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Use readOrThrow in MatroskaVideo::decodeBlock for EOF detection #9282

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Use readOrThrow in MatroskaVideo::decodeBlock for EOF detection #9282

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8 changes: 4 additions & 4 deletions src/matroskavideo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -642,7 +642,7 @@ void MatroskaVideo::decodeBlock() {

uint32_t block_size = findBlockSize(buf[0]); // 0-8
if (block_size > 0)
io_->read(buf + 1, block_size - 1);
io_->readOrThrow(buf + 1, block_size - 1, ErrorCode::kerCorruptedMetadata);

auto tag_id = returnTagValue(buf, block_size);
const MatroskaTag* tag = Exiv2::find(matroskaTags, tag_id);
Expand All @@ -659,11 +659,11 @@ void MatroskaVideo::decodeBlock() {
return;
}

io_->read(buf, 1);
io_->readOrThrow(buf, 1, ErrorCode::kerCorruptedMetadata);
Comment on lines 660 to +662
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Copilot AI Mar 29, 2026

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decodeBlock() still uses io_->read(buf, 1) for the first byte and only checks eof(). If the read fails due to an I/O error (e.g., ferror) without setting EOF, buf[0] can remain uninitialized and the subsequent tag parsing will use garbage. Consider checking the returned byte count and io_->error(), or switching to readOrThrow() with a special-case for clean EOF (0 bytes + eof()) to stop traversal.

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block_size = findBlockSize(buf[0]); // 0-8

if (block_size > 0)
io_->read(buf + 1, block_size - 1);
io_->readOrThrow(buf + 1, block_size - 1, ErrorCode::kerCorruptedMetadata);
size_t size = returnTagValue(buf, block_size);

if (tag->isComposite() && !tag->isSkipped())
Expand All @@ -683,7 +683,7 @@ void MatroskaVideo::decodeBlock() {
}

DataBuf buf2(bufMaxSize + 1);
io_->read(buf2.data(), size);
io_->readOrThrow(buf2.data(), size, ErrorCode::kerCorruptedMetadata);
Comment on lines 684 to +686
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Copilot AI Mar 29, 2026

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These new readOrThrow() paths change truncated-file behavior from “silently continue with stale/partial data” to “throw kerCorruptedMetadata”. Since there are existing gtest unit tests for MatroskaVideo, it would be good to add a regression test that feeds a minimal valid MKV header followed by a truncated element and asserts readMetadata() throws (and does not populate metadata).

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switch (tag->_type) {
case InternalField:
decodeInternalTags(tag, buf2.data());
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