inflate.c

GZip Compress Souce Code

  {
  int i;                /* temporary variable */
  struct huft *tl;      /* literal/length code table */
  struct huft *td;      /* distance code table */
  int bl;               /* lookup bits for tl */
  int bd;               /* lookup bits for td */
  unsigned l[288];      /* length list for huft_build */


  /* set up literal table */
  for (i = 0; i < 144; i++)
    l[i] = 8;
  for (; i < 256; i++)
    l[i] = 9;
  for (; i < 280; i++)
    l[i] = 7;
  for (; i < 288; i++)          /* make a complete, but wrong code set */
    l[i] = 8;
  bl = 7;
  tl =0;
  if ((i = huft_build(l, 288, 257, cplens,31, cplext,31, &tl, &bl)) != 0)
    { 
     if (tl) huft_free(tl);
     DBGPrintfo(("inflate_fixed(out1)\r\n"));
     return  i; 
    }


  /* set up distance table */
  for (i = 0; i < 30; i++)      /* make an incomplete code set */
    l[i] = 5;
  bd = 5;
  td=0;
  if ((i = huft_build(l, 30, 0, cpdist,30, cpdext,30, &td, &bd)) > 1)
  {
    if (tl) huft_free(tl);
    if (td) huft_free(td);
    
    DBGPrintfo(("inflate_fixed(out2)\r\n"));
    return  i;
  }


  /* decompress until an end-of-block code */
  if (inflate_codes(tl, td, bl, bd))
    { 
    if (tl) huft_free(tl);
    if (td) huft_free(td);
	
     DBGPrintfo(("inflate_fixed(out3)\r\n"));
     return  1; 
    }


  /* free the decoding tables, return */
    if (tl) huft_free(tl);
    if (td) huft_free(td);
  
  DBGPrintfo(("inflate_fixed(out4)\r\n"));
  return  0;

  }
}



int inflate_dynamic()
/* decompress an inflated type 2 (dynamic Huffman codes) block. */
{
  DBGPrintfi(("inflate_dynamic(In)\r\n"));
  {
  int i;                /* temporary variables */
  unsigned j;
  unsigned l;           /* last length */
  unsigned m;           /* mask for bit lengths table */
  unsigned n;           /* number of lengths to get */
  struct huft *tl;      /* literal/length code table */
  struct huft *td;      /* distance code table */
  int bl;               /* lookup bits for tl */
  int bd;               /* lookup bits for td */
  unsigned nb;          /* number of bit length codes */
  unsigned nl;          /* number of literal/length codes */
  unsigned nd;          /* number of distance codes */
#ifdef PKZIP_BUG_WORKAROUND
  unsigned ll[288+32];  /* literal/length and distance code lengths */
#else
  unsigned ll[286+30];  /* literal/length and distance code lengths */
#endif
  register ulg b;       /* bit buffer */
  register unsigned k;  /* number of bits in bit buffer */


  /* make local bit buffer */
  b = bb;
  k = bk;


  /* read in table lengths */
  NEEDBITS(5)
  nl = 257 + ((unsigned)b & 0x1f);      /* number of literal/length codes */
  DUMPBITS(5)
  NEEDBITS(5)
  nd = 1 + ((unsigned)b & 0x1f);        /* number of distance codes */
  DUMPBITS(5)
  NEEDBITS(4)
  nb = 4 + ((unsigned)b & 0xf);         /* number of bit length codes */
  DUMPBITS(4)
#ifdef PKZIP_BUG_WORKAROUND
  if (nl > 288 || nd > 32)
#else
  if (nl > 286 || nd > 30)
#endif
    { 
     DBGPrintfo(("inflate_dynamic(out1)\r\n"));
     return  1; 
    }                   /* bad lengths */


  /* read in bit-length-code lengths */
  for (j = 0; j < nb; j++)
  {
    NEEDBITS(3)
    ll[border[j]] = (unsigned)b & 7;
    DUMPBITS(3)
  }
  for (; j < 19; j++)
    ll[border[j]] = 0;


  /* build decoding table for trees--single level, 7 bit lookup */
  bl = 7;
  tl = 0;
  if ((i = huft_build(ll, 19, 19, NULL,0, NULL,0, &tl, &bl)) != 0)
  {
    if (tl) huft_free(tl);

    DBGPrintfo(("inflate_dynamic(out2)\r\n"));
    return  i;                   /* incomplete code set */
  }

