558 | /* |
---|
559 | * Process a dynamic codes block. |
---|
560 | * |
---|
561 | * Format notes: |
---|
562 | * |
---|
563 | * - A dynamic block starts with a description of the literal/length and |
---|
564 | * distance codes for that block. New dynamic blocks allow the compressor to |
---|
565 | * rapidly adapt to changing data with new codes optimized for that data. |
---|
566 | * |
---|
567 | * - The codes used by the deflate format are "canonical", which means that |
---|
568 | * the actual bits of the codes are generated in an unambiguous way simply |
---|
569 | * from the number of bits in each code. Therefore the code descriptions |
---|
570 | * are simply a list of code lengths for each symbol. |
---|
571 | * |
---|
572 | * - The code lengths are stored in order for the symbols, so lengths are |
---|
573 | * provided for each of the literal/length symbols, and for each of the |
---|
574 | * distance symbols. |
---|
575 | * |
---|
576 | * - If a symbol is not used in the block, this is represented by a zero as |
---|
577 | * as the code length. This does not mean a zero-length code, but rather |
---|
578 | * that no code should be created for this symbol. There is no way in the |
---|
579 | * deflate format to represent a zero-length code. |
---|
580 | * |
---|
581 | * - The maximum number of bits in a code is 15, so the possible lengths for |
---|
582 | * any code are 1..15. |
---|
583 | * |
---|
584 | * - The fact that a length of zero is not permitted for a code has an |
---|
585 | * interesting consequence. Normally if only one symbol is used for a given |
---|
586 | * code, then in fact that code could be represented with zero bits. However |
---|
587 | * in deflate, that code has to be at least one bit. So for example, if |
---|
588 | * only a single distance base symbol appears in a block, then it will be |
---|
589 | * represented by a single code of length one, in particular one 0 bit. This |
---|
590 | * is an incomplete code, since if a 1 bit is received, it has no meaning, |
---|
591 | * and should result in an error. So incomplete distance codes of one symbol |
---|
592 | * should be permitted, and the receipt of invalid codes should be handled. |
---|
593 | * |
---|
594 | * - It is also possible to have a single literal/length code, but that code |
---|
595 | * must be the end-of-block code, since every dynamic block has one. This |
---|
596 | * is not the most efficient way to create an empty block (an empty fixed |
---|
597 | * block is fewer bits), but it is allowed by the format. So incomplete |
---|
598 | * literal/length codes of one symbol should also be permitted. |
---|
599 | * |
---|
600 | * - If there are only literal codes and no lengths, then there are no distance |
---|
601 | * codes. This is represented by one distance code with zero bits. |
---|
602 | * |
---|
603 | * - The list of up to 286 length/literal lengths and up to 30 distance lengths |
---|
604 | * are themselves compressed using Huffman codes and run-length encoding. In |
---|
605 | * the list of code lengths, a 0 symbol means no code, a 1..15 symbol means |
---|
606 | * that length, and the symbols 16, 17, and 18 are run-length instructions. |
---|
607 | * Each of 16, 17, and 18 are follwed by extra bits to define the length of |
---|
608 | * the run. 16 copies the last length 3 to 6 times. 17 represents 3 to 10 |
---|
609 | * zero lengths, and 18 represents 11 to 138 zero lengths. Unused symbols |
---|
610 | * are common, hence the special coding for zero lengths. |
---|
611 | * |
---|
612 | * - The symbols for 0..18 are Huffman coded, and so that code must be |
---|
613 | * described first. This is simply a sequence of up to 19 three-bit values |
---|
614 | * representing no code (0) or the code length for that symbol (1..7). |
---|
615 | * |
---|
616 | * - A dynamic block starts with three fixed-size counts from which is computed |
