/* Source: https://github.com/madler/zlib
 * License: /licenses/madler-puff.txt
 *
 * puff.c is a simple inflate written to be an unambiguous way to specify the
 * deflate format.  It is not written for speed but rather simplicity.  As a
 * side benefit, this code might actually be useful when small code is more
 * important than speed, such as bootstrap applications. For typical deflate
 * data, zlib's inflate() is about four times as fast as puff(). zlib's
 * inflate compiles to around 20K on my machine, whereas puff.c compiles to
 * around 4K on my machine (a PowerPC using GNU cc). If the faster decode()
 * function here is used, then puff() is only twice as slow as zlib's
 * inflate().
 *
 * All dynamically allocated memory comes from the stack. The stack required
 * is less than 2K bytes. This code is compatible with 16-bit int's and
 * assumes that long's are at least 32 bits.  puff.c uses the short data type,
 * assumed to be 16 bits, for arrays in order to conserve memory. The code
 * works whether integers are stored big endian or little endian.
 *
 * In the comments below are "Format notes" that describe the inflate process
 * and document some of the less obvious aspects of the format.  This source
 * code is meant to supplement RFC 1951, which formally describes the deflate
 * format:
 *
 * http://www.zlib.org/rfc-deflate.html
 */

/*
 * Maximums for allocations and loops.  It is not useful to change these --
 * they are fixed by the deflate format.
 */
/* maximum bits in a code */
#define MAXBITS 15
/* maximum number of literal/length codes */
#define MAXLCODES 286
/* maximum number of distance codes */
#define MAXDCODES 30
/* maximum codes lengths to read */
#define MAXCODES (MAXLCODES+MAXDCODES)
/* number of fixed literal/length codes */
#define FIXLCODES 288
#define OUTBUFLEN $10000

/* Output and buffering
 * The puff algorithm needs to access its previously outputted contents up to
 * 32K back. For this reason, we can't spit directly to outhdl. Instead, what we
 * do is we have a buffer of twice the required size (64K) and spit there. This
 * buffer is split in 2 pages. Whenever we hit the limit of one of the pages, we
 * check if the other page is full. If yes, we spit it to outhdl and go on.
*/

Stream* inhdl;
Stream* outhdl;

/* input and output state */
struct state {
  uchar out[OUTBUFLEN]; /* output buffer */
  uint outptr;          /* current position in output buffer */
  uint outcnt;          /* total bytes written to out so far */
  int bitbuf;           /* bit buffer */
  int bitcnt;           /* number of bits in bit buffer */
};

state s;

void spit(uchar c) {
  uint pageptr;
  s.out[s.outptr++] = c;
  s.outcnt++;
  if ((s.outcnt>=OUTBUFLEN) && (!(s.outptr % (OUTBUFLEN/2)))) {
    // we finished a page and need to flush the "other"
    pageptr = s.outptr ^ (OUTBUFLEN/2); // ptr to "other"
    write(outhdl, OUTBUFLEN/2, &s.out[pageptr]);
  }
}

uchar nextchar() {
  uint c;
  c = getc(inhdl);
  if (c < 0) {
    stype("out of input\n");
    abort();
  }
  return c;
}

/*
 * Return need bits from the input stream.  This always leaves less than
 * eight bits in the buffer.  bits() works properly for need == 0.
 *
 * Format notes:
 *
 * - Bits are stored in bytes from the least significant bit to the most
 *   significant bit.  Therefore bits are dropped from the bottom of the bit
 *   buffer, using shift right, and new bytes are appended to the top of the
 *   bit buffer, using shift left.
 */
int bits(int need) {
  int val; /* bit accumulator (can use up to 20 bits) */

  /* load at least need bits into val */
  val = s.bitbuf;
  while (s.bitcnt < need) {
    val |= (int)nextchar() << s.bitcnt; /* load eight bits */
    s.bitcnt += 8;
  }

