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/* ucl_swd.c -- sliding window dictionary

   This file is part of the UCL data compression library.

   Copyright (C) 1996-2002 Markus Franz Xaver Johannes Oberhumer

   All Rights Reserved.

   The UCL 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 UCL 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 UCL library; see the file COPYING.

   If not, write to the Free Software Foundation, Inc.,

   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer

   <markus@oberhumer.com>

 */

#if (UCL_UINT_MAX < UCL_0xffffffffL)

#  error "UCL_UINT_MAX"

#endif

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

//

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

#ifndef SWD_N

#  define SWD_N             N

#endif

#ifndef SWD_F

#  define SWD_F             F

#endif

#ifndef SWD_THRESHOLD

#  define SWD_THRESHOLD     THRESHOLD

#endif

/* unsigned type for dictionary access - don't waste memory here */

#if (SWD_N + SWD_F + SWD_F < USHRT_MAX)

   typedef unsigned short   swd_uint;

#  define SWD_UINT_MAX      USHRT_MAX

#else

   typedef ucl_uint         swd_uint;

#  define SWD_UINT_MAX      UCL_UINT_MAX

#endif

#define SWD_UINT(x)         ((swd_uint)(x))

#ifndef SWD_HSIZE

#  define SWD_HSIZE         16384

#endif

#ifndef SWD_MAX_CHAIN

#  define SWD_MAX_CHAIN     2048

#endif

#if !defined(HEAD3)

#if 1

#  define HEAD3(b,p) \

    (((0x9f5f*(((((ucl_uint32)b[p]<<5)^b[p+1])<<5)^b[p+2]))>>5) & (SWD_HSIZE-1))

#else

#  define HEAD3(b,p) \

    (((0x9f5f*(((((ucl_uint32)b[p+2]<<5)^b[p+1])<<5)^b[p]))>>5) & (SWD_HSIZE-1))

#endif

#endif

#if (SWD_THRESHOLD == 1) && !defined(HEAD2)

#  if 1 && defined(UCL_UNALIGNED_OK_2)

#    define HEAD2(b,p)      (* (const ucl_ushortp) &(b[p]))

#  else

#    define HEAD2(b,p)      (b[p] ^ ((unsigned)b[p+1]<<8))

#  endif

#  define NIL2              SWD_UINT_MAX

#endif

#if defined(__UCL_CHECKER)

   /* malloc arrays of the exact size to detect any overrun */

#  ifndef SWD_USE_MALLOC

#    define SWD_USE_MALLOC

#  endif

#endif

typedef struct

{

/* public - "built-in" */

    ucl_uint n;

    ucl_uint f;

    ucl_uint threshold;

/* public - configuration */

    ucl_uint max_chain;

    ucl_uint nice_length;

    ucl_bool use_best_off;

    ucl_uint lazy_insert;

/* public - output */

    ucl_uint m_len;

    ucl_uint m_off;

    ucl_uint look;

    int b_char;

#if defined(SWD_BEST_OFF)

    ucl_uint best_off[ SWD_BEST_OFF ];

#endif

/* semi public */

    UCL_COMPRESS_T *c;

    ucl_uint m_pos;

#if defined(SWD_BEST_OFF)

    ucl_uint best_pos[ SWD_BEST_OFF ];

#endif

/* private */

    const ucl_byte *dict;

    const ucl_byte *dict_end;

    ucl_uint dict_len;

/* private */

    ucl_uint ip;                /* input pointer (lookahead) */

    ucl_uint bp;                /* buffer pointer */

    ucl_uint rp;                /* remove pointer */

    ucl_uint b_size;

    unsigned char *b_wrap;

    ucl_uint node_count;

    ucl_uint first_rp;

#if defined(SWD_USE_MALLOC)

    unsigned char *b;

    swd_uint *head3;

    swd_uint *succ3;

    swd_uint *best3;

    swd_uint *llen3;

#ifdef HEAD2

    swd_uint *head2;

#endif

#else

    unsigned char b [ SWD_N + SWD_F + SWD_F ];

    swd_uint head3 [ SWD_HSIZE ];

    swd_uint succ3 [ SWD_N + SWD_F ];

    swd_uint best3 [ SWD_N + SWD_F ];

    swd_uint llen3 [ SWD_HSIZE ];

#ifdef HEAD2

    swd_uint head2 [ UCL_UINT32_C(65536) ];

#endif

#endif

}

ucl_swd_t;

/* Access macro for head3.

 * head3[key] may be uninitialized if the list is emtpy,

 * but then its value will never be used.

