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Skip Matroska Cues with AudioProperties::Fast and read-only mode

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When the file is opened in read-only mode, it will not be written and
the Cues do not have to be updated. Skipping the Cues will make the
reading of large Matroska files over network filesystems (SMB/NFS)
faster.
This commit is contained in:
HomerJau
2026-05-09 09:15:02 +02:00
committed by Urs Fleisch
parent b02ff63916
commit 8511827fa1
1 changed files with 19 additions and 6 deletions
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25
taglib/matroska/ebml/ebmlmksegment.cpp
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@@ -83,6 +83,12 @@ bool EBML::MkSegment::readLimited(File &file, offset_t scanLimit)
const offset_t filePos = file.tell();
const offset_t maxOffset = filePos + dataSize;
const offset_t maxScanOffset = filePos + std::min(scanLimit, dataSize);
// When scanLimit is less than dataSize, the caller has requested a
// fast/limited scan (e.g. AudioProperties::Fast). In that case and if the
// file has been opened in read-only mode, we skip parsing the Cues element,
// which can be tens of MB on large files, causing severe slowdowns over
// network filesystems, and do not have to be updated in read-only mode.
const bool skipCues = file.readOnly() && scanLimit < dataSize;
MasterElement *pendingPaddingTarget = nullptr;
offset_t accumulatedPadding = 0;
std::unique_ptr<Element> element;
@@ -139,9 +145,11 @@ bool EBML::MkSegment::readLimited(File &file, offset_t scanLimit)
break;
}
case Id::MkCues:
if(!((cues = readElementAt<Id::MkCues, MkCues>(
file, absoluteOffset, maxOffset))))
return false;
if(!skipCues) {
if(!((cues = readElementAt<Id::MkCues, MkCues>(
file, absoluteOffset, maxOffset))))
return false;
}
break;
case Id::MkInfo:
if(!((info = readElementAt<Id::MkInfo, MkInfo>(
@@ -187,9 +195,14 @@ bool EBML::MkSegment::readLimited(File &file, offset_t scanLimit)
else if(id == Id::MkCues) {
pendingPaddingTarget = nullptr;
accumulatedPadding = 0;
cues = element_cast<Id::MkCues>(std::move(element));
if(!cues->read(file))
return false;
if(!skipCues) {
cues = element_cast<Id::MkCues>(std::move(element));
if(!cues->read(file))
return false;
}
else {
element->skipData(file);
}
}
else if(id == Id::MkInfo) {
pendingPaddingTarget = nullptr;