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avformat/matroskadec: Improve error/EOF checks III
Up until now, when an element was skipped, it was relied upon ffio_limit to make sure that there is enough data available to skip. ffio_limit itself relies upon the availability of the file's size. As this needn't be available, the check has been refined: First one byte less than intended is skipped, then another byte is read, followed by a check of the error flags. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
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@ -1258,13 +1258,23 @@ static int ebml_parse_elem(MatroskaDemuxContext *matroska,
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case EBML_STOP:
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return 1;
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default:
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if (length) {
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if (ffio_limit(pb, length) != length) {
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// ffio_limit emits its own error message,
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// so we don't have to.
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return AVERROR(EIO);
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}
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res = avio_skip(pb, length);
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res = res < 0 ? res : 0;
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if ((res = avio_skip(pb, length - 1)) >= 0) {
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// avio_skip might take us past EOF. We check for this
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// by skipping only length - 1 bytes, reading a byte and
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// checking the error flags. This is done in order to check
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// that the element has been properly skipped even when
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// no filesize (that ffio_limit relies on) is available.
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avio_r8(pb);
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res = NEEDS_CHECKING;
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}
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} else
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res = 0;
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}
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if (res) {
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if (res == NEEDS_CHECKING) {
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