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107 pj 1
/* inffast.c -- process literals and length/distance pairs fast
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 * Copyright (C) 1995-2002 Mark Adler
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 * For conditions of distribution and use, see copyright notice in zlib.h
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 */
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#include "zutil.h"
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#include "inftrees.h"
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#include "infblock.h"
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#include "infcodes.h"
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#include "infutil.h"
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#include "inffast.h"
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struct inflate_codes_state {int dummy;}; /* for buggy compilers */
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/* simplify the use of the inflate_huft type with some defines */
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#define exop word.what.Exop
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#define bits word.what.Bits
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/* macros for bit input with no checking and for returning unused bytes */
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#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}
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#define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;}
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/* Called with number of bytes left to write in window at least 258
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   (the maximum string length) and number of input bytes available
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   at least ten.  The ten bytes are six bytes for the longest length/
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   distance pair plus four bytes for overloading the bit buffer. */
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int inflate_fast(bl, bd, tl, td, s, z)
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uInt bl, bd;
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inflate_huft *tl;
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inflate_huft *td; /* need separate declaration for Borland C++ */
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inflate_blocks_statef *s;
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z_streamp z;
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{
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  inflate_huft *t;      /* temporary pointer */
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  uInt e;               /* extra bits or operation */
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  uLong b;              /* bit buffer */
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  uInt k;               /* bits in bit buffer */
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  Bytef *p;             /* input data pointer */
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  uInt n;               /* bytes available there */
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  Bytef *q;             /* output window write pointer */
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  uInt m;               /* bytes to end of window or read pointer */
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  uInt ml;              /* mask for literal/length tree */
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  uInt md;              /* mask for distance tree */
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  uInt c;               /* bytes to copy */
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  uInt d;               /* distance back to copy from */
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  Bytef *r;             /* copy source pointer */
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  /* load input, output, bit values */
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  LOAD
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  /* initialize masks */
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  ml = inflate_mask[bl];
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  md = inflate_mask[bd];
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  /* do until not enough input or output space for fast loop */
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  do {                          /* assume called with m >= 258 && n >= 10 */
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    /* get literal/length code */
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    GRABBITS(20)                /* max bits for literal/length code */
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    if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
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    {
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      DUMPBITS(t->bits)
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      Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
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                "inflate:         * literal '%c'\n" :
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                "inflate:         * literal 0x%02x\n", t->base));
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      *q++ = (Byte)t->base;
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      m--;
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      continue;
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    }
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    do {
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      DUMPBITS(t->bits)
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      if (e & 16)
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      {
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        /* get extra bits for length */
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        e &= 15;
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        c = t->base + ((uInt)b & inflate_mask[e]);
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        DUMPBITS(e)
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        Tracevv((stderr, "inflate:         * length %u\n", c));
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        /* decode distance base of block to copy */
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        GRABBITS(15);           /* max bits for distance code */
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        e = (t = td + ((uInt)b & md))->exop;
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        do {
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          DUMPBITS(t->bits)
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          if (e & 16)
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          {
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            /* get extra bits to add to distance base */
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            e &= 15;
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            GRABBITS(e)         /* get extra bits (up to 13) */
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            d = t->base + ((uInt)b & inflate_mask[e]);
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            DUMPBITS(e)
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            Tracevv((stderr, "inflate:         * distance %u\n", d));
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            /* do the copy */
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            m -= c;
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            r = q - d;
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            if (r < s->window)                  /* wrap if needed */
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            {
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              do {
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                r += s->end - s->window;        /* force pointer in window */
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              } while (r < s->window);          /* covers invalid distances */
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              e = s->end - r;
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              if (c > e)
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              {
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                c -= e;                         /* wrapped copy */
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                do {
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                    *q++ = *r++;
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                } while (--e);
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                r = s->window;
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                do {
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                    *q++ = *r++;
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                } while (--c);
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              }
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              else                              /* normal copy */
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              {
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                *q++ = *r++;  c--;
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                *q++ = *r++;  c--;
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                do {
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                    *q++ = *r++;
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                } while (--c);
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              }
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            }
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            else                                /* normal copy */
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            {
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              *q++ = *r++;  c--;
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              *q++ = *r++;  c--;
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              do {
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                *q++ = *r++;
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              } while (--c);
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            }
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            break;
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          }
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          else if ((e & 64) == 0)
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          {
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            t += t->base;
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            e = (t += ((uInt)b & inflate_mask[e]))->exop;
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          }
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          else
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          {
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            z->msg = (char*)"invalid distance code";
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            UNGRAB
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            UPDATE
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            return Z_DATA_ERROR;
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          }
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        } while (1);
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        break;
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      }
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      if ((e & 64) == 0)
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      {
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        t += t->base;
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        if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0)
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        {
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          DUMPBITS(t->bits)
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          Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
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                    "inflate:         * literal '%c'\n" :
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                    "inflate:         * literal 0x%02x\n", t->base));
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          *q++ = (Byte)t->base;
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          m--;
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          break;
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        }
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      }
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      else if (e & 32)
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      {
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        Tracevv((stderr, "inflate:         * end of block\n"));
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        UNGRAB
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        UPDATE
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        return Z_STREAM_END;
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      }
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      else
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      {
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        z->msg = (char*)"invalid literal/length code";
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        UNGRAB
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        UPDATE
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        return Z_DATA_ERROR;
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      }
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    } while (1);
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  } while (m >= 258 && n >= 10);
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  /* not enough input or output--restore pointers and return */
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  UNGRAB
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  UPDATE
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  return Z_OK;
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}