inffast.c revision 84228
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 <sys/cdefs.h> 7__FBSDID("$FreeBSD: head/lib/libz/inffast.c 84228 2001-09-30 22:39:00Z dillon $"); 8 9#include "zutil.h" 10#include "inftrees.h" 11#include "infblock.h" 12#include "infcodes.h" 13#include "infutil.h" 14#include "inffast.h" 15 16struct inflate_codes_state {int dummy;}; /* for buggy compilers */ 17 18/* simplify the use of the inflate_huft type with some defines */ 19#define exop word.what.Exop 20#define bits word.what.Bits 21 22/* macros for bit input with no checking and for returning unused bytes */ 23#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}} 24#define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;} 25 26/* Called with number of bytes left to write in window at least 258 27 (the maximum string length) and number of input bytes available 28 at least ten. The ten bytes are six bytes for the longest length/ 29 distance pair plus four bytes for overloading the bit buffer. */ 30 31int inflate_fast(bl, bd, tl, td, s, z) 32uInt bl, bd; 33inflate_huft *tl; 34inflate_huft *td; /* need separate declaration for Borland C++ */ 35inflate_blocks_statef *s; 36z_streamp z; 37{ 38 inflate_huft *t; /* temporary pointer */ 39 uInt e; /* extra bits or operation */ 40 uLong b; /* bit buffer */ 41 uInt k; /* bits in bit buffer */ 42 Bytef *p; /* input data pointer */ 43 uInt n; /* bytes available there */ 44 Bytef *q; /* output window write pointer */ 45 uInt m; /* bytes to end of window or read pointer */ 46 uInt ml; /* mask for literal/length tree */ 47 uInt md; /* mask for distance tree */ 48 uInt c; /* bytes to copy */ 49 uInt d; /* distance back to copy from */ 50 Bytef *r; /* copy source pointer */ 51 52 /* load input, output, bit values */ 53 LOAD 54 55 /* initialize masks */ 56 ml = inflate_mask[bl]; 57 md = inflate_mask[bd]; 58 59 /* do until not enough input or output space for fast loop */ 60 do { /* assume called with m >= 258 && n >= 10 */ 61 /* get literal/length code */ 62 GRABBITS(20) /* max bits for literal/length code */ 63 if ((e = (t = tl + ((uInt)b & ml))->exop) == 0) 64 { 65 DUMPBITS(t->bits) 66 Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? 67 "inflate: * literal '%c'\n" : 68 "inflate: * literal 0x%02x\n", t->base)); 69 *q++ = (Byte)t->base; 70 m--; 71 continue; 72 } 73 do { 74 DUMPBITS(t->bits) 75 if (e & 16) 76 { 77 /* get extra bits for length */ 78 e &= 15; 79 c = t->base + ((uInt)b & inflate_mask[e]); 80 DUMPBITS(e) 81 Tracevv((stderr, "inflate: * length %u\n", c)); 82 83 /* decode distance base of block to copy */ 84 GRABBITS(15); /* max bits for distance code */ 85 e = (t = td + ((uInt)b & md))->exop; 86 do { 87 DUMPBITS(t->bits) 88 if (e & 16) 89 { 90 /* get extra bits to add to distance base */ 91 e &= 15; 92 GRABBITS(e) /* get extra bits (up to 13) */ 93 d = t->base + ((uInt)b & inflate_mask[e]); 94 DUMPBITS(e) 95 Tracevv((stderr, "inflate: * distance %u\n", d)); 96 97 /* do the copy */ 98 m -= c; 99 if ((uInt)(q - s->window) >= d) /* offset before dest */ 100 { /* just copy */ 101 r = q - d; 102 *q++ = *r++; c--; /* minimum count is three, */ 103 *q++ = *r++; c--; /* so unroll loop a little */ 104 } 105 else /* else offset after destination */ 106 { 107 e = d - (uInt)(q - s->window); /* bytes from offset to end */ 108 r = s->end - e; /* pointer to offset */ 109 if (c > e) /* if source crosses, */ 110 { 111 c -= e; /* copy to end of window */ 112 do { 113 *q++ = *r++; 114 } while (--e); 115 r = s->window; /* copy rest from start of window */ 116 } 117 } 118 do { /* copy all or what's left */ 119 *q++ = *r++; 120 } while (--c); 121 break; 122 } 123 else if ((e & 64) == 0) 124 { 125 t += t->base; 126 e = (t += ((uInt)b & inflate_mask[e]))->exop; 127 } 128 else 129 { 130 z->msg = (char*)"invalid distance code"; 131 UNGRAB 132 UPDATE 133 return Z_DATA_ERROR; 134 } 135 } while (1); 136 break; 137 } 138 if ((e & 64) == 0) 139 { 140 t += t->base; 141 if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0) 142 { 143 DUMPBITS(t->bits) 144 Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ? 145 "inflate: * literal '%c'\n" : 146 "inflate: * literal 0x%02x\n", t->base)); 147 *q++ = (Byte)t->base; 148 m--; 149 break; 150 } 151 } 152 else if (e & 32) 153 { 154 Tracevv((stderr, "inflate: * end of block\n")); 155 UNGRAB 156 UPDATE 157 return Z_STREAM_END; 158 } 159 else 160 { 161 z->msg = (char*)"invalid literal/length code"; 162 UNGRAB 163 UPDATE 164 return Z_DATA_ERROR; 165 } 166 } while (1); 167 } while (m >= 258 && n >= 10); 168 169 /* not enough input or output--restore pointers and return */ 170 UNGRAB 171 UPDATE 172 return Z_OK; 173} 174