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ifd_enumerate.go: Handle cycles in next-IFD offsets 

Fixes #59
pull/69/head
Dustin Oprea 2021-05-12 00:20:36 -04:00
parent dca55bf8ca
commit cb1753e83a
1 changed files with 17 additions and 1 deletions
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18
v3/ifd_enumerate.go
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@ -163,6 +163,8 @@ type IfdEnumerate struct {
tagIndex *TagIndex
ifdMapping *exifcommon.IfdMapping
furthestOffset uint32
visitedIfdOffsets map[uint32]struct{}
}
// NewIfdEnumerate returns a new instance of IfdEnumerate.
@ -172,6 +174,8 @@ func NewIfdEnumerate(ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, ebs
byteOrder: byteOrder,
ifdMapping: ifdMapping,
tagIndex: tagIndex,
visitedIfdOffsets: make(map[uint32]struct{}),
}
}
@ -553,7 +557,19 @@ func (ie *IfdEnumerate) parseIfd(ii *exifcommon.IfdIdentity, bp *byteParser, vis
nextIfdOffset, _, err = bp.getUint32()
log.PanicIf(err)
ifdEnumerateLogger.Debugf(nil, "Next IFD at offset: (0x%08x)", nextIfdOffset)
_, alreadyVisited := ie.visitedIfdOffsets[nextIfdOffset]
if alreadyVisited == true {
ifdEnumerateLogger.Warningf(nil, "IFD at offset (0x%08x) has been linked-to more than once. There might be a cycle in the IFD chain. Not reparsing.", nextIfdOffset)
nextIfdOffset = 0
}
if nextIfdOffset != 0 {
ie.visitedIfdOffsets[nextIfdOffset] = struct{}{}
ifdEnumerateLogger.Debugf(nil, "[%s] Next IFD at offset: (0x%08x)", ii.String(), nextIfdOffset)
} else {
ifdEnumerateLogger.Debugf(nil, "[%s] IFD chain has terminated.", ii.String())
}
return nextIfdOffset, entries, thumbnailData, nil
}