C++ bytestream2_init函数代码示例

static int decompress_chunks_thread(AVCodecContext *avctx, void *arg,
                                    int chunk_nb, int thread_nb)
{
    HapContext *ctx = avctx->priv_data;

    HapChunk *chunk = &ctx->chunks[chunk_nb];
    GetByteContext gbc;
    uint8_t *dst = ctx->tex_buf + chunk->uncompressed_offset;

    bytestream2_init(&gbc, ctx->gbc.buffer + chunk->compressed_offset, chunk->compressed_size);

    if (chunk->compressor == HAP_COMP_SNAPPY) {
        int ret;
        int64_t uncompressed_size = ctx->tex_size;

        /* Uncompress the frame */
        ret = ff_snappy_uncompress(&gbc, dst, &uncompressed_size);
        if (ret < 0) {
             av_log(avctx, AV_LOG_ERROR, "Snappy uncompress error\n");
             return ret;
        }
    } else if (chunk->compressor == HAP_COMP_NONE) {
        bytestream2_get_buffer(&gbc, dst, chunk->compressed_size);
    }

    return 0;
}

static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
                            AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    GifState *s = avctx->priv_data;
    AVFrame *picture = data;
    int ret;

    bytestream2_init(&s->gb, buf, buf_size);
    if ((ret = gif_read_header1(s)) < 0)
        return ret;

    avctx->pix_fmt = AV_PIX_FMT_PAL8;

    if ((ret = ff_set_dimensions(avctx, s->screen_width, s->screen_height)) < 0)
        return ret;

    if ((ret = ff_get_buffer(avctx, picture, 0)) < 0) {
        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
        return ret;
    }
    s->image_palette = (uint32_t *)picture->data[1];
    ret = gif_parse_next_image(s, picture);
    if (ret < 0)
        return ret;

    *got_frame = 1;
    return bytestream2_tell(&s->gb);
}

static int mm_decode_frame(AVCodecContext *avctx,
                           void *data, int *data_size,
                           AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    MmContext *s = avctx->priv_data;
    int type, res;

    if (buf_size < MM_PREAMBLE_SIZE)
        return AVERROR_INVALIDDATA;
    type = AV_RL16(&buf[0]);
    buf += MM_PREAMBLE_SIZE;
    buf_size -= MM_PREAMBLE_SIZE;
    bytestream2_init(&s->gb, buf, buf_size);

    if (avctx->reget_buffer(avctx, &s->frame) < 0) {
        av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
        return -1;
    }

    switch(type) {
    case MM_TYPE_PALETTE   :
        res = mm_decode_pal(s);
        return buf_size;
    case MM_TYPE_INTRA     :
        res = mm_decode_intra(s, 0, 0);
        break;
    case MM_TYPE_INTRA_HH  :
        res = mm_decode_intra(s, 1, 0);
        break;
    case MM_TYPE_INTRA_HHV :
        res = mm_decode_intra(s, 1, 1);
        break;
    case MM_TYPE_INTER     :
        res = mm_decode_inter(s, 0, 0);
        break;
    case MM_TYPE_INTER_HH  :
        res = mm_decode_inter(s, 1, 0);
        break;
    case MM_TYPE_INTER_HHV :
        res = mm_decode_inter(s, 1, 1);
        break;
    default:
        res = AVERROR_INVALIDDATA;
        break;
    }
    if (res < 0)
        return res;

    memcpy(s->frame.data[1], s->palette, AVPALETTE_SIZE);