  /* drop need bits and update buffer, always zero to seven bits left */
  s.bitbuf = (val >> need);
  s.bitcnt -= need;

  /* return need bits, zeroing the bits above that */
  return (val & ((1 << need) - 1));
}

/*
 * Process a stored block.
 *
 * Format notes:
 *
 * - After the two-bit stored block type (00), the stored block length and
 *   stored bytes are byte-aligned for fast copying.  Therefore any leftover
 *   bits in the byte that has the last bit of the type, as many as seven, are
 *   discarded.  The value of the discarded bits are not defined and should not
 *   be checked against any expectation.
 *
 * - The second inverted copy of the stored block length does not have to be
 *   checked, but it's probably a good idea to do so anyway.
 *
 * - A stored block can have zero length.  This is sometimes used to byte-align
 *   subsets of the compressed data for random access or partial recovery.
 */
int stored() {
  uint len; /* length of stored block */

  /* discard leftover bits from current byte (assumes s->bitcnt < 8) */
  s.bitbuf = 0;
  s.bitcnt = 0;

  /* get length and check against its one's complement */
  len = (uint)nextchar();
  len |= (uint)nextchar() << 8;
  if (nextchar() != (~len & $ff) || nextchar() != ((~len >> 8) & $ff))
    return -2; /* didn't match complement! */

  /* copy len bytes from in to out */
  while (len--) spit(nextchar());

  /* done with a valid stored block */
  return 0;
}

/*
 * Huffman code decoding tables.  count[1..MAXBITS] is the number of symbols of
 * each length, which for a canonical code are stepped through in order.
 * symbol[] are the symbol values in canonical order, where the number of
 * entries is the sum of the counts in count[].  The decoding process can be
 * seen in the function decode() below.
 */
struct huffman {
  short *count;  /* number of symbols of each length */
  short *symbol; /* canonically ordered symbols */
};

/*
 * Decode a code from the stream s using huffman table h.  Return the symbol or
 * a negative value if there is an error.  If all of the lengths are zero, i.e.
 * an empty code, or if the code is incomplete and an invalid code is received,
 * then -10 is returned after reading MAXBITS bits.
 *
 * Format notes:
 *
 * - The codes as stored in the compressed data are bit-reversed relative to
 *   a simple integer ordering of codes of the same lengths.  Hence below the
 *   bits are pulled from the compressed data one at a time and used to
 *   build the code value reversed from what is in the stream in order to
 *   permit simple integer comparisons for decoding.  A table-based decoding
 *   scheme (as used in zlib) does not need to do this reversal.
 *
 * - The first code for the shortest length is all zeros.  Subsequent codes of
 *   the same length are simply integer increments of the previous code.  When
 *   moving up a length, a zero bit is appended to the code.  For a complete
 *   code, the last code of the longest length will be all ones.
 *
 * - Incomplete codes are handled by this decoder, since they are permitted
 *   in the deflate format.  See the format notes for fixed() and dynamic().
 */
int decode(huffman *h) {
  int len;   /* current number of bits in code */
  int code;  /* len bits being decoded */
  int first; /* first code of length len */
  int count; /* number of codes of length len */
  int index; /* index of first code of length len in symbol table */

  code = first = index = 0;
  for (len = 1; len <= MAXBITS; len++) {
    code |= bits(1); /* get next bit */
    count = h->count[len];
    if (code - count < first) /* if length len, return symbol */
      return h->symbol[index + (code - first)];
    index += count; /* else update for next length */
    first += count;
    first <<= 1;
    code <<= 1;
  }
  return -10; /* ran out of codes */
}

