/* inflate.c -- Not copyrighted 1992 by Mark Adler

   version c10p1, 10 January 1993 */

/* You can do whatever you like with this source file, though I would

   prefer that if you modify it and redistribute it that you include

   comments to that effect with your name and the date.  Thank you.

   [The history has been moved to the file ChangeLog.]

 */

/*

   Inflate deflated (PKZIP's method 8 compressed) data.  The compression

   method searches for as much of the current string of bytes (up to a

   length of 258) in the previous 32K bytes.  If it doesn't find any

   matches (of at least length 3), it codes the next byte.  Otherwise, it

   codes the length of the matched string and its distance backwards from

   the current position.  There is a single Huffman code that codes both

   single bytes (called "literals") and match lengths.  A second Huffman

   code codes the distance information, which follows a length code.  Each

   length or distance code actually represents a base value and a number

   of "extra" (sometimes zero) bits to get to add to the base value.  At

   the end of each deflated block is a special end-of-block (EOB) literal/

   length code.  The decoding process is basically: get a literal/length

   code; if EOB then done; if a literal, emit the decoded byte; if a

   length then get the distance and emit the referred-to bytes from the

   sliding window of previously emitted data.

   There are (currently) three kinds of inflate blocks: stored, fixed, and

   dynamic.  The compressor deals with some chunk of data at a time, and

   decides which method to use on a chunk-by-chunk basis.  A chunk might

   typically be 32K or 64K.  If the chunk is uncompressible, then the

   "stored" method is used.  In this case, the bytes are simply stored as

   is, eight bits per byte, with none of the above coding.  The bytes are

   preceded by a count, since there is no longer an EOB code.

   If the data is compressible, then either the fixed or dynamic methods

   are used.  In the dynamic method, the compressed data is preceded by

   an encoding of the literal/length and distance Huffman codes that are

   to be used to decode this block.  The representation is itself Huffman

   coded, and so is preceded by a description of that code.  These code

   descriptions take up a little space, and so for small blocks, there is

   a predefined set of codes, called the fixed codes.  The fixed method is

   used if the block codes up smaller that way (usually for quite small

   chunks), otherwise the dynamic method is used.  In the latter case, the

   codes are customized to the probabilities in the current block, and so

   can code it much better than the pre-determined fixed codes.

   The Huffman codes themselves are decoded using a mutli-level table

   lookup, in order to maximize the speed of decoding plus the speed of

   building the decoding tables.  See the comments below that precede the

   lbits and dbits tuning parameters.

 */

/*

   Notes beyond the 1.93a appnote.txt:

   1. Distance pointers never point before the beginning of the output

      stream.

   2. Distance pointers can point back across blocks, up to 32k away.

   3. There is an implied maximum of 7 bits for the bit length table and

      15 bits for the actual data.

   4. If only one code exists, then it is encoded using one bit.  (Zero

      would be more efficient, but perhaps a little confusing.)  If two

      codes exist, they are coded using one bit each (0 and 1).

   5. There is no way of sending zero distance codes--a dummy must be

      sent if there are none.  (History: a pre 2.0 version of PKZIP would

      store blocks with no distance codes, but this was discovered to be

      too harsh a criterion.)  Valid only for 1.93a.  2.04c does allow

      zero distance codes, which is sent as one code of zero bits in

      length.

   6. There are up to 286 literal/length codes.  Code 256 represents the

      end-of-block.  Note however that the static length tree defines

      288 codes just to fill out the Huffman codes.  Codes 286 and 287

      cannot be used though, since there is no length base or extra bits

      defined for them.  Similarly, there are up to 30 distance codes.

      However, static trees define 32 codes (all 5 bits) to fill out the

      Huffman codes, but the last two had better not show up in the data.

   7. Unzip can check dynamic Huffman blocks for complete code sets.

      The exception is that a single code would not be complete (see #4).

   8. The five bits following the block type is really the number of

      literal codes sent minus 257.

   9. Length codes 8,16,16 are interpreted as 13 length codes of 8 bits

      (1+6+6).  Therefore, to output three times the length, you output

      three codes (1+1+1), whereas to output four times the same length,

      you only need two codes (1+3).  Hmm.

  10. In the tree reconstruction algorithm, Code = Code + Increment

      only if BitLength(i) is not zero.  (Pretty obvious.)

