/src/lzo-2.10/src/lzo1x_d.ch

Source
/* lzo1x_d.ch -- implementation of the LZO1X decompression algorithm

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

   Copyright (C) 1996-2017 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 "lzo1_d.ch"


/***********************************************************************
// decompress a block of data.
************************************************************************/

#if defined(DO_DECOMPRESS)
LZO_PUBLIC(int)
DO_DECOMPRESS  ( const lzo_bytep in , lzo_uint  in_len,
                       lzo_bytep out, lzo_uintp out_len,
                       lzo_voidp wrkmem )
#endif
{
    lzo_bytep op;
    const lzo_bytep ip;
    lzo_uint t;
#if defined(COPY_DICT)
    lzo_uint m_off;
    const lzo_bytep dict_end;
#else
    const lzo_bytep m_pos;
#endif

    const lzo_bytep const ip_end = in + in_len;
#if defined(HAVE_ANY_OP)
    lzo_bytep const op_end = out + *out_len;
#endif
#if defined(LZO1Z)
    lzo_uint last_m_off = 0;
#endif

    LZO_UNUSED(wrkmem);

#if defined(COPY_DICT)
    if (dict)
    {
        if (dict_len > M4_MAX_OFFSET)
        {
            dict += dict_len - M4_MAX_OFFSET;
            dict_len = M4_MAX_OFFSET;
        }
        dict_end = dict + dict_len;
    }
    else
    {
        dict_len = 0;
        dict_end = NULL;
    }
#endif /* COPY_DICT */

    *out_len = 0;

    op = out;
    ip = in;

    NEED_IP(1);
    if (*ip > 17)
    {
        t = *ip++ - 17;
        if (t < 4)
            goto match_next;
        assert(t > 0); NEED_OP(t); NEED_IP(t+3);
        do *op++ = *ip++; while (--t > 0);
        goto first_literal_run;
    }

    for (;;)
    {
        NEED_IP(3);
        t = *ip++;
        if (t >= 16)
            goto match;
        /* a literal run */
        if (t == 0)
        {
            while (*ip == 0)
            {
                t += 255;
                ip++;
                TEST_IV(t);
                NEED_IP(1);
            }
            t += 15 + *ip++;
        }
        /* copy literals */
        assert(t > 0); NEED_OP(t+3); NEED_IP(t+6);
#if (LZO_OPT_UNALIGNED64) && (LZO_OPT_UNALIGNED32)
        t += 3;
        if (t >= 8) do
        {
            UA_COPY8(op,ip);
            op += 8; ip += 8; t -= 8;
        } while (t >= 8);
        if (t >= 4)
        {
            UA_COPY4(op,ip);
            op += 4; ip += 4; t -= 4;
        }
        if (t > 0)
        {
            *op++ = *ip++;
            if (t > 1) { *op++ = *ip++; if (t > 2) { *op++ = *ip++; } }
        }
#elif (LZO_OPT_UNALIGNED32) || (LZO_ALIGNED_OK_4)
#if !(LZO_OPT_UNALIGNED32)
        if (PTR_ALIGNED2_4(op,ip))
        {
#endif
        UA_COPY4(op,ip);
        op += 4; ip += 4;
        if (--t > 0)
        {
            if (t >= 4)
            {
                do {
                    UA_COPY4(op,ip);
                    op += 4; ip += 4; t -= 4;
                } while (t >= 4);
                if (t > 0) do *op++ = *ip++; while (--t > 0);
            }
            else
                do *op++ = *ip++; while (--t > 0);
        }
#if !(LZO_OPT_UNALIGNED32)
        }
        else
#endif
#endif
#if !(LZO_OPT_UNALIGNED32)
        {
            *op++ = *ip++; *op++ = *ip++; *op++ = *ip++;
            do *op++ = *ip++; while (--t > 0);
        }
#endif


first_literal_run:


        t = *ip++;
        if (t >= 16)
            goto match;
#if defined(COPY_DICT)
#if defined(LZO1Z)
        m_off = (1 + M2_MAX_OFFSET) + (t << 6) + (*ip++ >> 2);
        last_m_off = m_off;
#else
        m_off = (1 + M2_MAX_OFFSET) + (t >> 2) + (*ip++ << 2);
#endif
        NEED_OP(3);
        t = 3; COPY_DICT(t,m_off)
#else /* !COPY_DICT */
#if defined(LZO1Z)
        t = (1 + M2_MAX_OFFSET) + (t << 6) + (*ip++ >> 2);
        m_pos = op - t;
        last_m_off = t;
#else
        m_pos = op - (1 + M2_MAX_OFFSET);
        m_pos -= t >> 2;
        m_pos -= *ip++ << 2;
#endif
        TEST_LB(m_pos); NEED_OP(3);
        *op++ = *m_pos++; *op++ = *m_pos++; *op++ = *m_pos;
#endif /* COPY_DICT */
        goto match_done;


