Configures exiftool stdout and stderr command buffer (#6)

exiftool.go

@@ -29,6 +29,9 @@ type Exiftool struct {
 	stdin         io.WriteCloser
 	stdMergedOut  io.ReadCloser
 	scanMergedOut *bufio.Scanner
+	bufferSet     bool
+	buffer        []byte
+	bufferMaxSize int
 }
 
 // NewExiftool instanciates a new Exiftool with configuration functions. If anything went
@@ -55,6 +58,9 @@ func NewExiftool(opts ...func(*Exiftool) error) (*Exiftool, error) {
 	}
 
 	e.scanMergedOut = bufio.NewScanner(r)
+	if e.bufferSet {
+		e.scanMergedOut.Buffer(e.buffer, e.bufferMaxSize)
+	}
 	e.scanMergedOut.Split(splitReadyToken)
 
 	if err = cmd.Start(); err != nil {
@@ -154,3 +160,16 @@ func splitReadyToken(data []byte, atEOF bool) (int, []byte, error) {
 
 	return idx + readyTokenLen, data[:idx], nil
 }
+
+// Buffer defines the buffer used to read from stdout and stderr, see https://golang.org/pkg/bufio/#Scanner.Buffer
+// Sample :
+//  buf := make([]byte, 128*1000)
+//  e, err := e, err := NewExiftool(Buffer(buf, 64*1000))
+func Buffer(buf []byte, max int) func(*Exiftool) error {
+	return func(e *Exiftool) error {
+		e.bufferSet = true
+		e.buffer = buf
+		e.bufferMaxSize = max
+		return nil
+	}
+}

exiftool_test.go

@@ -189,3 +189,27 @@ func (e readWriteCloserMock) Close() error {
 	*(e.closed) = true
 	return e.closeErr
 }
+
+func TestBuffer(t *testing.T) {
+	e, err := NewExiftool()
+	assert.Nil(t, err)
+	defer e.Close()
+	assert.Equal(t, false, e.bufferSet)
+
+	buf := make([]byte, 128)
+	assert.Nil(t, Buffer(buf, 64)(e))
+	assert.Equal(t, true, e.bufferSet)
+	assert.Equal(t, buf, e.buffer)
+	assert.Equal(t, 64, e.bufferMaxSize)
+}
+
+func TestNewExifTool_WithBuffer(t *testing.T) {
+	buf := make([]byte, 128*1000)
+	e, err := NewExiftool(Buffer(buf, 64*1000))
+	assert.Nil(t, err)
+	defer e.Close()
+
+	metas := e.ExtractMetadata("./testdata/20190404_131804.jpg")
+	assert.Equal(t, 1, len(metas))
+	assert.Nil(t, metas[0].Err)
+}