gotosocial/vendor/github.com/dsoprea/go-exif/v3/ifd_enumerate.go

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package exif
import (
"bytes"
"errors"
"fmt"
"io"
"strconv"
"strings"
"time"
"encoding/binary"
"github.com/dsoprea/go-logging"
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"github.com/dsoprea/go-exif/v3/common"
"github.com/dsoprea/go-exif/v3/undefined"
)
var (
ifdEnumerateLogger = log.NewLogger("exif.ifd_enumerate")
)
var (
// ErrNoThumbnail means that no thumbnail was found.
ErrNoThumbnail = errors.New("no thumbnail")
// ErrNoGpsTags means that no GPS info was found.
ErrNoGpsTags = errors.New("no gps tags")
// ErrTagTypeNotValid means that the tag-type is not valid.
ErrTagTypeNotValid = errors.New("tag type invalid")
// ErrOffsetInvalid means that the file offset is not valid.
ErrOffsetInvalid = errors.New("file offset invalid")
)
var (
// ValidGpsVersions is the list of recognized EXIF GPS versions/signatures.
ValidGpsVersions = [][4]byte{
// 2.0.0.0 appears to have a very similar format to 2.2.0.0, so enabling
// it under that assumption.
//
// IFD-PATH=[IFD] ID=(0x8825) NAME=[GPSTag] COUNT=(1) TYPE=[LONG] VALUE=[114]
// IFD-PATH=[IFD/GPSInfo] ID=(0x0000) NAME=[GPSVersionID] COUNT=(4) TYPE=[BYTE] VALUE=[02 00 00 00]
// IFD-PATH=[IFD/GPSInfo] ID=(0x0001) NAME=[GPSLatitudeRef] COUNT=(2) TYPE=[ASCII] VALUE=[S]
// IFD-PATH=[IFD/GPSInfo] ID=(0x0002) NAME=[GPSLatitude] COUNT=(3) TYPE=[RATIONAL] VALUE=[38/1...]
// IFD-PATH=[IFD/GPSInfo] ID=(0x0003) NAME=[GPSLongitudeRef] COUNT=(2) TYPE=[ASCII] VALUE=[E]
// IFD-PATH=[IFD/GPSInfo] ID=(0x0004) NAME=[GPSLongitude] COUNT=(3) TYPE=[RATIONAL] VALUE=[144/1...]
// IFD-PATH=[IFD/GPSInfo] ID=(0x0012) NAME=[GPSMapDatum] COUNT=(7) TYPE=[ASCII] VALUE=[WGS-84]
//
{2, 0, 0, 0},
{2, 2, 0, 0},
// Suddenly appeared at the default in 2.31: https://home.jeita.or.jp/tsc/std-pdf/CP-3451D.pdf
//
// Note that the presence of 2.3.0.0 doesn't seem to guarantee
// coordinates. In some cases, we seen just the following:
//
// GPS Tag Version |2.3.0.0
// GPS Receiver Status |V
// Geodetic Survey Data|WGS-84
// GPS Differential Cor|0
//
{2, 3, 0, 0},
}
)
// byteParser knows how to decode an IFD and all of the tags it
// describes.
//
// The IFDs and the actual values can float throughout the EXIF block, but the
// IFD itself is just a minor header followed by a set of repeating,
// statically-sized records. So, the tags (though notnecessarily their values)
// are fairly simple to enumerate.
type byteParser struct {
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byteOrder binary.ByteOrder
rs io.ReadSeeker
ifdOffset uint32
currentOffset uint32
}
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// newByteParser returns a new byteParser struct.
//
// initialOffset is for arithmetic-based tracking of where we should be at in
// the stream.
func newByteParser(rs io.ReadSeeker, byteOrder binary.ByteOrder, initialOffset uint32) (bp *byteParser, err error) {
// TODO(dustin): Add test
bp = &byteParser{
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rs: rs,
byteOrder: byteOrder,
currentOffset: initialOffset,
}
return bp, nil
}
// getUint16 reads a uint16 and advances both our current and our current
// accumulator (which allows us to know how far to seek to the beginning of the
// next IFD when it's time to jump).
func (bp *byteParser) getUint16() (value uint16, raw []byte, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
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needBytes := 2
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raw = make([]byte, needBytes)
_, err = io.ReadFull(bp.rs, raw)
log.PanicIf(err)
value = bp.byteOrder.Uint16(raw)
bp.currentOffset += uint32(needBytes)
return value, raw, nil
}
// getUint32 reads a uint32 and advances both our current and our current
// accumulator (which allows us to know how far to seek to the beginning of the
// next IFD when it's time to jump).
func (bp *byteParser) getUint32() (value uint32, raw []byte, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
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needBytes := 4
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raw = make([]byte, needBytes)
_, err = io.ReadFull(bp.rs, raw)
log.PanicIf(err)
value = bp.byteOrder.Uint32(raw)
bp.currentOffset += uint32(needBytes)
return value, raw, nil
}
// CurrentOffset returns the starting offset but the number of bytes that we
// have parsed. This is arithmetic-based tracking, not a seek(0) operation.
func (bp *byteParser) CurrentOffset() uint32 {
return bp.currentOffset
}
// IfdEnumerate is the main enumeration type. It knows how to parse the IFD
// containers in the EXIF blob.
type IfdEnumerate struct {
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ebs ExifBlobSeeker
byteOrder binary.ByteOrder
tagIndex *TagIndex
ifdMapping *exifcommon.IfdMapping
furthestOffset uint32
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visitedIfdOffsets map[uint32]struct{}
}
// NewIfdEnumerate returns a new instance of IfdEnumerate.
