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10
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1 /* inftrees.c -- generate Huffman trees for efficient decoding
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2 * Copyright (C) 1995 Mark Adler
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3 * For conditions of distribution and use, see copyright notice in zlib.h
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4 */
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5
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6 #include "zutil.h"
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7 #include "inftrees.h"
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8
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9 struct internal_state {int dummy;}; /* for buggy compilers */
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10
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11 /* simplify the use of the inflate_huft type with some defines */
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12 #define base more.Base
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13 #define next more.Next
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14 #define exop word.what.Exop
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15 #define bits word.what.Bits
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16
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17
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18 local int huft_build OF((
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19 uIntf *, /* code lengths in bits */
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20 uInt, /* number of codes */
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21 uInt, /* number of "simple" codes */
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22 uIntf *, /* list of base values for non-simple codes */
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23 uIntf *, /* list of extra bits for non-simple codes */
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24 inflate_huft * FAR*,/* result: starting table */
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25 uIntf *, /* maximum lookup bits (returns actual) */
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26 z_stream *)); /* for zalloc function */
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27
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28 local voidpf falloc OF((
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29 voidpf, /* opaque pointer (not used) */
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30 uInt, /* number of items */
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31 uInt)); /* size of item */
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32
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33 local void ffree OF((
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34 voidpf q, /* opaque pointer (not used) */
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35 voidpf p)); /* what to free (not used) */
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36
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37 /* Tables for deflate from PKZIP's appnote.txt. */
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38 local uInt cplens[] = { /* Copy lengths for literal codes 257..285 */
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39 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
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40 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
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41 /* actually lengths - 2; also see note #13 above about 258 */
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42 local uInt cplext[] = { /* Extra bits for literal codes 257..285 */
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43 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
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44 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 192, 192}; /* 192==invalid */
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45 local uInt cpdist[] = { /* Copy offsets for distance codes 0..29 */
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46 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
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47 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
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48 8193, 12289, 16385, 24577};
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49 local uInt cpdext[] = { /* Extra bits for distance codes */
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50 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
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51 7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
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52 12, 12, 13, 13};
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53
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54 /*
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55 Huffman code decoding is performed using a multi-level table lookup.
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56 The fastest way to decode is to simply build a lookup table whose
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57 size is determined by the longest code. However, the time it takes
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58 to build this table can also be a factor if the data being decoded
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59 is not very long. The most common codes are necessarily the
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60 shortest codes, so those codes dominate the decoding time, and hence
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61 the speed. The idea is you can have a shorter table that decodes the
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62 shorter, more probable codes, and then point to subsidiary tables for
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63 the longer codes. The time it costs to decode the longer codes is
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64 then traded against the time it takes to make longer tables.
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65
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66 This results of this trade are in the variables lbits and dbits
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67 below. lbits is the number of bits the first level table for literal/
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68 length codes can decode in one step, and dbits is the same thing for
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69 the distance codes. Subsequent tables are also less than or equal to
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70 those sizes. These values may be adjusted either when all of the
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71 codes are shorter than that, in which case the longest code length in
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72 bits is used, or when the shortest code is *longer* than the requested
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73 table size, in which case the length of the shortest code in bits is
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74 used.
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75
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76 There are two different values for the two tables, since they code a
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77 different number of possibilities each. The literal/length table
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78 codes 286 possible values, or in a flat code, a little over eight
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79 bits. The distance table codes 30 possible values, or a little less
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80 than five bits, flat. The optimum values for speed end up being
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81 about one bit more than those, so lbits is 8+1 and dbits is 5+1.
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82 The optimum values may differ though from machine to machine, and
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83 possibly even between compilers. Your mileage may vary.