    *data_size = sizeof(AVFrame);
    *(AVFrame*)data = s->frame;

    return buf_size;
}

static int gif_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
{
    GifState *s = avctx->priv_data;
    AVFrame *picture = data;
    int ret;

    bytestream2_init(&s->gb, avpkt->data, avpkt->size);

    s->picture.pts          = avpkt->pts;
    s->picture.pkt_pts      = avpkt->pts;
    s->picture.pkt_dts      = avpkt->dts;
    s->picture.pkt_duration = avpkt->duration;

    if (avpkt->size >= 6) {
        s->keyframe = memcmp(avpkt->data, gif87a_sig, 6) == 0 ||
                      memcmp(avpkt->data, gif89a_sig, 6) == 0;
    } else {
        s->keyframe = 0;
    }

    if (s->keyframe) {
        if ((ret = gif_read_header1(s)) < 0)
            return ret;

        if ((ret = av_image_check_size(s->screen_width, s->screen_height, 0, avctx)) < 0)
            return ret;
        avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);

        if (s->picture.data[0])
            avctx->release_buffer(avctx, &s->picture);

        if ((ret = ff_get_buffer(avctx, &s->picture)) < 0) {
            av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
            return ret;
        }

        s->picture.pict_type = AV_PICTURE_TYPE_I;
        s->picture.key_frame = 1;
    } else {
        if ((ret = avctx->reget_buffer(avctx, &s->picture)) < 0) {
            av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
            return ret;
        }

        s->picture.pict_type = AV_PICTURE_TYPE_P;
        s->picture.key_frame = 0;
    }

    ret = gif_parse_next_image(s, got_frame);
    if (ret < 0)
        return ret;
    else if (*got_frame)
        *picture = s->picture;

    return avpkt->size;
}

/*
 * To be a valid APNG file, we mandate, in this order:
 *     PNGSIG
 *     IHDR
 *     ...
 *     acTL
 *     ...
 *     IDAT
 */
static int apng_probe(AVProbeData *p)
{
    GetByteContext gb;
    int state = 0;
    uint32_t len, tag;

    bytestream2_init(&gb, p->buf, p->buf_size);

    if (bytestream2_get_be64(&gb) != PNGSIG)
        return 0;

    for (;;) {
        len = bytestream2_get_be32(&gb);
        if (len > 0x7fffffff)
            return 0;

        tag = bytestream2_get_le32(&gb);
        /* we don't check IDAT size, as this is the last tag
         * we check, and it may be larger than the probe buffer */
        if (tag != MKTAG('I', 'D', 'A', 'T') &&
            len > bytestream2_get_bytes_left(&gb))
            return 0;

        switch (tag) {
        case MKTAG('I', 'H', 'D', 'R'):
            if (len != 13)
                return 0;
            if (av_image_check_size(bytestream2_get_be32(&gb), bytestream2_get_be32(&gb), 0, NULL))
                return 0;
            bytestream2_skip(&gb, 9);
            state++;
            break;
        case MKTAG('a', 'c', 'T', 'L'):
            if (state != 1 ||
                len != 8 ||
                bytestream2_get_be32(&gb) == 0) /* 0 is not a valid value for number of frames */
                return 0;
            bytestream2_skip(&gb, 8);
            state++;
            break;
        case MKTAG('I', 'D', 'A', 'T'):
            if (state != 2)
                return 0;
            goto end;
        default:
            /* skip other tags */
            bytestream2_skip(&gb, len + 4);
            break;
        }
    }

end:
    return AVPROBE_SCORE_MAX;
}

static int tgq_decode_frame(AVCodecContext *avctx,
                            void *data, int *got_frame,
                            AVPacket *avpkt){
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    TgqContext *s = avctx->priv_data;
    int x,y;
    int big_endian;

    if (buf_size < 16) {
        av_log(avctx, AV_LOG_WARNING, "truncated header\n");
        return -1;
    }
    big_endian = AV_RL32(&buf[4]) > 0x000FFFFF;
    bytestream2_init(&s->gb, buf + 8, buf_size - 8);
    if (big_endian) {
        s->width  = bytestream2_get_be16u(&s->gb);
        s->height = bytestream2_get_be16u(&s->gb);
    } else {
        s->width  = bytestream2_get_le16u(&s->gb);
        s->height = bytestream2_get_le16u(&s->gb);
    }