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func NewIfdEnumerate(ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, ebs ExifBlobSeeker, byteOrder binary.ByteOrder) *IfdEnumerate {
return &IfdEnumerate{
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ebs: ebs,
byteOrder: byteOrder,
ifdMapping: ifdMapping,
tagIndex: tagIndex,
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visitedIfdOffsets: make(map[uint32]struct{}),
}
}
func (ie *IfdEnumerate) getByteParser(ifdOffset uint32) (bp *byteParser, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
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initialOffset := ExifAddressableAreaStart + ifdOffset
rs, err := ie.ebs.GetReadSeeker(int64(initialOffset))
log.PanicIf(err)
bp, err =
newByteParser(
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rs,
ie.byteOrder,
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initialOffset)
if err != nil {
if err == ErrOffsetInvalid {
return nil, err
}
log.Panic(err)
}
return bp, nil
}
func (ie *IfdEnumerate) parseTag(ii *exifcommon.IfdIdentity, tagPosition int, bp *byteParser) (ite *IfdTagEntry, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
tagId, _, err := bp.getUint16()
log.PanicIf(err)
tagTypeRaw, _, err := bp.getUint16()
log.PanicIf(err)
tagType := exifcommon.TagTypePrimitive(tagTypeRaw)
unitCount, _, err := bp.getUint32()
log.PanicIf(err)
valueOffset, rawValueOffset, err := bp.getUint32()
log.PanicIf(err)
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// Check whether the embedded type indicator is valid.
if tagType.IsValid() == false {
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// Technically, we have the type on-file in the tags-index, but
// if the type stored alongside the data disagrees with it,
// which it apparently does, all bets are off.
ifdEnumerateLogger.Warningf(nil,
"Tag (0x%04x) in IFD [%s] at position (%d) has invalid type (0x%04x) and will be skipped.",
tagId, ii, tagPosition, int(tagType))
ite = &IfdTagEntry{
tagId: tagId,
tagType: tagType,
}
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return ite, ErrTagTypeNotValid
}
// Check whether the embedded type is listed among the supported types for
// the registered tag. If not, skip processing the tag.
it, err := ie.tagIndex.Get(ii, tagId)
if err != nil {
if log.Is(err, ErrTagNotFound) == true {
ifdEnumerateLogger.Warningf(nil, "Tag (0x%04x) is not known and will be skipped.", tagId)
ite = &IfdTagEntry{
tagId: tagId,
}
return ite, ErrTagNotFound
}
log.Panic(err)
}
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// If we're trying to be as forgiving as possible then use whatever type was
// reported in the format. Otherwise, only accept a type that's expected for
// this tag.
if ie.tagIndex.UniversalSearch() == false && it.DoesSupportType(tagType) == false {
// The type in the stream disagrees with the type that this tag is
// expected to have. This can present issues with how we handle the
// special-case tags (e.g. thumbnails, GPS, etc..) when those tags
// suddenly have data that we no longer manipulate correctly/
// accurately.
ifdEnumerateLogger.Warningf(nil,
"Tag (0x%04x) in IFD [%s] at position (%d) has unsupported type (0x%02x) and will be skipped.",
tagId, ii, tagPosition, int(tagType))
return nil, ErrTagTypeNotValid
}
// Construct tag struct.
rs, err := ie.ebs.GetReadSeeker(0)
log.PanicIf(err)
ite = newIfdTagEntry(
ii,
tagId,
tagPosition,
tagType,
unitCount,
valueOffset,
rawValueOffset,
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rs,
ie.byteOrder)
ifdPath := ii.UnindexedString()
// If it's an IFD but not a standard one, it'll just be seen as a LONG
// (the standard IFD tag type), later, unless we skip it because it's
// [likely] not even in the standard list of known tags.
mi, err := ie.ifdMapping.GetChild(ifdPath, tagId)
if err == nil {
currentIfdTag := ii.IfdTag()
childIt := exifcommon.NewIfdTag(&currentIfdTag, tagId, mi.Name)
iiChild := ii.NewChild(childIt, 0)
ite.SetChildIfd(iiChild)
// We also need to set `tag.ChildFqIfdPath` but can't do it here
// because we don't have the IFD index.
} else if log.Is(err, exifcommon.ErrChildIfdNotMapped) == false {
log.Panic(err)
}
return ite, nil
}
// TagVisitorFn is called for each tag when enumerating through the EXIF.
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type TagVisitorFn func(ite *IfdTagEntry) (err error)
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// tagPostParse do some tag-level processing here following the parse of each.
func (ie *IfdEnumerate) tagPostParse(ite *IfdTagEntry, med *MiscellaneousExifData) (err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
ii := ite.IfdIdentity()
tagId := ite.TagId()
tagType := ite.TagType()
it, err := ie.tagIndex.Get(ii, tagId)
if err == nil {
ite.setTagName(it.Name)
} else {
if err != ErrTagNotFound {
log.Panic(err)
}
// This is an unknown tag.
originalBt := exifcommon.BasicTag{
FqIfdPath: ii.String(),
IfdPath: ii.UnindexedString(),
TagId: tagId,
}
if med != nil {
med.unknownTags[originalBt] = exifcommon.BasicTag{}
}
utilityLogger.Debugf(nil,
"Tag (0x%04x) is not valid for IFD [%s]. Attempting secondary "+
"lookup.", tagId, ii.String())
// This will overwrite the existing `it` and `err`. Since `FindFirst()`
// might generate different Errors than `Get()`, the log message above
// is import to try and mitigate confusion in that case.
it, err = ie.tagIndex.FindFirst(tagId, tagType, nil)
if err != nil {
if err != ErrTagNotFound {
log.Panic(err)
}
// This is supposed to be a convenience function and if we were
// to keep the name empty or set it to some placeholder, it
// might be mismanaged by the package that is calling us. If
// they want to specifically manage these types of tags, they
// can use more advanced functionality to specifically -handle
// unknown tags.
utilityLogger.Warningf(nil,
"Tag with ID (0x%04x) in IFD [%s] is not recognized and "+
"will be ignored.", tagId, ii.String())
return ErrTagNotFound
}
ite.setTagName(it.Name)
utilityLogger.Warningf(nil,
"Tag with ID (0x%04x) is not valid for IFD [%s], but it *is* "+
"valid as tag [%s] under IFD [%s] and has the same type "+
"[%s], so we will use that. This EXIF blob was probably "+
"written by a buggy implementation.",
tagId, ii.UnindexedString(), it.Name, it.IfdPath,
tagType)
if med != nil {
med.unknownTags[originalBt] = exifcommon.BasicTag{
IfdPath: it.IfdPath,
TagId: tagId,
}
}
}
// This is a known tag (from the standard, unless the user did
// something different).
// Skip any tags that have a type that doesn't match the type in the
// index (which is loaded with the standard and accept tag
// information unless configured otherwise).
