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