---|
617 | * the number of literal/length code lengths, the number of distance code |
---|
618 | * lengths, and the number of code length code lengths (ok, you come up with |
---|
619 | * a better name!) in the code descriptions. For the literal/length and |
---|
620 | * distance codes, lengths after those provided are considered zero, i.e. no |
---|
621 | * code. The code length code lengths are received in a permuted order (see |
---|
622 | * the order[] array below) to make a short code length code length list more |
---|
623 | * likely. As it turns out, very short and very long codes are less likely |
---|
624 | * to be seen in a dynamic code description, hence what may appear initially |
---|
625 | * to be a peculiar ordering. |
---|
626 | * |
---|
627 | * - Given the number of literal/length code lengths (nlen) and distance code |
---|
628 | * lengths (ndist), then they are treated as one long list of nlen + ndist |
---|
629 | * code lengths. Therefore run-length coding can and often does cross the |
---|
630 | * boundary between the two sets of lengths. |
---|
631 | * |
---|
632 | * - So to summarize, the code description at the start of a dynamic block is |
---|
633 | * three counts for the number of code lengths for the literal/length codes, |
---|
634 | * the distance codes, and the code length codes. This is followed by the |
---|
635 | * code length code lengths, three bits each. This is used to construct the |
---|
636 | * code length code which is used to read the remainder of the lengths. Then |
---|
637 | * the literal/length code lengths and distance lengths are read as a single |
---|
638 | * set of lengths using the code length codes. Codes are constructed from |
---|
639 | * the resulting two sets of lengths, and then finally you can start |
---|
640 | * decoding actual compressed data in the block. |
---|
641 | * |
---|
642 | * - For reference, a "typical" size for the code description in a dynamic |
---|
643 | * block is around 80 bytes. |
---|
644 | */ |
---|
645 | local int dynamic(struct state *s) |
---|
646 | { |
---|
647 | int nlen, ndist, ncode; /* number of lengths in descriptor */ |
---|
648 | int index; /* index of lengths[] */ |
---|
649 | int err; /* construct() return value */ |
---|
650 | short lengths[MAXCODES]; /* descriptor code lengths */ |
---|
651 | short lencnt[MAXBITS+1], lensym[MAXLCODES]; /* lencode memory */ |
---|
652 | short distcnt[MAXBITS+1], distsym[MAXDCODES]; /* distcode memory */ |
---|
653 | struct huffman lencode, distcode; /* length and distance codes */ |
---|
654 | static const short order[19] = /* permutation of code length codes */ |
---|
655 | {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}; |
---|
656 | |
---|
657 | /* construct lencode and distcode */ |
---|
658 | lencode.count = lencnt; |
---|
659 | lencode.symbol = lensym; |
---|
660 | distcode.count = distcnt; |
---|
661 | distcode.symbol = distsym; |
---|
662 | |
---|
663 | /* get number of lengths in each table, check lengths */ |
---|
664 | nlen = bits(s, 5) + 257; |
---|
665 | ndist = bits(s, 5) + 1; |
---|
666 | ncode = bits(s, 4) + 4; |
---|
667 | if (nlen > MAXLCODES || ndist > MAXDCODES) |
---|
668 | return -3; /* bad counts */ |
---|
669 | |
---|
670 | /* read code length code lengths (really), missing lengths are zero */ |
---|
671 | for (index = 0; index < ncode; index++) |
---|
672 | lengths[order[index]] = bits(s, 3); |
---|
673 | for (; index < 19; index++) |
---|
674 | lengths[order[index]] = 0; |
---|
675 | |
---|
676 | /* build huffman table for code lengths codes (use lencode temporarily) */ |
---|
677 | err = construct(&lencode, lengths, 19); |
---|
678 | if (err != 0) return -4; /* require complete code set here */ |
---|
679 | |
---|
680 | /* read length/literal and distance code length tables */ |
---|
681 | index = 0; |
---|
682 | while (index < nlen + ndist) { |
