path: root/src/lzo1a.c

/* lzo1a.c -- implementation of the LZO1A 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 "lzo_conf.h"
#include "lzo/lzo1a.h"


/***********************************************************************
// The next two defines can be changed to customize LZO1A.
// The default version is LZO1A-5/1.
************************************************************************/

/* run bits (3 - 5) - the compressor and the decompressor
 * must use the same value. */
#if !defined(RBITS)
#  define RBITS     5
#endif

/* compression level (1 - 9) - this only affects the compressor.
 * 1 is fastest, 9 is best compression ratio
 */
#if !defined(CLEVEL)
#  define CLEVEL    1           /* fastest by default */
#endif


/* Collect statistics */
#if 0 && !defined(LZO_COLLECT_STATS)
#  define LZO_COLLECT_STATS
#endif


/***********************************************************************
// You should not have to change anything below this line.
************************************************************************/

/* check configuration */
#if (RBITS < 3 || RBITS > 5)
#  error "invalid RBITS"
#endif
#if (CLEVEL < 1 || CLEVEL > 9)
#  error "invalid CLEVEL"
#endif


/***********************************************************************
// internal configuration
// all of these affect compression only
************************************************************************/

/* choose the hashing strategy */
#ifndef LZO_HASH
#define LZO_HASH    LZO_HASH_LZO_INCREMENTAL_A
#endif
#define D_INDEX1(d,p)       d = DM(DMUL(0x21,DX2(p,5,5)) >> 5)
#define D_INDEX2(d,p)       d = d ^ D_MASK

#include "lzo1a_de.h"
#include "stats1a.h"


/* check other constants */
#if (LBITS < 5 || LBITS > 8)
#  error "invalid LBITS"
#endif


#if defined(LZO_COLLECT_STATS)
   static lzo1a_stats_t lzo_statistics;
   lzo1a_stats_t *lzo1a_stats = &lzo_statistics;
#  define lzo_stats lzo1a_stats
#endif


/***********************************************************************
// get algorithm info, return memory required for compression
************************************************************************/

LZO_EXTERN(lzo_uint) lzo1a_info ( int *rbits, int *clevel );

LZO_PUBLIC(lzo_uint)
lzo1a_info ( int *rbits, int *clevel )
{
    if (rbits)
        *rbits = RBITS;
    if (clevel)
        *clevel = CLEVEL;
    return D_SIZE * lzo_sizeof(lzo_bytep);
}


/***********************************************************************
// LZO1A decompress a block of data.
//
// Could be easily translated into assembly code.
************************************************************************/

LZO_PUBLIC(int)
lzo1a_decompress ( const lzo_bytep in , lzo_uint  in_len,
                         lzo_bytep out, lzo_uintp out_len,
                         lzo_voidp wrkmem )
{
    register lzo_bytep op;
    register const lzo_bytep ip;
    register lzo_uint t;
    register const lzo_bytep m_pos;
    const lzo_bytep const ip_end = in + in_len;

    LZO_UNUSED(wrkmem);

    op = out;
    ip = in;
    while (ip < ip_end)
    {
        t = *ip++;      /* get marker */
        LZO_STATS(lzo_stats->marker[t]++);

        if (t == 0)             /* a R0 literal run */
        {
            t = *ip++;
            if (t >= R0FAST - R0MIN)            /* a long R0 run */
            {
                t -= R0FAST - R0MIN;
                if (t == 0)
                    t = R0FAST;
                else
                {
#if 0
                    t = 256u << ((unsigned) t);
#else
                    /* help the optimizer */
                    lzo_uint tt = 256;
                    do tt <<= 1; while (--t > 0);
                    t = tt;
#endif
                }
                MEMCPY8_DS(op,ip,t);
                continue;
            }
            t += R0MIN;
            goto literal;
        }
        else if (t < R0MIN)     /* a short literal run */
        {
literal:
            MEMCPY_DS(op,ip,t);

        /* after a literal a match must follow */
            while (ip < ip_end)
            {
                t = *ip++;          /* get R1 marker */
                if (t >= R0MIN)
                    goto match;