  
  /* read in literal and distance code lengths */
  n = nl + nd;
  m = mask_bits[bl];
  i = l = 0;
  while ((unsigned)i < n)
  {
    NEEDBITS((unsigned)bl)
    j = (td = tl + ((unsigned)b & m))->b;
    DUMPBITS(j)
    j = td->v.n;
    if (j < 16)                 /* length of code in bits (0..15) */
      ll[i++] = l = j;          /* save last length in l */
    else if (j == 16)           /* repeat last length 3 to 6 times */
    {
      NEEDBITS(2)
      j = 3 + ((unsigned)b & 3);
      DUMPBITS(2)
      if ((unsigned)i + j > n)
        { 
	  if (tl) huft_free(tl);
         DBGPrintfo(("inflate_dynamic(out3)\r\n"));
         return  1; 
        }
      while (j--)
        ll[i++] = l;
    }
    else if (j == 17)           /* 3 to 10 zero length codes */
    {
      NEEDBITS(3)
      j = 3 + ((unsigned)b & 7);
      DUMPBITS(3)
      if ((unsigned)i + j > n)
        {
         if (tl) huft_free(tl);
         DBGPrintfo(("inflate_dynamic(out4)\r\n"));
         return  1; 
        }
      while (j--)
        ll[i++] = 0;
      l = 0;
    }
    else                        /* j == 18: 11 to 138 zero length codes */
    {
      NEEDBITS(7)
      j = 11 + ((unsigned)b & 0x7f);
      DUMPBITS(7)
      if ((unsigned)i + j > n)
        { 
	  if (tl) huft_free(tl);
         DBGPrintfo(("inflate_dynamic(out5)\r\n"));
         return  1; 
        }
      while (j--)
        ll[i++] = 0;
      l = 0;
    }
  }

  /* free decoding table for trees */
 if (tl) huft_free(tl);

  /* restore the global bit buffer */
  bb = b;
  bk = k;


  /* build the decoding tables for literal/length and distance codes */
  bl = lbits;
  tl = 0;
  if ((i = huft_build(ll, nl, 257, cplens, 31, cplext, 31,&tl, &bl)) != 0)
  {
    if (tl) huft_free(tl);  	
    DBGPrintfo(("inflate_dynamic(out6)\r\n"));
    return  i;                   /* incomplete code set */
  }

  bd = dbits;
  td = 0;
  if ((i = huft_build(ll + nl, nd, 0, cpdist, 30, cpdext, 30, &td, &bd)) != 0)
  {
    if (tl) huft_free(tl);
    if (td) huft_free(td);
    DBGPrintfo(("inflate_dynamic(out7)\r\n"));
    return  i;                   /* incomplete code set */
  }


  /* decompress until an end-of-block code */
  if (inflate_codes(tl, td, bl, bd))
    { 
    if (tl) huft_free(tl);
    if (td) huft_free(td);
     DBGPrintfo(("inflate_dynamic(out8)\r\n"));
     return  1; 
    }


  /* free the decoding tables, return */
    if (tl) huft_free(tl);
    if (td) huft_free(td);
  DBGPrintfo(("inflate_dynamic(out9)\r\n"));
  return  0;

  }
}



int inflate_block(e)
int *e;                 /* last block flag */
/* decompress an inflated block */
{
  DBGPrintfi(("inflate_block(In)\r\n"));
  {
  unsigned t;           /* block type */
  register ulg b;       /* bit buffer */
  register unsigned k;  /* number of bits in bit buffer */


  /* make local bit buffer */
  b = bb;
  k = bk;


  /* read in last block bit */
  NEEDBITS(1)
  *e = (int)b & 1;
  DUMPBITS(1)


  /* read in block type */
  NEEDBITS(2)
  t = (unsigned)b & 3;
  DUMPBITS(2)


  /* restore the global bit buffer */
  bb = b;
  bk = k;


  /* inflate that block type */
  if (t == 2)
    { 
     int retTemp;
	 
     retTemp=(int)( inflate_dynamic());
	 
     DBGPrintfo(("inflate_block(out1)\r\n"));
     return retTemp;
    }
  if (t == 0)
    { 
     int retTemp;
     retTemp=(int)( inflate_stored());
     DBGPrintfo(("inflate_block(out2)\r\n"));
     return retTemp;
    }
  if (t == 1)
    { 
     int retTemp;
     retTemp=(int)( inflate_fixed());
     DBGPrintfo(("inflate_block(out3)\r\n"));
     return retTemp;
    }


  /* bad block type */
  DBGPrintfo(("inflate_block(out4)\r\n"));
  return  2;

  }
}



int gzip_inflate()
/* decompress an inflated entry */
{
  DBGPrintfi(("inflate(In)\r\n"));
  {
  int e;                /* last block flag */
  int r;                /* result code */
  unsigned h;           /* maximum struct huft's malloc'ed */


  /* initialize window, bit buffer */
  wp = 0;
  bk = 0;
  bb = 0;


  /* decompress until the last block */
  h = 0;
  do {
    hufts = 0;
    if ((r = inflate_block(&e)) != 0)
      { 
       DBGPrintfo(("inflate(out1)\r\n"));
       return  r; 
      }
    if (hufts > h)
      h = hufts;
  } while (!e);

  /* Undo too much lookahead. The next read will be byte aligned so we
   * can discard unused bits in the last meaningful byte.
   */
  while (bk >= 8) {
    bk -= 8;
    inptr--;
  }

  /* flush out slide */
  flush_output(wp);

  /* return success */
#ifdef DEBUG
  fprintf(stderr, "<%u> ", h);
#endif /* DEBUG */
  
  DBGPrintfo(("inflate(out2)\r\n"));
  return  0;

  }
}