/*
 * Given the list of code lengths length[0..n-1] representing a canonical
 * Huffman code for n symbols, construct the tables required to decode those
 * codes.  Those tables are the number of codes of each length, and the symbols
 * sorted by length, retaining their original order within each length.  The
 * return value is zero for a complete code set, negative for an over-
 * subscribed code set, and positive for an incomplete code set.  The tables
 * can be used if the return value is zero or positive, but they cannot be used
 * if the return value is negative.  If the return value is zero, it is not
 * possible for decode() using that table to return an error--any stream of
 * enough bits will resolve to a symbol.  If the return value is positive, then
 * it is possible for decode() using that table to return an error for received
 * codes past the end of the incomplete lengths.
 *
 * Not used by decode(), but used for error checking, h->count[0] is the number
 * of the n symbols not in the code.  So n - h->count[0] is the number of
 * codes.  This is useful for checking for incomplete codes that have more than
 * one symbol, which is an error in a dynamic block.
 *
 * Assumption: for all i in 0..n-1, 0 <= length[i] <= MAXBITS
 * This is assured by the construction of the length arrays in dynamic() and
 * fixed() and is not verified by construct().
 *
 * Format notes:
 *
 * - Permitted and expected examples of incomplete codes are one of the fixed
 *   codes and any code with a single symbol which in deflate is coded as one
 *   bit instead of zero bits.  See the format notes for fixed() and dynamic().
 *
 * - Within a given code length, the symbols are kept in ascending order for
 *   the code bits definition.
 */
int construct(huffman *h, short *length, int n) {
  int symbol; /* current symbol when stepping through length[] */
  int len;    /* current length when stepping through h->count[] */
  int left;   /* number of possible codes left of current length */
  short offs[MAXBITS+1]; /* offsets in symbol table for each length */

  /* count number of codes of each length */
  for (len = 0; len <= MAXBITS; len++)
    h->count[len] = 0;
  for (symbol = 0; symbol < n; symbol++)
    (h->count[length[symbol]])++; /* assumes lengths are within bounds */
  if ((h->count[0]) == n) /* no codes! */
    return 0; /* complete, but decode() will fail */

  /* check for an over-subscribed or incomplete set of lengths */
  left = 1; /* one possible code of zero length */
  for (len = 1; len <= MAXBITS; len++) {
    left <<= 1; /* one more bit, double codes left */
    left -= h->count[len]; /* deduct count from possible codes */
    if (left < 0)
      return left; /* over-subscribed--return negative */
  } /* left > 0 means incomplete */

  /* generate offsets into symbol table for each length for sorting */
  offs[1] = 0;
  for (len = 1; len < MAXBITS; len++)
    offs[len + 1] = offs[len] + h->count[len];

  /*
   * put symbols in table sorted by length, by symbol order within each
   * length
   */
  for (symbol = 0; symbol < n; symbol++)
    if (length[symbol] != 0)
      h->symbol[offs[length[symbol]]++] = symbol;

