/*

 * LZO 1x decompression

 * Copyright (c) 2006 Reimar Doeffinger

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include <limits.h>

#include <stdint.h>

#include <string.h>

#include "avassert.h"

#include "intreadwrite.h"

#include "lzo.h"

#include "macros.h"

#include "mem.h"

/// Define if we may write up to 12 bytes beyond the output buffer.

#define OUTBUF_PADDED 1

/// Define if we may read up to 8 bytes beyond the input buffer.

#define INBUF_PADDED 1

typedef struct LZOContext {

    const uint8_t *in, *in_end;

    uint8_t *out_start, *out, *out_end;

    int error;

} LZOContext;

/**

 * @brief Reads one byte from the input buffer, avoiding an overrun.

 * @return byte read

 */

static inline int get_byte(LZOContext *c)

{

    if (c->in < c->in_end)

        return *c->in++;

    c->error |= AV_LZO_INPUT_DEPLETED;

    return 1;

}

#ifdef INBUF_PADDED

#define GETB(c) (*(c).in++)

#else

#define GETB(c) get_byte(&(c))

#endif

/**

 * @brief Decodes a length value in the coding used by lzo.

 * @param x previous byte value

 * @param mask bits used from x

 * @return decoded length value

 */

static inline int get_len(LZOContext *c, int x, int mask)

{

    int cnt = x & mask;

    if (!cnt) {

        while (!(x = get_byte(c))) {

            if (cnt >= INT_MAX - 1000) {

                c->error |= AV_LZO_ERROR;

                break;

            }

            cnt += 255;

        }

        cnt += mask + x;

    }

    return cnt;

}

/**

 * @brief Copies bytes from input to output buffer with checking.

 * @param cnt number of bytes to copy, must be >= 0

 */

static inline void copy(LZOContext *c, int cnt)

{

    register const uint8_t *src = c->in;

    register uint8_t *dst       = c->out;

    av_assert0(cnt >= 0);

    if (cnt > c->in_end - src) {

        cnt       = FFMAX(c->in_end - src, 0);

        c->error |= AV_LZO_INPUT_DEPLETED;

    }

    if (cnt > c->out_end - dst) {

        cnt       = FFMAX(c->out_end - dst, 0);

        c->error |= AV_LZO_OUTPUT_FULL;

    }

#if defined(INBUF_PADDED) && defined(OUTBUF_PADDED)

    AV_COPY32U(dst, src);

    src += 4;

    dst += 4;

    cnt -= 4;

    if (cnt > 0)

#endif

    memcpy(dst, src, cnt);

    c->in  = src + cnt;

    c->out = dst + cnt;

}

/**

 * @brief Copies previously decoded bytes to current position.

 * @param back how many bytes back we start, must be > 0

 * @param cnt number of bytes to copy, must be > 0

 *

 * cnt > back is valid, this will copy the bytes we just copied,

 * thus creating a repeating pattern with a period length of back.

 */

static inline void copy_backptr(LZOContext *c, int back, int cnt)

{

    register uint8_t *dst       = c->out;

    av_assert0(cnt > 0);

    if (dst - c->out_start < back) {

        c->error |= AV_LZO_INVALID_BACKPTR;

        return;

    }

    if (cnt > c->out_end - dst) {

        cnt       = FFMAX(c->out_end - dst, 0);

        c->error |= AV_LZO_OUTPUT_FULL;

    }

    av_memcpy_backptr(dst, back, cnt);

    c->out = dst + cnt;

}

int av_lzo1x_decode(void *out, int *outlen, const void *in, int *inlen)

{

    int state = 0;

    int x;

    LZOContext c;

    if (*outlen <= 0 || *inlen <= 0) {

        int res = 0;

        if (*outlen <= 0)

            res |= AV_LZO_OUTPUT_FULL;

        if (*inlen <= 0)

            res |= AV_LZO_INPUT_DEPLETED;

        return res;

    }

    c.in      = in;

    c.in_end  = (const uint8_t *)in + *inlen;

    c.out     = c.out_start = out;

    c.out_end = (uint8_t *)out + *outlen;

    c.error   = 0;

    x         = GETB(c);

    if (x > 17) {

        copy(&c, x - 17);

        x = GETB(c);

        if (x < 16)

            c.error |= AV_LZO_ERROR;

    }

    if (c.in > c.in_end)

        c.error |= AV_LZO_INPUT_DEPLETED;

    while (!c.error) {

        int cnt, back;

        if (x > 15) {

            if (x > 63) {

                cnt  = (x >> 5) - 1;

                back = (GETB(c) << 3) + ((x >> 2) & 7) + 1;

            } else if (x > 31) {

                cnt  = get_len(&c, x, 31);

                x    = GETB(c);

                back = (GETB(c) << 6) + (x >> 2) + 1;

            } else {

                cnt   = get_len(&c, x, 7);

                back  = (1 << 14) + ((x & 8) << 11);

                x     = GETB(c);

                back += (GETB(c) << 6) + (x >> 2);

                if (back == (1 << 14)) {

                    if (cnt != 1)

                        c.error |= AV_LZO_ERROR;

                    break;

                }

            }

        } else if (!state) {

            cnt = get_len(&c, x, 15);

            copy(&c, cnt + 3);

            x = GETB(c);

            if (x > 15)

                continue;

            cnt  = 1;

            back = (1 << 11) + (GETB(c) << 2) + (x >> 2) + 1;

        } else {

            cnt  = 0;

            back = (GETB(c) << 2) + (x >> 2) + 1;

        }

        copy_backptr(&c, back, cnt + 2);

        state =

        cnt   = x & 3;

        copy(&c, cnt);

        x = GETB(c);

    }

    *inlen = c.in_end - c.in;

    if (c.in > c.in_end)

        *inlen = 0;

    *outlen = c.out_end - c.out;

    return c.error;

}