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inflate.c

/*
 * inflate.c -- Not copyrighted 1992 by Mark Adler
 * version c10p1, 10 January 1993
 */
/* 
 * Adapted for booting Linux by Hannu Savolainen 1993
 * based on gzip-1.0.3 
 */

#include "gzip.h"
#define slide window

#include <linux/types.h>

extern void *malloc(size_t size);
extern void free(void *ptr);

#if 0
#define DEBG(x)         {register long sp asm("30"); \
                   printf("%s (sp=%lx)\n", x, sp);}
#define DEBG1(x)  {register long sp asm("30"); \
                   printf("    %s (sp=%lx)\n", x, sp);}
#else
#define DEBG(x)
#define DEBG1(x)
#endif


struct huft {
  unsigned char e;      /* number of extra bits or operation */
  unsigned char b;      /* number of bits in this code or subcode */
  union {
    unsigned short n;   /* literal, length base, or distance base */
    struct huft *t;     /* pointer to next level of table */
  } v;
};


/* Function prototypes */
int huft_build (unsigned *, unsigned, unsigned, unsigned short *,
            unsigned short *, struct huft **, int *);
int huft_free (struct huft *);
int inflate_codes (struct huft *, struct huft *, int, int);
int inflate_stored (void);
int inflate_fixed (void);
int inflate_dynamic (void);
int inflate_block (int *);
int inflate (void);


#define wp outcnt
#define flush_output(w) (wp=(w),flush_window())

/* Tables for deflate from PKZIP's appnote.txt. */
static unsigned border[] = {
    /* Order of the bit length code lengths */
    16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
};

static unsigned short cplens[] = {
    /* Copy lengths for literal codes 257..285 */
    3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
    35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0
};

/* note: see note #13 above about the 258 in this list. */
static unsigned short cplext[] = {
    /* Extra bits for literal codes 257..285 */
    0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
    3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 99, 99     /* 99==invalid */
};

static unsigned short cpdist[] = {
    /* Copy offsets for distance codes 0..29 */
    1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
    257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
    8193, 12289, 16385, 24577
};

static unsigned short cpdext[] = {
    /* Extra bits for distance codes */
    0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
    7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
    12, 12, 13, 13
};


unsigned long bb;       /* bit buffer */
unsigned bk;                  /* bits in bit buffer */

unsigned short mask_bits[] = {
    0x0000,
    0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
    0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
};

#define NEXTBYTE()  (unsigned char)get_byte()
#define NEEDBITS(n) {while(k<(n)){b|=((unsigned long)NEXTBYTE())<<k;k+=8;}}
#define DUMPBITS(n) {b>>=(n);k-=(n);}

int lbits = 9;          /* bits in base literal/length lookup table */
int dbits = 6;          /* bits in base distance lookup table */


/*
 * If BMAX needs to be larger than 16, then h and x[] should be
 * unsigned long.
 */
#define BMAX 16         /* maximum bit length of any code (16 for explode) */
#define N_MAX 288       /* maximum number of codes in any set */


unsigned hufts;         /* track memory usage */


/*
 * Given a list of code lengths and a maximum table size, make a set
 * of tables to decode that set of codes.  Return zero on success, one
 * if the given code set is incomplete (the tables are still built in
 * this case), two if the input is invalid (all zero length codes or
 * an oversubscribed set of lengths), and three if not enough
 * memory.
 */
int
huft_build(b, n, s, d, e, t, m)
unsigned *b;            /* code lengths in bits (all assumed <= BMAX) */
unsigned n;             /* number of codes (assumed <= N_MAX) */
unsigned s;             /* number of simple-valued codes (0..s-1) */
unsigned short *d;                 /* list of base values for non-simple codes */
unsigned short *e;                 /* list of extra bits for non-simple codes */
struct huft **t;        /* result: starting table */
int *m;                 /* maximum lookup bits, returns actual */
{
  unsigned a;                   /* counter for codes of length k */
  unsigned c[BMAX+1];           /* bit length count table */
  unsigned f;                   /* i repeats in table every f entries */
  int g;                        /* maximum code length */
  int h;                        /* table level */
  register unsigned i;          /* counter, current code */
  register unsigned j;          /* counter */
  register int k;               /* number of bits in current code */
  int l;                        /* bits per table (returned in m) */
  register unsigned *p;         /* pointer into c[], b[], or v[] */
  register struct huft *q;      /* points to current table */
  struct huft r;                /* table entry for structure assignment */
  struct huft *u[BMAX];         /* table stack */
  unsigned v[N_MAX];            /* values in order of bit length */
  register int w;               /* bits before this table == (l * h) */
  unsigned x[BMAX+1];           /* bit offsets, then code stack */
  unsigned *xp;                 /* pointer into x */
  int y;                        /* number of dummy codes added */
  unsigned z;                   /* number of entries in current table */