  /* return zero for complete set, positive for incomplete set */
  return left;
}

/*
 * Decode literal/length and distance codes until an end-of-block code.
 *
 * Format notes:
 *
 * - Compressed data that is after the block type if fixed or after the code
 *   description if dynamic is a combination of literals and length/distance
 *   pairs terminated by and end-of-block code.  Literals are simply Huffman
 *   coded bytes.  A length/distance pair is a coded length followed by a
 *   coded distance to represent a string that occurs earlier in the
 *   uncompressed data that occurs again at the current location.
 *
 * - Literals, lengths, and the end-of-block code are combined into a single
 *   code of up to 286 symbols.  They are 256 literals (0..255), 29 length
 *   symbols (257..285), and the end-of-block symbol (256).
 *
 * - There are 256 possible lengths (3..258), and so 29 symbols are not enough
 *   to represent all of those.  Lengths 3..10 and 258 are in fact represented
 *   by just a length symbol.  Lengths 11..257 are represented as a symbol and
 *   some number of extra bits that are added as an integer to the base length
 *   of the length symbol.  The number of extra bits is determined by the base
 *   length symbol.  These are in the static arrays below, lens[] for the base
 *   lengths and lext[] for the corresponding number of extra bits.
 *
 * - The reason that 258 gets its own symbol is that the longest length is used
 *   often in highly redundant files.  Note that 258 can also be coded as the
 *   base value 227 plus the maximum extra value of 31.  While a good deflate
 *   should never do this, it is not an error, and should be decoded properly.
 *
 * - If a length is decoded, including its extra bits if any, then it is
 *   followed a distance code.  There are up to 30 distance symbols.  Again
 *   there are many more possible distances (1..32768), so extra bits are added
 *   to a base value represented by the symbol.  The distances 1..4 get their
 *   own symbol, but the rest require extra bits.  The base distances and
 *   corresponding number of extra bits are below in the static arrays dist[]
 *   and dext[].
 *
 * - Literal bytes are simply written to the output.  A length/distance pair is
 *   an instruction to copy previously uncompressed bytes to the output.  The
 *   copy is from distance bytes back in the output stream, copying for length
 *   bytes.
 *
 * - Distances pointing before the beginning of the output data are not
 *   permitted.
 *
 * - Overlapped copies, where the length is greater than the distance, are
 *   allowed and common.  For example, a distance of one and a length of 258
 *   simply copies the last byte 258 times.  A distance of four and a length of
 *   twelve copies the last four bytes three times.  A simple forward copy
 *   ignoring whether the length is greater than the distance or not implements
 *   this correctly.  You should not use memcpy() since its behavior is not
 *   defined for overlapped arrays.  You should not use memmove() or bcopy()
 *   since though their behavior -is- defined for overlapping arrays, it is
 *   defined to do the wrong thing in this case.
 */
short lens[29] = { /* Size base for length 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};
short lext[29] = { /* Extra bits for length 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};
short dists[30] = { /* Offset base 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};
short dext[30] = { /* Extra bits for distance codes 0..29 */
  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};
int codes(huffman *lencode, huffman *distcode) {
  int symbol; /* decoded symbol */
  int len;    /* length for copy */
  uint dist;  /* distance for copy */

  /* decode literals and length/distance pairs */
  do {
    symbol = decode(lencode);
    if (symbol < 0)
      return symbol; /* invalid symbol */
    if (symbol < 256) { /* literal: symbol is the byte */
      /* write out the literal */
      spit((uchar)symbol);
    }
    else if (symbol > 256) { /* length */
      /* get and compute length */
      symbol -= 257;
      if (symbol >= 29)
        return -10; /* invalid fixed code */
      len = lens[symbol] + bits(lext[symbol]);

      /* get and check distance */
      symbol = decode(distcode);
      if (symbol < 0)
        return symbol; /* invalid symbol */
      dist = (uint)dists[symbol] + (uint)bits(dext[symbol]);
      if (dist > s.outcnt)
        return -11; /* distance too far back */

      /* copy length bytes from distance bytes back */
      while (len--) {
        spit(dist > s.outcnt ? 0 : s.out[(s.outcnt - dist) % OUTBUFLEN]);
      }
    }
  } while (symbol != 256); /* end of block symbol */

  /* done with a valid fixed or dynamic block */
  return 0;
}

/*
 * Process a fixed codes block.
 *
 * Format notes:
 *
 * - This block type can be useful for compressing small amounts of data for
 *   which the size of the code descriptions in a dynamic block exceeds the
 *   benefit of custom codes for that block.  For fixed codes, no bits are
 *   spent on code descriptions.  Instead the code lengths for literal/length
 *   codes and distance codes are fixed.  The specific lengths for each symbol
 *   can be seen in the "for" loops below.
 *
 * - The literal/length code is complete, but has two symbols that are invalid
 *   and should result in an error if received.  This cannot be implemented
 *   simply as an incomplete code since those two symbols are in the "middle"
 *   of the code.  They are eight bits long and the longest literal/length\
 *   code is nine bits.  Therefore the code must be constructed with those
 *   symbols, and the invalid symbols must be detected after decoding.
 *
 * - The fixed distance codes also have two invalid symbols that should result
 *   in an error if received.  Since all of the distance codes are the same
 *   length, this can be implemented as an incomplete code.  Then the invalid
 *   codes are detected while decoding.
 */

int virgin = 1;
short lencnt[MAXBITS+1], lensym[FIXLCODES];
short distcnt[MAXBITS+1], distsym[MAXDCODES];
huffman lencode, distcode;

int fixed() {
  int symbol;
  short lengths[FIXLCODES];

