From 2bd9e91588c59e64bcb3642adc07cee75ed50812 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Fri, 16 Jul 2021 14:16:23 +0200
Subject: [PATCH] exif: Use the stream based API
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Also, do not return an error when input format isn't supported. Just return `nil` exif.

Using the stream API makes it a little faster:

```
name           old time/op    new time/op    delta
DecodeExif-16    1.94ms ± 1%    1.81ms ± 1%   -6.74%  (p=0.029 n=4+4)

name           old alloc/op   new alloc/op   delta
DecodeExif-16    1.51MB ± 0%    1.13MB ± 0%  -25.32%  (p=0.029 n=4+4)

name           old allocs/op  new allocs/op  delta
DecodeExif-16     12.9k ± 0%     12.9k ± 0%   -0.15%  (p=0.029 n=4+4)
```

It's still much slower than what we had:

```
name           old time/op    new time/op    delta
DecodeExif-16     108µs ± 1%    1857µs ± 2%  +1624.52%  (p=0.029 n=4+4)

name           old alloc/op   new alloc/op   delta
DecodeExif-16     184kB ± 0%    1130kB ± 0%   +513.72%  (p=0.029 n=4+4)

name           old allocs/op  new allocs/op  delta
DecodeExif-16     1.20k ± 0%    12.91k ± 0%   +972.82%  (p=0.029 n=4+4)
```

See #8586
---
 resources/images/exif/exif.go      | 13 +------------
 resources/images/exif/exif_test.go |  5 +++--
 2 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/resources/images/exif/exif.go b/resources/images/exif/exif.go
index 929c25bd378..0985ec5fec7 100644
--- a/resources/images/exif/exif.go
+++ b/resources/images/exif/exif.go
@@ -14,9 +14,7 @@
 package exif
 
 import (
-	"fmt"
 	"io"
-	"io/ioutil"
 	"math/big"
 	"regexp"
 	"strings"
@@ -26,7 +24,6 @@ import (
 
 	_exif "github.com/dsoprea/go-exif/v3"
 	exifcommon "github.com/dsoprea/go-exif/v3/common"
-	png "github.com/dsoprea/go-png-image-structure"
 )
 
 const (
@@ -110,17 +107,9 @@ func NewDecoder(options ...func(*Decoder) error) (*Decoder, error) {
 }
 
 func (d *Decoder) Decode(r io.Reader) (*Exif, error) {
-	rawBytes, err := ioutil.ReadAll(r)
-	if err != nil {
-		return nil, err
-	}
-	rawExif, err := _exif.SearchAndExtractExif(rawBytes)
+	rawExif, err := _exif.SearchAndExtractExifWithReader(r)
 
 	if err != nil {
-		parsed := png.NewPngMediaParser()
-		if parsed.LooksLikeFormat(rawBytes) {
-			return nil, fmt.Errorf("type not supported")
-		}
 		// No Exif data
 		return nil, nil
 	}
diff --git a/resources/images/exif/exif_test.go b/resources/images/exif/exif_test.go
index 555d28c3045..9f649e9f8f1 100644
--- a/resources/images/exif/exif_test.go
+++ b/resources/images/exif/exif_test.go
@@ -143,8 +143,9 @@ func TestExifPNG(t *testing.T) {
 
 	d, err := NewDecoder()
 	c.Assert(err, qt.IsNil)
-	_, err = d.Decode(f)
-	c.Assert(err, qt.Not(qt.IsNil))
+	x, err := d.Decode(f)
+	c.Assert(err, qt.IsNil)
+	c.Assert(x, qt.IsNil)
 }
 
 func TestIssue8079(t *testing.T) {