DEBG("huft1 ");

  /* Generate counts for each bit length */
  memzero(c, sizeof(c));
  p = b;  i = n;
  do {
    c[*p++]++;                  /* assume all entries <= BMAX */
  } while (--i);
  if (c[0] == n)                /* null input--all zero length codes */
  {
    *t = (struct huft *)NULL;
    *m = 0;
    return 0;
  }

DEBG("huft2 ");

  /* Find minimum and maximum length, bound *m by those */
  l = *m;
  for (j = 1; j <= BMAX; j++)
    if (c[j])
      break;
  k = j;                        /* minimum code length */
  if ((unsigned)l < j)
    l = j;
  for (i = BMAX; i; i--)
    if (c[i])
      break;
  g = i;                        /* maximum code length */
  if ((unsigned)l > i)
    l = i;
  *m = l;

DEBG("huft3 ");

  /* Adjust last length count to fill out codes, if needed */
  for (y = 1 << j; j < i; j++, y <<= 1)
    if ((y -= c[j]) < 0)
      return 2;                 /* bad input: more codes than bits */
  if ((y -= c[i]) < 0)
    return 2;
  c[i] += y;

DEBG("huft4 ");

  /* Generate starting offsets into the value table for each length */
  x[1] = j = 0;
  p = c + 1;  xp = x + 2;
  while (--i) {                 /* note that i == g from above */
    *xp++ = (j += *p++);
  }

DEBG("huft5 ");

  /* Make a table of values in order of bit lengths */
  p = b;  i = 0;
  do {
    if ((j = *p++) != 0)
      v[x[j]++] = i;
  } while (++i < n);

DEBG("h6 ");

  /* Generate the Huffman codes and for each, make the table entries */
  x[0] = i = 0;                 /* first Huffman code is zero */
  p = v;                        /* grab values in bit order */
  h = -1;                       /* no tables yet--level -1 */
  w = -l;                       /* bits decoded == (l * h) */
  u[0] = (struct huft *)NULL;   /* just to keep compilers happy */
  q = (struct huft *)NULL;      /* ditto */
  z = 0;                        /* ditto */
DEBG("h6a ");

  /* go through the bit lengths (k already is bits in shortest code) */
  for (; k <= g; k++)
  {
DEBG("h6b ");
    a = c[k];
    while (a--)
    {
DEBG("h6b1 ");
      /* here i is the Huffman code of length k bits for value *p */
      /* make tables up to required level */
      while (k > w + l)
      {
DEBG1("1 ");
        h++;
        w += l;                 /* previous table always l bits */

        /* compute minimum size table less than or equal to l bits */
        z = (z = g - w) > (unsigned)l ? l : z;  /* upper limit on table size */
        if ((f = 1 << (j = k - w)) > a + 1)     /* try a k-w bit table */
        {                       /* too few codes for k-w bit table */
DEBG1("2 ");
          f -= a + 1;           /* deduct codes from patterns left */
          xp = c + k;
          while (++j < z)       /* try smaller tables up to z bits */
          {
            if ((f <<= 1) <= *++xp)
              break;            /* enough codes to use up j bits */
            f -= *xp;           /* else deduct codes from patterns */
          }
        }
DEBG1("3 ");
        z = 1 << j;             /* table entries for j-bit table */

