/*
 * Copyright (c) 2000-2007 Marc Alexander Lehmann <schmorp@schmorp.de>
 *
 * Redistribution and use in source and binary forms, with or without modifica-
 * tion, are permitted provided that the following conditions are met:
 *
 *   1.  Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *
 *   2.  Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License ("GPL") version 2 or any later version,
 * in which case the provisions of the GPL are applicable instead of
 * the above. If you wish to allow the use of your version of this file
 * only under the terms of the GPL and not to allow others to use your
 * version of this file under the BSD license, indicate your decision
 * by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL. If you do not delete the
 * provisions above, a recipient may use your version of this file under
 * either the BSD or the GPL.
 */

#include "lzfP.h"

#define HSIZE (1 << (HLOG))

/*
 * don't play with this unless you benchmark!
 * decompression is not dependent on the hash function
 * the hashing function might seem strange, just believe me
 * it works ;)
 */
#ifndef FRST
# define FRST(p) (((p[0]) << 8) | p[1])
# define NEXT(v,p) (((v) << 8) | p[2])
# if ULTRA_FAST
#  define IDX(h) ((( h             >> (3*8 - HLOG)) - h  ) & (HSIZE - 1))
# elif VERY_FAST
#  define IDX(h) ((( h             >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
# else
#  define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
# endif
#endif
/*
 * IDX works because it is very similar to a multiplicative hash, e.g.
 * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
 * the latter is also quite fast on newer CPUs, and compresses similarly.
 *
 * the next one is also quite good, albeit slow ;)
 * (int)(cos(h & 0xffffff) * 1e6)
 */

#if 0
/* original lzv-like hash function, much worse and thus slower */
# define FRST(p) (p[0] << 5) ^ p[1]
# define NEXT(v,p) ((v) << 5) ^ p[2]
# define IDX(h) ((h) & (HSIZE - 1))
#endif

#define        MAX_LIT        (1 <<  5)
#define        MAX_OFF        (1 << 13)
#define        MAX_REF        ((1 << 8) + (1 << 3))

#if __GNUC__ >= 3
# define expect(expr,value)         __builtin_expect ((expr),(value))
# define inline                     inline
#else
# define expect(expr,value)         (expr)
# define inline                     static
#endif

#define expect_false(expr) expect ((expr) != 0, 0)
#define expect_true(expr)  expect ((expr) != 0, 1)

/*
 * compressed format
 *
 * 000LLLLL <L+1>    ; literal
 * LLLooooo oooooooo ; backref L
 * 111ooooo LLLLLLLL oooooooo ; backref L+7
 *
 */

unsigned int
lzf_compress(const void *const in_data, unsigned int in_len,
             void *out_data, unsigned int out_len
#if LZF_STATE_ARG
             , LZF_STATE htab
#endif
            )
{
#if !LZF_STATE_ARG
    LZF_STATE htab;
#endif
    const u8 **hslot;
    const u8 *ip = (const u8 *)in_data;
    u8 *op = (u8 *)out_data;
    const u8 *in_end  = ip + in_len;
    u8 *out_end = op + out_len;
    const u8 *ref;

    /* off requires a type wide enough to hold a general pointer difference.
     * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only
     * works for differences within a single object). We also assume that no
     * no bit pattern traps. Since the only platform that is both non-POSIX
     * and fails to support both assumptions is windows 64 bit, we make a
     * special workaround for it.
     */
#if defined (WIN32) && defined (_M_X64)
    unsigned _int64 off; /* workaround for missing POSIX compliance */
#else
    unsigned long off;
#endif
    unsigned int hval;
    int lit;

    if (!in_len || !out_len)
        return 0;

#if INIT_HTAB
    memset(htab, 0, sizeof(htab));
# if 0
    for (hslot = htab; hslot < htab + HSIZE; hslot++)
        *hslot++ = ip;
# endif
#endif

    lit = 0; op++; /* start run */

    hval = FRST(ip);
    while (ip < in_end - 2)
    {
        hval = NEXT(hval, ip);
        hslot = htab + IDX(hval);
        ref = *hslot; *hslot = ip;

        if (1
#if INIT_HTAB
                && ref < ip /* the next test will actually take care of this, but this is faster */
#endif
                && (off = ip - ref - 1) < MAX_OFF
                && ip + 4 < in_end
                && ref > (u8 *)in_data
#if STRICT_ALIGN
                && ref[0] == ip[0]
                && ref[1] == ip[1]
                && ref[2] == ip[2]
#else
                && *(u16 *)ref == *(u16 *)ip
                && ref[2] == ip[2]
#endif
           )
        {
            /* match found at *ref++ */
            unsigned int len = 2;
            unsigned int maxlen = in_end - ip - len;
            maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;

            op [- lit - 1] = lit - 1; /* stop run */
            op -= !lit; /* undo run if length is zero */

            if (expect_false(op + 3 + 1 >= out_end))
                return 0;

            for (;;)
            {
                if (expect_true(maxlen > 16))
                {
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;

                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;

                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;

                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                    len++; if (ref [len] != ip [len]) break;
                }

                do
                    len++;
                while (len < maxlen && ref[len] == ip[len]);

                break;
            }

            len -= 2;
            ip++;

            if (len < 7)
            {
                *op++ = (off >> 8) + (len << 5);
            }
            else
            {
                *op++ = (off >> 8) + (7 << 5);
                *op++ = len - 7;
            }

            *op++ = off;

#if ULTRA_FAST || VERY_FAST
            ip += len;
#if VERY_FAST && !ULTRA_FAST
            --ip;
#endif
            hval = FRST(ip);

            hval = NEXT(hval, ip);
            htab[IDX(hval)] = ip;
            ip++;

#if VERY_FAST && !ULTRA_FAST
            hval = NEXT(hval, ip);
            htab[IDX(hval)] = ip;
            ip++;
#endif
#else
            do
            {
                hval = NEXT(hval, ip);
                htab[IDX(hval)] = ip;
                ip++;
            }
            while (len--);
#endif

            lit = 0; op++; /* start run */
        }
        else
        {
            /* one more literal byte we must copy */
            if (expect_false(op >= out_end))
                return 0;

            lit++; *op++ = *ip++;

            if (expect_false(lit == MAX_LIT))
            {
                op [- lit - 1] = lit - 1; /* stop run */
                lit = 0; op++; /* start run */
            }
        }
    }

    if (op + 3 > out_end) /* at most 3 bytes can be missing here */
        return 0;

    while (ip < in_end)
    {
        lit++; *op++ = *ip++;

        if (expect_false(lit == MAX_LIT))
        {
            op [- lit - 1] = lit - 1; /* stop run */
            lit = 0; op++; /* start run */
        }
    }

    op [- lit - 1] = lit - 1; /* end run */
    op -= !lit; /* undo run if length is zero */

    return op - (u8 *)out_data;
}