//
// We've run into multiple instances of the same tag, where a) no
// tag should ever be repeated, and b) all but one had an incorrect
// type and caused parsing/conversion woes. So, this is a quick fix
// for those scenarios.
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if ie.tagIndex.UniversalSearch() == false && it.DoesSupportType(tagType) == false {
ifdEnumerateLogger.Warningf(nil,
"Skipping tag [%s] (0x%04x) [%s] with an unexpected type: %v ∉ %v",
ii.UnindexedString(), tagId, it.Name,
tagType, it.SupportedTypes)
return ErrTagNotFound
}
return nil
}
// parseIfd decodes the IFD block that we're currently sitting on the first
// byte of.
func (ie *IfdEnumerate) parseIfd(ii *exifcommon.IfdIdentity, bp *byteParser, visitor TagVisitorFn, doDescend bool, med *MiscellaneousExifData) (nextIfdOffset uint32, entries []*IfdTagEntry, thumbnailData []byte, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
tagCount, _, err := bp.getUint16()
log.PanicIf(err)
ifdEnumerateLogger.Debugf(nil, "IFD [%s] tag-count: (%d)", ii.String(), tagCount)
entries = make([]*IfdTagEntry, 0)
var enumeratorThumbnailOffset *IfdTagEntry
var enumeratorThumbnailSize *IfdTagEntry
for i := 0; i < int(tagCount); i++ {
ite, err := ie.parseTag(ii, i, bp)
if err != nil {
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if log.Is(err, ErrTagNotFound) == true || log.Is(err, ErrTagTypeNotValid) == true {
// These tags should've been fully logged in parseTag(). The
// ITE returned is nil so we can't print anything about them, now.
continue
}
log.Panic(err)
}
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err = ie.tagPostParse(ite, med)
if err == nil {
if err == ErrTagNotFound {
continue
}
log.PanicIf(err)
}
tagId := ite.TagId()
if visitor != nil {
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err := visitor(ite)
log.PanicIf(err)
}
if ite.IsThumbnailOffset() == true {
ifdEnumerateLogger.Debugf(nil, "Skipping the thumbnail offset tag (0x%04x). Use accessors to get it or set it.", tagId)
enumeratorThumbnailOffset = ite
entries = append(entries, ite)
continue
} else if ite.IsThumbnailSize() == true {
ifdEnumerateLogger.Debugf(nil, "Skipping the thumbnail size tag (0x%04x). Use accessors to get it or set it.", tagId)
enumeratorThumbnailSize = ite
entries = append(entries, ite)
continue
}
if ite.TagType() != exifcommon.TypeUndefined {
// If this tag's value is an offset, bump our max-offset value to
// what that offset is plus however large that value is.
vc := ite.getValueContext()
farOffset, err := vc.GetFarOffset()
if err == nil {
candidateOffset := farOffset + uint32(vc.SizeInBytes())
if candidateOffset > ie.furthestOffset {
ie.furthestOffset = candidateOffset
}
} else if err != exifcommon.ErrNotFarValue {
log.PanicIf(err)
}
}
// If it's an IFD but not a standard one, it'll just be seen as a LONG
// (the standard IFD tag type), later, unless we skip it because it's
// [likely] not even in the standard list of known tags.
if ite.ChildIfdPath() != "" {
if doDescend == true {
ifdEnumerateLogger.Debugf(nil, "Descending from IFD [%s] to IFD [%s].", ii, ite.ChildIfdPath())
currentIfdTag := ii.IfdTag()
childIfdTag :=
exifcommon.NewIfdTag(
&currentIfdTag,
ite.TagId(),
ite.ChildIfdName())
iiChild := ii.NewChild(childIfdTag, 0)
err := ie.scan(iiChild, ite.getValueOffset(), visitor, med)
log.PanicIf(err)
ifdEnumerateLogger.Debugf(nil, "Ascending from IFD [%s] to IFD [%s].", ite.ChildIfdPath(), ii)
}
}
entries = append(entries, ite)
}
if enumeratorThumbnailOffset != nil && enumeratorThumbnailSize != nil {
thumbnailData, err = ie.parseThumbnail(enumeratorThumbnailOffset, enumeratorThumbnailSize)
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if err != nil {
ifdEnumerateLogger.Errorf(
nil, err,
"We tried to bump our furthest-offset counter but there was an issue first seeking past the thumbnail.")
} else {
// In this case, the value is always an offset.
offset := enumeratorThumbnailOffset.getValueOffset()
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// This this case, the value is always a length.
length := enumeratorThumbnailSize.getValueOffset()
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ifdEnumerateLogger.Debugf(nil, "Found thumbnail in IFD [%s]. Its offset is (%d) and is (%d) bytes.", ii, offset, length)
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furthestOffset := offset + length
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if furthestOffset > ie.furthestOffset {
ie.furthestOffset = furthestOffset
}
}
}
nextIfdOffset, _, err = bp.getUint32()
log.PanicIf(err)
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_, 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
}
func (ie *IfdEnumerate) parseThumbnail(offsetIte, lengthIte *IfdTagEntry) (thumbnailData []byte, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
vRaw, err := lengthIte.Value()
log.PanicIf(err)
vList := vRaw.([]uint32)
if len(vList) != 1 {
log.Panicf("not exactly one long: (%d)", len(vList))
}
length := vList[0]
// The tag is official a LONG type, but it's actually an offset to a blob of bytes.
offsetIte.updateTagType(exifcommon.TypeByte)
offsetIte.updateUnitCount(length)
thumbnailData, err = offsetIte.GetRawBytes()
log.PanicIf(err)
return thumbnailData, nil
}
// 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(iiGeneral *exifcommon.IfdIdentity, ifdOffset uint32, visitor TagVisitorFn, med *MiscellaneousExifData) (err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
for ifdIndex := 0; ; ifdIndex++ {
iiSibling := iiGeneral.NewSibling(ifdIndex)
ifdEnumerateLogger.Debugf(nil, "Parsing IFD [%s] at offset (0x%04x) (scan).", iiSibling.String(), 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.", iiSibling.String(), ifdOffset)
break
}
log.Panic(err)
}
nextIfdOffset, _, _, err := ie.parseIfd(iiSibling, bp, visitor, true, med)
log.PanicIf(err)
currentOffset := bp.CurrentOffset()
if currentOffset > ie.furthestOffset {
ie.furthestOffset = currentOffset
}
if nextIfdOffset == 0 {
break
}
ifdOffset = nextIfdOffset
}
return nil
}
// MiscellaneousExifData is reports additional data collected during the parse.
type MiscellaneousExifData struct {
// UnknownTags contains all tags that were invalid for their containing
// IFDs. The values represent alternative IFDs that were correctly matched
// to those tags and used instead.
unknownTags map[exifcommon.BasicTag]exifcommon.BasicTag
}
// UnknownTags returns the unknown tags encountered during the scan.
func (med *MiscellaneousExifData) UnknownTags() map[exifcommon.BasicTag]exifcommon.BasicTag {
return med.unknownTags
}
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// ScanOptions tweaks parser behavior/choices.
type ScanOptions struct {
// NOTE(dustin): Reserved for future usage.