    if (s->avctx->width!=s->width || s->avctx->height!=s->height) {
        avcodec_set_dimensions(s->avctx, s->width, s->height);
        if (s->frame.data[0])
            avctx->release_buffer(avctx, &s->frame);
    }
    tgq_calculate_qtable(s, bytestream2_get_byteu(&s->gb));
    bytestream2_skip(&s->gb, 3);

    if (!s->frame.data[0]) {
        s->frame.key_frame = 1;
        s->frame.pict_type = AV_PICTURE_TYPE_I;
        s->frame.buffer_hints = FF_BUFFER_HINTS_VALID;
        if (ff_get_buffer(avctx, &s->frame)) {
            av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
            return -1;
        }
    }

    for (y = 0; y < FFALIGN(avctx->height, 16) >> 4; y++)
        for (x = 0; x < FFALIGN(avctx->width, 16) >> 4; x++)
            if (tgq_decode_mb(s, y, x) < 0)
                return AVERROR_INVALIDDATA;

    *got_frame = 1;
    *(AVFrame*)data = s->frame;

    return avpkt->size;
}

/**
 * @param half_horiz Half horizontal resolution (0 or 1)
 * @param half_vert Half vertical resolution (0 or 1)
 */
static int mm_decode_inter(MmContext * s, int half_horiz, int half_vert)
{
    int data_off = bytestream2_get_le16(&s->gb);
    int y = 0;
    GetByteContext data_ptr;

    if (bytestream2_get_bytes_left(&s->gb) < data_off)
        return AVERROR_INVALIDDATA;

    bytestream2_init(&data_ptr, s->gb.buffer + data_off, bytestream2_get_bytes_left(&s->gb) - data_off);
    while (s->gb.buffer < data_ptr.buffer_start) {
        int i, j;
        int length = bytestream2_get_byte(&s->gb);
        int x = bytestream2_get_byte(&s->gb) + ((length & 0x80) << 1);
        length &= 0x7F;

        if (length==0) {
            y += x;
            continue;
        }

        if (y + half_vert >= s->avctx->height)
            return 0;

        for(i=0; i<length; i++) {
            int replace_array = bytestream2_get_byte(&s->gb);
            for(j=0; j<8; j++) {
                int replace = (replace_array >> (7-j)) & 1;
                if (x + half_horiz >= s->avctx->width)
                    return AVERROR_INVALIDDATA;
                if (replace) {
                    int color = bytestream2_get_byte(&data_ptr);
                    s->frame->data[0][y*s->frame->linesize[0] + x] = color;
                    if (half_horiz)
                        s->frame->data[0][y*s->frame->linesize[0] + x + 1] = color;
                    if (half_vert) {
                        s->frame->data[0][(y+1)*s->frame->linesize[0] + x] = color;
                        if (half_horiz)
                            s->frame->data[0][(y+1)*s->frame->linesize[0] + x + 1] = color;
                    }
                }
                x += 1 + half_horiz;
            }
        }

        y += 1 + half_vert;
    }

    return 0;
}

static int tgq_decode_frame(AVCodecContext *avctx,
                            void *data, int *got_frame,
                            AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size       = avpkt->size;
    TgqContext *s      = avctx->priv_data;
    AVFrame *frame     = data;
    int x, y, ret;
    int big_endian;

    if (buf_size < 16) {
        av_log(avctx, AV_LOG_WARNING, "truncated header\n");
        return AVERROR_INVALIDDATA;
    }
    big_endian = AV_RL32(&buf[4]) > 0x000FFFFF;
    bytestream2_init(&s->gb, buf + 8, buf_size - 8);
    if (big_endian) {
        s->width  = bytestream2_get_be16u(&s->gb);
        s->height = bytestream2_get_be16u(&s->gb);
    } else {
        s->width  = bytestream2_get_le16u(&s->gb);
        s->height = bytestream2_get_le16u(&s->gb);
    }

    ret = ff_set_dimensions(s->avctx, s->width, s->height);
    if (ret < 0)
        return ret;

    tgq_calculate_qtable(s, bytestream2_get_byteu(&s->gb));
    bytestream2_skip(&s->gb, 3);