            /* R1 match - a context sensitive 3 byte match + 1 byte literal */
                assert((t & OMASK) == t);
                m_pos = op - MIN_OFFSET;
                m_pos -= t | (((lzo_uint) *ip++) << OBITS);
                assert(m_pos >= out); assert(m_pos < op);
                *op++ = *m_pos++;
                *op++ = *m_pos++;
                *op++ = *m_pos++;
                *op++ = *ip++;
            }
        }
        else                    /* a match */
        {
match:
            /* get match offset */
            m_pos = op - MIN_OFFSET;
            m_pos -= (t & OMASK) | (((lzo_uint) *ip++) << OBITS);
            assert(m_pos >= out); assert(m_pos < op);

            /* get match len */
            if (t < ((MSIZE - 1) << OBITS))         /* a short match */
            {
                t >>= OBITS;
                *op++ = *m_pos++;
                *op++ = *m_pos++;
                MEMCPY_DS(op,m_pos,t);
            }
            else                                     /* a long match */
            {
#if (LBITS < 8)
                t = (MIN_MATCH_LONG - THRESHOLD) + ((lzo_uint)(*ip++) & LMASK);
#else
                t = (MIN_MATCH_LONG - THRESHOLD) + (lzo_uint)(*ip++);
#endif
                *op++ = *m_pos++;
                *op++ = *m_pos++;
                MEMCPY_DS(op,m_pos,t);
#if (LBITS < 8)
                /* a very short literal following a long match */
                t = ip[-1] >> LBITS;
                if (t) do
                    *op++ = *ip++;
                while (--t);
#endif
            }
        }
    }

    *out_len = pd(op, out);

    /* the next line is the only check in the decompressor */
    return (ip == ip_end ? LZO_E_OK :
           (ip < ip_end  ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN));
}



/***********************************************************************
// LZO1A compress a block of data.
//
// I apologize for the spaghetti code, but it really helps the optimizer.
************************************************************************/

#include "lzo1a_cr.ch"

static int
do_compress    ( const lzo_bytep in , lzo_uint  in_len,
                       lzo_bytep out, lzo_uintp out_len,
                       lzo_voidp wrkmem )
{
    register const lzo_bytep ip;
#if defined(__LZO_HASH_INCREMENTAL)
    lzo_xint dv;
#endif
    const lzo_bytep m_pos;
    lzo_bytep op;
    const lzo_bytep const ip_end = in+in_len - DVAL_LEN - MIN_MATCH_LONG;
    const lzo_bytep const in_end = in+in_len - DVAL_LEN;
    const lzo_bytep ii;
    lzo_dict_p const dict = (lzo_dict_p) wrkmem;
    const lzo_bytep r1 = ip_end;    /* pointer for R1 match (none yet) */
#if (LBITS < 8)
    const lzo_bytep im = ip_end;    /* pointer to last match start */
#endif

#if !defined(NDEBUG)
    const lzo_bytep m_pos_sav;
#endif

    op = out;
    ip = in;
    ii = ip;            /* point to start of current literal run */

    /* init dictionary */
#if defined(LZO_DETERMINISTIC)
    BZERO8_PTR(wrkmem,sizeof(lzo_dict_t),D_SIZE);
#endif

    DVAL_FIRST(dv,ip); UPDATE_D(dict,0,dv,ip,in); ip++;
    DVAL_NEXT(dv,ip);

    do {
        lzo_uint m_off;
        lzo_uint dindex;

        DINDEX1(dindex,ip);
        GINDEX(m_pos,m_off,dict,dindex,in);
        if (LZO_CHECK_MPOS_NON_DET(m_pos,m_off,in,ip,MAX_OFFSET))
            goto literal;
        if (m_pos[0] == ip[0] && m_pos[1] == ip[1] && m_pos[2] == ip[2])
            goto match;
        DINDEX2(dindex,ip);
        GINDEX(m_pos,m_off,dict,dindex,in);
        if (LZO_CHECK_MPOS_NON_DET(m_pos,m_off,in,ip,MAX_OFFSET))
            goto literal;
        if (m_pos[0] == ip[0] && m_pos[1] == ip[1] && m_pos[2] == ip[2])
            goto match;
        goto literal;

literal:
        UPDATE_I(dict,0,dindex,ip,in);
        if (++ip >= ip_end)
            break;
        continue;

match:
        UPDATE_I(dict,0,dindex,ip,in);
#if !defined(NDEBUG) && defined(LZO_DICT_USE_PTR)
        assert(m_pos == NULL || m_pos >= in);
        m_pos_sav = m_pos;
#endif
        m_pos += 3;
        {
    /* we have found a match (of at least length 3) */