}
// Scan enumerates the different EXIF blocks (called IFDs). `rootIfdName` will
// be "IFD" in the TIFF standard.
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func (ie *IfdEnumerate) Scan(iiRoot *exifcommon.IfdIdentity, ifdOffset uint32, visitor TagVisitorFn, so *ScanOptions) (med *MiscellaneousExifData, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
med = &MiscellaneousExifData{
unknownTags: make(map[exifcommon.BasicTag]exifcommon.BasicTag),
}
err = ie.scan(iiRoot, ifdOffset, visitor, med)
log.PanicIf(err)
ifdEnumerateLogger.Debugf(nil, "Scan: It looks like the furthest offset that contained EXIF data in the EXIF blob was (%d) (Scan).", ie.FurthestOffset())
return med, nil
}
// Ifd represents a single, parsed IFD.
type Ifd struct {
ifdIdentity *exifcommon.IfdIdentity
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ifdMapping *exifcommon.IfdMapping
tagIndex *TagIndex
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offset uint32
byteOrder binary.ByteOrder
id int
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parentIfd *Ifd
// ParentTagIndex is our tag position in the parent IFD, if we had a parent
// (if `ParentIfd` is not nil and we weren't an IFD referenced as a sibling
// instead of as a child).
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parentTagIndex int
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entries []*IfdTagEntry
entriesByTagId map[uint16][]*IfdTagEntry
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children []*Ifd
childIfdIndex map[string]*Ifd
thumbnailData []byte
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nextIfdOffset uint32
nextIfd *Ifd
}
// IfdIdentity returns IFD identity that this struct represents.
func (ifd *Ifd) IfdIdentity() *exifcommon.IfdIdentity {
return ifd.ifdIdentity
}
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// Entries returns a flat list of all tags for this IFD.
func (ifd *Ifd) Entries() []*IfdTagEntry {
// TODO(dustin): Add test
return ifd.entries
}
// EntriesByTagId returns a map of all tags for this IFD.
func (ifd *Ifd) EntriesByTagId() map[uint16][]*IfdTagEntry {
// TODO(dustin): Add test
return ifd.entriesByTagId
}
// Children returns a flat list of all child IFDs of this IFD.
func (ifd *Ifd) Children() []*Ifd {
// TODO(dustin): Add test
return ifd.children
}
// ChildWithIfdPath returns a map of all child IFDs of this IFD.
func (ifd *Ifd) ChildIfdIndex() map[string]*Ifd {
// TODO(dustin): Add test
return ifd.childIfdIndex
}
// ParentTagIndex returns the position of this IFD's tag in its parent IFD (*if*
// there is a parent).
func (ifd *Ifd) ParentTagIndex() int {
// TODO(dustin): Add test
return ifd.parentTagIndex
}
// Offset returns the offset of the IFD in the stream.
func (ifd *Ifd) Offset() uint32 {
// TODO(dustin): Add test
return ifd.offset
}
// Offset returns the offset of the IFD in the stream.
func (ifd *Ifd) ByteOrder() binary.ByteOrder {
// TODO(dustin): Add test
return ifd.byteOrder
}
// NextIfd returns the Ifd struct for the next IFD in the chain.
func (ifd *Ifd) NextIfd() *Ifd {
// TODO(dustin): Add test
return ifd.nextIfd
}
// ChildWithIfdPath returns an `Ifd` struct for the given child of the current
// IFD.
func (ifd *Ifd) ChildWithIfdPath(iiChild *exifcommon.IfdIdentity) (childIfd *Ifd, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): This is a bridge while we're introducing the IFD type-system. We should be able to use the (IfdIdentity).Equals() method for this.
ifdPath := iiChild.UnindexedString()
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for _, childIfd := range ifd.children {
if childIfd.ifdIdentity.UnindexedString() == ifdPath {
return childIfd, nil
}
}
log.Panic(ErrTagNotFound)
return nil, nil
}
// FindTagWithId returns a list of tags (usually just zero or one) that match
// the given tag ID. This is efficient.
func (ifd *Ifd) FindTagWithId(tagId uint16) (results []*IfdTagEntry, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
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results, found := ifd.entriesByTagId[tagId]
if found != true {
log.Panic(ErrTagNotFound)
}
return results, nil
}
// FindTagWithName returns a list of tags (usually just zero or one) that match
// the given tag name. This is not efficient (though the labor is trivial).
func (ifd *Ifd) FindTagWithName(tagName string) (results []*IfdTagEntry, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
it, err := ifd.tagIndex.GetWithName(ifd.ifdIdentity, tagName)
if log.Is(err, ErrTagNotFound) == true {
log.Panic(ErrTagNotKnown)
} else if err != nil {
log.Panic(err)
}
results = make([]*IfdTagEntry, 0)
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for _, ite := range ifd.entries {
if ite.TagId() == it.Id {
results = append(results, ite)
}
}
if len(results) == 0 {
log.Panic(ErrTagNotFound)
}
return results, nil
}
// String returns a description string.
