/*
  puff.c
  Copyright (C) 2002-2004 Mark Adler, all rights reserved
  version 1.8, 9 Jan 2004

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the author be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  Mark Adler    madler@alumni.caltech.edu
*/

/* Adapted for TrueCrypt */
/* Adapted for VeraCrypt */


#define local static            /* for local function definitions */
#define NIL ((unsigned char *)0)        /* for no output option */

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

/* input and output state */
struct state {
    /* output state */
    unsigned char *out;         /* output buffer */
    unsigned int outlen;       /* available space at out */
    unsigned int outcnt;       /* bytes written to out so far */

    /* input state */
    unsigned char *in;          /* input buffer */
    unsigned int inlen;			 /* available input at in */
    unsigned int incnt;        /* bytes read so far */
    int bitbuf;                 /* bit buffer */
    int bitcnt;                 /* number of bits in bit buffer */
};


local int bits(struct state *s, int need)
{
    long val;           /* bit accumulator (can use up to 20 bits) */

    /* load at least need bits into val */
    val = s->bitbuf;
    while (s->bitcnt < need) {
        val |= (long)(s->in[s->incnt++]) << s->bitcnt;  /* load eight bits */
        s->bitcnt += 8;
    }

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

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


local int stored(struct state *s)
{
    unsigned len;       /* length of stored block */

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

    if (s->incnt + 4 > s->inlen)
        return 2;                               /* not enough input */

    /* get length and check against its one's complement */
    len = s->in[s->incnt++];
    len |= s->in[s->incnt++] << 8;
    if (s->in[s->incnt++] != (~len & 0xff) ||
        s->in[s->incnt++] != ((~len >> 8) & 0xff))
        return -2;                              /* didn't match complement! */

    if (s->incnt + len > s->inlen)
        return 2;                               /* not enough input */

    /* copy len bytes from in to out */
    if (s->out != NIL) {
        if (s->outcnt + len > s->outlen)
            return 1;                           /* not enough output space */
        while (len--)
            s->out[s->outcnt++] = s->in[s->incnt++];
    }
    else {                                      /* just scanning */
        s->outcnt += len;
        s->incnt += len;
    }

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


struct huffman {
    short *count;       /* number of symbols of each length */
    short *symbol;      /* canonically ordered symbols */
};

/* reduce code size by using slow version of the decompressor */
#define SLOW

#ifdef SLOW
local int decode(struct state *s, struct 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(s, 1);             /* get next bit */
        count = h->count[len];
        if (code < first + count)       /* 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 -9;                          /* ran out of codes */
}

/*
 * A faster version of decode() for real applications of this code.   It's not
 * as readable, but it makes puff() twice as fast.  And it only makes the code
 * a few percent larger.
 */
#else /* !SLOW */
local int decode(struct state *s, struct 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 */
    int bitbuf;         /* bits from stream */
    int left;           /* bits left in next or left to process */
    short *next;        /* next number of codes */

    bitbuf = s->bitbuf;
    left = s->bitcnt;
    code = first = index = 0;
    len = 1;
    next = h->count + 1;
    while (1) {
        while (left--) {
            code |= bitbuf & 1;
            bitbuf >>= 1;
            count = *next++;
            if (code < first + count) { /* if length len, return symbol */
                s->bitbuf = bitbuf;
                s->bitcnt = (s->bitcnt - len) & 7;
                return h->symbol[index + (code - first)];
            }
            index += count;             /* else update for next length */
            first += count;
            first <<= 1;
            code <<= 1;
            len++;
        }
        left = (MAXBITS+1) - len;
        if (left == 0) break;
        bitbuf = s->in[s->incnt++];
        if (left > 8) left = 8;
    }
    return -9;                          /* ran out of codes */
}
#endif /* SLOW */


local int construct(struct 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;
}


local int codes(struct state *s,
                struct huffman *lencode,
                struct huffman *distcode)
{
    int symbol;         /* decoded symbol */
    int len;            /* length for copy */
    unsigned dist;      /* distance for copy */
    static const 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};
    static const 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};
    static const 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};
    static const 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};