 */

#if defined(__UCL_CHECKER)

#  define s_head3(s,key) \

        ((s->llen3[key] == 0) ? SWD_UINT_MAX : s->head3[key])

#else

#  define s_head3(s,key)        s->head3[key]

#endif

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

//

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

static

void swd_initdict(ucl_swd_t *s, const ucl_byte *dict, ucl_uint dict_len)

{

    s->dict = s->dict_end = NULL;

    s->dict_len = 0;

    if (!dict || dict_len <= 0)

        return;

    if (dict_len > s->n)

    {

        dict += dict_len - s->n;

        dict_len = s->n;

    }

    s->dict = dict;

    s->dict_len = dict_len;

    s->dict_end = dict + dict_len;

    ucl_memcpy(s->b,dict,dict_len);

    s->ip = dict_len;

}

static

void swd_insertdict(ucl_swd_t *s, ucl_uint node, ucl_uint len)

{

    ucl_uint key;

    s->node_count = s->n - len;

    s->first_rp = node;

    while (len-- > 0)

    {

        key = HEAD3(s->b,node);

        s->succ3[node] = s_head3(s,key);

        s->head3[key] = SWD_UINT(node);

        s->best3[node] = SWD_UINT(s->f + 1);

        s->llen3[key]++;

        assert(s->llen3[key] <= s->n);

#ifdef HEAD2

        key = HEAD2(s->b,node);

        s->head2[key] = SWD_UINT(node);

#endif

        node++;

    }

}

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

//

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

static

int swd_init(ucl_swd_t *s, const ucl_byte *dict, ucl_uint dict_len)

{

    ucl_uint i = 0;

    int c = 0;

    if (s->n == 0)

        s->n = SWD_N;

    if (s->f == 0)

        s->f = SWD_F;

    s->threshold = SWD_THRESHOLD;

    if (s->n > SWD_N || s->f > SWD_F)

        return UCL_E_INVALID_ARGUMENT;

#if defined(SWD_USE_MALLOC)

    s->b = (unsigned char *) ucl_alloc(s->n + s->f + s->f, 1);

    s->head3 = (swd_uint *) ucl_alloc(SWD_HSIZE, sizeof(*s->head3));

    s->succ3 = (swd_uint *) ucl_alloc(s->n + s->f, sizeof(*s->succ3));

    s->best3 = (swd_uint *) ucl_alloc(s->n + s->f, sizeof(*s->best3));

    s->llen3 = (swd_uint *) ucl_alloc(SWD_HSIZE, sizeof(*s->llen3));

    if (!s->b || !s->head3  || !s->succ3 || !s->best3 || !s->llen3)

        return UCL_E_OUT_OF_MEMORY;

#ifdef HEAD2

    s->head2 = (swd_uint *) ucl_alloc(UCL_UINT32_C(65536), sizeof(*s->head2));

    if (!s->head2)

        return UCL_E_OUT_OF_MEMORY;

#endif

#endif

    /* defaults */

    s->max_chain = SWD_MAX_CHAIN;

    s->nice_length = s->f;

    s->use_best_off = 0;

    s->lazy_insert = 0;

    s->b_size = s->n + s->f;

    if (s->b_size + s->f >= SWD_UINT_MAX)

        return UCL_E_ERROR;

    s->b_wrap = s->b + s->b_size;

    s->node_count = s->n;

    ucl_memset(s->llen3, 0, sizeof(s->llen3[0]) * SWD_HSIZE);

#ifdef HEAD2

#if 1

    ucl_memset(s->head2, 0xff, sizeof(s->head2[0]) * UCL_UINT32_C(65536));

    assert(s->head2[0] == NIL2);

#else

    for (i = 0; i < UCL_UINT32_C(65536); i++)

        s->head2[i] = NIL2;

#endif

#endif

    s->ip = 0;

    swd_initdict(s,dict,dict_len);

    s->bp = s->ip;

    s->first_rp = s->ip;

    assert(s->ip + s->f <= s->b_size);

#if 1

    s->look = (ucl_uint) (s->c->in_end - s->c->ip);

    if (s->look > 0)

    {

        if (s->look > s->f)

            s->look = s->f;

        ucl_memcpy(&s->b[s->ip],s->c->ip,s->look);

        s->c->ip += s->look;

        s->ip += s->look;

    }

#else

    s->look = 0;

    while (s->look < s->f)

    {

        if ((c = getbyte(*(s->c))) < 0)

            break;

        s->b[s->ip] = UCL_BYTE(c);

        s->ip++;

        s->look++;

    }

#endif

    if (s->ip == s->b_size)

        s->ip = 0;

    if (s->look >= 2 && s->dict_len > 0)

        swd_insertdict(s,0,s->dict_len);

    s->rp = s->first_rp;

    if (s->rp >= s->node_count)

        s->rp -= s->node_count;

    else

        s->rp += s->b_size - s->node_count;