func (ifd *Ifd) String() string {
parentOffset := uint32(0)
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if ifd.parentIfd != nil {
parentOffset = ifd.parentIfd.offset
}
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return fmt.Sprintf("Ifd<ID=(%d) IFD-PATH=[%s] INDEX=(%d) COUNT=(%d) OFF=(0x%04x) CHILDREN=(%d) PARENT=(0x%04x) NEXT-IFD=(0x%04x)>", ifd.id, ifd.ifdIdentity.UnindexedString(), ifd.ifdIdentity.Index(), len(ifd.entries), ifd.offset, len(ifd.children), parentOffset, ifd.nextIfdOffset)
}
// Thumbnail returns the raw thumbnail bytes. This is typically directly
// readable by any standard image viewer.
func (ifd *Ifd) Thumbnail() (data []byte, err error) {
if ifd.thumbnailData == nil {
return nil, ErrNoThumbnail
}
return ifd.thumbnailData, nil
}
// dumpTags recursively builds a list of tags from an IFD.
func (ifd *Ifd) dumpTags(tags []*IfdTagEntry) []*IfdTagEntry {
if tags == nil {
tags = make([]*IfdTagEntry, 0)
}
// Now, print the tags while also descending to child-IFDS as we encounter them.
ifdsFoundCount := 0
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for _, ite := range ifd.entries {
tags = append(tags, ite)
childIfdPath := ite.ChildIfdPath()
if childIfdPath != "" {
ifdsFoundCount++
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childIfd, found := ifd.childIfdIndex[childIfdPath]
if found != true {
log.Panicf("alien child IFD referenced by a tag: [%s]", childIfdPath)
}
tags = childIfd.dumpTags(tags)
}
}
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if len(ifd.children) != ifdsFoundCount {
log.Panicf("have one or more dangling child IFDs: (%d) != (%d)", len(ifd.children), ifdsFoundCount)
}
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if ifd.nextIfd != nil {
tags = ifd.nextIfd.dumpTags(tags)
}
return tags
}
// DumpTags prints the IFD hierarchy.
func (ifd *Ifd) DumpTags() []*IfdTagEntry {
return ifd.dumpTags(nil)
}
func (ifd *Ifd) printTagTree(populateValues bool, index, level int, nextLink bool) {
indent := strings.Repeat(" ", level*2)
prefix := " "
if nextLink {
prefix = ">"
}
fmt.Printf("%s%sIFD: %s\n", indent, prefix, ifd)
// Now, print the tags while also descending to child-IFDS as we encounter them.
ifdsFoundCount := 0
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for _, ite := range ifd.entries {
if ite.ChildIfdPath() != "" {
fmt.Printf("%s - TAG: %s\n", indent, ite)
} else {
// This will just add noise to the output (byte-tags are fully
// dumped).
if ite.IsThumbnailOffset() == true || ite.IsThumbnailSize() == true {
continue
}
it, err := ifd.tagIndex.Get(ifd.ifdIdentity, ite.TagId())
tagName := ""
if err == nil {
tagName = it.Name
}
var valuePhrase string
if populateValues == true {
var err error
valuePhrase, err = ite.Format()
if err != nil {
if log.Is(err, exifcommon.ErrUnhandledUndefinedTypedTag) == true {
ifdEnumerateLogger.Warningf(nil, "Skipping non-standard undefined tag: [%s] (%04x)", ifd.ifdIdentity.UnindexedString(), ite.TagId())
continue
} else if err == exifundefined.ErrUnparseableValue {
ifdEnumerateLogger.Warningf(nil, "Skipping unparseable undefined tag: [%s] (%04x) [%s]", ifd.ifdIdentity.UnindexedString(), ite.TagId(), it.Name)
continue
}
log.Panic(err)
}
} else {
valuePhrase = "!UNRESOLVED"
}
fmt.Printf("%s - TAG: %s NAME=[%s] VALUE=[%v]\n", indent, ite, tagName, valuePhrase)
}
childIfdPath := ite.ChildIfdPath()
if childIfdPath != "" {
ifdsFoundCount++
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childIfd, found := ifd.childIfdIndex[childIfdPath]
if found != true {
log.Panicf("alien child IFD referenced by a tag: [%s]", childIfdPath)
}
childIfd.printTagTree(populateValues, 0, level+1, false)
}
}
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if len(ifd.children) != ifdsFoundCount {
log.Panicf("have one or more dangling child IFDs: (%d) != (%d)", len(ifd.children), ifdsFoundCount)
}
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if ifd.nextIfd != nil {
ifd.nextIfd.printTagTree(populateValues, index+1, level, true)
}
}
// PrintTagTree prints the IFD hierarchy.
func (ifd *Ifd) PrintTagTree(populateValues bool) {
ifd.printTagTree(populateValues, 0, 0, false)
}
func (ifd *Ifd) printIfdTree(level int, nextLink bool) {
indent := strings.Repeat(" ", level*2)
prefix := " "
if nextLink {
prefix = ">"
}
fmt.Printf("%s%s%s\n", indent, prefix, ifd)
// Now, print the tags while also descending to child-IFDS as we encounter them.
ifdsFoundCount := 0
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for _, ite := range ifd.entries {
childIfdPath := ite.ChildIfdPath()
if childIfdPath != "" {
ifdsFoundCount++
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childIfd, found := ifd.childIfdIndex[childIfdPath]
if found != true {
log.Panicf("alien child IFD referenced by a tag: [%s]", childIfdPath)
}
childIfd.printIfdTree(level+1, false)
}
}
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if len(ifd.children) != ifdsFoundCount {
log.Panicf("have one or more dangling child IFDs: (%d) != (%d)", len(ifd.children), ifdsFoundCount)
}
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if ifd.nextIfd != nil {
ifd.nextIfd.printIfdTree(level, true)
}
}
// PrintIfdTree prints the IFD hierarchy.