    /* decode literals and length/distance pairs */
    do {
        symbol = decode(s, lencode);
        if (symbol < 0) return symbol;  /* invalid symbol */
        if (symbol < 256) {             /* literal: symbol is the byte */
            /* write out the literal */
            if (s->out != NIL) {
                if (s->outcnt == s->outlen) return 1;
                s->out[s->outcnt] = symbol;
            }
            s->outcnt++;
        }
        else if (symbol > 256) {        /* length */
            /* get and compute length */
            symbol -= 257;
            if (symbol >= 29) return -9;        /* invalid fixed code */
            len = lens[symbol] + bits(s, lext[symbol]);

            /* get and check distance */
            symbol = decode(s, distcode);
            if (symbol < 0) return symbol;          /* invalid symbol */
            dist = dists[symbol] + bits(s, dext[symbol]);
            if (dist > s->outcnt)
                return -10;     /* distance too far back */

            /* copy length bytes from distance bytes back */
            if (s->out != NIL) {
                if (s->outcnt + len > s->outlen) return 1;
                while (len--) {
                    s->out[s->outcnt] = s->out[s->outcnt - dist];
                    s->outcnt++;
                }
            }
            else
                s->outcnt += len;
        }
    } while (symbol != 256);            /* end of block symbol */

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


local int fixed(struct state *s)
{
    static int virgin = 1;
    static short lencnt[MAXBITS+1], lensym[FIXLCODES];
    static short distcnt[MAXBITS+1], distsym[MAXDCODES];
    static struct huffman lencode = {lencnt, lensym};
    static struct huffman distcode = {distcnt, distsym};

    /* build fixed huffman tables if first call (may not be thread safe) */
    if (virgin) {
        int symbol;
        short lengths[FIXLCODES];

        /* 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(s, &lencode, &distcode);
}


local int dynamic(struct state *s)
{
    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 */
    struct huffman lencode = {lencnt, lensym};          /* length code */
    struct huffman distcode = {distcnt, distsym};       /* distance code */
    static const 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};

    /* get number of lengths in each table, check lengths */
    nlen = bits(s, 5) + 257;
    ndist = bits(s, 5) + 1;
    ncode = bits(s, 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(s, 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) return -4;            /* require complete code set here */

    /* read length/literal and distance code length tables */
    index = 0;
    while (index < nlen + ndist) {
        int symbol;             /* decoded value */
        int len;                /* last length to repeat */

        symbol = decode(s, &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 */
            switch(symbol)
            {
               case 16: {         /* repeat last length 3..6 times */
                  if (index == 0) return -5;      /* no last length! */
                  len = lengths[index - 1];       /* last length */
                  symbol = 3 + bits(s, 2);
                  break;
               }
               case  17:      /* repeat zero 3..10 times */
                  symbol = 3 + bits(s, 3);
                  break;
               default:                  /* == 18, repeat zero 11..138 times */
                   symbol = 11 + bits(s, 7);
                   break;
             }
            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 < 0 || (err > 0 && nlen - lencode.count[0] != 1))
        return -7;      /* only allow incomplete codes if just one code */

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

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


void _acrtused () { }

// Decompress deflated data
int far main (
         unsigned char *dest,         /* pointer to destination pointer */
         unsigned int destlen,        /* amount of output space */
         unsigned char *source,       /* pointer to source data pointer */
         unsigned int sourcelen)
{
    struct state s;             /* input/output state */
    int last, type;             /* block information */
    int err;                    /* return value */

    /* initialize output state */
    s.out = dest;
    s.outlen = destlen;                /* ignored if dest is NIL */
    s.outcnt = 0;

    /* initialize input state */
    s.in = source;
    s.inlen = sourcelen;
    s.incnt = 0;
    s.bitbuf = 0;
    s.bitcnt = 0;

	/* process blocks until last block or error */
	do {
		last = bits(&s, 1);         /* one if last block */
		type = bits(&s, 2);         /* block type 0..3 */
		switch(type)
		{
		case 0:
			err = stored(&s);
			break;
		case 1:
			err = fixed(&s);
			break;
		case 2:
			err = dynamic(&s);
			break;
		default:
			err = -1; /* type == 3, invalid */
			break;
		}

		if (err != 0) break;        /* return with error */
	} while (!last);

	return err;
}