#if !defined(NDEBUG) && !defined(LZO_DICT_USE_PTR)
            assert((m_pos_sav = ip - m_off) == (m_pos - 3));
#endif

            assert(m_pos >= in);
            assert(ip < ip_end);

            /* 1) store the current literal run */
            if (pd(ip,ii) > 0)
            {
                lzo_uint t = pd(ip,ii);

                if (ip - r1 == MIN_MATCH + 1)
                {
                /* Code a context sensitive R1 match.
                 * This is tricky and somewhat difficult to explain:
                 * multiplex a literal run of length 1 into the previous
                 * short match of length MIN_MATCH.
                 * The key idea is:
                 *  - after a short run a match MUST follow
                 *  - therefore the value m = 000 in the mmmooooo marker is free
                 *  - use 000ooooo to indicate a MIN_MATCH match (this
                 *    is already coded) plus a 1 byte literal
                 */
                    assert(t == 1);
                    /* modify marker byte */
                    assert((op[-2] >> OBITS) == (MIN_MATCH - THRESHOLD));
                    op[-2] &= OMASK;
                    assert((op[-2] >> OBITS) == 0);
                    /* copy 1 literal */
                    *op++ = *ii;
                    LZO_STATS(lzo_stats->r1_matches++);
                    r1 = ip;                /* set new R1 pointer */
                }
                else if (t < R0MIN)
                {
                    /* inline the copying of a short run */
#if (LBITS < 8)
                    if (t < (1 << (8-LBITS)) && ii - im >= MIN_MATCH_LONG)
                    {
                    /* Code a very short literal run into the
                     * previous long match length byte.
                     */
                        LZO_STATS(lzo_stats->lit_runs_after_long_match++);
                        LZO_STATS(lzo_stats->lit_run_after_long_match[t]++);
                        assert(ii - im <= MAX_MATCH_LONG);
                        assert((op[-1] >> LBITS) == 0);
                        op[-1] |= t << LBITS;
                        MEMCPY_DS(op, ii, t);
                    }
                    else
#endif
                    {
                        LZO_STATS(lzo_stats->lit_runs++);
                        LZO_STATS(lzo_stats->lit_run[t]++);
                        *op++ = LZO_BYTE(t);
                        MEMCPY_DS(op, ii, t);
                        r1 = ip;                /* set new R1 pointer */
                    }
                }
                else if (t < R0FAST)
                {
                    /* inline the copying of a short R0 run */
                    LZO_STATS(lzo_stats->r0short_runs++);
                    *op++ = 0; *op++ = LZO_BYTE(t - R0MIN);
                    MEMCPY_DS(op, ii, t);
                    r1 = ip;                /* set new R1 pointer */
                }
                else
                    op = store_run(op,ii,t);
            }
#if (LBITS < 8)
            im = ip;
#endif


            /* 2) compute match len */
            ii = ip;        /* point to start of current match */

            /* we already matched MIN_MATCH bytes,
             * m_pos also already advanced MIN_MATCH bytes */
            ip += MIN_MATCH;
            assert(m_pos < ip);

            /* try to match another MIN_MATCH_LONG - MIN_MATCH bytes
             * to see if we get a long match */

#define PS  *m_pos++ != *ip++

#if (MIN_MATCH_LONG - MIN_MATCH == 2)                   /* MBITS == 2 */
            if (PS || PS)
#elif (MIN_MATCH_LONG - MIN_MATCH == 6)                 /* MBITS == 3 */
            if (PS || PS || PS || PS || PS || PS)
#elif (MIN_MATCH_LONG - MIN_MATCH == 14)                /* MBITS == 4 */
            if (PS || PS || PS || PS || PS || PS || PS ||
                PS || PS || PS || PS || PS || PS || PS)
#elif (MIN_MATCH_LONG - MIN_MATCH == 30)                /* MBITS == 5 */
            if (PS || PS || PS || PS || PS || PS || PS || PS ||
                PS || PS || PS || PS || PS || PS || PS || PS ||
                PS || PS || PS || PS || PS || PS || PS || PS ||
                PS || PS || PS || PS || PS || PS)
#else
#  error "MBITS not yet implemented"
#endif
            {
            /* we've found a short match */
                lzo_uint m_len;