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84 */
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85
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86
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87 /* If BMAX needs to be larger than 16, then h and x[] should be uLong. */
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88 #define BMAX 15 /* maximum bit length of any code */
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89 #define N_MAX 288 /* maximum number of codes in any set */
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90
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91 #ifdef DEBUG
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92 uInt inflate_hufts;
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93 #endif
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94
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95 local int huft_build(b, n, s, d, e, t, m, zs)
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96 uIntf *b; /* code lengths in bits (all assumed <= BMAX) */
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97 uInt n; /* number of codes (assumed <= N_MAX) */
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98 uInt s; /* number of simple-valued codes (0..s-1) */
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99 uIntf *d; /* list of base values for non-simple codes */
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100 uIntf *e; /* list of extra bits for non-simple codes */
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101 inflate_huft * FAR *t; /* result: starting table */
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102 uIntf *m; /* maximum lookup bits, returns actual */
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103 z_stream *zs; /* for zalloc function */
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104 /* Given a list of code lengths and a maximum table size, make a set of
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105 tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR
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106 if the given code set is incomplete (the tables are still built in this
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107 case), Z_DATA_ERROR if the input is invalid (all zero length codes or an
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108 over-subscribed set of lengths), or Z_MEM_ERROR if not enough memory. */
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109 {
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110
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111 uInt a; /* counter for codes of length k */
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112 uInt c[BMAX+1]; /* bit length count table */
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113 uInt f; /* i repeats in table every f entries */
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114 int g; /* maximum code length */
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115 int h; /* table level */
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116 register uInt i; /* counter, current code */
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117 register uInt j; /* counter */
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118 register int k; /* number of bits in current code */
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119 int l; /* bits per table (returned in m) */
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120 register uIntf *p; /* pointer into c[], b[], or v[] */
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121 inflate_huft *q; /* points to current table */
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122 struct inflate_huft_s r; /* table entry for structure assignment */
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123 inflate_huft *u[BMAX]; /* table stack */
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124 uInt v[N_MAX]; /* values in order of bit length */
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125 register int w; /* bits before this table == (l * h) */
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126 uInt x[BMAX+1]; /* bit offsets, then code stack */
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127 uIntf *xp; /* pointer into x */
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128 int y; /* number of dummy codes added */
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129 uInt z; /* number of entries in current table */
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130
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131
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132 /* Generate counts for each bit length */
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133 p = c;
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134 #define C0 *p++ = 0;
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135 #define C2 C0 C0 C0 C0
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136 #define C4 C2 C2 C2 C2
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137 C4 /* clear c[]--assume BMAX+1 is 16 */
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138 p = b; i = n;
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139 do {
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140 c[*p++]++; /* assume all entries <= BMAX */
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141 } while (--i);
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142 if (c[0] == n) /* null input--all zero length codes */
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143 {
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144 *t = (inflate_huft *)Z_NULL;
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145 *m = 0;
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146 return Z_OK;
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147 }
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148
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149
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150 /* Find minimum and maximum length, bound *m by those */
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151 l = *m;
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152 for (j = 1; j <= BMAX; j++)
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153 if (c[j])
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154 break;
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155 k = j; /* minimum code length */
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156 if ((uInt)l < j)
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157 l = j;
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158 for (i = BMAX; i; i--)
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159 if (c[i])
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160 break;
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161 g = i; /* maximum code length */
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162 if ((uInt)l > i)
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163 l = i;
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164 *m = l;
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165
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166
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167 /* Adjust last length count to fill out codes, if needed */
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168 for (y = 1 << j; j < i; j++, y <<= 1)
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169 if ((y -= c[j]) < 0)
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170 return Z_DATA_ERROR;
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171 if ((y -= c[i]) < 0)
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172 return Z_DATA_ERROR;
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173 c[i] += y;
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174
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175
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176 /* Generate starting offsets into the value table for each length */
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177 x[1] = j = 0;
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178 p = c + 1; xp = x + 2;
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179 while (--i) { /* note that i == g from above */
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180 *xp++ = (j += *p++);
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181 }
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182
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183
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184 /* Make a table of values in order of bit lengths */
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185 p = b; i = 0;
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186 do {
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187 if ((j = *p++) != 0)
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188 v[x[j]++] = i;
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189 } while (++i < n);
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190
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191
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192 /* Generate the Huffman codes and for each, make the table entries */
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193 x[0] = i = 0; /* first Huffman code is zero */
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194 p = v; /* grab values in bit order */
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195 h = -1; /* no tables yet--level -1 */
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196 w = -l; /* bits decoded == (l * h) */
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197 u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */
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198 q = (inflate_huft *)Z_NULL; /* ditto */
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199 z = 0; /* ditto */
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200
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201 /* go through the bit lengths (k already is bits in shortest code) */
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202 for (; k <= g; k++)
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203 {
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204 a = c[k];
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205 while (a--)
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206 {
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207 /* here i is the Huffman code of length k bits for value *p */