  /* build fixed huffman tables if first call (may not be thread safe) */
  if (virgin) {
    /* construct lencode and distcode */
    lencode.count = lencnt;
    lencode.symbol = lensym;
    distcode.count = distcnt;
    distcode.symbol = distsym;

    /* literal/length table */
    for (symbol = 0; symbol < 144; symbol++)
      lengths[symbol] = 8;
    for (; symbol < 256; symbol++)
      lengths[symbol] = 9;
    for (; symbol < 280; symbol++)
      lengths[symbol] = 7;
    for (; symbol < FIXLCODES; symbol++)
      lengths[symbol] = 8;
    construct(&lencode, lengths, FIXLCODES);

    /* distance table */
    for (symbol = 0; symbol < MAXDCODES; symbol++)
      lengths[symbol] = 5;
    construct(&distcode, lengths, MAXDCODES);

    /* do this just once */
    virgin = 0;
  }

  /* decode data until end-of-block code */
  return codes(&lencode, &distcode);
}

/*
 * Process a dynamic codes block.
 *
 * Format notes:
 *
 * - A dynamic block starts with a description of the literal/length and
 *   distance codes for that block.  New dynamic blocks allow the compressor to
 *   rapidly adapt to changing data with new codes optimized for that data.
 *
 * - The codes used by the deflate format are "canonical", which means that
 *   the actual bits of the codes are generated in an unambiguous way simply
 *   from the number of bits in each code.  Therefore the code descriptions
 *   are simply a list of code lengths for each symbol.
 *
 * - The code lengths are stored in order for the symbols, so lengths are
 *   provided for each of the literal/length symbols, and for each of the
 *   distance symbols.
 *
 * - If a symbol is not used in the block, this is represented by a zero as
 *   as the code length.  This does not mean a zero-length code, but rather
 *   that no code should be created for this symbol.  There is no way in the
 *   deflate format to represent a zero-length code.
 *
 * - The maximum number of bits in a code is 15, so the possible lengths for
 *   any code are 1..15.
 *
 * - The fact that a length of zero is not permitted for a code has an
 *   interesting consequence.  Normally if only one symbol is used for a given
 *   code, then in fact that code could be represented with zero bits.  However
 *   in deflate, that code has to be at least one bit.  So for example, if
 *   only a single distance base symbol appears in a block, then it will be
 *   represented by a single code of length one, in particular one 0 bit.  This
 *   is an incomplete code, since if a 1 bit is received, it has no meaning,
 *   and should result in an error.  So incomplete distance codes of one symbol
 *   should be permitted, and the receipt of invalid codes should be handled.
 *
 * - It is also possible to have a single literal/length code, but that code
 *   must be the end-of-block code, since every dynamic block has one.  This
 *   is not the most efficient way to create an empty block (an empty fixed
 *   block is fewer bits), but it is allowed by the format.  So incomplete
 *   literal/length codes of one symbol should also be permitted.
 *
 * - If there are only literal codes and no lengths, then there are no distance
 *   codes.  This is represented by one distance code with zero bits.
 *
 * - The list of up to 286 length/literal lengths and up to 30 distance lengths
 *   are themselves compressed using Huffman codes and run-length encoding.  In
 *   the list of code lengths, a 0 symbol means no code, a 1..15 symbol means
 *   that length, and the symbols 16, 17, and 18 are run-length instructions.
 *   Each of 16, 17, and 18 are followed by extra bits to define the length of
 *   the run.  16 copies the last length 3 to 6 times.  17 represents 3 to 10
 *   zero lengths, and 18 represents 11 to 138 zero lengths.  Unused symbols
 *   are common, hence the special coding for zero lengths.
 *
 * - The symbols for 0..18 are Huffman coded, and so that code must be
 *   described first.  This is simply a sequence of up to 19 three-bit values
 *   representing no code (0) or the code length for that symbol (1..7).
 *
 * - A dynamic block starts with three fixed-size counts from which is computed
 *   the number of literal/length code lengths, the number of distance code
 *   lengths, and the number of code length code lengths (ok, you come up with
 *   a better name!) in the code descriptions.  For the literal/length and
 *   distance codes, lengths after those provided are considered zero, i.e. no
 *   code.  The code length code lengths are received in a permuted order (see
 *   the order[] array below) to make a short code length code length list more
 *   likely.  As it turns out, very short and very long codes are less likely
 *   to be seen in a dynamic code description, hence what may appear initially
 *   to be a peculiar ordering.
 *
 * - Given the number of literal/length code lengths (nlen) and distance code
 *   lengths (ndist), then they are treated as one long list of nlen + ndist
 *   code lengths.  Therefore run-length coding can and often does cross the
 *   boundary between the two sets of lengths.
 *
 * - So to summarize, the code description at the start of a dynamic block is
 *   three counts for the number of code lengths for the literal/length codes,
 *   the distance codes, and the code length codes.  This is followed by the
 *   code length code lengths, three bits each.  This is used to construct the
 *   code length code which is used to read the remainder of the lengths.  Then
 *   the literal/length code lengths and distance lengths are read as a single
 *   set of lengths using the code length codes.  Codes are constructed from
 *   the resulting two sets of lengths, and then finally you can start
 *   decoding actual compressed data in the block.
 *
 * - For reference, a "typical" size for the code description in a dynamic
 *   block is around 80 bytes.
 */
short order[19] =    /* permutation of code length codes */
  {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
int dynamic() {
  int nlen, ndist, ncode; /* number of lengths in descriptor */
  int index; /* index of lengths[] */
  int err;   /* construct() return value */
  short lengths[MAXCODES]; /* descriptor code lengths */
  short lencnt[MAXBITS+1], lensym[MAXLCODES];   /* lencode memory */
  short distcnt[MAXBITS+1], distsym[MAXDCODES]; /* distcode memory */
  huffman lencode, distcode; /* length and distance codes */
  int symbol; /* decoded value */
  int len;    /* last length to repeat */

