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1 /* inffast.c -- process literals and length/distance pairs fast
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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 #include "infblock.h"
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9 #include "infcodes.h"
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10 #include "infutil.h"
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11 #include "inffast.h"
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12
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13 struct inflate_codes_state {int dummy;}; /* for buggy compilers */
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14
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15 /* simplify the use of the inflate_huft type with some defines */
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16 #define base more.Base
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17 #define next more.Next
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18 #define exop word.what.Exop
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19 #define bits word.what.Bits
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20
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21 /* macros for bit input with no checking and for returning unused bytes */
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22 #define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}
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23 #define UNGRAB {n+=(c=k>>3);p-=c;k&=7;}
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24
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25 /* Called with number of bytes left to write in window at least 258
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26 (the maximum string length) and number of input bytes available
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27 at least ten. The ten bytes are six bytes for the longest length/
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28 distance pair plus four bytes for overloading the bit buffer. */
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29
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30 int inflate_fast(bl, bd, tl, td, s, z)
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31 uInt bl, bd;
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32 inflate_huft *tl, *td;
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33 inflate_blocks_statef *s;
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34 z_stream *z;
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35 {
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36 inflate_huft *t; /* temporary pointer */
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37 uInt e; /* extra bits or operation */
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38 uLong b; /* bit buffer */
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39 uInt k; /* bits in bit buffer */
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40 Bytef *p; /* input data pointer */
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41 uInt n; /* bytes available there */
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42 Bytef *q; /* output window write pointer */
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43 uInt m; /* bytes to end of window or read pointer */
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44 uInt ml; /* mask for literal/length tree */
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45 uInt md; /* mask for distance tree */
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46 uInt c; /* bytes to copy */
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47 uInt d; /* distance back to copy from */
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48 Bytef *r; /* copy source pointer */
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49
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50 /* load input, output, bit values */
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51 LOAD
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52
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53 /* initialize masks */
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54 ml = inflate_mask[bl];
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55 md = inflate_mask[bd];
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56
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57 /* do until not enough input or output space for fast loop */
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58 do { /* assume called with m >= 258 && n >= 10 */
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59 /* get literal/length code */
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60 GRABBITS(20) /* max bits for literal/length code */
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61 if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
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62 {
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63 DUMPBITS(t->bits)
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64 Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
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65 "inflate: * literal '%c'\n" :
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66 "inflate: * literal 0x%02x\n", t->base));
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67 *q++ = (Byte)t->base;
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68 m--;
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69 continue;
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70 }
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71 do {
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72 DUMPBITS(t->bits)
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73 if (e & 16)
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74 {
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75 /* get extra bits for length */
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76 e &= 15;
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77 c = t->base + ((uInt)b & inflate_mask[e]);
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78 DUMPBITS(e)
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79 Tracevv((stderr, "inflate: * length %u\n", c));
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80
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81 /* decode distance base of block to copy */
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82 GRABBITS(15); /* max bits for distance code */
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83 e = (t = td + ((uInt)b & md))->exop;
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84 do {
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85 DUMPBITS(t->bits)
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86 if (e & 16)
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87 {
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88 /* get extra bits to add to distance base */
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89 e &= 15;
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90 GRABBITS(e) /* get extra bits (up to 13) */
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91 d = t->base + ((uInt)b & inflate_mask[e]);
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92 DUMPBITS(e)
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93 Tracevv((stderr, "inflate: * distance %u\n", d));
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94
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95 /* do the copy */
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96 m -= c;
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97 if ((uInt)(q - s->window) >= d) /* offset before dest */
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98 { /* just copy */
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99 r = q - d;
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100 *q++ = *r++; c--; /* minimum count is three, */
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101 *q++ = *r++; c--; /* so unroll loop a little */
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102 }
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103 else /* else offset after destination */
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104 {
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105 e = d - (q - s->window); /* bytes from offset to end */
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106 r = s->end - e; /* pointer to offset */
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107 if (c > e) /* if source crosses, */
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108 {
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109 c -= e; /* copy to end of window */
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110 do {
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111 *q++ = *r++;
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112 } while (--e);
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113 r = s->window; /* copy rest from start of window */
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114 }
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115 }
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116 do { /* copy all or what's left */
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117 *q++ = *r++;
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118 } while (--c);
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119 break;
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120 }
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121 else if ((e & 64) == 0)
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122 e = (t = t->next + ((uInt)b & inflate_mask[e]))->exop;
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123 else
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124 {
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125 z->msg = "invalid distance code";
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126 UNGRAB
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127 UPDATE
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128 return Z_DATA_ERROR;
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129 }
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130 } while (1);
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131 break;
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132 }
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133 if ((e & 64) == 0)
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134 {
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135 if ((e = (t = t->next + ((uInt)b & inflate_mask[e]))->exop) == 0)
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136 {
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137 DUMPBITS(t->bits)
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138 Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
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139 "inflate: * literal '%c'\n" :
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140 "inflate: * literal 0x%02x\n", t->base));
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141 *q++ = (Byte)t->base;
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142 m--;
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143 break;
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144 }
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145 }
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146 else if (e & 32)
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147 {
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148 Tracevv((stderr, "inflate: * end of block\n"));
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149 UNGRAB
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150 UPDATE
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151 return Z_STREAM_END;
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152 }
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153 else
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154 {
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155 z->msg = "invalid literal/length code";
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156 UNGRAB
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157 UPDATE
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158 return Z_DATA_ERROR;
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159 }
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160 } while (1);
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161 } while (m >= 258 && n >= 10);
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162
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163 /* not enough input or output--restore pointers and return */
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164 UNGRAB
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165 UPDATE
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166 return Z_OK;
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167 }
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