| 1 | /* inffast.c -- process literals and length/distance pairs fast |
| 2 | * Copyright (C) 1995-1998 Mark Adler |
| 3 | * For conditions of distribution and use, see copyright notice in zlib.h |
| 4 | */ |
| 5 | |
| 6 | #include "zutil.h" |
| 7 | #include "inftrees.h" |
| 8 | #include "infblock.h" |
| 9 | #include "infcodes.h" |
| 10 | #include "infutil.h" |
| 11 | #include "inffast.h" |
| 12 | |
| 13 | struct inflate_codes_state {int dummy;}; /* for buggy compilers */ |
| 14 | |
| 15 | /* simplify the use of the inflate_huft type with some defines */ |
| 16 | #define exop word.what.Exop |
| 17 | #define bits word.what.Bits |
| 18 | |
| 19 | /* macros for bit input with no checking and for returning unused bytes */ |
| 20 | #define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}} |
| 21 | #define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;} |
| 22 | |
| 23 | /* Called with number of bytes left to write in window at least 258 |
| 24 | (the maximum string length) and number of input bytes available |
| 25 | at least ten. The ten bytes are six bytes for the longest length/ |
| 26 | distance pair plus four bytes for overloading the bit buffer. */ |
| 27 | |
| 28 | int inflate_fast(bl, bd, tl, td, s, z) |
| 29 | uInt bl, bd; |
| 30 | inflate_huft *tl; |
| 31 | inflate_huft *td; /* need separate declaration for Borland C++ */ |
| 32 | inflate_blocks_statef *s; |
| 33 | z_streamp z; |
| 34 | { |
| 35 | inflate_huft *t; /* temporary pointer */ |
| 36 | uInt e; /* extra bits or operation */ |
| 37 | uLong b; /* bit buffer */ |
| 38 | uInt k; /* bits in bit buffer */ |
| 39 | Bytef *p; /* input data pointer */ |
| 40 | uInt n; /* bytes available there */ |
| 41 | Bytef *q; /* output window write pointer */ |
| 42 | uInt m; /* bytes to end of window or read pointer */ |
| 43 | uInt ml; /* mask for literal/length tree */ |
| 44 | uInt md; /* mask for distance tree */ |
| 45 | uInt c; /* bytes to copy */ |
| 46 | uInt d; /* distance back to copy from */ |
| 47 | Bytef *r; /* copy source pointer */ |
| 48 | |
| 49 | /* load input, output, bit values */ |
| 50 | LOAD |
| 51 | |
| 52 | /* initialize masks */ |
| 53 | ml = inflate_mask[bl]; |
| 54 | md = inflate_mask[bd]; |
| 55 | |
| 56 | /* do until not enough input or output space for fast loop */ |
| 57 | do { /* assume called with m >= 258 && n >= 10 */ |
| 58 | /* get literal/length code */ |
| 59 | GRABBITS(20) /* max bits for literal/length code */ |
| 60 | if ((e = (t = tl + ((uInt)b & ml))->exop) == 0) |
| 61 | { |
| 62 | DUMPBITS(t->bits) |
| 63 | Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? |
| 64 | "inflate: * literal '%c'\n" : |
| 65 | "inflate: * literal 0x%02x\n", t->base)); |
| 66 | *q++ = (Byte)t->base; |
| 67 | m--; |
| 68 | continue; |
| 69 | } |
| 70 | do { |
| 71 | DUMPBITS(t->bits) |
| 72 | if (e & 16) |
| 73 | { |
| 74 | /* get extra bits for length */ |
| 75 | e &= 15; |
| 76 | c = t->base + ((uInt)b & inflate_mask[e]); |
| 77 | DUMPBITS(e) |
| 78 | Tracevv((stderr, "inflate: * length %u\n", c)); |
| 79 | |
| 80 | /* decode distance base of block to copy */ |
| 81 | GRABBITS(15); /* max bits for distance code */ |
| 82 | e = (t = td + ((uInt)b & md))->exop; |
| 83 | do { |
| 84 | DUMPBITS(t->bits) |
| 85 | if (e & 16) |
| 86 | { |
| 87 | /* get extra bits to add to distance base */ |
| 88 | e &= 15; |
| 89 | GRABBITS(e) /* get extra bits (up to 13) */ |
| 90 | d = t->base + ((uInt)b & inflate_mask[e]); |
| 91 | DUMPBITS(e) |
| 92 | Tracevv((stderr, "inflate: * distance %u\n", d)); |
| 93 | |
| 94 | /* do the copy */ |
| 95 | m -= c; |
| 96 | if ((uInt)(q - s->window) >= d) /* offset before dest */ |
| 97 | { /* just copy */ |
| 98 | r = q - d; |
| 99 | *q++ = *r++; c--; /* minimum count is three, */ |
| 100 | *q++ = *r++; c--; /* so unroll loop a little */ |
| 101 | } |
| 102 | else /* else offset after destination */ |
| 103 | { |
| 104 | e = d - (uInt)(q - s->window); /* bytes from offset to end */ |
| 105 | r = s->end - e; /* pointer to offset */ |
| 106 | if (c > e) /* if source crosses, */ |
| 107 | { |
| 108 | c -= e; /* copy to end of window */ |
| 109 | do { |
| 110 | *q++ = *r++; |
| 111 | } while (--e); |
| 112 | r = s->window; /* copy rest from start of window */ |
| 113 | } |
| 114 | } |
| 115 | do { /* copy all or what's left */ |
| 116 | *q++ = *r++; |
| 117 | } while (--c); |
| 118 | break; |
| 119 | } |
| 120 | else if ((e & 64) == 0) |
| 121 | { |
| 122 | t += t->base; |
| 123 | e = (t += ((uInt)b & inflate_mask[e]))->exop; |
| 124 | } |
| 125 | else |
| 126 | { |
| 127 | z->msg = (char*)"invalid distance code"; |
| 128 | UNGRAB |
| 129 | UPDATE |
| 130 | return Z_DATA_ERROR; |
| 131 | } |
| 132 | } while (1); |
| 133 | break; |
| 134 | } |
| 135 | if ((e & 64) == 0) |
| 136 | { |
| 137 | t += t->base; |
| 138 | if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0) |
| 139 | { |
| 140 | DUMPBITS(t->bits) |
| 141 | Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? |
| 142 | "inflate: * literal '%c'\n" : |
| 143 | "inflate: * literal 0x%02x\n", t->base)); |
| 144 | *q++ = (Byte)t->base; |
| 145 | m--; |
| 146 | break; |
| 147 | } |
| 148 | } |
| 149 | else if (e & 32) |
| 150 | { |
| 151 | Tracevv((stderr, "inflate: * end of block\n")); |
| 152 | UNGRAB |
| 153 | UPDATE |
| 154 | return Z_STREAM_END; |
| 155 | } |
| 156 | else |
| 157 | { |
| 158 | z->msg = (char*)"invalid literal/length code"; |
| 159 | UNGRAB |
| 160 | UPDATE |
| 161 | return Z_DATA_ERROR; |
| 162 | } |
| 163 | } while (1); |
| 164 | } while (m >= 258 && n >= 10); |
| 165 | |
| 166 | /* not enough input or output--restore pointers and return */ |
| 167 | UNGRAB |
| 168 | UPDATE |
| 169 | return Z_OK; |
| 170 | } |