        /* allocate and link in new table */
        q = (struct huft *)malloc((z + 1)*sizeof(struct huft));
DEBG1("4 ");
        hufts += z + 1;         /* track memory usage */
        *t = q + 1;             /* link to list for huft_free() */
        *(t = &(q->v.t)) = (struct huft *)NULL;
        u[h] = ++q;             /* table starts after link */

DEBG1("5 ");
        /* connect to last table, if there is one */
        if (h)
        {
          x[h] = i;             /* save pattern for backing up */
          r.b = (unsigned char)l;         /* bits to dump before this table */
          r.e = (unsigned char)(16 + j);  /* bits in this table */
          r.v.t = q;            /* pointer to this table */
          j = i >> (w - l);     /* (get around Turbo C bug) */
          u[h-1][j] = r;        /* connect to last table */
        }
DEBG1("6 ");
      }
DEBG("h6c ");

      /* set up table entry in r */
      r.b = (unsigned char)(k - w);
      if (p >= v + n)
        r.e = 99;               /* out of values--invalid code */
      else if (*p < s)
      {
        r.e = (unsigned char)(*p < 256 ? 16 : 15);    /* 256 is end-of-block code */
        r.v.n = *p++;           /* simple code is just the value */
      }
      else
      {
        r.e = (unsigned char)e[*p - s];   /* non-simple--look up in lists */
        r.v.n = d[*p++ - s];
      }
DEBG("h6d ");

      /* fill code-like entries with r */
      f = 1 << (k - w);
      for (j = i >> w; j < z; j += f)
        q[j] = r;

      /* backwards increment the k-bit code i */
      for (j = 1 << (k - 1); i & j; j >>= 1)
        i ^= j;
      i ^= j;

      /* backup over finished tables */
      while ((i & ((1 << w) - 1)) != x[h])
      {
        h--;                    /* don't need to update q */
        w -= l;
      }
DEBG("h6e ");
    }
DEBG("h6f ");
  }

DEBG("huft7 ");

  /* Return true (1) if we were given an incomplete table */
  return y != 0 && g != 1;
}



int huft_free(t)
struct huft *t;         /* table to free */
/* Free the malloc'ed tables built by huft_build(), which makes a linked
   list of the tables it made, with the links in a dummy first entry of
   each table. */
{
  register struct huft *p, *q;


  /* Go through linked list, freeing from the malloced (t[-1]) address. */
  p = t;
  while (p != (struct huft *)NULL)
  {
    q = (--p)->v.t;
    free(p);
    p = q;
  } 
  return 0;
}


int inflate_codes(tl, td, bl, bd)
struct huft *tl, *td;   /* literal/length and distance decoder tables */
int bl, bd;             /* number of bits decoded by tl[] and td[] */
/* inflate (decompress) the codes in a deflated (compressed) block.
   Return an error code or zero if it all goes ok. */
{
  register unsigned e;  /* table entry flag/number of extra bits */
  unsigned n, d;        /* length and index for copy */
  unsigned w;           /* current window position */
  struct huft *t;       /* pointer to table entry */
  unsigned ml, md;      /* masks for bl and bd bits */
  register unsigned long b;   /* bit buffer */
  register unsigned k;        /* number of bits in bit buffer */


  /* make local copies of globals */
  b = bb;                       /* initialize bit buffer */
  k = bk;
  w = wp;                       /* initialize window position */

  /* inflate the coded data */
  ml = mask_bits[bl];           /* precompute masks for speed */
  md = mask_bits[bd];
  for (;;)                      /* do until end of block */
  {
    NEEDBITS((unsigned)bl)
    if ((e = (t = tl + ((unsigned)b & ml))->e) > 16)
      do {
        if (e == 99)
          return 1;
        DUMPBITS(t->b)
        e -= 16;
        NEEDBITS(e)
      } while ((e = (t = t->v.t + ((unsigned)b & mask_bits[e]))->e) > 16);
    DUMPBITS(t->b)
    if (e == 16)                /* then it's a literal */
    {
      slide[w++] = (unsigned char)t->v.n;
      if (w == WSIZE)
      {
        flush_output(w);
        w = 0;
      }
    }
    else                        /* it's an EOB or a length */
    {
      /* exit if end of block */
      if (e == 15)
        break;

