path: root/src/lzo1b_9x.c

/* lzo1b_9x.c -- implementation of the LZO1B-999 compression algorithm

   This file is part of the LZO real-time data compression library.

   Copyright (C) 2008 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2007 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2006 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2005 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2004 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2003 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2002 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2001 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 2000 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1999 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1998 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1997 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996 Markus Franz Xaver Johannes Oberhumer
   All Rights Reserved.

   The LZO library is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of
   the License, or (at your option) any later version.

   The LZO library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with the LZO library; see the file COPYING.
   If not, write to the Free Software Foundation, Inc.,
   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

   Markus F.X.J. Oberhumer
   <markus@oberhumer.com>
   http://www.oberhumer.com/opensource/lzo/
 */


#include "config1b.h"


/***********************************************************************
//
************************************************************************/

#define N          0xffffL          /* size of ring buffer */
#define THRESHOLD       2           /* lower limit for match length */
#define F            2048           /* upper limit for match length */


#define LZO1B
#define LZO_COMPRESS_T  lzo1b_999_t
#define lzo_swd_t       lzo1b_999_swd_t
#include "lzo_mchw.ch"



/***********************************************************************
//
************************************************************************/

static lzo_bytep
code_match ( LZO_COMPRESS_T *c, lzo_bytep op, lzo_uint m_len, lzo_uint m_off )
{
    if (m_len <= M2_MAX_LEN && m_off <= M2_MAX_OFFSET)
    {
        assert(m_len >= M2_MIN_LEN);
        assert(m_off >= M2_MIN_OFFSET);

        m_off -= M2_MIN_OFFSET;
        /* code match len + low offset bits */
        *op++ = LZO_BYTE(((m_len - (M2_MIN_LEN - 2)) << M2O_BITS) |
                          (m_off & M2O_MASK));
        /* code high offset bits */
        *op++ = LZO_BYTE(m_off >> M2O_BITS);
        c->m2_m++;
    }
    else
    {
        assert(m_len >= M3_MIN_LEN);
        assert(m_off <= M3_MAX_OFFSET);

        m_off -= M3_MIN_OFFSET - M3_EOF_OFFSET;
        /* code match len */
        if (m_len <= M3_MAX_LEN)
            *op++ = LZO_BYTE(M3_MARKER | (m_len - (M3_MIN_LEN - 1)));
        else
        {
            assert(m_len >= M4_MIN_LEN);
            /* code M4 match len flag */
            *op++ = M4_MARKER;
            /* code match len */
            m_len -= M4_MIN_LEN - 1;
            while (m_len > 255)
            {
                m_len -= 255;
                *op++ = 0;
            }
            assert(m_len > 0);
            *op++ = LZO_BYTE(m_len);
        }
        /* code low offset bits */
        *op++ = LZO_BYTE(m_off & M3O_MASK);
        /* code high offset bits */
        *op++ = LZO_BYTE(m_off >> M3O_BITS);

        c->r1_m_len = 0;
        c->m3_m++;
    }
    return op;
}


/***********************************************************************
// this is a public function, but there is no prototype in a header file
************************************************************************/

LZO_EXTERN(int)
lzo1b_999_compress_callback ( const lzo_bytep in , lzo_uint  in_len,
                                    lzo_bytep out, lzo_uintp out_len,
                                    lzo_voidp wrkmem,
                                    lzo_callback_p cb,
                                    lzo_uint max_chain );

LZO_PUBLIC(int)
lzo1b_999_compress_callback ( const lzo_bytep in , lzo_uint  in_len,
                                    lzo_bytep out, lzo_uintp out_len,
                                    lzo_voidp wrkmem,
                                    lzo_callback_p cb,
                                    lzo_uint max_chain )
{
    lzo_bytep op;
    const lzo_bytep ii;
    lzo_uint lit;
    lzo_uint m_len, m_off;
    LZO_COMPRESS_T cc;
    LZO_COMPRESS_T * const c = &cc;
    lzo_swd_p const swd = (lzo_swd_p) wrkmem;
    int r;

    /* sanity check */
    LZO_COMPILE_TIME_ASSERT(LZO1B_999_MEM_COMPRESS >= SIZEOF_LZO_SWD_T)

    c->init = 0;
    c->ip = c->in = in;
    c->in_end = in + in_len;
    c->cb = cb;
    c->r1_r = c->m3_r = c->m2_m = c->m3_m = 0;

    op = out;
    ii = c->ip;             /* point to start of literal run */
    lit = 0;
    c->r1_m_len = 0;

    r = init_match(c,swd,NULL,0,0);
    if (r != 0)
        return r;
    if (max_chain > 0)
        swd->max_chain = max_chain;

    r = find_match(c,swd,0,0);
    if (r != 0)
        return r;
    while (c->look > 0)
    {
        int lazy_match_min_gain = -1;
        lzo_uint ahead = 0;

        m_len = c->m_len;
        m_off = c->m_off;