---|
683 | int symbol; /* decoded value */ |
---|
684 | int len; /* last length to repeat */ |
---|
685 | |
---|
686 | symbol = decode(s, &lencode); |
---|
687 | if (symbol < 16) /* length in 0..15 */ |
---|
688 | lengths[index++] = symbol; |
---|
689 | else { /* repeat instruction */ |
---|
690 | len = 0; /* assume repeating zeros */ |
---|
691 | if (symbol == 16) { /* repeat last length 3..6 times */ |
---|
692 | if (index == 0) return -5; /* no last length! */ |
---|
693 | len = lengths[index - 1]; /* last length */ |
---|
694 | symbol = 3 + bits(s, 2); |
---|
695 | } |
---|
696 | else if (symbol == 17) /* repeat zero 3..10 times */ |
---|
697 | symbol = 3 + bits(s, 3); |
---|
698 | else /* == 18, repeat zero 11..138 times */ |
---|
699 | symbol = 11 + bits(s, 7); |
---|
700 | if (index + symbol > nlen + ndist) |
---|
701 | return -6; /* too many lengths! */ |
---|
702 | while (symbol--) /* repeat last or zero symbol times */ |
---|
703 | lengths[index++] = len; |
---|
704 | } |
---|
705 | } |
---|
706 | |
---|
707 | /* check for end-of-block code -- there better be one! */ |
---|
708 | if (lengths[256] == 0) |
---|
709 | return -9; |
---|
710 | |
---|
711 | /* build huffman table for literal/length codes */ |
---|
712 | err = construct(&lencode, lengths, nlen); |
---|
713 | if (err < 0 || (err > 0 && nlen - lencode.count[0] != 1)) |
---|
714 | return -7; /* only allow incomplete codes if just one code */ |
---|
715 | |
---|
716 | /* build huffman table for distance codes */ |
---|
717 | err = construct(&distcode, lengths + nlen, ndist); |
---|
718 | if (err < 0 || (err > 0 && ndist - distcode.count[0] != 1)) |
---|
719 | return -8; /* only allow incomplete codes if just one code */ |
---|
720 | |
---|
721 | /* decode data until end-of-block code */ |
---|
722 | return codes(s, &lencode, &distcode); |
---|
723 | } |
---|
724 | |
---|
725 | /* |
---|
726 | * Inflate source to dest. On return, destlen and sourcelen are updated to the |
---|
727 | * size of the uncompressed data and the size of the deflate data respectively. |
---|
728 | * On success, the return value of puff() is zero. If there is an error in the |
---|
729 | * source data, i.e. it is not in the deflate format, then a negative value is |
---|
730 | * returned. If there is not enough input available or there is not enough |
---|
731 | * output space, then a positive error is returned. In that case, destlen and |
---|
732 | * sourcelen are not updated to facilitate retrying from the beginning with the |
---|
733 | * provision of more input data or more output space. In the case of invalid |
---|
734 | * inflate data (a negative error), the dest and source pointers are updated to |
---|
735 | * facilitate the debugging of deflators. |
---|
736 | * |
---|
737 | * puff() also has a mode to determine the size of the uncompressed output with |
---|
738 | * no output written. For this dest must be (unsigned char *)0. In this case, |
---|
739 | * the input value of *destlen is ignored, and on return *destlen is set to the |
---|
740 | * size of the uncompressed output. |
---|
741 | * |
---|
742 | * The return codes are: |
---|
743 | * |
---|
744 | * 2: available inflate data did not terminate |
---|
745 | * 1: output space exhausted before completing inflate |
---|
746 | * 0: successful inflate |
---|
747 | * -1: invalid block type (type == 3) |
---|
748 | * -2: stored block length did not match one's complement |
---|
749 | * -3: dynamic block code description: too many length or distance codes |
---|
750 | * -4: dynamic block code description: code lengths codes incomplete |
---|
751 | * -5: dynamic block code description: repeat lengths with no first length |
---|
752 | * -6: dynamic block code description: repeat more than specified lengths |
---|
753 | * -7: dynamic block code description: invalid literal/length code lengths |
---|