      /* get length of block to copy */
      NEEDBITS(e)
      n = t->v.n + ((unsigned)b & mask_bits[e]);
      DUMPBITS(e);

      /* decode distance of block to copy */
      NEEDBITS((unsigned)bd)
      if ((e = (t = td + ((unsigned)b & md))->e) > 16)
        do {
          if (e == 99)
            return 1;
          DUMPBITS(t->b)
          e -= 16;
          NEEDBITS(e)
        } while ((e = (t = t->v.t + ((unsigned)b & mask_bits[e]))->e) > 16);
      DUMPBITS(t->b)
      NEEDBITS(e)
      d = w - t->v.n - ((unsigned)b & mask_bits[e]);
      DUMPBITS(e)

      /* do the copy */
      do {
        n -= (e = (e = WSIZE - ((d &= WSIZE-1) > w ? d : w)) > n ? n : e);
#if !defined(NOMEMCPY) && !defined(DEBUG)
        if (w - d >= e)         /* (this test assumes unsigned comparison) */
        {
          memcpy(slide + w, slide + d, e);
          w += e;
          d += e;
        }
        else                      /* do it slow to avoid memcpy() overlap */
#endif /* !NOMEMCPY */
          do {
            slide[w++] = slide[d++];
          } while (--e);
        if (w == WSIZE)
        {
          flush_output(w);
          w = 0;
        }
      } while (n);
    }
  }


  /* restore the globals from the locals */
  wp = w;                       /* restore global window pointer */
  bb = b;                       /* restore global bit buffer */
  bk = k;

  /* done */
  return 0;
}



int inflate_stored()
/* "decompress" an inflated type 0 (stored) block. */
{
  unsigned n;           /* number of bytes in block */
  unsigned w;           /* current window position */
  register unsigned long b;   /* bit buffer */
  register unsigned k;        /* number of bits in bit buffer */

DEBG("<stor");

  /* make local copies of globals */
  b = bb;                       /* initialize bit buffer */
  k = bk;
  w = wp;                       /* initialize window position */


  /* go to byte boundary */
  n = k & 7;
  DUMPBITS(n);


  /* get the length and its complement */
  NEEDBITS(16)
  n = ((unsigned)b & 0xffff);
  DUMPBITS(16)
  NEEDBITS(16)
  if (n != (unsigned)((~b) & 0xffff))
    return 1;                   /* error in compressed data */
  DUMPBITS(16)


  /* read and output the compressed data */
  while (n--)
  {
    NEEDBITS(8)
    slide[w++] = (unsigned char)b;
    if (w == WSIZE)
    {
      flush_output(w);
      w = 0;
    }
    DUMPBITS(8)
  }


  /* restore the globals from the locals */
  wp = w;                       /* restore global window pointer */
  bb = b;                       /* restore global bit buffer */
  bk = k;

  DEBG(">");
  return 0;
}



int inflate_fixed()
/* decompress an inflated type 1 (fixed Huffman codes) block.  We should
   either replace this with a custom decoder, or at least precompute the
   Huffman tables. */
{
  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 */

DEBG("<fix");

  /* 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;
  if ((i = huft_build(l, 288, 257, cplens, cplext, &tl, &bl)) != 0)
    return i;


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

    DEBG(">");
    return i;
  }


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


  /* free the decoding tables, return */
  huft_free(tl);
  huft_free(td);
  return 0;
}



int inflate_dynamic()
/* decompress an inflated type 2 (dynamic Huffman codes) block. */
{
  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 unsigned long 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) {
      unzip_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) {
      unzip_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;
}



int inflate_block(e)
int *e;                 /* last block flag */
/* decompress an inflated block */
{
  unsigned t;                 /* block type */
  register unsigned long 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;
}



int inflate()
/* decompress an inflated entry */
{
  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)
      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 */
  return 0;
}

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