            /* 2a) compute match parameters */
                    assert(ip-m_pos == (int)m_off);
                --ip;   /* ran one too far, point back to non-match */
                m_len = pd(ip, ii);
                    assert(m_len >= MIN_MATCH_SHORT);
                    assert(m_len <= MAX_MATCH_SHORT);
                    assert(m_off >= MIN_OFFSET);
                    assert(m_off <= MAX_OFFSET);
                    assert(ii-m_off == m_pos_sav);
                    assert(lzo_memcmp(m_pos_sav,ii,m_len) == 0);
                m_off -= MIN_OFFSET;

            /* 2b) code a short match */
                /* code short match len + low offset bits */
                *op++ = LZO_BYTE(((m_len - THRESHOLD) << OBITS) |
                                 (m_off & OMASK));
                /* code high offset bits */
                *op++ = LZO_BYTE(m_off >> OBITS);


#if defined(LZO_COLLECT_STATS)
                lzo_stats->short_matches++;
                lzo_stats->short_match[m_len]++;
                if (m_off < OSIZE)
                    lzo_stats->short_match_offset_osize[m_len]++;
                if (m_off < 256)
                    lzo_stats->short_match_offset_256[m_len]++;
                if (m_off < 1024)
                    lzo_stats->short_match_offset_1024[m_len]++;
#endif


            /* 2c) Insert phrases (beginning with ii+1) into the dictionary. */

#define SI      /* nothing */
#define DI      ++ii; DVAL_NEXT(dv,ii); UPDATE_D(dict,0,dv,ii,in);
#define XI      assert(ii < ip); ii = ip; DVAL_FIRST(dv,(ip));

#if (CLEVEL == 9) || (CLEVEL >= 7 && MBITS <= 4) || (CLEVEL >= 5 && MBITS <= 3)
            /* Insert the whole match (ii+1)..(ip-1) into dictionary.  */
                ++ii;
                do {
                    DVAL_NEXT(dv,ii);
                    UPDATE_D(dict,0,dv,ii,in);
                } while (++ii < ip);
                DVAL_NEXT(dv,ii);
                assert(ii == ip);
                DVAL_ASSERT(dv,ip);
#elif (CLEVEL >= 3)
                SI   DI DI   XI
#elif (CLEVEL >= 2)
                SI   DI      XI
#else
                             XI
#endif

            }
            else
            {
            /* we've found a long match - see how far we can still go */
                const lzo_bytep end;
                lzo_uint m_len;

                assert(ip <= in_end);
                assert(ii == ip - MIN_MATCH_LONG);

                if (pd(in_end,ip) <= (MAX_MATCH_LONG - MIN_MATCH_LONG))
                    end = in_end;
                else
                {
                    end = ip + (MAX_MATCH_LONG - MIN_MATCH_LONG);
                    assert(end < in_end);
                }

                while (ip < end  &&  *m_pos == *ip)
                    m_pos++, ip++;
                assert(ip <= in_end);

            /* 2a) compute match parameters */
                m_len = pd(ip, ii);
                    assert(m_len >= MIN_MATCH_LONG);
                    assert(m_len <= MAX_MATCH_LONG);
                    assert(m_off >= MIN_OFFSET);
                    assert(m_off <= MAX_OFFSET);
                    assert(ii-m_off == m_pos_sav);
                    assert(lzo_memcmp(m_pos_sav,ii,m_len) == 0);
                    assert(pd(ip,m_pos) == m_off);
                m_off -= MIN_OFFSET;

            /* 2b) code the long match */
                /* code long match flag + low offset bits */
                *op++ = LZO_BYTE(((MSIZE - 1) << OBITS) | (m_off & OMASK));
                /* code high offset bits */
                *op++ = LZO_BYTE(m_off >> OBITS);
                /* code match len */
                *op++ = LZO_BYTE(m_len - MIN_MATCH_LONG);