754 | * -8: dynamic block code description: invalid distance code lengths |
---|
755 | * -9: dynamic block code description: missing end-of-block code |
---|
756 | * -10: invalid literal/length or distance code in fixed or dynamic block |
---|
757 | * -11: distance is too far back in fixed or dynamic block |
---|
758 | * |
---|
759 | * Format notes: |
---|
760 | * |
---|
761 | * - Three bits are read for each block to determine the kind of block and |
---|
762 | * whether or not it is the last block. Then the block is decoded and the |
---|
763 | * process repeated if it was not the last block. |
---|
764 | * |
---|
765 | * - The leftover bits in the last byte of the deflate data after the last |
---|
766 | * block (if it was a fixed or dynamic block) are undefined and have no |
---|
767 | * expected values to check. |
---|
768 | */ |
---|
769 | int puff(unsigned char *dest, /* pointer to destination pointer */ |
---|
770 | unsigned long *destlen, /* amount of output space */ |
---|
771 | unsigned char *source, /* pointer to source data pointer */ |
---|
772 | unsigned long *sourcelen) /* amount of input available */ |
---|
773 | { |
---|
774 | struct state s; /* input/output state */ |
---|
775 | int last, type; /* block information */ |
---|
776 | int err; /* return value */ |
---|
777 | |
---|
778 | /* initialize output state */ |
---|
779 | s.out = dest; |
---|
780 | s.outlen = *destlen; /* ignored if dest is NIL */ |
---|
781 | s.outcnt = 0; |
---|
782 | |
---|
783 | /* initialize input state */ |
---|
784 | s.in = source; |
---|
785 | s.inlen = *sourcelen; |
---|
786 | s.incnt = 0; |
---|
787 | s.bitbuf = 0; |
---|
788 | s.bitcnt = 0; |
---|
789 | |
---|
790 | /* return if bits() or decode() tries to read past available input */ |
---|
791 | if (setjmp(s.env) != 0) /* if came back here via longjmp() */ |
---|
792 | err = 2; /* then skip do-loop, return error */ |
---|
793 | else { |
---|
794 | /* process blocks until last block or error */ |
---|
795 | do { |
---|
796 | last = bits(&s, 1); /* one if last block */ |
---|
797 | type = bits(&s, 2); /* block type 0..3 */ |
---|
798 | err = type == 0 ? stored(&s) : |
---|
799 | (type == 1 ? fixed(&s) : |
---|
800 | (type == 2 ? dynamic(&s) : |
---|
801 | -1)); /* type == 3, invalid */ |
---|
802 | if (err != 0) break; /* return with error */ |
---|
803 | } while (!last); |
---|
804 | } |
---|
805 | |
---|
806 | /* update the lengths and return */ |
---|
807 | if (err <= 0) { |
---|
808 | *destlen = s.outcnt; |
---|
809 | *sourcelen = s.incnt; |
---|
810 | } |
---|
811 | return err; |
---|
812 | } |
---|
813 | |
---|
814 | #ifdef TEST |
---|
815 | /* Examples of how to use puff(). |
---|
816 | |
---|
817 | Usage: puff [-w] [-nnn] file |
---|
818 | ... | puff [-w] [-nnn] |
---|
819 | |
---|
820 | where file is the input file with deflate data, nnn is the number of bytes |
---|
821 | of input to skip before inflating (e.g. to skip a zlib or gzip header), and |
---|
822 | -w is used to write the decompressed data to stdout */ |
---|
823 | |
---|
824 | #include <stdio.h> |
---|
825 | #include <stdlib.h> |
---|
826 | |
---|
827 | /* Return size times approximately the cube root of 2, keeping the result as 1, |
---|
828 | 3, or 5 times a power of 2 -- the result is always > size, until the result |
---|
829 | is the maximum value of an unsigned long, where it remains. This is useful |
---|
830 | to keep reallocations less than ~33% over the actual data. */ |
---|
831 | local size_t bythirds(size_t size) |
---|
832 | { |
---|
833 | int n; |
---|
834 | size_t m; |
---|
835 | |
---|
836 | m = size; |
---|
837 | for (n = 0; m; n++) |
---|
838 | m >>= 1; |
---|
839 | if (n < 3) |
---|
840 | return size + 1; |
---|
841 | n -= 3; |
---|
842 | m = size >> n; |
---|
843 | m += m == 6 ? 2 : 1; |
---|
844 | m <<= n; |
---|
845 | return m > size ? m : (size_t)(-1); |
---|
846 | } |
---|
847 | |