    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
        return ret;
    frame->key_frame = 1;
    frame->pict_type = AV_PICTURE_TYPE_I;

    for (y = 0; y < FFALIGN(avctx->height, 16) >> 4; y++)
        for (x = 0; x < FFALIGN(avctx->width, 16) >> 4; x++)
            if (tgq_decode_mb(s, frame, y, x) < 0)
                return AVERROR_INVALIDDATA;

    *got_frame = 1;

    return avpkt->size;
}

static int aasc_decode_frame(AVCodecContext *avctx,
                              void *data, int *got_frame,
                              AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size       = avpkt->size;
    AascContext *s     = avctx->priv_data;
    int compr, i, stride, ret;

    if (buf_size < 4)
        return AVERROR_INVALIDDATA;

    if ((ret = ff_reget_buffer(avctx, s->frame)) < 0) {
        av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
        return ret;
    }

    compr     = AV_RL32(buf);
    buf      += 4;
    buf_size -= 4;
    switch (compr) {
    case 0:
        stride = (avctx->width * 3 + 3) & ~3;
        if (buf_size < stride * avctx->height)
            return AVERROR_INVALIDDATA;
        for (i = avctx->height - 1; i >= 0; i--) {
            memcpy(s->frame->data[0] + i * s->frame->linesize[0], buf, avctx->width * 3);
            buf += stride;
        }
        break;
    case 1:
        bytestream2_init(&s->gb, buf, buf_size);
        ff_msrle_decode(avctx, (AVPicture*)s->frame, 8, &s->gb);
        break;
    default:
        av_log(avctx, AV_LOG_ERROR, "Unknown compression type %d\n", compr);
        return AVERROR_INVALIDDATA;
    }

    *got_frame = 1;
    if ((ret = av_frame_ref(data, s->frame)) < 0)
        return ret;

    /* report that the buffer was completely consumed */
    return avpkt->size;
}

/* There are (invalid) samples in the wild with mp4-style extradata, where the
 * parameter sets are stored unescaped (i.e. as RBSP).
 * This function catches the parameter set decoding failure and tries again
 * after escaping it */
static int decode_extradata_ps_mp4(const uint8_t *buf, int buf_size, H264ParamSets *ps,
                                   int err_recognition, void *logctx)
{
    int ret;

    ret = decode_extradata_ps(buf, buf_size, ps, 1, logctx);
    if (ret < 0 && !(err_recognition & AV_EF_EXPLODE)) {
        GetByteContext gbc;
        PutByteContext pbc;
        uint8_t *escaped_buf;
        int escaped_buf_size;

        av_log(logctx, AV_LOG_WARNING,
               "SPS decoding failure, trying again after escaping the NAL\n");

        if (buf_size / 2 >= (INT16_MAX - AV_INPUT_BUFFER_PADDING_SIZE) / 3)
            return AVERROR(ERANGE);
        escaped_buf_size = buf_size * 3 / 2 + AV_INPUT_BUFFER_PADDING_SIZE;
        escaped_buf = av_mallocz(escaped_buf_size);
        if (!escaped_buf)
            return AVERROR(ENOMEM);

        bytestream2_init(&gbc, buf, buf_size);
        bytestream2_init_writer(&pbc, escaped_buf, escaped_buf_size);

        while (bytestream2_get_bytes_left(&gbc)) {
            if (bytestream2_get_bytes_left(&gbc) >= 3 &&
                bytestream2_peek_be24(&gbc) <= 3) {
                bytestream2_put_be24(&pbc, 3);
                bytestream2_skip(&gbc, 2);
            } else
                bytestream2_put_byte(&pbc, bytestream2_get_byte(&gbc));
        }

