static intebml_read_element_id (MatroskaDemuxContext *matroska,                      uint32_t             *id,                      int                  *level_up){    int read;    uint64_t total;    /* if we re-call this, use our cached ID */    if (matroska->peek_id != 0) {        if (level_up)            *level_up = 0;        *id = matroska->peek_id;        return 0;    }    /* read out the "EBML number", include tag in ID */    if ((read = ebml_read_num(matroska, 4, &total)) < 0)        return read;    *id = matroska->peek_id  = total | (1 << (read * 7));    /* level tracking */    if (level_up)        *level_up = ebml_read_element_level_up(matroska);    return read;}/* * Read: element content length. * Return: the number of bytes read or < 0 on error. */static intebml_read_element_length (MatroskaDemuxContext *matroska,                          uint64_t             *length){    /* clear cache since we're now beyond that data point */    matroska->peek_id = 0;    /* read out the "EBML number", include tag in ID */    return ebml_read_num(matroska, 8, length);}/* * Return: the ID of the next element, or 0 on error. * Level_up contains the amount of levels that this * next element lies higher than the previous one. */static uint32_tebml_peek_id (MatroskaDemuxContext *matroska,              int                  *level_up){    uint32_t id;    assert(level_up != NULL);    if (ebml_read_element_id(matroska, &id, level_up) < 0)        return 0;    return id;}/* * Seek to a given offset. * 0 is success, -1 is failure. */static intebml_read_seek (MatroskaDemuxContext *matroska,                offset_t              offset){    ByteIOContext *pb = &matroska->ctx->pb;    /* clear ID cache, if any */    matroska->peek_id = 0;    return (url_fseek(pb, offset, SEEK_SET) == offset) ? 0 : -1;}/* * Skip the next element. * 0 is success, -1 is failure. */static intebml_read_skip (MatroskaDemuxContext *matroska){    ByteIOContext *pb = &matroska->ctx->pb;    uint32_t id;    uint64_t length;    int res;    if ((res = ebml_read_element_id(matroska, &id, NULL)) < 0 ||        (res = ebml_read_element_length(matroska, &length)) < 0)        return res;    url_fskip(pb, length);    return 0;}/* * Read the next element as an unsigned int. * 0 is success, < 0 is failure. */static intebml_read_uint (MatroskaDemuxContext *matroska,                uint32_t             *id,                uint64_t             *num){    ByteIOContext *pb = &matroska->ctx->pb;    int n = 0, size, res;    uint64_t rlength;    if ((res = ebml_read_element_id(matroska, id, NULL)) < 0 ||        (res = ebml_read_element_length(matroska, &rlength)) < 0)        return res;    size = rlength;    if (size < 1 || size > 8) {        offset_t pos = url_ftell(pb);        av_log(matroska->ctx, AV_LOG_ERROR,               "Invalid uint element size %d at position %lld (0x%llx)\n",                size, pos, pos);        return AVERROR_INVALIDDATA;    }    /* big-endian ordening; build up number */    *num = 0;    while (n++ < size)        *num = (*num << 8) | get_byte(pb);    return 0;}/* * Read the next element as a signed int. * 0 is success, < 0 is failure. */static intebml_read_sint (MatroskaDemuxContext *matroska,                uint32_t             *id,                int64_t              *num){    ByteIOContext *pb = &matroska->ctx->pb;    int size, n = 1, negative = 0, res;    uint64_t rlength;    if ((res = ebml_read_element_id(matroska, id, NULL)) < 0 ||        (res = ebml_read_element_length(matroska, &rlength)) < 0)        return res;    size = rlength;    if (size < 1 || size > 8) {        offset_t pos = url_ftell(pb);        av_log(matroska->ctx, AV_LOG_ERROR,               "Invalid sint element size %d at position %lld (0x%llx)\n",                size, pos, pos);        return AVERROR_INVALIDDATA;    }    if ((*num = get_byte(pb)) & 0x80) {        negative = 1;        *num &= ~0x80;    }    *num = 0;    while (n++ < size)        *num = (*num << 8) | get_byte(pb);    /* make signed */    if (negative)        *num = *num - (1LL << ((8 * size) - 1));    return 0;}/* * Read the next element as a float. * 0 is success, < 0 is failure. */static intebml_read_float (MatroskaDemuxContext *matroska,		 uint32_t             *id,		 double               *num){    ByteIOContext *pb = &matroska->ctx->pb;    int size, res;    uint64_t rlength;    if ((res = ebml_read_element_id(matroska, id, NULL)) < 0 ||        (res = ebml_read_element_length(matroska, &rlength)) < 0)        return res;    size = rlength;    if (size != 4 && size != 8 && size != 10) {        offset_t pos = url_ftell(pb);        av_log(matroska->ctx, AV_LOG_ERROR,               "Invalid float element size %d at position %llu (0x%llx)\n",               size, pos, pos);        return AVERROR_INVALIDDATA;    }    if (size == 10) {        av_log(matroska->ctx, AV_LOG_ERROR,               "FIXME! 