---|
848 | /* Read the input file *name, or stdin if name is NULL, into allocated memory. |
---|
849 | Reallocate to larger buffers until the entire file is read in. Return a |
---|
850 | pointer to the allocated data, or NULL if there was a memory allocation |
---|
851 | failure. *len is the number of bytes of data read from the input file (even |
---|
852 | if load() returns NULL). If the input file was empty or could not be opened |
---|
853 | or read, *len is zero. */ |
---|
854 | local void *load(char *name, size_t *len) |
---|
855 | { |
---|
856 | size_t size; |
---|
857 | void *buf, *swap; |
---|
858 | FILE *in; |
---|
859 | |
---|
860 | *len = 0; |
---|
861 | buf = malloc(size = 4096); |
---|
862 | if (buf == NULL) |
---|
863 | return NULL; |
---|
864 | in = name == NULL ? stdin : fopen(name, "rb"); |
---|
865 | if (in != NULL) { |
---|
866 | for (;;) { |
---|
867 | *len += fread((char *)buf + *len, 1, size - *len, in); |
---|
868 | if (*len < size) break; |
---|
869 | size = bythirds(size); |
---|
870 | if (size == *len || (swap = realloc(buf, size)) == NULL) { |
---|
871 | free(buf); |
---|
872 | buf = NULL; |
---|
873 | break; |
---|
874 | } |
---|
875 | buf = swap; |
---|
876 | } |
---|
877 | fclose(in); |
---|
878 | } |
---|
879 | return buf; |
---|
880 | } |
---|
881 | |
---|
882 | int main(int argc, char **argv) |
---|
883 | { |
---|
884 | int ret, put = 0; |
---|
885 | unsigned skip = 0; |
---|
886 | char *arg, *name = NULL; |
---|
887 | unsigned char *source = NULL, *dest; |
---|
888 | size_t len = 0; |
---|
889 | unsigned long sourcelen, destlen; |
---|
890 | |
---|
891 | /* process arguments */ |
---|
892 | while (arg = *++argv, --argc) |
---|
893 | if (arg[0] == '-') { |
---|
894 | if (arg[1] == 'w' && arg[2] == 0) |
---|
895 | put = 1; |
---|
896 | else if (arg[1] >= '0' && arg[1] <= '9') |
---|
897 | skip = (unsigned)atoi(arg + 1); |
---|
898 | else { |
---|
899 | fprintf(stderr, "invalid option %s\n", arg); |
---|
900 | return 3; |
---|
901 | } |
---|
902 | } |
---|
903 | else if (name != NULL) { |
---|
904 | fprintf(stderr, "only one file name allowed\n"); |
---|
905 | return 3; |
---|
906 | } |
---|
907 | else |
---|
908 | name = arg; |
---|
909 | source = load(name, &len); |
---|
910 | if (source == NULL) { |
---|
911 | fprintf(stderr, "memory allocation failure\n"); |
---|
912 | return 4; |
---|
913 | } |
---|
914 | if (len == 0) { |
---|
915 | fprintf(stderr, "could not read %s, or it was empty\n", |
---|
916 | name == NULL ? "<stdin>" : name); |
---|
917 | free(source); |
---|
918 | return 3; |
---|
919 | } |
---|
920 | if (skip >= len) { |
---|
921 | fprintf(stderr, "skip request of %d leaves no input\n", skip); |
---|
922 | free(source); |
---|
923 | return 3; |
---|
924 | } |
---|
925 | |
---|
926 | /* test inflate data with offset skip */ |
---|
927 | len -= skip; |
---|
928 | sourcelen = (unsigned long)len; |
---|
929 | ret = puff(NIL, &destlen, source + skip, &sourcelen); |
---|
930 | if (ret) |
---|
931 | fprintf(stderr, "puff() failed with return code %d\n", ret); |
---|
932 | else { |
---|
933 | fprintf(stderr, "puff() succeeded uncompressing %lu bytes\n", destlen); |
---|
934 | if (sourcelen < len) fprintf(stderr, "%lu compressed bytes unused\n", |
---|
935 | len - sourcelen); |
---|
936 | } |
---|
937 | |
---|
938 | /* if requested, inflate again and write decompressd data to stdout */ |
---|
939 | if (put) { |
---|
940 | dest = malloc(destlen); |
---|
941 | if (dest == NULL) { |
---|
942 | fprintf(stderr, "memory allocation failure\n"); |
---|
943 | free(source); |
---|
944 | return 4; |
---|
945 | } |
---|
946 | puff(dest, &destlen, source + skip, &sourcelen); |
---|
947 | fwrite(dest, 1, destlen, stdout); |
---|
948 | free(dest); |
---|
949 | } |
---|
950 | |
---|
951 | /* clean up */ |
---|
952 | free(source); |
---|
953 | return ret; |
---|
954 | } |
---|
955 | #endif |
---|