FFmpeg/libavcodec/bytestream.h

/*
 * Bytestream functions
 * copyright (c) 2006 Baptiste Coudurier <baptiste.coudurier@free.fr>
 *
 * 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
 */

#ifndef AVCODEC_BYTESTREAM_H
#define AVCODEC_BYTESTREAM_H

#include <string.h>
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"

typedef struct {
    const uint8_t *buffer, *buffer_end, *buffer_start;
} GetByteContext;

#define DEF_T(type, name, bytes, read, write)                             \
static av_always_inline type bytestream_get_ ## name(const uint8_t **b){\
    (*b) += bytes;\
    return read(*b - bytes);\
}\
static av_always_inline void bytestream_put_ ##name(uint8_t **b, const type value){\
    write(*b, value);\
    (*b) += bytes;\
}\
static av_always_inline type bytestream2_get_ ## name ## u(GetByteContext *g)\
{\
    return bytestream_get_ ## name(&g->buffer);\
}\
static av_always_inline type bytestream2_get_ ## name(GetByteContext *g)\
{\
    if (g->buffer_end - g->buffer < bytes)\
        return 0;\
    return bytestream2_get_ ## name ## u(g);\
}\
static av_always_inline type bytestream2_peek_ ## name(GetByteContext *g)\
{\
    if (g->buffer_end - g->buffer < bytes)\
        return 0;\
    return read(g->buffer);\
}

#define DEF(name, bytes, read, write) \
    DEF_T(unsigned int, name, bytes, read, write)
#define DEF64(name, bytes, read, write) \
    DEF_T(uint64_t, name, bytes, read, write)

DEF64(le64, 8, AV_RL64, AV_WL64)
DEF  (le32, 4, AV_RL32, AV_WL32)
DEF  (le24, 3, AV_RL24, AV_WL24)
DEF  (le16, 2, AV_RL16, AV_WL16)
DEF64(be64, 8, AV_RB64, AV_WB64)
DEF  (be32, 4, AV_RB32, AV_WB32)
DEF  (be24, 3, AV_RB24, AV_WB24)
DEF  (be16, 2, AV_RB16, AV_WB16)
DEF  (byte, 1, AV_RB8 , AV_WB8 )

#undef DEF
#undef DEF64
#undef DEF_T

static av_always_inline void bytestream2_init(GetByteContext *g,
                                              const uint8_t *buf, int buf_size)
{
    g->buffer =  buf;
    g->buffer_start = buf;
    g->buffer_end = buf + buf_size;
}

static av_always_inline unsigned int bytestream2_get_bytes_left(GetByteContext *g)
{
    return g->buffer_end - g->buffer;
}

static av_always_inline void bytestream2_skip(GetByteContext *g,
                                              unsigned int size)
{
    g->buffer += FFMIN(g->buffer_end - g->buffer, size);
}

static av_always_inline int bytestream2_tell(GetByteContext *g)
{
    return (int)(g->buffer - g->buffer_start);
}

static av_always_inline int bytestream2_seek(GetByteContext *g, int offset,
                                             int whence)
{
    switch (whence) {
    case SEEK_CUR:
        offset = av_clip(offset, -(g->buffer - g->buffer_start),
                         g->buffer_end - g->buffer);
        g->buffer += offset;
        break;
    case SEEK_END:
        offset = av_clip(offset, -(g->buffer_end - g->buffer_start), 0);
        g->buffer = g->buffer_end + offset;
        break;
    case SEEK_SET:
        offset = av_clip(offset, 0, g->buffer_end - g->buffer_start);
        g->buffer = g->buffer_start + offset;
        break;
    default:
        return AVERROR(EINVAL);
    }
    return bytestream2_tell(g);
}

static av_always_inline unsigned int bytestream2_get_buffer(GetByteContext *g,
                                                            uint8_t *dst,
                                                            unsigned int size)
{
    int size2 = FFMIN(g->buffer_end - g->buffer, size);
    memcpy(dst, g->buffer, size2);
    g->buffer += size2;
    return size2;
}

static av_always_inline unsigned int bytestream_get_buffer(const uint8_t **b, uint8_t *dst, unsigned int size)
{
    memcpy(dst, *b, size);
    (*b) += size;
    return size;
}

static av_always_inline void bytestream_put_buffer(uint8_t **b, const uint8_t *src, unsigned int size)
{
    memcpy(*b, src, size);
    (*b) += size;
}

#endif /* AVCODEC_BYTESTREAM_H */