func (ifd *Ifd) PrintIfdTree() {
ifd.printIfdTree(0, false)
}
func (ifd *Ifd) dumpTree(tagsDump []string, level int) []string {
if tagsDump == nil {
tagsDump = make([]string, 0)
}
indent := strings.Repeat(" ", level*2)
var ifdPhrase string
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if ifd.parentIfd != nil {
ifdPhrase = fmt.Sprintf("[%s]->[%s]:(%d)", ifd.parentIfd.ifdIdentity.UnindexedString(), ifd.ifdIdentity.UnindexedString(), ifd.ifdIdentity.Index())
} else {
ifdPhrase = fmt.Sprintf("[ROOT]->[%s]:(%d)", ifd.ifdIdentity.UnindexedString(), ifd.ifdIdentity.Index())
}
startBlurb := fmt.Sprintf("%s> IFD %s TOP", indent, ifdPhrase)
tagsDump = append(tagsDump, startBlurb)
ifdsFoundCount := 0
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for _, ite := range ifd.entries {
tagsDump = append(tagsDump, fmt.Sprintf("%s - (0x%04x)", indent, ite.TagId()))
childIfdPath := ite.ChildIfdPath()
if childIfdPath != "" {
ifdsFoundCount++
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childIfd, found := ifd.childIfdIndex[childIfdPath]
if found != true {
log.Panicf("alien child IFD referenced by a tag: [%s]", childIfdPath)
}
tagsDump = childIfd.dumpTree(tagsDump, level+1)
}
}
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if len(ifd.children) != ifdsFoundCount {
log.Panicf("have one or more dangling child IFDs: (%d) != (%d)", len(ifd.children), ifdsFoundCount)
}
finishBlurb := fmt.Sprintf("%s< IFD %s BOTTOM", indent, ifdPhrase)
tagsDump = append(tagsDump, finishBlurb)
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if ifd.nextIfd != nil {
siblingBlurb := fmt.Sprintf("%s* LINKING TO SIBLING IFD [%s]:(%d)", indent, ifd.nextIfd.ifdIdentity.UnindexedString(), ifd.nextIfd.ifdIdentity.Index())
tagsDump = append(tagsDump, siblingBlurb)
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tagsDump = ifd.nextIfd.dumpTree(tagsDump, level)
}
return tagsDump
}
// DumpTree returns a list of strings describing the IFD hierarchy.
func (ifd *Ifd) DumpTree() []string {
return ifd.dumpTree(nil, 0)
}
// GpsInfo parses and consolidates the GPS info. This can only be called on the
// GPS IFD.
func (ifd *Ifd) GpsInfo() (gi *GpsInfo, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
gi = new(GpsInfo)
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if ifd.ifdIdentity.Equals(exifcommon.IfdGpsInfoStandardIfdIdentity) == false {
log.Panicf("GPS can only be read on GPS IFD: [%s]", ifd.ifdIdentity.UnindexedString())
}
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if tags, found := ifd.entriesByTagId[TagGpsVersionId]; found == false {
// We've seen this. We'll just have to default to assuming we're in a
// 2.2.0.0 format.
ifdEnumerateLogger.Warningf(nil, "No GPS version tag (0x%04x) found.", TagGpsVersionId)
} else {
versionBytes, err := tags[0].GetRawBytes()
log.PanicIf(err)
hit := false
for _, acceptedGpsVersion := range ValidGpsVersions {
if bytes.Compare(versionBytes, acceptedGpsVersion[:]) == 0 {
hit = true
break
}
}
if hit != true {
ifdEnumerateLogger.Warningf(nil, "GPS version not supported: %v", versionBytes)
log.Panic(ErrNoGpsTags)
}
}
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tags, found := ifd.entriesByTagId[TagLatitudeId]
if found == false {
ifdEnumerateLogger.Warningf(nil, "latitude not found")
log.Panic(ErrNoGpsTags)
}
latitudeValue, err := tags[0].Value()
log.PanicIf(err)
// Look for whether North or South.
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tags, found = ifd.entriesByTagId[TagLatitudeRefId]
if found == false {
ifdEnumerateLogger.Warningf(nil, "latitude-ref not found")
log.Panic(ErrNoGpsTags)
}
latitudeRefValue, err := tags[0].Value()
log.PanicIf(err)
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tags, found = ifd.entriesByTagId[TagLongitudeId]
if found == false {
ifdEnumerateLogger.Warningf(nil, "longitude not found")
log.Panic(ErrNoGpsTags)
}
longitudeValue, err := tags[0].Value()
log.PanicIf(err)
// Look for whether West or East.
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tags, found = ifd.entriesByTagId[TagLongitudeRefId]
if found == false {
ifdEnumerateLogger.Warningf(nil, "longitude-ref not found")
log.Panic(ErrNoGpsTags)
}
longitudeRefValue, err := tags[0].Value()
log.PanicIf(err)
// Parse location.
latitudeRaw := latitudeValue.([]exifcommon.Rational)
gi.Latitude, err = NewGpsDegreesFromRationals(latitudeRefValue.(string), latitudeRaw)
log.PanicIf(err)
longitudeRaw := longitudeValue.([]exifcommon.Rational)
gi.Longitude, err = NewGpsDegreesFromRationals(longitudeRefValue.(string), longitudeRaw)
log.PanicIf(err)
// Parse altitude.
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altitudeTags, foundAltitude := ifd.entriesByTagId[TagAltitudeId]
altitudeRefTags, foundAltitudeRef := ifd.entriesByTagId[TagAltitudeRefId]
if foundAltitude == true && foundAltitudeRef == true {
altitudePhrase, err := altitudeTags[0].Format()
log.PanicIf(err)
ifdEnumerateLogger.Debugf(nil, "Altitude is [%s].", altitudePhrase)
altitudeValue, err := altitudeTags[0].Value()
log.PanicIf(err)
altitudeRefPhrase, err := altitudeRefTags[0].Format()
log.PanicIf(err)
ifdEnumerateLogger.Debugf(nil, "Altitude-reference is [%s].", altitudeRefPhrase)
altitudeRefValue, err := altitudeRefTags[0].Value()
log.PanicIf(err)
altitudeRaw := altitudeValue.([]exifcommon.Rational)
if altitudeRaw[0].Denominator > 0 {
altitude := int(altitudeRaw[0].Numerator / altitudeRaw[0].Denominator)
if altitudeRefValue.([]byte)[0] == 1 {
altitude *= -1
}
gi.Altitude = altitude
}
}
// Parse timestamp from separate date and time tags.
