From 4692087c1a8840c3d1593b3df89a19ea2c8d31c4 Mon Sep 17 00:00:00 2001
From: Dustin Oprea <dustin@randomingenuity.com>
Date: Wed, 8 Jul 2020 02:16:45 -0400
Subject: [PATCH] ifd_enumerate.go: Eliminate unnecessary buffering

A simplification prior to some upcoming data-access changes.
---
 v2/ifd_enumerate.go | 26 +++++++-------------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/v2/ifd_enumerate.go b/v2/ifd_enumerate.go
index ed8b805..1359333 100644
--- a/v2/ifd_enumerate.go
+++ b/v2/ifd_enumerate.go
@@ -77,7 +77,6 @@ type byteParser struct {
 	byteOrder       binary.ByteOrder
 	addressableData []byte
 	ifdOffset       uint32
-	buffer          *bytes.Buffer
 	currentOffset   uint32
 }
 
@@ -91,7 +90,6 @@ func newByteParser(addressableData []byte, byteOrder binary.ByteOrder, ifdOffset
 	bp = &byteParser{
 		addressableData: addressableData,
 		byteOrder:       byteOrder,
-		buffer:          bytes.NewBuffer(addressableData[ifdOffset:]),
 		currentOffset:   ifdOffset,
 	}
 
@@ -111,16 +109,12 @@ func (bp *byteParser) getUint16() (value uint16, raw []byte, err error) {
 	// TODO(dustin): Add test
 
 	needBytes := 2
-	offset := 0
-	raw = make([]byte, needBytes)
 
-	for offset < needBytes {
-		n, err := bp.buffer.Read(raw[offset:])
-		log.PanicIf(err)
-
-		offset += n
+	if bp.currentOffset+needBytes >= len(bp.addressableData) {
+		return 0, nil, io.EOF
 	}
 
+	raw = addressableData[bp.currentOffset : bp.currentOffset+needBytes]
 	value = bp.byteOrder.Uint16(raw)
 
 	bp.currentOffset += uint32(needBytes)
@@ -141,17 +135,13 @@ func (bp *byteParser) getUint32() (value uint32, raw []byte, err error) {
 	// TODO(dustin): Add test
 
 	needBytes := 4
-	offset := 0
-	raw = make([]byte, needBytes)
 
-	for offset < needBytes {
-		n, err := bp.buffer.Read(raw[offset:])
-		log.PanicIf(err)
-
-		offset += n
+	if bp.currentOffset+needBytes >= len(bp.addressableData) {
+		return 0, nil, io.EOF
 	}
 
-	value = bp.byteOrder.Uint32(raw)
+	raw = addressableData[bp.currentOffset : bp.currentOffset+needBytes]
+	value = bp.byteOrder.Uint16(raw)
 
 	bp.currentOffset += uint32(needBytes)
 
@@ -168,7 +158,6 @@ func (bp *byteParser) CurrentOffset() uint32 {
 // containers in the EXIF blob.
 type IfdEnumerate struct {
 	exifData       []byte
-	buffer         *bytes.Buffer
 	byteOrder      binary.ByteOrder
 	tagIndex       *TagIndex
 	ifdMapping     *exifcommon.IfdMapping
@@ -179,7 +168,6 @@ type IfdEnumerate struct {
 func NewIfdEnumerate(ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, exifData []byte, byteOrder binary.ByteOrder) *IfdEnumerate {
 	return &IfdEnumerate{
 		exifData:   exifData,
-		buffer:     bytes.NewBuffer(exifData),
 		byteOrder:  byteOrder,
 		ifdMapping: ifdMapping,
 		tagIndex:   tagIndex,