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Handle Mkv files with unknown element sizes correctly 

Those elements are still assumed to fill the max available
space. However, if it turns out one "child" is more likely
a sibling, the wrong assumption is fixed.
This commit is contained in:
Martchus 2017-08-18 00:14:29 +02:00
parent 618efe3f96
commit b69aab0cd1
2 changed files with 43 additions and 3 deletions
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43
matroska/ebmlelement.cpp
View File

@ -77,6 +77,7 @@ void EbmlElement::internalParse()
throw TruncatedDataException();
}
stream().seekg(startOffset());
// read ID
char buf[maximumIdLengthSupported() > maximumSizeLengthSupported() ? maximumIdLengthSupported() : maximumSizeLengthSupported()] = {0};
byte beg = static_cast<byte>(stream().peek()), mask = 0x80;
@ -100,10 +101,50 @@ void EbmlElement::internalParse()
reader().read(buf + (maximumIdLengthSupported() - m_idLength), m_idLength);
m_id = BE::toUInt32(buf);
// check whether this element is actually a sibling of one of its parents rather then a child
// (might be the case if the parent's size is unknown and hence assumed to be the max file size)
if(m_parent && m_parent->m_sizeUnknown) {
// check at which level in the hierarchy the element is supposed to occour using its ID
// (the only chance to find out whether the element belongs higher up in the hierarchy)
const MatroskaElementLevel supposedLevel = matroskaIdLevel(m_id);
const byte actualLevel = level();
if(actualLevel > supposedLevel) {
// the file belongs higher up in the hierarchy so find a better parent
if(EbmlElement *betterParent = m_parent->parent(actualLevel - static_cast<byte>(supposedLevel))) {
// recompute the parent size (assumption - which was rest of the available space - was wrong)
m_parent->m_dataSize = m_startOffset - m_parent->m_startOffset - m_parent->headerSize();
m_parent->m_sizeUnknown = false;
// detatch from ...
if(m_parent->firstChild() == this) {
// ... parent
m_parent->m_firstChild.release();
m_parent->m_firstChild = move(m_nextSibling);
} else {
// ... previous sibling
for(EbmlElement *sibling = m_parent->firstChild(); sibling; sibling = sibling->nextSibling()) {
if(sibling->nextSibling() == this) {
sibling->m_nextSibling.release();
sibling->m_nextSibling = move(m_nextSibling);
break;
}
}
}
// insert as child of better parent
if(EbmlElement *previousSibling = betterParent->lastChild()) {
previousSibling->m_nextSibling.reset(this);
} else {
betterParent->m_firstChild.reset(this);
}
// update own reference to parent
m_parent = betterParent;
}
}
}
// read size
beg = static_cast<byte>(stream().peek()), mask = 0x80;
m_sizeLength = 1;
if(beg == 0xFF) {
if((m_sizeUnknown = (beg == 0xFF))) {
// this indicates that the element size is unknown
// -> just assume the element takes the maximum available size
m_dataSize = maxTotalSize() - headerSize();

3
tests/overallmkv.cpp
View File

@ -152,8 +152,7 @@ void OverallTests::checkMkvTestfile3()
/*!
* \brief Checks "matroska_wave1/test4.mkv".
* \remarks This file is using the EBML feature that allows Master elements to have no known size. Handling
* such files is not supported yet.
* \remarks This file is using the EBML feature that allows Master elements to have no known size.
*/
void OverallTests::checkMkvTestfile4()
{