  /* construct lencode and distcode */
  lencode.count = lencnt;
  lencode.symbol = lensym;
  distcode.count = distcnt;
  distcode.symbol = distsym;

  /* get number of lengths in each table, check lengths */
  nlen = bits(5) + 257;
  ndist = bits(5) + 1;
  ncode = bits(4) + 4;
  if (nlen > MAXLCODES || ndist > MAXDCODES)
    return -3; /* bad counts */

  /* read code length code lengths (really), missing lengths are zero */
  for (index = 0; index < ncode; index++)
    lengths[order[index]] = bits(3);
  for (; index < 19; index++)
    lengths[order[index]] = 0;

  /* build huffman table for code lengths codes (use lencode temporarily) */
  err = construct(&lencode, lengths, 19);
  if (err != 0) /* require complete code set here */
    return -4;

  /* read length/literal and distance code length tables */
  index = 0;
  while (index < nlen + ndist) {
    symbol = decode(&lencode);
    if (symbol < 0)
      return symbol; /* invalid symbol */
    if (symbol < 16) /* length in 0..15 */
      lengths[index++] = symbol;
    else {     /* repeat instruction */
      len = 0; /* assume repeating zeros */
      if (symbol == 16) { /* repeat last length 3..6 times */
        if (index == 0)
          return -5; /* no last length! */
        len = lengths[index - 1]; /* last length */
        symbol = 3 + bits(2);
      }
      else if (symbol == 17) /* repeat zero 3..10 times */
        symbol = 3 + bits(3);
      else /* == 18, repeat zero 11..138 times */
        symbol = 11 + bits(7);
      if (index + symbol > nlen + ndist)
        return -6; /* too many lengths! */
      while (symbol--) /* repeat last or zero symbol times */
        lengths[index++] = len;
    }
  }