        /* handle matches */
        for (;;) {
match:
            if (t >= 64)                /* a M2 match */
            {
#if defined(COPY_DICT)
#if defined(LZO1X)
                m_off = 1 + ((t >> 2) & 7) + (*ip++ << 3);
                t = (t >> 5) - 1;
#elif defined(LZO1Y)
                m_off = 1 + ((t >> 2) & 3) + (*ip++ << 2);
                t = (t >> 4) - 3;
#elif defined(LZO1Z)
                m_off = t & 0x1f;
                if (m_off >= 0x1c)
                    m_off = last_m_off;
                else
                {
                    m_off = 1 + (m_off << 6) + (*ip++ >> 2);
                    last_m_off = m_off;
                }
                t = (t >> 5) - 1;
#endif
#else /* !COPY_DICT */
#if defined(LZO1X)
                m_pos = op - 1;
                m_pos -= (t >> 2) & 7;
                m_pos -= *ip++ << 3;
                t = (t >> 5) - 1;
#elif defined(LZO1Y)
                m_pos = op - 1;
                m_pos -= (t >> 2) & 3;
                m_pos -= *ip++ << 2;
                t = (t >> 4) - 3;
#elif defined(LZO1Z)
                {
                    lzo_uint off = t & 0x1f;
                    m_pos = op;
                    if (off >= 0x1c)
                    {
                        assert(last_m_off > 0);
                        m_pos -= last_m_off;
                    }
                    else
                    {
                        off = 1 + (off << 6) + (*ip++ >> 2);
                        m_pos -= off;
                        last_m_off = off;
                    }
                }
                t = (t >> 5) - 1;
#endif
                TEST_LB(m_pos); assert(t > 0); NEED_OP(t+3-1);
                goto copy_match;
#endif /* COPY_DICT */
            }
            else if (t >= 32)           /* a M3 match */
            {
                t &= 31;
                if (t == 0)
                {
                    while (*ip == 0)
                    {
                        t += 255;
                        ip++;
                        TEST_OV(t);
                        NEED_IP(1);
                    }
                    t += 31 + *ip++;
                    NEED_IP(2);
                }
#if defined(COPY_DICT)
#if defined(LZO1Z)
                m_off = 1 + (ip[0] << 6) + (ip[1] >> 2);
                last_m_off = m_off;
#else
                m_off = 1 + (ip[0] >> 2) + (ip[1] << 6);
#endif
#else /* !COPY_DICT */
#if defined(LZO1Z)
                {
                    lzo_uint off = 1 + (ip[0] << 6) + (ip[1] >> 2);
                    m_pos = op - off;
                    last_m_off = off;
                }
#elif (LZO_OPT_UNALIGNED16) && (LZO_ABI_LITTLE_ENDIAN)
                m_pos = op - 1;
                m_pos -= UA_GET_LE16(ip) >> 2;
#else
                m_pos = op - 1;
                m_pos -= (ip[0] >> 2) + (ip[1] << 6);
#endif
#endif /* COPY_DICT */
                ip += 2;
            }
            else if (t >= 16)           /* a M4 match */
            {
#if defined(COPY_DICT)
                m_off = (t & 8) << 11;
#else /* !COPY_DICT */
                m_pos = op;
                m_pos -= (t & 8) << 11;
#endif /* COPY_DICT */
                t &= 7;
                if (t == 0)
                {
                    while (*ip == 0)
                    {
                        t += 255;
                        ip++;
                        TEST_OV(t);
                        NEED_IP(1);
                    }
                    t += 7 + *ip++;
                    NEED_IP(2);
                }
#if defined(COPY_DICT)
#if defined(LZO1Z)
                m_off += (ip[0] << 6) + (ip[1] >> 2);
#else
                m_off += (ip[0] >> 2) + (ip[1] << 6);
#endif
                ip += 2;
                if (m_off == 0)
                    goto eof_found;
                m_off += 0x4000;
#if defined(LZO1Z)
                last_m_off = m_off;
#endif
#else /* !COPY_DICT */
#if defined(LZO1Z)
                m_pos -= (ip[0] << 6) + (ip[1] >> 2);
#elif (LZO_OPT_UNALIGNED16) && (LZO_ABI_LITTLE_ENDIAN)
                m_pos -= UA_GET_LE16(ip) >> 2;
#else
                m_pos -= (ip[0] >> 2) + (ip[1] << 6);
#endif
                ip += 2;
                if (m_pos == op)
                    goto eof_found;
                m_pos -= 0x4000;
#if defined(LZO1Z)
                last_m_off = pd((const lzo_bytep)op, m_pos);
#endif
#endif /* COPY_DICT */
            }
            else                            /* a M1 match */
            {
#if defined(COPY_DICT)
#if defined(LZO1Z)
                m_off = 1 + (t << 6) + (*ip++ >> 2);
                last_m_off = m_off;
#else
                m_off = 1 + (t >> 2) + (*ip++ << 2);
#endif
                NEED_OP(2);
                t = 2; COPY_DICT(t,m_off)
#else /* !COPY_DICT */
#if defined(LZO1Z)
                t = 1 + (t << 6) + (*ip++ >> 2);
                m_pos = op - t;
                last_m_off = t;
#else
                m_pos = op - 1;
                m_pos -= t >> 2;
                m_pos -= *ip++ << 2;
#endif
                TEST_LB(m_pos); NEED_OP(2);
                *op++ = *m_pos++; *op++ = *m_pos;
#endif /* COPY_DICT */
                goto match_done;
            }