#if 0
        printf("%5ld: %5d len:%3d off:%5d\n", (c->ip-c->look)-in, c->look,
                m_len, m_off);
#endif

        assert(c->ip - c->look >= in);
        if (lit == 0)
            ii = c->ip - c->look;
        assert(ii + lit == c->ip - c->look);
        assert(swd->b_char == *(c->ip - c->look));

        if ((m_len < M2_MIN_LEN) ||
            (m_len < M3_MIN_LEN && m_off > M2_MAX_OFFSET))
        {
            m_len = 0;
        }
        else
        {
            assert(c->ip - c->look - m_off >= in);
            assert(c->ip - c->look - m_off + m_len < c->ip);
            assert(lzo_memcmp(c->ip - c->look, c->ip - c->look - m_off,
                              m_len) == 0);

            if (lit > 0)
            {
                /* we have a current literal run: do not try a lazy match,
                   if the literal could be coded into a r1 match */
                if (lit == 1 && c->r1_m_len == M2_MIN_LEN)
                    lazy_match_min_gain = -1;
                else
                    lazy_match_min_gain = 1;

#if (M2_MIN_LEN == 2)
                if (m_len == 2)
                {
                    /* don't code a match of len 2 if we have to
                       code a literal run. Code a literal instead. */
                    m_len = 0;
                }
#endif
#if (M2_MIN_LEN == M3_MIN_LEN)
                if (m_len == M2_MIN_LEN && m_off > M2_MAX_OFFSET)
                {
                    /* don't code a M3 match of len 3 if we have to
                       code a literal run. Code a literal instead. */
                    m_len = 0;
                }
#endif
            }
            else
            {
                /* no current literal run: only try a lazy match,
                   if the literal could be coded into a r1 match */
                if (c->r1_m_len == M2_MIN_LEN)
                    lazy_match_min_gain = 0;
                else
                    lazy_match_min_gain = -1;
            }
        }


        /* try a lazy match */
        if (m_len == 0)
            lazy_match_min_gain = -1;
        if (lazy_match_min_gain >= 0 && c->look > m_len)
        {
            assert(m_len > 0);

            r = find_match(c,swd,1,0);
            assert(r == 0);
            assert(c->look > 0);

            if (m_len <= M2_MAX_LEN && m_off <= M2_MAX_OFFSET &&
                c->m_off > M2_MAX_OFFSET)
                lazy_match_min_gain += 1;

            if (c->m_len >= m_len + lazy_match_min_gain)
            {
                c->lazy++;
#if !defined(NDEBUG)
                m_len = c->m_len;
                m_off = c->m_off;
                assert(lzo_memcmp(c->ip - c->look, c->ip - c->look - m_off,
                                  m_len) == 0);
#endif
                lit++;
                assert(ii + lit == c->ip - c->look);
                continue;
            }
            else
            {
                ahead = 1;
                assert(ii + lit + 1 == c->ip - c->look);
            }
            assert(m_len > 0);
        }
        assert(ii + lit + ahead == c->ip - c->look);


        if (m_len == 0)
        {
            /* a literal */
            lit++;
            r = find_match(c,swd,1,0);
            assert(r == 0);
        }
        else
        {
            /* 1 - store run */
            if (lit > 0)
            {
                /* code current literal run */
                if (lit == 1 && c->r1_m_len == M2_MIN_LEN)
                {
                    /* Code a context sensitive R1 match. */
                    assert((op[-2] >> M2O_BITS) == (M2_MARKER >> M2O_BITS));
                    op[-2] &= M2O_MASK;
                    assert((op[-2] >> M2O_BITS) == 0);
                    /* copy 1 literal */
                    *op++ = *ii++;
                    assert(ii + ahead == c->ip - c->look);
                    c->r1_r++;
                }
                else
                {
                    op = STORE_RUN(op,ii,lit);
                }
                if (lit < R0FAST)
                    c->r1_m_len = m_len;
                else
                    c->r1_m_len = 0;
                lit = 0;
            }
            else
                c->r1_m_len = 0;

            /* 2 - code match */
            op = code_match(c,op,m_len,m_off);
            r = find_match(c,swd,m_len,1+ahead);
            assert(r == 0);
        }

        c->codesize = pd(op, out);
    }


    /* store final run */
    if (lit > 0)
        op = STORE_RUN(op,ii,lit);

#if defined(LZO_EOF_CODE)
    *op++ = M3_MARKER | 1;
    *op++ = 0;
    *op++ = 0;
#endif

    c->codesize = pd(op, out);
    assert(c->textsize == in_len);

    *out_len = pd(op, out);

    if (c->cb && c->cb->nprogress)
        (*c->cb->nprogress)(c->cb, c->textsize, c->codesize, 0);

#if 0
    printf("%ld %ld -> %ld: %ld %ld %ld %ld %ld\n",
        (long) c->textsize, (long)in_len, (long) c->codesize,
        c->r1_r, c->m3_r, c->m2_m, c->m3_m, c->lazy);
#endif
    return LZO_E_OK;
}



/***********************************************************************
//
************************************************************************/

LZO_PUBLIC(int)
lzo1b_999_compress  ( const lzo_bytep in , lzo_uint  in_len,
                            lzo_bytep out, lzo_uintp out_len,
                            lzo_voidp wrkmem )
{
    return lzo1b_999_compress_callback(in,in_len,out,out_len,wrkmem,
                                       (lzo_callback_p) 0, 0);
}


/*
vi:ts=4:et
*/