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ifd_enumerate.go: scan() now parses one IFD and the parent is responsible for looping 

A simplification in lieu of moving Ifd construction to scan() and then
using Scan() from Collect().
dustin/scan_builds_ifd_structs
Dustin Oprea 2020-05-19 05:02:53 -04:00
parent 1b9bb61b5f
commit 24c57a0cee
1 changed files with 39 additions and 30 deletions
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69
v2/ifd_enumerate.go
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@ -386,8 +386,17 @@ func (ie *IfdEnumerate) parseIfd(fqIfdPath string, ifdIndex int, bp *byteParser,
if doDescend == true {
ifdEnumerateLogger.Debugf(nil, "Descending from IFD [%s] to IFD [%s].", fqIfdPath, ite.ChildIfdPath())
err := ie.scan(ite.ChildFqIfdPath(), ite.getValueOffset(), visitor)
log.PanicIf(err)
ifdOffset := ite.getValueOffset()
for ifdNumber := 0; ; ifdNumber++ {
nextIfdOffset, err := ie.scan(ite.ChildFqIfdPath(), ifdNumber, ifdOffset, visitor)
log.PanicIf(err)
if nextIfdOffset == 0 {
break
}
ifdOffset = nextIfdOffset
}
ifdEnumerateLogger.Debugf(nil, "Ascending from IFD [%s] to IFD [%s].", ite.ChildIfdPath(), fqIfdPath)
}
@ -452,7 +461,7 @@ func (ie *IfdEnumerate) parseThumbnail(offsetIte, lengthIte *IfdTagEntry) (thumb
// scan parses and enumerates the different IFD blocks and invokes a visitor
// callback for each tag. No information is kept or returned.
func (ie *IfdEnumerate) scan(ifdName string, ifdOffset uint32, visitor TagVisitorFn) (err error) {
func (ie *IfdEnumerate) scan(ifdName string, ifdIndex int, ifdOffset uint32, visitor TagVisitorFn) (nextIfdOffset uint32, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
@ -461,37 +470,29 @@ func (ie *IfdEnumerate) scan(ifdName string, ifdOffset uint32, visitor TagVisito
// TODO(dustin): Add test
for ifdIndex := 0; ; ifdIndex++ {
fqIfdPath := FqIfdPath("", ifdName, ifdIndex)
fqIfdPath := FqIfdPath("", ifdName, ifdIndex)
ifdEnumerateLogger.Debugf(nil, "Parsing IFD [%s] at offset (0x%04x) (scan).", fqIfdPath, ifdOffset)
ifdEnumerateLogger.Debugf(nil, "Parsing IFD [%s] at offset (0x%04x) (scan).", fqIfdPath, ifdOffset)
bp, err := ie.getByteParser(ifdOffset)
if err != nil {
if err == ErrOffsetInvalid {
ifdEnumerateLogger.Errorf(nil, nil, "IFD [%s] at offset (0x%04x) is unreachable. Terminating scan.", fqIfdPath, ifdOffset)
break
}
log.Panic(err)
bp, err := ie.getByteParser(ifdOffset)
if err != nil {
if err == ErrOffsetInvalid {
ifdEnumerateLogger.Errorf(nil, nil, "IFD [%s] at offset (0x%04x) is unreachable. Terminating scan.", fqIfdPath, ifdOffset)
return 0, nil
}
nextIfdOffset, _, _, err := ie.parseIfd(fqIfdPath, ifdIndex, bp, visitor, true)
log.PanicIf(err)
currentOffset := bp.CurrentOffset()
if currentOffset > ie.furthestOffset {
ie.furthestOffset = currentOffset
}
if nextIfdOffset == 0 {
break
}
ifdOffset = nextIfdOffset
log.Panic(err)
}
return nil
nextIfdOffset, _, _, err = ie.parseIfd(fqIfdPath, ifdIndex, bp, visitor, true)
log.PanicIf(err)
currentOffset := bp.CurrentOffset()
if currentOffset > ie.furthestOffset {
ie.furthestOffset = currentOffset
}
return nextIfdOffset, nil
}
// Scan enumerates the different EXIF blocks (called IFDs). `rootIfdName` will
@ -505,8 +506,16 @@ func (ie *IfdEnumerate) Scan(rootIfdName string, ifdOffset uint32, visitor TagVi
// TODO(dustin): Add test
err = ie.scan(rootIfdName, ifdOffset, visitor)
log.PanicIf(err)
for ifdNumber := 0; ; ifdNumber++ {
nextIfdOffset, err := ie.scan(rootIfdName, ifdNumber, ifdOffset, visitor)
log.PanicIf(err)
if nextIfdOffset == 0 {
break
}
ifdOffset = nextIfdOffset
}
ifdEnumerateLogger.Debugf(nil, "Scan: It looks like the furthest offset that contained EXIF data in the EXIF blob was (%d) (Scan).", ie.FurthestOffset())