  11. Correction: 4 Bits: # of Bit Length codes - 4     (4 - 19)

  12. Note: length code 284 can represent 227-258, but length code 285

      really is 258.  The last length deserves its own, short code

      since it gets used a lot in very redundant files.  The length

      258 is special since 258 - 3 (the min match length) is 255.

  13. The literal/length and distance code bit lengths are read as a

      single stream of lengths.  It is possible (and advantageous) for

      a repeat code (16, 17, or 18) to go across the boundary between

      the two sets of lengths.

 */

#include "inflate.h"

extern void* memcpy(void*, const void*, unsigned);

extern void* memset(void*, int, unsigned);

/* Huffman code lookup table entry--this entry is four bytes for machines

   that have 16-bit pointers (e.g. PC's in the small or medium model).

   Valid extra bits are 0..13.  e == 15 is EOB (end of block), e == 16

   means that v is a literal, 16 < e < 32 means that v is a pointer to

   the next table, which codes e - 16 bits, and lastly e == 99 indicates

   an unused code.  If a code with e == 99 is looked up, this implies an

   error in the data. */

struct huft {

  uch e;                /* number of extra bits or operation */

  uch b;                /* number of bits in this code or subcode */

  union {

    ush 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, const ush *, const ush *,

                   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);

/* The inflate algorithm uses a sliding 32K byte window on the uncompressed

   stream to find repeated byte strings.  This is implemented here as a

   circular buffer.  The index is updated simply by incrementing and then

   and'ing with 0x7fff (32K-1). */

/* It is left to other modules to supply the 32K area.  It is assumed

   to be usable as if it were declared "uch slide[32768];" or as just

   "uch *slide;" and then malloc'ed in the latter case.  The definition

   must be in unzip.h, included above. */

/* unsigned wp;             current position in slide */

/*#define wp outcnt*/

/*#define flush_output(w) (wp=(w),flush_window())*/

/* Tables for deflate from PKZIP's appnote.txt. */

static const 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 const ush 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 const ush 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 const ush 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 const ush 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};

/* Macros for inflate() bit peeking and grabbing.

   The usage is:

        NEEDBITS(j)

        x = b & mask_bits[j];

        DUMPBITS(j)

   where NEEDBITS makes sure that b has at least j bits in it, and

   DUMPBITS removes the bits from b.  The macros use the variable k

   for the number of bits in b.  Normally, b and k are register

   variables for speed, and are initialized at the beginning of a

   routine that uses these macros from a global bit buffer and count.

   If we assume that EOB will be the longest code, then we will never

   ask for bits with NEEDBITS that are beyond the end of the stream.

   So, NEEDBITS should not read any more bytes than are needed to

   meet the request.  Then no bytes need to be "returned" to the buffer

   at the end of the last block.

   However, this assumption is not true for fixed blocks--the EOB code

   is 7 bits, but the other literal/length codes can be 8 or 9 bits.

   (The EOB code is shorter than other codes because fixed blocks are

   generally short.  So, while a block always has an EOB, many other

   literal/length codes have a significantly lower probability of

   showing up at all.)  However, by making the first table have a

   lookup of seven bits, the EOB code will be found in that first

   lookup, and so will not require that too many bits be pulled from

   the stream.

 */

ulg bb;                         /* bit buffer */

unsigned bk;                    /* bits in bit buffer */

static const ush mask_bits[] = {

    0x0000,

    0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,

    0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff

};

#define get_byte()  (inptr < inbuf_end ? *inptr++ : fill_inbuf())

#define NEXTBYTE()  (uch)get_byte()

#define NEEDBITS(n) {while(k<(n)){b|=((ulg)NEXTBYTE())<<k;k+=8;}}

#define DUMPBITS(n) {b>>=(n);k-=(n);}

/*

   Huffman code decoding is performed using a multi-level table lookup.

   The fastest way to decode is to simply build a lookup table whose

   size is determined by the longest code.  However, the time it takes

   to build this table can also be a factor if the data being decoded

   is not very long.  The most common codes are necessarily the

   shortest codes, so those codes dominate the decoding time, and hence

   the speed.  The idea is you can have a shorter table that decodes the

   shorter, more probable codes, and then point to subsidiary tables for

   the longer codes.  The time it costs to decode the longer codes is

   then traded against the time it takes to make longer tables.