#if defined(__UCL_CHECKER)

    /* initialize memory for the first few HEAD3 (if s->ip is not far

     * enough ahead to do this job for us). The value doesn't matter. */

    if (s->look < 3)

        ucl_memset(&s->b[s->bp+s->look],0,3);

#endif

    UCL_UNUSED(i);

    UCL_UNUSED(c);

    return UCL_E_OK;

}

static

void swd_exit(ucl_swd_t *s)

{

#if defined(SWD_USE_MALLOC)

    /* free in reverse order of allocations */

#ifdef HEAD2

    ucl_free(s->head2); s->head2 = NULL;

#endif

    ucl_free(s->llen3); s->llen3 = NULL;

    ucl_free(s->best3); s->best3 = NULL;

    ucl_free(s->succ3); s->succ3 = NULL;

    ucl_free(s->head3); s->head3 = NULL;

    ucl_free(s->b); s->b = NULL;

#else

    UCL_UNUSED(s);

#endif

}

#define swd_pos2off(s,pos) \

    (s->bp > (pos) ? s->bp - (pos) : s->b_size - ((pos) - s->bp))

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

//

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

static __inline__

void swd_getbyte(ucl_swd_t *s)

{

    int c;

    if ((c = getbyte(*(s->c))) < 0)

    {

        if (s->look > 0)

            --s->look;

#if defined(__UCL_CHECKER)

        /* initialize memory - value doesn't matter */

        s->b[s->ip] = 0;

        if (s->ip < s->f)

            s->b_wrap[s->ip] = 0;

#endif

    }

    else

    {

        s->b[s->ip] = UCL_BYTE(c);

        if (s->ip < s->f)

            s->b_wrap[s->ip] = UCL_BYTE(c);

    }

    if (++s->ip == s->b_size)

        s->ip = 0;

    if (++s->bp == s->b_size)

        s->bp = 0;

    if (++s->rp == s->b_size)

        s->rp = 0;

}

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

// remove node from lists

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

static __inline__

void swd_remove_node(ucl_swd_t *s, ucl_uint node)

{

    if (s->node_count == 0)

    {

        ucl_uint key;

#ifdef UCL_DEBUG

        if (s->first_rp != UCL_UINT_MAX)

        {

            if (node != s->first_rp)

                printf("Remove %5d: %5d %5d %5d %5d  %6d %6d\n",

                        node, s->rp, s->ip, s->bp, s->first_rp,

                        s->ip - node, s->ip - s->bp);

            assert(node == s->first_rp);

            s->first_rp = UCL_UINT_MAX;

        }

#endif

        key = HEAD3(s->b,node);

        assert(s->llen3[key] > 0);

        --s->llen3[key];

#ifdef HEAD2

        key = HEAD2(s->b,node);

        assert(s->head2[key] != NIL2);

        if ((ucl_uint) s->head2[key] == node)

            s->head2[key] = NIL2;

#endif

    }

    else

        --s->node_count;

}

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

//

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

static

void swd_accept(ucl_swd_t *s, ucl_uint n)

{

    assert(n <= s->look);

    if (n > 0) do

    {

        ucl_uint key;

        swd_remove_node(s,s->rp);

        /* add bp into HEAD3 */

        key = HEAD3(s->b,s->bp);

        s->succ3[s->bp] = s_head3(s,key);

        s->head3[key] = SWD_UINT(s->bp);

        s->best3[s->bp] = SWD_UINT(s->f + 1);

        s->llen3[key]++;

        assert(s->llen3[key] <= s->n);

#ifdef HEAD2

        /* add bp into HEAD2 */

        key = HEAD2(s->b,s->bp);

        s->head2[key] = SWD_UINT(s->bp);

#endif

        swd_getbyte(s);

    } while (--n > 0);

}

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

//

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

static

void swd_search(ucl_swd_t *s, ucl_uint node, ucl_uint cnt)

{

#if 0 && defined(__GNUC__) && defined(__i386__)

    register const unsigned char *p1 __asm__("%edi");

    register const unsigned char *p2 __asm__("%esi");

    register const unsigned char *px __asm__("%edx");

#else

    const unsigned char *p1;

    const unsigned char *p2;

    const unsigned char *px;

#endif

    ucl_uint m_len = s->m_len;

    const unsigned char * b  = s->b;

    const unsigned char * bp = s->b + s->bp;

    const unsigned char * bx = s->b + s->bp + s->look;

    unsigned char scan_end1;

    assert(s->m_len > 0);

    scan_end1 = bp[m_len - 1];

    for ( ; cnt-- > 0; node = s->succ3[node])

