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plt-scheme  4.2.1
Classes | Defines | Functions
inffast.c File Reference
#include "zutil.h"
#include "inftrees.h"
#include "infblock.h"
#include "infcodes.h"
#include "infutil.h"
#include "inffast.h"

Go to the source code of this file.

Classes

struct  inflate_codes_state

Defines

#define exop   word.what.Exop
#define bits   word.what.Bits
#define GRABBITS(j)   {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}
#define UNGRAB   {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;}

Functions

int inflate_fast (uInt bl, uInt bd, inflate_huft *tl, inflate_huft *td, inflate_blocks_statef *s, z_streamp z)

Class Documentation

struct inflate_codes_state

Definition at line 12 of file infblock.c.

Class Members
Byte dbits
inflate_huft * dtree
int dummy
Byte lbits
uInt len
inflate_huft * ltree
inflate_codes_mode mode
union inflate_codes_state sub
union inflate_codes_state sub

Define Documentation

#define bits   word.what.Bits

Definition at line 17 of file inffast.c.

#define exop   word.what.Exop

Definition at line 16 of file inffast.c.

#define GRABBITS (   j)    {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}

Definition at line 20 of file inffast.c.

#define UNGRAB   {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;}

Definition at line 21 of file inffast.c.


Function Documentation

int inflate_fast ( uInt  bl,
uInt  bd,
inflate_huft *  tl,
inflate_huft *  td,
inflate_blocks_statef *  s,
z_streamp  z 
)

Definition at line 28 of file inffast.c.

{
  inflate_huft *t;      /* temporary pointer */
  uInt e;               /* extra bits or operation */
  uLong b;              /* bit buffer */
  uInt k;               /* bits in bit buffer */
  Bytef *p;             /* input data pointer */
  uInt n;               /* bytes available there */
  Bytef *q;             /* output window write pointer */
  uInt m;               /* bytes to end of window or read pointer */
  uInt ml;              /* mask for literal/length tree */
  uInt md;              /* mask for distance tree */
  uInt c;               /* bytes to copy */
  uInt d;               /* distance back to copy from */
  Bytef *r;             /* copy source pointer */

  /* load input, output, bit values */
  LOAD

  /* initialize masks */
  ml = inflate_mask[bl];
  md = inflate_mask[bd];

  /* do until not enough input or output space for fast loop */
  do {                          /* assume called with m >= 258 && n >= 10 */
    /* get literal/length code */
    GRABBITS(20)                /* max bits for literal/length code */
    if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
    {
      DUMPBITS(t->bits)
      Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
                "inflate:         * literal '%c'\n" :
                "inflate:         * literal 0x%02x\n", t->base));
      *q++ = (Byte)t->base;
      m--;
      continue;
    }
    do {
      DUMPBITS(t->bits)
      if (e & 16)
      {
        /* get extra bits for length */
        e &= 15;
        c = t->base + ((uInt)b & inflate_mask[e]);
        DUMPBITS(e)
        Tracevv((stderr, "inflate:         * length %u\n", c));

        /* decode distance base of block to copy */
        GRABBITS(15);           /* max bits for distance code */
        e = (t = td + ((uInt)b & md))->exop;
        do {
          DUMPBITS(t->bits)
          if (e & 16)
          {
            /* get extra bits to add to distance base */
            e &= 15;
            GRABBITS(e)         /* get extra bits (up to 13) */
            d = t->base + ((uInt)b & inflate_mask[e]);
            DUMPBITS(e)
            Tracevv((stderr, "inflate:         * distance %u\n", d));

            /* do the copy */
            m -= c;
            r = q - d;
            if (r < s->window)                  /* wrap if needed */
            {
              do {
                r += s->end - s->window;        /* force pointer in window */
              } while (r < s->window);          /* covers invalid distances */
              e = s->end - r;
              if (c > e)
              {
                c -= e;                         /* wrapped copy */
                do {
                    *q++ = *r++;
                } while (--e);
                r = s->window;
                do {
                    *q++ = *r++;
                } while (--c);
              }
              else                              /* normal copy */
              {
                *q++ = *r++;  c--;
                *q++ = *r++;  c--;
                do {
                    *q++ = *r++;
                } while (--c);
              }
            }
            else                                /* normal copy */
            {
              *q++ = *r++;  c--;
              *q++ = *r++;  c--;
              do {
                *q++ = *r++;
              } while (--c);
            }
            break;
          }
          else if ((e & 64) == 0)
          {
            t += t->base;
            e = (t += ((uInt)b & inflate_mask[e]))->exop;
          }
          else
          {
            z->msg = (char*)"invalid distance code";
            UNGRAB
            UPDATE
            return Z_DATA_ERROR;
          }
        } while (1);
        break;
      }
      if ((e & 64) == 0)
      {
        t += t->base;
        if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0)
        {
          DUMPBITS(t->bits)
          Tracevv((stderr, t->base >= 0x20 && t->base < 0x7f ?
                    "inflate:         * literal '%c'\n" :
                    "inflate:         * literal 0x%02x\n", t->base));
          *q++ = (Byte)t->base;
          m--;
          break;
        }
      }
      else if (e & 32)
      {
        Tracevv((stderr, "inflate:         * end of block\n"));
        UNGRAB
        UPDATE
        return Z_STREAM_END;
      }
      else
      {
        z->msg = (char*)"invalid literal/length code";
        UNGRAB
        UPDATE
        return Z_DATA_ERROR;
      }
    } while (1);
  } while (m >= 258 && n >= 10);

  /* not enough input or output--restore pointers and return */
  UNGRAB
  UPDATE
  return Z_OK;
}