#if defined(LZO_COLLECT_STATS)
                lzo_stats->long_matches++;
                lzo_stats->long_match[m_len]++;
#endif


            /* 2c) Insert phrases (beginning with ii+1) into the dictionary. */
#if (CLEVEL == 9)
            /* Insert the whole match (ii+1)..(ip-1) into dictionary.  */
            /* This is not recommended because it is slow. */
                ++ii;
                do {
                    DVAL_NEXT(dv,ii);
                    UPDATE_D(dict,0,dv,ii,in);
                } while (++ii < ip);
                DVAL_NEXT(dv,ii);
                assert(ii == ip);
                DVAL_ASSERT(dv,ip);
#elif (CLEVEL >= 8)
                SI   DI DI DI DI DI DI DI DI   XI
#elif (CLEVEL >= 7)
                SI   DI DI DI DI DI DI DI      XI
#elif (CLEVEL >= 6)
                SI   DI DI DI DI DI DI         XI
#elif (CLEVEL >= 5)
                SI   DI DI DI DI               XI
#elif (CLEVEL >= 4)
                SI   DI DI DI                  XI
#elif (CLEVEL >= 3)
                SI   DI DI                     XI
#elif (CLEVEL >= 2)
                SI   DI                        XI
#else
                                               XI
#endif
            }

            /* ii now points to the start of the next literal run */
            assert(ii == ip);
        }

    } while (ip < ip_end);

    assert(ip <= in_end);


#if defined(LZO_RETURN_IF_NOT_COMPRESSIBLE)
    /* return -1 if op == out to indicate that we
     * couldn't compress and didn't copy anything.
     */
    if (op == out)
    {
        *out_len = 0;
        return LZO_E_NOT_COMPRESSIBLE;
    }
#endif

    /* store the final literal run */
    if (pd(in_end+DVAL_LEN,ii) > 0)
        op = store_run(op,ii,pd(in_end+DVAL_LEN,ii));

    *out_len = pd(op, out);
    return 0;               /* compression went ok */
}


/***********************************************************************
// LZO1A compress public entry point.
************************************************************************/

LZO_PUBLIC(int)
lzo1a_compress ( const lzo_bytep in , lzo_uint  in_len,
                       lzo_bytep out, lzo_uintp out_len,
                       lzo_voidp wrkmem )
{
    int r = LZO_E_OK;


#if defined(LZO_COLLECT_STATS)
    lzo_memset(lzo_stats,0,sizeof(*lzo_stats));
    lzo_stats->rbits  = RBITS;
    lzo_stats->clevel = CLEVEL;
    lzo_stats->dbits  = DBITS;
    lzo_stats->lbits  = LBITS;
    lzo_stats->min_match_short = MIN_MATCH_SHORT;
    lzo_stats->max_match_short = MAX_MATCH_SHORT;
    lzo_stats->min_match_long  = MIN_MATCH_LONG;
    lzo_stats->max_match_long  = MAX_MATCH_LONG;
    lzo_stats->min_offset      = MIN_OFFSET;
    lzo_stats->max_offset      = MAX_OFFSET;
    lzo_stats->r0min  = R0MIN;
    lzo_stats->r0fast = R0FAST;
    lzo_stats->r0max  = R0MAX;
    lzo_stats->in_len = in_len;
#endif


    /* don't try to compress a block that's too short */
    if (in_len <= 0)
        *out_len = 0;
    else if (in_len <= MIN_MATCH_LONG + DVAL_LEN + 1)
    {
#if defined(LZO_RETURN_IF_NOT_COMPRESSIBLE)
        r = LZO_E_NOT_COMPRESSIBLE;
#else
        *out_len = pd(store_run(out,in,in_len), out);
#endif
    }
    else
        r = do_compress(in,in_len,out,out_len,wrkmem);


#if defined(LZO_COLLECT_STATS)
    lzo_stats->short_matches -= lzo_stats->r1_matches;
    lzo_stats->short_match[MIN_MATCH] -= lzo_stats->r1_matches;
    lzo_stats->out_len = *out_len;
#endif

    return r;
}


/*
vi:ts=4:et
*/