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208 /* make tables up to required level */
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209 while (k > w + l)
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210 {
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211 h++;
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212 w += l; /* previous table always l bits */
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213
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214 /* compute minimum size table less than or equal to l bits */
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215 z = (z = g - w) > (uInt)l ? l : z; /* table size upper limit */
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216 if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */
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217 { /* too few codes for k-w bit table */
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218 f -= a + 1; /* deduct codes from patterns left */
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219 xp = c + k;
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220 if (j < z)
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221 while (++j < z) /* try smaller tables up to z bits */
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222 {
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223 if ((f <<= 1) <= *++xp)
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224 break; /* enough codes to use up j bits */
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225 f -= *xp; /* else deduct codes from patterns */
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226 }
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227 }
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228 z = 1 << j; /* table entries for j-bit table */
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229
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230 /* allocate and link in new table */
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231 if ((q = (inflate_huft *)ZALLOC
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232 (zs,z + 1,sizeof(inflate_huft))) == Z_NULL)
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233 {
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234 if (h)
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235 inflate_trees_free(u[0], zs);
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236 return Z_MEM_ERROR; /* not enough memory */
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237 }
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238 #ifdef DEBUG
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239 inflate_hufts += z + 1;
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240 #endif
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241 *t = q + 1; /* link to list for huft_free() */
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242 *(t = &(q->next)) = Z_NULL;
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243 u[h] = ++q; /* table starts after link */
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244
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245 /* connect to last table, if there is one */
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246 if (h)
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247 {
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248 x[h] = i; /* save pattern for backing up */
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249 r.bits = (Byte)l; /* bits to dump before this table */
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250 r.exop = (Byte)j; /* bits in this table */
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251 r.next = q; /* pointer to this table */
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252 j = i >> (w - l); /* (get around Turbo C bug) */
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253 u[h-1][j] = r; /* connect to last table */
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254 }
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255 }
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256
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257 /* set up table entry in r */
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258 r.bits = (Byte)(k - w);
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259 if (p >= v + n)
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260 r.exop = 128 + 64; /* out of values--invalid code */
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261 else if (*p < s)
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262 {
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263 r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */
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264 r.base = *p++; /* simple code is just the value */
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265 }
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266 else
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267 {
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268 r.exop = (Byte)e[*p - s] + 16 + 64; /* non-simple--look up in lists */
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269 r.base = d[*p++ - s];
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270 }
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271
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272 /* fill code-like entries with r */
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273 f = 1 << (k - w);
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274 for (j = i >> w; j < z; j += f)
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275 q[j] = r;
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276
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277 /* backwards increment the k-bit code i */
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278 for (j = 1 << (k - 1); i & j; j >>= 1)
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279 i ^= j;
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280 i ^= j;
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281
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282 /* backup over finished tables */
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283 while ((i & ((1 << w) - 1)) != x[h])
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284 {
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285 h--; /* don't need to update q */
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286 w -= l;
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287 }
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288 }
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289 }
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290
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291
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292 /* Return Z_BUF_ERROR if we were given an incomplete table */
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293 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
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294 }
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295
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296
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297 int inflate_trees_bits(c, bb, tb, z)
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298 uIntf *c; /* 19 code lengths */
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299 uIntf *bb; /* bits tree desired/actual depth */
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300 inflate_huft * FAR *tb; /* bits tree result */
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301 z_stream *z; /* for zfree function */
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302 {
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303 int r;
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304
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305 r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL, tb, bb, z);
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306 if (r == Z_DATA_ERROR)
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307 z->msg = "oversubscribed dynamic bit lengths tree";
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308 else if (r == Z_BUF_ERROR)
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309 {
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310 inflate_trees_free(*tb, z);
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311 z->msg = "incomplete dynamic bit lengths tree";
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312 r = Z_DATA_ERROR;
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313 }
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314 return r;
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315 }
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316
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317
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318 int inflate_trees_dynamic(nl, nd, c, bl, bd, tl, td, z)
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319 uInt nl; /* number of literal/length codes */
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320 uInt nd; /* number of distance codes */
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321 uIntf *c; /* that many (total) code lengths */
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322 uIntf *bl; /* literal desired/actual bit depth */
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323 uIntf *bd; /* distance desired/actual bit depth */
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324 inflate_huft * FAR *tl; /* literal/length tree result */
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325 inflate_huft * FAR *td; /* distance tree result */
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326 z_stream *z; /* for zfree function */
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327 {
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328 int r;
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329
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330 /* build literal/length tree */
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331 if ((r = huft_build(c, nl, 257, cplens, cplext, tl, bl, z)) != Z_OK)
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332 {
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333 if (r == Z_DATA_ERROR)
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334 z->msg = "oversubscribed literal/length tree";
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335 else if (r == Z_BUF_ERROR)