        escaped_buf_size = bytestream2_tell_p(&pbc);
        AV_WB16(escaped_buf, escaped_buf_size - 2);

        ret = decode_extradata_ps(escaped_buf, escaped_buf_size, ps, 1, logctx);
        av_freep(&escaped_buf);
        if (ret < 0)
            return ret;
    }

    return 0;
}

static av_cold int decode_init(AVCodecContext *avctx)
{
    AnmContext *s = avctx->priv_data;
    int i;

    avctx->pix_fmt = PIX_FMT_PAL8;

    s->frame.reference = 1;
    bytestream2_init(&s->gb, avctx->extradata, avctx->extradata_size);
    if (bytestream2_get_bytes_left(&s->gb) < 16 * 8 + 4 * 256)
        return -1;

    bytestream2_skipu(&s->gb, 16 * 8);
    for (i = 0; i < 256; i++)
        s->palette[i] = bytestream2_get_le32u(&s->gb);

    return 0;
}

static int hq_hqa_decode_frame(AVCodecContext *avctx, void *data,
                               int *got_frame, AVPacket *avpkt)
{
    HQContext *ctx = avctx->priv_data;
    AVFrame *pic = data;
    uint32_t info_tag;
    unsigned int data_size;
    int ret;
    unsigned tag;

    bytestream2_init(&ctx->gbc, avpkt->data, avpkt->size);
    if (bytestream2_get_bytes_left(&ctx->gbc) < 4 + 4) {
        av_log(avctx, AV_LOG_ERROR, "Frame is too small (%d).\n", avpkt->size);
        return AVERROR_INVALIDDATA;
    }

    info_tag = bytestream2_peek_le32(&ctx->gbc);
    if (info_tag == MKTAG('I', 'N', 'F', 'O')) {
        int info_size;
        bytestream2_skip(&ctx->gbc, 4);
        info_size = bytestream2_get_le32(&ctx->gbc);
        if (bytestream2_get_bytes_left(&ctx->gbc) < info_size) {
            av_log(avctx, AV_LOG_ERROR, "Invalid INFO size (%d).\n", info_size);
            return AVERROR_INVALIDDATA;
        }
        ff_canopus_parse_info_tag(avctx, ctx->gbc.buffer, info_size);

        bytestream2_skip(&ctx->gbc, info_size);
    }

    data_size = bytestream2_get_bytes_left(&ctx->gbc);
    if (data_size < 4) {
        av_log(avctx, AV_LOG_ERROR, "Frame is too small (%d).\n", data_size);
        return AVERROR_INVALIDDATA;
    }

    /* HQ defines dimensions and number of slices, and thus slice traversal
     * order. HQA has no size constraint and a fixed number of slices, so it
     * needs a separate scheme for it. */
    tag = bytestream2_get_le32(&ctx->gbc);
    if ((tag & 0x00FFFFFF) == (MKTAG('U', 'V', 'C', ' ') & 0x00FFFFFF)) {
        ret = hq_decode_frame(ctx, pic, tag >> 24, data_size);
    } else if (tag == MKTAG('H', 'Q', 'A', '1')) {

static int mm_decode_frame(AVCodecContext *avctx,
                            void *data, int *got_frame,
                            AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    MmContext *s = avctx->priv_data;
    int type, res;

    if (buf_size < MM_PREAMBLE_SIZE)
        return AVERROR_INVALIDDATA;
    type = AV_RL16(&buf[0]);
    buf += MM_PREAMBLE_SIZE;
    buf_size -= MM_PREAMBLE_SIZE;
    bytestream2_init(&s->gb, buf, buf_size);

    if ((res = ff_reget_buffer(avctx, s->frame)) < 0)
        return res;

