inflate.c

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{
  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 */

DEBG("<dyn");

  /* 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
    return 1;                   /* bad lengths */

DEBG("dyn1 ");

  /* 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;

DEBG("dyn2 ");

  /* build decoding table for trees--single level, 7 bit lookup */
  bl = 7;
  if ((i = huft_build(ll, 19, 19, NULL, NULL, &tl, &bl)) != 0)
  {
    if (i == 1)
      huft_free(tl);
    return i;                   /* incomplete code set */
  }

DEBG("dyn3 ");

  /* 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)
        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)
        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)
        return 1;
      while (j--)
        ll[i++] = 0;
      l = 0;
    }
  }

DEBG("dyn4 ");

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

DEBG("dyn5 ");

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

DEBG("dyn5a ");

  /* build the decoding tables for literal/length and distance codes */
  bl = lbits;
  if ((i = huft_build(ll, nl, 257, cplens, cplext, &tl, &bl)) != 0)
  {
DEBG("dyn5b ");
    if (i == 1) {
      error(" incomplete literal tree");
      huft_free(tl);
    }
    return i;                   /* incomplete code set */
  }
DEBG("dyn5c ");
  bd = dbits;
  if ((i = huft_build(ll + nl, nd, 0, cpdist, cpdext, &td, &bd)) != 0)
  {
DEBG("dyn5d ");
    if (i == 1) {
      error(" incomplete distance tree");
#ifdef PKZIP_BUG_WORKAROUND
      i = 0;
    }
#else
      huft_free(td);
    }
    huft_free(tl);
    return i;                   /* incomplete code set */
#endif
  }

DEBG("dyn6 ");

  /* decompress until an end-of-block code */
  if (inflate_codes(tl, td, bl, bd))
    return 1;

DEBG("dyn7 ");

  /* free the decoding tables, return */
  huft_free(tl);
  huft_free(td);

  DEBG(">");
  return 0;
}



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

  DEBG("<blk");

  /* 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)
    return inflate_dynamic();
  if (t == 0)
    return inflate_stored();
  if (t == 1)
    return inflate_fixed();

  DEBG(">");

  /* bad block type */
  return 2;
}



STATIC int inflate()
/* decompress an inflated entry */
{
  int e;                /* last block flag */
  int r;                /* result code */
  unsigned h;           /* maximum struct huft's malloc'ed */
  void *ptr;

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


  /* decompress until the last block */
  h = 0;
  do {
    hufts = 0;
    gzip_mark(&ptr);
    if ((r = inflate_block(&e)) != 0) {
      gzip_release(&ptr);	    
      return r;
    }
    gzip_release(&ptr);
    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;
    unget_byte();
  }

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


  /* return success */
#ifdef DEBUG
  fprintf(stderr, "<%u> ", h);
#endif /* DEBUG */
  return 0;
}

/**********************************************************************
 *
 * The following are support routines for inflate.c
 *
 **********************************************************************/

static ulg crc_32_tab[256];
static ulg crc;		/* initialized in makecrc() so it'll reside in bss */
#define CRC_VALUE (crc ^ 0xffffffffL)

/*
 * Code to compute the CRC-32 table. Borrowed from 
 * gzip-1.0.3/makecrc.c.
 */

static void
makecrc(void)
{
/* Not copyrighted 1990 Mark Adler	*/

  unsigned long c;      /* crc shift register */
  unsigned long e;      /* polynomial exclusive-or pattern */
  int i;                /* counter for all possible eight bit values */
  int k;                /* byte being shifted into crc apparatus */

  /* terms of polynomial defining this crc (except x^32): */
  static const int p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};

  /* Make exclusive-or pattern from polynomial */
  e = 0;
  for (i = 0; i < sizeof(p)/sizeof(int); i++)
    e |= 1L << (31 - p[i]);

  crc_32_tab[0] = 0;

  for (i = 1; i < 256; i++)
  {
    c = 0;
    for (k = i | 256; k != 1; k >>= 1)
    {
      c = c & 1 ? (c >> 1) ^ e : c >> 1;
      if (k & 1)
        c ^= e;
    }
    crc_32_tab[i] = c;
  }

  /* this is initialized here so this code could reside in ROM */
  crc = (ulg)0xffffffffL; /* shift register contents */
}

/* gzip flag byte */
#define ASCII_FLAG   0x01 /* bit 0 set: file probably ASCII text */
#define CONTINUATION 0x02 /* bit 1 set: continuation of multi-part gzip file */
#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
#define ORIG_NAME    0x08 /* bit 3 set: original file name present */
#define COMMENT      0x10 /* bit 4 set: file comment present */
#define ENCRYPTED    0x20 /* bit 5 set: file is encrypted */
#define RESERVED     0xC0 /* bit 6,7:   reserved */

/*
 * Do the uncompression!
 */
int gunzip()
{
    int res;

    /* Decompress */
    if ((res = inflate())) {
	    switch (res) {
	    case 0:
		    break;
	    case 1:
		    error("invalid compressed format (err=1)");
		    break;
	    case 2:
		    error("invalid compressed format (err=2)");
		    break;
	    case 3:
		    error("out of memory");
		    break;
	    default:
		    error("invalid compressed format (other)");
	    }
	    return -1;
    }

    return 0;
}