   This results of this trade are in the variables lbits and dbits

   below.  lbits is the number of bits the first level table for literal/

   length codes can decode in one step, and dbits is the same thing for

   the distance codes.  Subsequent tables are also less than or equal to

   those sizes.  These values may be adjusted either when all of the

   codes are shorter than that, in which case the longest code length in

   bits is used, or when the shortest code is *longer* than the requested

   table size, in which case the length of the shortest code in bits is

   used.

   There are two different values for the two tables, since they code a

   different number of possibilities each.  The literal/length table

   codes 286 possible values, or in a flat code, a little over eight

   bits.  The distance table codes 30 possible values, or a little less

   than five bits, flat.  The optimum values for speed end up being

   about one bit more than those, so lbits is 8+1 and dbits is 5+1.

   The optimum values may differ though from machine to machine, and

   possibly even between compilers.  Your mileage may vary.

 */

static const int lbits = 9;          /* bits in base literal/length lookup table */

static const int dbits = 6;          /* bits in base distance lookup table */

/* If BMAX needs to be larger than 16, then h and x[] should be ulg. */

#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 */

int huft_build(

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) */

const ush *d,                 /* list of base values for non-simple codes */

const ush *e,                 /* list of extra bits for non-simple codes */

struct huft **t,        /* result: starting table */

int *m                 /* maximum lookup bits, returns actual */

)

/* 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. */

{

  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 */

  /* Generate counts for each bit length */

  memset(c, 0, sizeof(c));

  p = b;  i = n;

  do {

/*    Tracecv(*p, (stderr, (n-i >= ' ' && n-i <= '~' ? "%c %d\n" : "0x%x %d\n"), 

	    n-i, *p));*/

    c[*p]++;                    /* assume all entries <= BMAX */

    p++;                      /* Can't combine with above line (Solaris bug) */

  } while (--i);

  if (c[0] == n)                /* null input--all zero length codes */

  {

    *t = (struct huft *)NULL;

    *m = 0;

    return 0;

  }

  /* 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;

  /* 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;

  /* 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++);

  }

  /* 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);

  /* 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 */

  /* go through the bit lengths (k already is bits in shortest code) */

  for (; k <= g; k++)

  {

    a = c[k];

    while (a--)

    {

      /* here i is the Huffman code of length k bits for value *p */

      /* make tables up to required level */

      while (k > w + l)

      {

        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 */

          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 */

          }

        }

        z = 1 << j;             /* table entries for j-bit table */

        /* allocate and link in new table */

        if ((q = (struct huft *)malloc((z + 1)*sizeof(struct huft))) ==

            (struct huft *)NULL)

        {

          if (h)

            huft_free(u[0]);

          return 3;             /* not enough memory */

        }

        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 */

        /* connect to last table, if there is one */

        if (h)

        {

          x[h] = i;             /* save pattern for backing up */

          r.b = (uch)l;         /* bits to dump before this table */

          r.e = (uch)(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 */

        }

      }

      /* set up table entry in r */

      r.b = (uch)(k - w);

      if (p >= v + n)

        r.e = 99;               /* out of values--invalid code */

      else if (*p < s)

      {

        r.e = (uch)(*p < 256 ? 16 : 15);    /* 256 is end-of-block code */

        r.v.n = (ush)(*p);             /* simple code is just the value */

	p++;                           /* one compiler does not like *p++ */

      }

      else

      {

        r.e = (uch)e[*p - s];   /* non-simple--look up in lists */

        r.v.n = d[*p++ - s];

      }

      /* 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;

      }

    }

  }

  /* Return true (1) if we were given an incomplete table */

  return y != 0 && g != 1;

}

int huft_free(struct huft *t)

/* 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((char*)p);

    p = q;

  } 

  return 0;

}

int inflate_codes(

struct huft *tl,

struct huft *td,   /* literal/length and distance decoder tables */

int bl,

int 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 */

  struct huft *t;       /* pointer to table entry */

  unsigned ml, md;      /* masks for bl and bd bits */

  register ulg b=bb;       /* bit buffer */

  register unsigned k=bk;  /* number of bits in bit buffer */

  register uch* p=(uch*)outptr;

  /* 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 */

    {

      *p++ = (uch)t->v.n;

    }

    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)