ifd_enumerate: Implemented ChildWithIfdIdentity.

ifd_builder_test.go

@@ -1412,6 +1412,7 @@ func Test_IfdBuilder_CreateIfdBuilderFromExistingChain_RealData(t *testing.T) {
             t.Fatalf("Tag-type not as expected: %d != %d  ITE=%s", recoveredIte.TagType, originalIte.TagType, recoveredIte)
         }
 
+// TODO(dustin): We're always accessing the addressable-data using the root-IFD. It shouldn't matter, but we'd rather access it from our specific IFD.
         originalValueBytes, err := originalIte.ValueBytes(originalIndex.RootIfd.addressableData, originalIndex.RootIfd.ByteOrder)
         log.PanicIf(err)
 
@@ -1460,7 +1461,6 @@ func Test_IfdBuilder_CreateIfdBuilderFromExistingChain_RealData_WithUpdate(t *te
     ucBt, err := exifBt.value.Ib().FindTagWithName("UserComment")
     log.PanicIf(err)
 
-// TODO(dustin): !! Create an example for this.
     uc := TagUnknownType_9298_UserComment{
         EncodingType: TagUnknownType_9298_UserComment_Encoding_ASCII,
         EncodingBytes: []byte("TEST COMMENT"),

ifd_enumerate.go

@@ -355,6 +355,23 @@ type Ifd struct {
     thumbnailData []byte
 }
 
+func (ifd *Ifd) ChildWithIfdIdentity(ii IfdIdentity) (childIfd *Ifd, err error) {
+    defer func() {
+        if state := recover(); state != nil {
+            err = log.Wrap(state.(error))
+        }
+    }()
+
+    for _, childIfd := range ifd.Children {
+        if childIfd.Ii == ii {
+            return childIfd, nil
+        }
+    }
+
+    log.Panic(ErrTagNotFound)
+    return nil, nil
+}
+
 func (ifd *Ifd) TagValue(ite *IfdTagEntry) (value interface{}, err error) {
     defer func() {
         if state := recover(); state != nil {

ifd_tag_entry.go

@@ -24,6 +24,8 @@ type IfdTagEntry struct {
     // ChildIfdName is a name if this tag represents a child IFD.
     ChildIfdName string
 
+// TODO(dustin): !! IB's host the child-IBs directly in the tag, but that's not the case here. Refactor to accomodate it for a consistent experience.
+
     // IfdName is the IFD that this tag belongs to.
     Ii IfdIdentity
 }