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timestampTags, foundTimestamp := ifd.entriesByTagId[TagTimestampId]
datestampTags, foundDatestamp := ifd.entriesByTagId[TagDatestampId]
if foundTimestamp == true && foundDatestamp == true {
datestampValue, err := datestampTags[0].Value()
log.PanicIf(err)
datePhrase := datestampValue.(string)
ifdEnumerateLogger.Debugf(nil, "Date tag value is [%s].", datePhrase)
// Normalize the separators.
datePhrase = strings.ReplaceAll(datePhrase, "-", ":")
dateParts := strings.Split(datePhrase, ":")
year, err1 := strconv.ParseUint(dateParts[0], 10, 16)
month, err2 := strconv.ParseUint(dateParts[1], 10, 8)
day, err3 := strconv.ParseUint(dateParts[2], 10, 8)
if err1 == nil && err2 == nil && err3 == nil {
timestampValue, err := timestampTags[0].Value()
log.PanicIf(err)
timePhrase, err := timestampTags[0].Format()
log.PanicIf(err)
ifdEnumerateLogger.Debugf(nil, "Time tag value is [%s].", timePhrase)
timestampRaw := timestampValue.([]exifcommon.Rational)
hour := int(timestampRaw[0].Numerator / timestampRaw[0].Denominator)
minute := int(timestampRaw[1].Numerator / timestampRaw[1].Denominator)
second := int(timestampRaw[2].Numerator / timestampRaw[2].Denominator)
gi.Timestamp = time.Date(int(year), time.Month(month), int(day), hour, minute, second, 0, time.UTC)
}
}
return gi, nil
}
// ParsedTagVisitor is a callback used if wanting to visit through all tags and
// child IFDs from the current IFD and going down.
type ParsedTagVisitor func(*Ifd, *IfdTagEntry) error
// EnumerateTagsRecursively calls the given visitor function for every tag and
// IFD in the current IFD, recursively.
func (ifd *Ifd) EnumerateTagsRecursively(visitor ParsedTagVisitor) (err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
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for ptr := ifd; ptr != nil; ptr = ptr.nextIfd {
for _, ite := range ifd.entries {
childIfdPath := ite.ChildIfdPath()
if childIfdPath != "" {
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childIfd := ifd.childIfdIndex[childIfdPath]
err := childIfd.EnumerateTagsRecursively(visitor)
log.PanicIf(err)
} else {
err := visitor(ifd, ite)
log.PanicIf(err)
}
}
}
return nil
}
// QueuedIfd is one IFD that has been identified but yet to be processed.
type QueuedIfd struct {
IfdIdentity *exifcommon.IfdIdentity
Offset uint32
Parent *Ifd
// ParentTagIndex is our tag position in the parent IFD, if we had a parent
// (if `ParentIfd` is not nil and we weren't an IFD referenced as a sibling
// instead of as a child).
ParentTagIndex int
}
// IfdIndex collects a bunch of IFD and tag information stored in several
// different ways in order to provide convenient lookups.
type IfdIndex struct {
RootIfd *Ifd
Ifds []*Ifd
Tree map[int]*Ifd
Lookup map[string]*Ifd
}
// Collect enumerates the different EXIF blocks (called IFDs) and builds out an
// index struct for referencing all of the parsed data.
func (ie *IfdEnumerate) Collect(rootIfdOffset uint32) (index IfdIndex, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add MiscellaneousExifData to IfdIndex
tree := make(map[int]*Ifd)
ifds := make([]*Ifd, 0)
lookup := make(map[string]*Ifd)
queue := []QueuedIfd{
{
IfdIdentity: exifcommon.IfdStandardIfdIdentity,
Offset: rootIfdOffset,
},
}
edges := make(map[uint32]*Ifd)
for {
if len(queue) == 0 {
break
}
qi := queue[0]
ii := qi.IfdIdentity
offset := qi.Offset
parentIfd := qi.Parent
queue = queue[1:]
ifdEnumerateLogger.Debugf(nil, "Parsing IFD [%s] (%d) at offset (0x%04x) (Collect).", ii.String(), ii.Index(), offset)
bp, err := ie.getByteParser(offset)
if err != nil {
if err == ErrOffsetInvalid {
return index, err
}
log.Panic(err)
}
// TODO(dustin): We don't need to pass the index in as a separate argument. Get from the II.
nextIfdOffset, entries, thumbnailData, err := ie.parseIfd(ii, bp, nil, false, nil)
log.PanicIf(err)
currentOffset := bp.CurrentOffset()
if currentOffset > ie.furthestOffset {
ie.furthestOffset = currentOffset
}
id := len(ifds)
entriesByTagId := make(map[uint16][]*IfdTagEntry)
for _, ite := range entries {
tagId := ite.TagId()
tags, found := entriesByTagId[tagId]
if found == false {
tags = make([]*IfdTagEntry, 0)
}
entriesByTagId[tagId] = append(tags, ite)
}
ifd := &Ifd{
ifdIdentity: ii,
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byteOrder: ie.byteOrder,
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id: id,
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parentIfd: parentIfd,
parentTagIndex: qi.ParentTagIndex,
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offset: offset,
entries: entries,
entriesByTagId: entriesByTagId,
// This is populated as each child is processed.
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children: make([]*Ifd, 0),
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nextIfdOffset: nextIfdOffset,
thumbnailData: thumbnailData,
ifdMapping: ie.ifdMapping,
tagIndex: ie.tagIndex,
}
// Add ourselves to a big list of IFDs.
ifds = append(ifds, ifd)
// Install ourselves into a by-id lookup table (keys are unique).
tree[id] = ifd
// Install into by-name buckets.
lookup[ii.String()] = ifd
// Add a link from the previous IFD in the chain to us.
if previousIfd, found := edges[offset]; found == true {
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previousIfd.nextIfd = ifd
}
// Attach as a child to our parent (where we appeared as a tag in
// that IFD).
if parentIfd != nil {
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parentIfd.children = append(parentIfd.children, ifd)
}
// Determine if any of our entries is a child IFD and queue it.
for i, ite := range entries {
if ite.ChildIfdPath() == "" {
continue
}
tagId := ite.TagId()
childIfdName := ite.ChildIfdName()
currentIfdTag := ii.IfdTag()
childIfdTag :=
exifcommon.NewIfdTag(
&currentIfdTag,
tagId,
childIfdName)
iiChild := ii.NewChild(childIfdTag, 0)
qi := QueuedIfd{
IfdIdentity: iiChild,
Offset: ite.getValueOffset(),
Parent: ifd,
ParentTagIndex: i,
}
queue = append(queue, qi)
}
// If there's another IFD in the chain.