    {

        p1 = bp;

        p2 = b + node;

        px = bx;

        assert(m_len < s->look);

        if (

#if 1

            p2[m_len - 1] == scan_end1 &&

            p2[m_len] == p1[m_len] &&

#endif

            p2[0] == p1[0] &&

            p2[1] == p1[1])

        {

            ucl_uint i;

            assert(ucl_memcmp(bp,&b[node],3) == 0);

#if 0 && defined(UCL_UNALIGNED_OK_4)

            p1 += 3; p2 += 3;

            while (p1 < px && * (const ucl_uint32p) p1 == * (const ucl_uint32p) p2)

                p1 += 4, p2 += 4;

            while (p1 < px && *p1 == *p2)

                p1 += 1, p2 += 1;

#else

            p1 += 2; p2 += 2;

            do {} while (++p1 < px && *p1 == *++p2);

#endif

            i = p1 - bp;

#ifdef UCL_DEBUG

            if (ucl_memcmp(bp,&b[node],i) != 0)

                printf("%5ld %5ld %02x%02x %02x%02x\n",

                        (long)s->bp, (long) node,

                        bp[0], bp[1], b[node], b[node+1]);

#endif

            assert(ucl_memcmp(bp,&b[node],i) == 0);

#if defined(SWD_BEST_OFF)

            if (i < SWD_BEST_OFF)

            {

                if (s->best_pos[i] == 0)

                    s->best_pos[i] = node + 1;

            }

#endif

            if (i > m_len)

            {

                s->m_len = m_len = i;

                s->m_pos = node;

                if (m_len == s->look)

                    return;

                if (m_len >= s->nice_length)

                    return;

                if (m_len > (ucl_uint) s->best3[node])

                    return;

                scan_end1 = bp[m_len - 1];

            }

        }

    }

}

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

//

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

#ifdef HEAD2

static

ucl_bool swd_search2(ucl_swd_t *s)

{

    ucl_uint key;

    assert(s->look >= 2);

    assert(s->m_len > 0);

    key = s->head2[ HEAD2(s->b,s->bp) ];

    if (key == NIL2)

        return 0;

#ifdef UCL_DEBUG

    if (ucl_memcmp(&s->b[s->bp],&s->b[key],2) != 0)

        printf("%5ld %5ld %02x%02x %02x%02x\n", (long)s->bp, (long)key,

                s->b[s->bp], s->b[s->bp+1], s->b[key], s->b[key+1]);

#endif

    assert(ucl_memcmp(&s->b[s->bp],&s->b[key],2) == 0);

#if defined(SWD_BEST_OFF)

    if (s->best_pos[2] == 0)

        s->best_pos[2] = key + 1;

#endif

    if (s->m_len < 2)

    {

        s->m_len = 2;

        s->m_pos = key;

    }

    return 1;

}

#endif

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

//

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

static

void swd_findbest(ucl_swd_t *s)

{

    ucl_uint key;

    ucl_uint cnt, node;

    ucl_uint len;

    assert(s->m_len > 0);

    /* get current head, add bp into HEAD3 */

    key = HEAD3(s->b,s->bp);

    node = s->succ3[s->bp] = s_head3(s,key);

    cnt = s->llen3[key]++;

    assert(s->llen3[key] <= s->n + s->f);

    if (cnt > s->max_chain && s->max_chain > 0)

        cnt = s->max_chain;

    s->head3[key] = SWD_UINT(s->bp);

    s->b_char = s->b[s->bp];

    len = s->m_len;

    if (s->m_len >= s->look)

    {

        if (s->look == 0)

            s->b_char = -1;

        s->m_off = 0;

        s->best3[s->bp] = SWD_UINT(s->f + 1);

    }

    else

    {

#ifdef HEAD2

        if (swd_search2(s))

#endif

            if (s->look >= 3)

                swd_search(s,node,cnt);

        if (s->m_len > len)

            s->m_off = swd_pos2off(s,s->m_pos);

        s->best3[s->bp] = SWD_UINT(s->m_len);

#if defined(SWD_BEST_OFF)

        if (s->use_best_off)

        {

            int i;

            for (i = 2; i < SWD_BEST_OFF; i++)

                if (s->best_pos[i] > 0)

                    s->best_off[i] = swd_pos2off(s,s->best_pos[i]-1);

                else

                    s->best_off[i] = 0;

        }

#endif

    }

    swd_remove_node(s,s->rp);

#ifdef HEAD2

    /* add bp into HEAD2 */

    key = HEAD2(s->b,s->bp);

    s->head2[key] = SWD_UINT(s->bp);

#endif

}

#undef HEAD3

#undef HEAD2

#undef s_head3

/*

vi:ts=4:et

*/