    switch(type) {
    case MM_TYPE_PALETTE   : mm_decode_pal(s); return avpkt->size;
    case MM_TYPE_INTRA     : res = mm_decode_intra(s, 0, 0); break;
    case MM_TYPE_INTRA_HH  : res = mm_decode_intra(s, 1, 0); break;
    case MM_TYPE_INTRA_HHV : res = mm_decode_intra(s, 1, 1); break;
    case MM_TYPE_INTER     : res = mm_decode_inter(s, 0, 0); break;
    case MM_TYPE_INTER_HH  : res = mm_decode_inter(s, 1, 0); break;
    case MM_TYPE_INTER_HHV : res = mm_decode_inter(s, 1, 1); break;
    default:
        res = AVERROR_INVALIDDATA;
        break;
    }
    if (res < 0)
        return res;

    memcpy(s->frame->data[1], s->palette, AVPALETTE_SIZE);

    if ((res = av_frame_ref(data, s->frame)) < 0)
        return res;

    *got_frame      = 1;

    return avpkt->size;
}

static int aasc_decode_frame(AVCodecContext *avctx,
                              void *data, int *data_size,
                              AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    AascContext *s = avctx->priv_data;
    int compr, i, stride;

    s->frame.reference = 1;
    s->frame.buffer_hints = FF_BUFFER_HINTS_VALID | FF_BUFFER_HINTS_PRESERVE | FF_BUFFER_HINTS_REUSABLE;
    if (avctx->reget_buffer(avctx, &s->frame)) {
        av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
        return -1;
    }

    compr = AV_RL32(buf);
    buf += 4;
    buf_size -= 4;
    switch(compr){
    case 0:
        stride = (avctx->width * 3 + 3) & ~3;
        for(i = avctx->height - 1; i >= 0; i--){
            memcpy(s->frame.data[0] + i*s->frame.linesize[0], buf, avctx->width*3);
            buf += stride;
        }
        break;
    case 1:
        bytestream2_init(&s->gb, buf - 4, buf_size + 4);
        ff_msrle_decode(avctx, (AVPicture*)&s->frame, 8, &s->gb);
        break;
    default:
        av_log(avctx, AV_LOG_ERROR, "Unknown compression type %d\n", compr);
        return -1;
    }

    *data_size = sizeof(AVFrame);
    *(AVFrame*)data = s->frame;

    /* report that the buffer was completely consumed */
    return buf_size;
}

static int tm2_read_stream(TM2Context *ctx, const uint8_t *buf, int stream_id, int buf_size)
{
    int i, ret;
    int skip = 0;
    int len, toks, pos;
    TM2Codes codes;
    GetByteContext gb;

    if (buf_size < 4) {
        av_log(ctx->avctx, AV_LOG_ERROR, "not enough space for len left\n");
        return AVERROR_INVALIDDATA;
    }

    /* get stream length in dwords */
    bytestream2_init(&gb, buf, buf_size);
    len  = bytestream2_get_be32(&gb);
    skip = len * 4 + 4;

    if (len == 0)
        return 4;

    if (len >= INT_MAX / 4 - 1 || len < 0 || skip > buf_size) {
        av_log(ctx->avctx, AV_LOG_ERROR, "Error, invalid stream size.\n");
        return AVERROR_INVALIDDATA;
    }

    toks = bytestream2_get_be32(&gb);
    if (toks & 1) {
        len = bytestream2_get_be32(&gb);
        if (len == TM2_ESCAPE) {
            len = bytestream2_get_be32(&gb);
        }
        if (len > 0) {
            pos = bytestream2_tell(&gb);
            if (skip <= pos)
                return AVERROR_INVALIDDATA;
            init_get_bits(&ctx->gb, buf + pos, (skip - pos) * 8);
            if ((ret = tm2_read_deltas(ctx, stream_id)) < 0)
                return ret;
            bytestream2_skip(&gb, ((get_bits_count(&ctx->gb) + 31) >> 5) << 2);
        }