if nextIfdOffset != 0 {
iiSibling := ii.NewSibling(ii.Index() + 1)
// Allow the next link to know what the previous link was.
edges[nextIfdOffset] = ifd
qi := QueuedIfd{
IfdIdentity: iiSibling,
Offset: nextIfdOffset,
}
queue = append(queue, qi)
}
}
index.RootIfd = tree[0]
index.Ifds = ifds
index.Tree = tree
index.Lookup = lookup
err = ie.setChildrenIndex(index.RootIfd)
log.PanicIf(err)
ifdEnumerateLogger.Debugf(nil, "Collect: It looks like the furthest offset that contained EXIF data in the EXIF blob was (%d).", ie.FurthestOffset())
return index, nil
}
func (ie *IfdEnumerate) setChildrenIndex(ifd *Ifd) (err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
childIfdIndex := make(map[string]*Ifd)
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for _, childIfd := range ifd.children {
childIfdIndex[childIfd.ifdIdentity.UnindexedString()] = childIfd
}
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ifd.childIfdIndex = childIfdIndex
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for _, childIfd := range ifd.children {
err := ie.setChildrenIndex(childIfd)
log.PanicIf(err)
}
return nil
}
// FurthestOffset returns the furthest offset visited in the EXIF blob. This
// *does not* account for the locations of any undefined tags since we always
// evaluate the furthest offset, whether or not the user wants to know it.
//
// We are not willing to incur the cost of actually parsing those tags just to
// know their length when there are still undefined tags that are out there
// that we still won't have any idea how to parse, thus making this an
// approximation regardless of how clever we get.
func (ie *IfdEnumerate) FurthestOffset() uint32 {
// TODO(dustin): Add test
return ie.furthestOffset
}
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// parseOneIfd is a hack to use an IE to parse a raw IFD block. Can be used for
// testing. The fqIfdPath ("fully-qualified IFD path") will be less qualified
// in that the numeric index will always be zero (the zeroth child) rather than
// the proper number (if its actually a sibling to the first child, for
// instance).
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func parseOneIfd(ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, ii *exifcommon.IfdIdentity, byteOrder binary.ByteOrder, ifdBlock []byte, visitor TagVisitorFn) (nextIfdOffset uint32, entries []*IfdTagEntry, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
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// TODO(dustin): Add test
ebs := NewExifReadSeekerWithBytes(ifdBlock)
rs, err := ebs.GetReadSeeker(0)
log.PanicIf(err)
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bp, err := newByteParser(rs, byteOrder, 0)
if err != nil {
if err == ErrOffsetInvalid {
return 0, nil, err
}
log.Panic(err)
}
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dummyEbs := NewExifReadSeekerWithBytes([]byte{})
ie := NewIfdEnumerate(ifdMapping, tagIndex, dummyEbs, byteOrder)
nextIfdOffset, entries, _, err = ie.parseIfd(ii, bp, visitor, true, nil)
log.PanicIf(err)
return nextIfdOffset, entries, nil
}
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// parseOneTag is a hack to use an IE to parse a raw tag block.
func parseOneTag(ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, ii *exifcommon.IfdIdentity, byteOrder binary.ByteOrder, tagBlock []byte) (ite *IfdTagEntry, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
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// TODO(dustin): Add test
ebs := NewExifReadSeekerWithBytes(tagBlock)
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rs, err := ebs.GetReadSeeker(0)
log.PanicIf(err)
bp, err := newByteParser(rs, byteOrder, 0)
if err != nil {
if err == ErrOffsetInvalid {
return nil, err
}
log.Panic(err)
}
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dummyEbs := NewExifReadSeekerWithBytes([]byte{})
ie := NewIfdEnumerate(ifdMapping, tagIndex, dummyEbs, byteOrder)
ite, err = ie.parseTag(ii, 0, bp)
log.PanicIf(err)
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err = ie.tagPostParse(ite, nil)
if err != nil {
if err == ErrTagNotFound {
return nil, err
}
log.Panic(err)
}
return ite, nil
}
// FindIfdFromRootIfd returns the given `Ifd` given the root-IFD and path of the
// desired IFD.
func FindIfdFromRootIfd(rootIfd *Ifd, ifdPath string) (ifd *Ifd, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): !! Add test.
lineage, err := rootIfd.ifdMapping.ResolvePath(ifdPath)
log.PanicIf(err)
// Confirm the first IFD is our root IFD type, and then prune it because
// from then on we'll be searching down through our children.
if len(lineage) == 0 {
log.Panicf("IFD path must be non-empty.")
} else if lineage[0].Name != exifcommon.IfdStandardIfdIdentity.Name() {
log.Panicf("First IFD path item must be [%s].", exifcommon.IfdStandardIfdIdentity.Name())
}
desiredRootIndex := lineage[0].Index
lineage = lineage[1:]
// TODO(dustin): !! This is a poorly conceived fix that just doubles the work we already have to do below, which then interacts badly with the indices not being properly represented in the IFD-phrase.
// TODO(dustin): !! <-- However, we're not sure whether we shouldn't store a secondary IFD-path with the indices. Some IFDs may not necessarily restrict which IFD indices they can be a child of (only the IFD itself matters). Validation should be delegated to the caller.
thisIfd := rootIfd
for currentRootIndex := 0; currentRootIndex < desiredRootIndex; currentRootIndex++ {
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if thisIfd.nextIfd == nil {
log.Panicf("Root-IFD index (%d) does not exist in the data.", currentRootIndex)
}
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thisIfd = thisIfd.nextIfd
}
for _, itii := range lineage {
var hit *Ifd
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for _, childIfd := range thisIfd.children {
if childIfd.ifdIdentity.TagId() == itii.TagId {
hit = childIfd
break
}
}
// If we didn't find the child, add it.
if hit == nil {
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log.Panicf("IFD [%s] in [%s] not found: %s", itii.Name, ifdPath, thisIfd.children)
}
thisIfd = hit
// If we didn't find the sibling, add it.
for i := 0; i < itii.Index; i++ {
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if thisIfd.nextIfd == nil {
log.Panicf("IFD [%s] does not have (%d) occurrences/siblings", thisIfd.ifdIdentity.UnindexedString(), itii.Index)
}
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thisIfd = thisIfd.nextIfd
}
}
return thisIfd, nil
}