FFmpeg/libavcodec/lzf.c

/*
 * lzf decompression algorithm
 * Copyright (c) 2015 Luca Barbato
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * lzf decompression
 *
 * LZF is a fast compression/decompression algorithm that takes very little
 * code space and working memory, ideal for real-time and block compression.
 *
 * https://en.wikibooks.org/wiki/Data_Compression/Dictionary_compression#LZF
 */

#include "libavutil/mem.h"

#include "bytestream.h"
#include "lzf.h"

#define LZF_LITERAL_MAX (1 << 5)
#define LZF_LONG_BACKREF 7 + 2

int ff_lzf_uncompress(GetByteContext *gb, uint8_t **buf, int64_t *size)
{
    int ret     = 0;
    uint8_t *p  = *buf;
    int64_t len = 0;

    while (bytestream2_get_bytes_left(gb) > 2) {
        uint8_t s = bytestream2_get_byte(gb);

        if (s < LZF_LITERAL_MAX) {
            s++;
            if (s > *size - len) {
                *size += *size /2;
                ret = av_reallocp(buf, *size);
                if (ret < 0)
                    return ret;
                p = *buf + len;
            }

            bytestream2_get_buffer(gb, p, s);
            p   += s;
            len += s;
        } else {
            int l   = 2 + (s >> 5);
            int off = ((s & 0x1f) << 8) + 1;

            if (l == LZF_LONG_BACKREF)
                l += bytestream2_get_byte(gb);

            off += bytestream2_get_byte(gb);

            if (off > len)
                return AVERROR_INVALIDDATA;

            if (l > *size - len) {
                *size += *size / 2;
                ret = av_reallocp(buf, *size);
                if (ret < 0)
                    return ret;
                p = *buf + len;
            }

            av_memcpy_backptr(p, off, l);

            p   += l;
            len += l;
        }
    }

    *size = len;

    return 0;
}