From cc316fb4407dc6b138ec79915c6d399cbef8f756 Mon Sep 17 00:00:00 2001
From: Dustin Oprea <dustin@randomingenuity.com>
Date: Sat, 2 May 2020 17:10:36 -0400
Subject: [PATCH] ifd_enumerate.go: (*Ifd).PrintTagTree() no longer fails on
 parseable undefined values

https://github.com/dsoprea/go-exif/issues/33
---
 v2/ifd_enumerate.go  | 13 ++++++++++++-
 v2/ifd_tag_entry.go  |  2 ++
 v2/undefined/type.go | 10 ++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/v2/ifd_enumerate.go b/v2/ifd_enumerate.go
index 3c8a7fc..c02cbf5 100644
--- a/v2/ifd_enumerate.go
+++ b/v2/ifd_enumerate.go
@@ -13,6 +13,7 @@ import (
 	"github.com/dsoprea/go-logging"
 
 	"github.com/dsoprea/go-exif/v2/common"
+	"github.com/dsoprea/go-exif/v2/undefined"
 )
 
 var (
@@ -557,7 +558,17 @@ func (ifd *Ifd) printTagTree(populateValues bool, index, level int, nextLink boo
 				var err error
 
 				valuePhrase, err = ite.Format()
-				log.PanicIf(err)
+				if err != nil {
+					if log.Is(err, exifcommon.ErrUnhandledUndefinedTypedTag) == true {
+						ifdEnumerateLogger.Warningf(nil, "Skipping non-standard undefined tag: [%s] (%04x)", ifd.IfdPath, ite.TagId())
+						continue
+					} else if err == exifundefined.ErrUnparseableValue {
+						ifdEnumerateLogger.Warningf(nil, "Skipping unparseable undefined tag: [%s] (%04x) [%s]", ifd.IfdPath, ite.TagId(), it.Name)
+						continue
+					}
+
+					log.Panic(err)
+				}
 			} else {
 				valuePhrase = "!UNRESOLVED"
 			}
diff --git a/v2/ifd_tag_entry.go b/v2/ifd_tag_entry.go
index 21273fa..1037271 100644
--- a/v2/ifd_tag_entry.go
+++ b/v2/ifd_tag_entry.go
@@ -178,6 +178,8 @@ func (ite *IfdTagEntry) Format() (phrase string, err error) {
 	if err != nil {
 		if err == exifcommon.ErrUnhandledUndefinedTypedTag {
 			return exifundefined.UnparseableUnknownTagValuePlaceholder, nil
+		} else if err == exifundefined.ErrUnparseableValue {
+			return exifundefined.UnparseableHandledTagValuePlaceholder, nil
 		}
 
 		log.Panic(err)
diff --git a/v2/undefined/type.go b/v2/undefined/type.go
index c87fbf8..5e55e4c 100644
--- a/v2/undefined/type.go
+++ b/v2/undefined/type.go
@@ -9,10 +9,18 @@ import (
 )
 
 const (
+	// UnparseableUnknownTagValuePlaceholder is the string to use for an unknown
+	// undefined tag.
 	UnparseableUnknownTagValuePlaceholder = "!UNKNOWN"
+
+	// UnparseableHandledTagValuePlaceholder is the string to use for a known
+	// value that is not parseable.
+	UnparseableHandledTagValuePlaceholder = "!MALFORMED"
 )
 
 var (
+	// ErrUnparseableValue is the error for a value that we should have been
+	// able to parse but were not able to.
 	ErrUnparseableValue = errors.New("unparseable undefined tag")
 )
 
@@ -22,6 +30,8 @@ type UndefinedValueEncoder interface {
 	Encode(value interface{}, byteOrder binary.ByteOrder) (encoded []byte, unitCount uint32, err error)
 }
 
+// EncodeableValue wraps a value with the information that will be needed to re-
+// encode it later.
 type EncodeableValue interface {
 	EncoderName() string
 	String() string