            /* copy match */
#if defined(COPY_DICT)

            NEED_OP(t+3-1);
            t += 3-1; COPY_DICT(t,m_off)

#else /* !COPY_DICT */

            TEST_LB(m_pos); assert(t > 0); NEED_OP(t+3-1);
#if (LZO_OPT_UNALIGNED64) && (LZO_OPT_UNALIGNED32)
            if (op - m_pos >= 8)
            {
                t += (3 - 1);
                if (t >= 8) do
                {
                    UA_COPY8(op,m_pos);
                    op += 8; m_pos += 8; t -= 8;
                } while (t >= 8);
                if (t >= 4)
                {
                    UA_COPY4(op,m_pos);
                    op += 4; m_pos += 4; t -= 4;
                }
                if (t > 0)
                {
                    *op++ = m_pos[0];
                    if (t > 1) { *op++ = m_pos[1]; if (t > 2) { *op++ = m_pos[2]; } }
                }
            }
            else
#elif (LZO_OPT_UNALIGNED32) || (LZO_ALIGNED_OK_4)
#if !(LZO_OPT_UNALIGNED32)
            if (t >= 2 * 4 - (3 - 1) && PTR_ALIGNED2_4(op,m_pos))
            {
                assert((op - m_pos) >= 4);  /* both pointers are aligned */
#else
            if (t >= 2 * 4 - (3 - 1) && (op - m_pos) >= 4)
            {
#endif
                UA_COPY4(op,m_pos);
                op += 4; m_pos += 4; t -= 4 - (3 - 1);
                do {
                    UA_COPY4(op,m_pos);
                    op += 4; m_pos += 4; t -= 4;
                } while (t >= 4);
                if (t > 0) do *op++ = *m_pos++; while (--t > 0);
            }
            else
#endif
            {
copy_match:
                *op++ = *m_pos++; *op++ = *m_pos++;
                do *op++ = *m_pos++; while (--t > 0);
            }

#endif /* COPY_DICT */

match_done:
#if defined(LZO1Z)
            t = ip[-1] & 3;
#else
            t = ip[-2] & 3;
#endif
            if (t == 0)
                break;

            /* copy literals */
match_next:
            assert(t > 0); assert(t < 4); NEED_OP(t); NEED_IP(t+3);
#if 0
            do *op++ = *ip++; while (--t > 0);
#else
            *op++ = *ip++;
            if (t > 1) { *op++ = *ip++; if (t > 2) { *op++ = *ip++; } }
#endif
            t = *ip++;
        }
    }

eof_found:
    *out_len = pd(op, out);
    return (ip == ip_end ? LZO_E_OK :
           (ip < ip_end  ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN));


#if defined(HAVE_NEED_IP)
input_overrun:
    *out_len = pd(op, out);
    return LZO_E_INPUT_OVERRUN;
#endif

#if defined(HAVE_NEED_OP)
output_overrun:
    *out_len = pd(op, out);
    return LZO_E_OUTPUT_OVERRUN;
#endif

#if defined(LZO_TEST_OVERRUN_LOOKBEHIND)
lookbehind_overrun:
    *out_len = pd(op, out);
    return LZO_E_LOOKBEHIND_OVERRUN;
#endif
}


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

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Created: 2026-08-13 06:42