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