src/zlib/inffast.c

   1 /* inffast.c -- process literals and length/distance pairs fast
   2  * Copyright (C) 1995-2002 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 #if defined(__VISAGECPP__) /* Visualage can't handle this antiquated interface */
  29 int inflate_fast(uInt bl, uInt bd, inflate_huft* tl, inflate_huft* td, inflate_blocks_statef* s, z_streamp z)
  30 #else
  31 int inflate_fast(bl, bd, tl, td, s, z)
  32 uInt bl, bd;
  33 inflate_huft *tl;
  34 inflate_huft *td; /* need separate declaration for Borland C++ */
  35 inflate_blocks_statef *s;
  36 z_streamp z;
  37 #endif
  38 {
  39   inflate_huft *t;      /* temporary pointer */
  40   uInt e;               /* extra bits or operation */
  41   uLong b;              /* bit buffer */
  42   uInt k;               /* bits in bit buffer */
  43   Bytef *p;             /* input data pointer */
  44   uInt n;               /* bytes available there */
  45   Bytef *q;             /* output window write pointer */
  46   uInt m;               /* bytes to end of window or read pointer */
  47   uInt ml;              /* mask for literal/length tree */
  48   uInt md;              /* mask for distance tree */
  49   uInt c;               /* bytes to copy */
  50   uInt d;               /* distance back to copy from */
  51   Bytef *r;             /* copy source pointer */
  52
  53   /* load input, output, bit values */
  54   LOAD
  55
  56   /* initialize masks */
  57   ml = inflate_mask[bl];
  58   md = inflate_mask[bd];
  59
  60   /* do until not enough input or output space for fast loop */
  61   do {                          /* assume called with m >= 258 && n >= 10 */
  62     /* get literal/length code */
  63     GRABBITS(20)                /* max bits for literal/length code */
  64     if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
  65     {
  66       DUMPBITS(t->bits)
  67       Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
  68                 "inflate:         * literal '%c'\n" :
  69                 "inflate:         * literal 0x%02x\n", t->base));
  70       *q++ = (Byte)t->base;
  71       m--;
  72       continue;
  73     }
  74     do {
  75       DUMPBITS(t->bits)
  76       if (e & 16)
  77       {
  78         /* get extra bits for length */
  79         e &= 15;
  80         c = t->base + ((uInt)b & inflate_mask[e]);
  81         DUMPBITS(e)
  82         Tracevv((stderr, "inflate:         * length %u\n", c));
  83
  84         /* decode distance base of block to copy */
  85         GRABBITS(15);           /* max bits for distance code */
  86         e = (t = td + ((uInt)b & md))->exop;
  87         do {
  88           DUMPBITS(t->bits)
  89           if (e & 16)
  90           {
  91             /* get extra bits to add to distance base */
  92             e &= 15;
  93             GRABBITS(e)         /* get extra bits (up to 13) */
  94             d = t->base + ((uInt)b & inflate_mask[e]);
  95             DUMPBITS(e)
  96             Tracevv((stderr, "inflate:         * distance %u\n", d));
  97
  98             /* do the copy */
  99             m -= c;
 100               r = q - d;
 101             if (r < s->window)                  /* wrap if needed */
 102             {
 103               do {
 104                 r += s->end - s->window;        /* force pointer in window */
 105               } while (r < s->window);          /* covers invalid distances */
 106               e = s->end - r;
 107               if (c > e)
 108               {
 109                 c -= e;                         /* wrapped copy */
 110                 do {
 111                   *q++ = *r++;
 112                 } while (--e);
 113                 r = s->window;
 114                 do {
 115                     *q++ = *r++;
 116                 } while (--c);
 117               }
 118               else                              /* normal copy */
 119               {
 120                 *q++ = *r++;  c--;
 121                 *q++ = *r++;  c--;
 122                 do {
 123                     *q++ = *r++;
 124                 } while (--c);
 125               }
 126             }
 127             else                                /* normal copy */
 128             {
 129               *q++ = *r++;  c--;
 130               *q++ = *r++;  c--;
 131               do {
 132               *q++ = *r++;
 133             } while (--c);
 134             }
 135             break;
 136           }
 137           else if ((e & 64) == 0)
 138           {
 139             t += t->base;
 140             e = (t += ((uInt)b & inflate_mask[e]))->exop;
 141           }
 142           else
 143           {
 144             z->msg = (char*)"invalid distance code";
 145             UNGRAB
 146             UPDATE
 147             return Z_DATA_ERROR;
 148           }
 149         } while (1);
 150         break;
 151       }
 152       if ((e & 64) == 0)
 153       {
 154         t += t->base;
 155         if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0)
 156         {
 157           DUMPBITS(t->bits)
 158           Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
 159                     "inflate:         * literal '%c'\n" :
 160                     "inflate:         * literal 0x%02x\n", t->base));
 161           *q++ = (Byte)t->base;
 162           m--;
 163           break;
 164         }
 165       }
 166       else if (e & 32)
 167       {
 168         Tracevv((stderr, "inflate:         * end of block\n"));
 169         UNGRAB
 170         UPDATE
 171         return Z_STREAM_END;
 172       }
 173       else
 174       {
 175         z->msg = (char*)"invalid literal/length code";
 176         UNGRAB
 177         UPDATE
 178         return Z_DATA_ERROR;
 179       }
 180     } while (1);
 181   } while (m >= 258 && n >= 10);
 182
 183   /* not enough input or output--restore pointers and return */
 184   UNGRAB
 185   UPDATE
 186   return Z_OK;
 187 }