  /* check for end-of-block code -- there better be one! */
  if (lengths[256] == 0)
    return -9;

  /* build huffman table for literal/length codes */
  err = construct(&lencode, lengths, nlen);
  if (err && (err < 0 || nlen != (lencode.count[0] + lencode.count[1])))
    return -7; /* incomplete code ok only for single length 1 code */

  /* build huffman table for distance codes */
  err = construct(&distcode, lengths + nlen, ndist);
  if (err && (err < 0 || ndist != (distcode.count[0] + distcode.count[1])))
    return -8; /* incomplete code ok only for single length 1 code */

  /* decode data until end-of-block code */
  return codes(&lencode, &distcode);
}

/*
 * Inflate source to dest.  On return, destlen and sourcelen are updated to the
 * size of the uncompressed data and the size of the deflate data respectively.
 * On success, the return value of puff() is zero.  If there is an error in the
 * source data, i.e. it is not in the deflate format, then a negative value is
 * returned.  If there is not enough input available or there is not enough
 * output space, then a positive error is returned.  In that case, destlen and
 * sourcelen are not updated to facilitate retrying from the beginning with the
 * provision of more input data or more output space.  In the case of invalid
 * inflate data (a negative error), the dest and source pointers are updated to
 * facilitate the debugging of deflators.
 *
 * puff() also has a mode to determine the size of the uncompressed output with
 * no output written.  For this dest must be (uchar *)0.  In this case,
 * the input value of *destlen is ignored, and on return *destlen is set to the
 * size of the uncompressed output.
 *
 * The return codes are:
 *
 *   2:  available inflate data did not terminate
 *   1:  output space exhausted before completing inflate
 *   0:  successful inflate
 *  -1:  invalid block type (type == 3)
 *  -2:  stored block length did not match one's complement
 *  -3:  dynamic block code description: too many length or distance codes
 *  -4:  dynamic block code description: code lengths codes incomplete
 *  -5:  dynamic block code description: repeat lengths with no first length
 *  -6:  dynamic block code description: repeat more than specified lengths
 *  -7:  dynamic block code description: invalid literal/length code lengths
 *  -8:  dynamic block code description: invalid distance code lengths
 *  -9:  dynamic block code description: missing end-of-block code
 * -10:  invalid literal/length or distance code in fixed or dynamic block
 * -11:  distance is too far back in fixed or dynamic block
 *
 * Format notes:
 *
 * - Three bits are read for each block to determine the kind of block and
 *   whether or not it is the last block.  Then the block is decoded and the
 *   process repeated if it was not the last block.
 *
 * - The leftover bits in the last byte of the deflate data after the last
 *   block (if it was a fixed or dynamic block) are undefined and have no
 *   expected values to check.
 */
int puff(Stream *in, Stream *out) {
  int last, type; /* block information */
  int err;        /* return value */
  uint pageptr;

  inhdl = in;
  outhdl = out;
  s.outptr = 0;
  s.outcnt = 0;
  s.bitbuf = 0;
  s.bitcnt = 0;

  /* process blocks until last block or error */
  do {
    last = bits(1); /* one if last block */
    type = bits(2); /* block type 0..3 */
    if (type == 0) err = stored();
    else if (type == 1) err = fixed();
    else if (type == 2) err = dynamic();
    else err = -1;
    if (err != 0)
      break; /* return with error */
  } while (!last);

  if (err <= 0) {
    pageptr = s.outptr & (OUTBUFLEN/2);
    if (s.outptr-pageptr) {
      write(outhdl, s.outptr-pageptr, &s.out[pageptr]);
    }
  }
  return err;
}