10-byte floats unimplemented\n");        return AVERROR_UNKNOWN;    }    if (size == 4) {        float f;        while (size-- > 0)#ifdef WORDS_BIGENDIAN            ((uint8_t *) &f)[3 - size] = get_byte(pb);#else            ((uint8_t *) &f)[size] = get_byte(pb);#endif        *num = f;    } else {        double d;        while (size-- > 0)#ifdef WORDS_BIGENDIAN            ((uint8_t *) &d)[7 - size] = get_byte(pb);#else            ((uint8_t *) &d)[size] = get_byte(pb);#endif        *num = d;    }    return 0;}/* * Read the next element as an ASCII string. * 0 is success, < 0 is failure. */static intebml_read_ascii (MatroskaDemuxContext *matroska,                 uint32_t             *id,                 char                **str){    ByteIOContext *pb = &matroska->ctx->pb;    int size, res;    uint64_t rlength;    if ((res = ebml_read_element_id(matroska, id, NULL)) < 0 ||        (res = ebml_read_element_length(matroska, &rlength)) < 0)        return res;    size = rlength;    /* ebml strings are usually not 0-terminated, so we allocate one     * byte more, read the string and NULL-terminate it ourselves. */    if (!(*str = av_malloc(size + 1))) {        av_log(matroska->ctx, AV_LOG_ERROR, "Memory allocation failed\n");        return AVERROR_NOMEM;    }    if (get_buffer(pb, (uint8_t *) *str, size) != size) {        offset_t pos = url_ftell(pb);        av_log(matroska->ctx, AV_LOG_ERROR,               "Read error at pos. %llu (0x%llx)\n", pos, pos);        return AVERROR_IO;    }    (*str)[size] = '\0';    return 0;}/* * Read the next element as a UTF-8 string. * 0 is success, < 0 is failure. */static intebml_read_utf8 (MatroskaDemuxContext *matroska,                uint32_t             *id,                char                **str){  return ebml_read_ascii(matroska, id, str);}/* * Read the next element as a date (nanoseconds since 1/1/2000). * 0 is success, < 0 is failure. */static intebml_read_date (MatroskaDemuxContext *matroska,                uint32_t             *id,                int64_t              *date){  return ebml_read_sint(matroska, id, date);}/* * Read the next element, but only the header. The contents * are supposed to be sub-elements which can be read separately. * 0 is success, < 0 is failure. */static intebml_read_master (MatroskaDemuxContext *matroska,                  uint32_t             *id){    ByteIOContext *pb = &matroska->ctx->pb;    uint64_t length;    MatroskaLevel *level;    int res;    if ((res = ebml_read_element_id(matroska, id, NULL)) < 0 ||        (res = ebml_read_element_length(matroska, &length)) < 0)        return res;    /* protect... (Heaven forbids that the '>' is true) */    if (matroska->num_levels >= EBML_MAX_DEPTH) {        av_log(matroska->ctx, AV_LOG_ERROR,               "File moves beyond max. allowed depth (%d)\n", EBML_MAX_DEPTH);        return AVERROR_NOTSUPP;    }    /* remember level */    level = &matroska->levels[matroska->num_levels++];    level->start = url_ftell(pb);    level->length = length;    return 0;}/* * Read the next element as binary data. * 0 is success, < 0 is failure. */static intebml_read_binary (MatroskaDemuxContext *matroska,                  uint32_t             *id,                  uint8_t             **binary,                  int                  *size){    ByteIOContext *pb = &matroska->ctx->pb;    uint64_t rlength;    int res;    if ((res = ebml_read_element_id(matroska, id, NULL)) < 0 ||        (res = ebml_read_element_length(matroska, &rlength)) < 0)        return res;    *size = rlength;    if (!(*binary = av_malloc(*size))) {        av_log(matroska->ctx, AV_LOG_ERROR,               "Memory allocation error\n");        return AVERROR_NOMEM;    }    if (get_buffer(pb, *binary, *size) != *size) {        offset_t pos = url_ftell(pb);        av_log(matroska->ctx, AV_LOG_ERROR,               "Read error at pos. %llu (0x%llx)\n", pos, pos);        return AVERROR_IO;    }    return 0;}/* * Read signed/unsigned "EBML" numbers. * Return: number of bytes processed, < 0 on error. * XXX: use ebml_read_num(). */static intmatroska_ebmlnum_uint (uint8_t  *data,                       uint32_t  size,                       uint64_t *num){    int len_mask = 0x80, read = 1, n = 1, num_ffs = 0;    uint64_t total;    if (size <= 0)        return AVERROR_INVALIDDATA;    total = data[0];    while (read <= 8 && !(total & len_mask)) {        read++;        len_mask >>= 1;    }    if (read > 8)        return AVERROR_INVALIDDATA;    if ((total &= (len_mask - 1)) == len_mask - 1)        num_ffs++;    if (size < read)        return AVERROR_INVALIDDATA;    while (n < read) {        if (data[n] == 0xff)            num_ffs++;        total = (total << 8) | data[n];        n++;    }    if (!total)        return AVERROR_INVALIDDATA;    if (read == num_ffs)        *num = (uint64_t)-1;    else        *num = total;