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336 {
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337 inflate_trees_free(*tl, z);
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338 z->msg = "incomplete literal/length tree";
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339 r = Z_DATA_ERROR;
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340 }
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341 return r;
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342 }
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343
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344 /* build distance tree */
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345 if ((r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, z)) != Z_OK)
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346 {
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347 if (r == Z_DATA_ERROR)
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348 z->msg = "oversubscribed literal/length tree";
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349 else if (r == Z_BUF_ERROR) {
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350 #ifdef PKZIP_BUG_WORKAROUND
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351 r = Z_OK;
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352 }
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353 #else
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354 inflate_trees_free(*td, z);
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355 z->msg = "incomplete literal/length tree";
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356 r = Z_DATA_ERROR;
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357 }
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358 inflate_trees_free(*tl, z);
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359 return r;
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360 #endif
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361 }
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362
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363 /* done */
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364 return Z_OK;
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365 }
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366
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367
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368 /* build fixed tables only once--keep them here */
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369 local int fixed_lock = 0;
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370 local int fixed_built = 0;
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371 #define FIXEDH 530 /* number of hufts used by fixed tables */
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372 local uInt fixed_left = FIXEDH;
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373 local inflate_huft fixed_mem[FIXEDH];
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374 local uInt fixed_bl;
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375 local uInt fixed_bd;
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376 local inflate_huft *fixed_tl;
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377 local inflate_huft *fixed_td;
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378
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379
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380 local voidpf falloc(q, n, s)
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381 voidpf q; /* opaque pointer (not used) */
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382 uInt n; /* number of items */
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383 uInt s; /* size of item */
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384 {
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385 Assert(s == sizeof(inflate_huft) && n <= fixed_left,
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386 "inflate_trees falloc overflow");
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387 if (q) s++; /* to make some compilers happy */
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388 fixed_left -= n;
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389 return (voidpf)(fixed_mem + fixed_left);
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390 }
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391
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392
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393 local void ffree(q, p)
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394 voidpf q;
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395 voidpf p;
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396 {
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397 Assert(0, "inflate_trees ffree called!");
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398 if (q) q = p; /* to make some compilers happy */
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399 }
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400
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401
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402 int inflate_trees_fixed(bl, bd, tl, td)
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403 uIntf *bl; /* literal desired/actual bit depth */
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404 uIntf *bd; /* distance desired/actual bit depth */
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405 inflate_huft * FAR *tl; /* literal/length tree result */
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406 inflate_huft * FAR *td; /* distance tree result */
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407 {
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408 /* build fixed tables if not built already--lock out other instances */
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409 while (++fixed_lock > 1)
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410 fixed_lock--;
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411 if (!fixed_built)
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412 {
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413 int k; /* temporary variable */
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414 unsigned c[288]; /* length list for huft_build */
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415 z_stream z; /* for falloc function */
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416
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417 /* set up fake z_stream for memory routines */
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418 z.zalloc = falloc;
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419 z.zfree = ffree;
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420 z.opaque = Z_NULL;
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421
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422 /* literal table */
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423 for (k = 0; k < 144; k++)
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424 c[k] = 8;
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425 for (; k < 256; k++)
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426 c[k] = 9;
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427 for (; k < 280; k++)
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428 c[k] = 7;
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429 for (; k < 288; k++)
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430 c[k] = 8;
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431 fixed_bl = 7;
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432 huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl, &z);
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433
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434 /* distance table */
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435 for (k = 0; k < 30; k++)
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436 c[k] = 5;
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437 fixed_bd = 5;
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438 huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd, &z);
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439
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440 /* done */
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441 fixed_built = 1;
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442 }
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443 fixed_lock--;
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444 *bl = fixed_bl;
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445 *bd = fixed_bd;
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446 *tl = fixed_tl;
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447 *td = fixed_td;
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448 return Z_OK;
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449 }
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450
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451
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452 int inflate_trees_free(t, z)
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453 inflate_huft *t; /* table to free */
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454 z_stream *z; /* for zfree function */
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455 /* Free the malloc'ed tables built by huft_build(), which makes a linked
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456 list of the tables it made, with the links in a dummy first entry of
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457 each table. */
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458 {
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459 register inflate_huft *p, *q;
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460
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461 /* Go through linked list, freeing from the malloced (t[-1]) address. */
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462 p = t;
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463 while (p != Z_NULL)
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464 {
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465 q = (--p)->next;
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466 ZFREE(z,p);
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467 p = q;
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468 }
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469 return Z_OK;
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470 }
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