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) 1996-2015 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 SWD_N          0xffffL          /* size of ring buffer */
#define SWD_THRESHOLD       2           /* lower limit for match length */
#define SWD_F            2048           /* upper limit for match length */


#define LZO1B 1
#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); LZO_UNUSED(r);
            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); LZO_UNUSED(r);
        }
        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); LZO_UNUSED(r);
        }

        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);
}


/* vim:set ts=4 sw=4 et: */