src/zlib/inffast.c

   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 #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             if ((uInt)(q - s->window) >= d)     /* offset before dest */
 101             {                                   /*  just copy */
 102               r = q - d;
 103               *q++ = *r++;  c--;        /* minimum count is three, */
 104               *q++ = *r++;  c--;        /*  so unroll loop a little */
 105             }
 106             else                        /* else offset after destination */
 107             {
 108               e = d - (uInt)(q - s->window); /* bytes from offset to end */
 109               r = s->end - e;           /* pointer to offset */
 110               if (c > e)                /* if source crosses, */
 111               {
 112                 c -= e;                 /* copy to end of window */
 113                 do {
 114                   *q++ = *r++;
 115                 } while (--e);
 116                 r = s->window;          /* copy rest from start of window */
 117               }
 118             }
 119             do {                        /* copy all or what's left */
 120               *q++ = *r++;
 121             } while (--c);
 122             break;
 123           }
 124           else if ((e & 64) == 0)
 125           {
 126             t += t->base;
 127             e = (t += ((uInt)b & inflate_mask[e]))->exop;
 128           }
 129           else
 130           {
 131             z->msg = (char*)"invalid distance code";
 132             UNGRAB
 133             UPDATE
 134             return Z_DATA_ERROR;
 135           }
 136         } while (1);
 137         break;
 138       }
 139       if ((e & 64) == 0)
 140       {
 141         t += t->base;
 142         if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0)
 143         {
 144           DUMPBITS(t->bits)
 145           Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
 146                     "inflate:         * literal '%c'\n" :
 147                     "inflate:         * literal 0x%02x\n", t->base));
 148           *q++ = (Byte)t->base;
 149           m--;
 150           break;
 151         }
 152       }
 153       else if (e & 32)
 154       {
 155         Tracevv((stderr, "inflate:         * end of block\n"));
 156         UNGRAB
 157         UPDATE
 158         return Z_STREAM_END;
 159       }
 160       else
 161       {
 162         z->msg = (char*)"invalid literal/length code";
 163         UNGRAB
 164         UPDATE
 165         return Z_DATA_ERROR;
 166       }
 167     } while (1);
 168   } while (m >= 258 && n >= 10);
 169
 170   /* not enough input or output--restore pointers and return */
 171   UNGRAB
 172   UPDATE
 173   return Z_OK;
 174 }