allow callback break and return error (#9)

parser.go

@@ -45,6 +45,8 @@ var (
 	ErrInvalidLabel = xerrors.New("invalid label")
 	// ErrInvalidValue is an error to describe value contains invalid char (ex. 'my_label:my_value\n')
 	ErrInvalidValue = xerrors.New("invalid value")
+	// Break is an error for break loop
+	Break = xerrors.New("break")
 )
 
 // ParseField parse LTSV-encoded field and return the label and value.
@@ -75,7 +77,7 @@ func (p Parser) ParseField(field []byte) (label []byte, value []byte, err error)
 
 // ParseLine parse one line of LTSV-encoded data and call callback.
 // The callback function will be called for each field.
-func (p Parser) ParseLine(line []byte, callback func(label []byte, value []byte)) error {
+func (p Parser) ParseLine(line []byte, callback func(label []byte, value []byte) error) error {
 	oriLine := line
 	for len(line) > 0 {
 		idx := bytes.IndexByte(line, p.FieldDelimiter)
@@ -95,7 +97,12 @@ func (p Parser) ParseLine(line []byte, callback func(label []byte, value []byte)
 			return xerrors.Errorf("bad line syntax %q: %w", string(oriLine), err)
 		}
 
-		callback(label, value)
+		if err = callback(label, value); err != nil {
+			if err == Break {
+				break
+			}
+			return xerrors.Errorf("ParseLine callback error: %w", err)
+		}
 	}
 	return nil
 }
@@ -106,8 +113,9 @@ func (p Parser) ParseLineAsMap(line []byte, record map[string]string) (map[strin
 	if record == nil {
 		record = map[string]string{}
 	}
-	err := p.ParseLine(line, func(label []byte, value []byte) {
+	err := p.ParseLine(line, func(label []byte, value []byte) error {
 		record[string(label)] = string(value)
+		return nil
 	})
 	if err != nil {
 		return nil, xerrors.Errorf(": %w", err)
@@ -119,8 +127,9 @@ func (p Parser) ParseLineAsMap(line []byte, record map[string]string) (map[strin
 // For reducing memory allocation, you can pass a slice to record to reuse the given slice.
 func (p Parser) ParseLineAsSlice(line []byte, record []Field) ([]Field, error) {
 	record = record[:0]
-	err := p.ParseLine(line, func(label []byte, value []byte) {
+	err := p.ParseLine(line, func(label []byte, value []byte) error {
 		record = append(record, Field{string(label), string(value)})
+		return nil
 	})
 	if err != nil {
 		return nil, xerrors.Errorf(": %w", err)

parser_test.go

@@ -12,7 +12,7 @@ import (
 
 func TestParseLine(t *testing.T) {
 	line := []byte("foo:123\tbar:456")
-	ParseLine(line, func(label []byte, value []byte) {
+	ParseLine(line, func(label []byte, value []byte) error {
 		val := string(value)
 		switch string(label) {
 		case "foo":
@@ -22,9 +22,34 @@ func TestParseLine(t *testing.T) {
 		default:
 			t.Errorf("unknown label: %s", string(label))
 		}
+		return nil
 	})
 }
 
+func TestParseLine_break(t *testing.T) {
+	line := []byte("foo:123\tbar:456")
+	counter := 0
+	err := ParseLine(line, func(label []byte, value []byte) error {
+		counter++
+		return Break
+	})
+	assert.NoError(t, err)
+	assert.Equal(t, 1, counter)
+}
+
+func TestParseLine_error(t *testing.T) {
+	line := []byte("foo:123\tbar:456")
+	counter := 0
+	customErr := xerrors.New("custom error")
+	err := ParseLine(line, func(label []byte, value []byte) error {
+		counter++
+		return customErr
+	})
+	assert.Error(t, err)
+	assert.True(t, xerrors.Is(err, customErr))
+	assert.Equal(t, 1, counter)
+}
+
 func TestParseLineAsMap(t *testing.T) {
 	tests := []struct {
 		name string
@@ -136,7 +161,7 @@ func TestParseField(t *testing.T) {
 	}
 }
 
-func BenchmarkParseLine(b *testing.B) {
+func BenchmarkParseLineAsMap(b *testing.B) {
 	parser := DefaultParser
 	parser.StrictMode = false
 	line := []byte("host:127.0.0.1\tident:-\tuser:frank\ttime:[10/Oct/2000:13:55:36 -0700]\treq:GET /apache_pb.gif HTTP/1.0\tstatus:200\tsize:2326\treferer:http://www.example.com/start.html\tua:Mozilla/4.08 [en] (Win98; I ;Nav)")
@@ -145,3 +170,14 @@ func BenchmarkParseLine(b *testing.B) {
 		parser.ParseLineAsMap(line, m)
 	}
 }
+
+func BenchmarkParseLine(b *testing.B) {
+	parser := DefaultParser
+	parser.StrictMode = false
+	line := []byte("host:127.0.0.1\tident:-\tuser:frank\ttime:[10/Oct/2000:13:55:36 -0700]\treq:GET /apache_pb.gif HTTP/1.0\tstatus:200\tsize:2326\treferer:http://www.example.com/start.html\tua:Mozilla/4.08 [en] (Win98; I ;Nav)")
+	for i := 0; i < b.N; i++ {
+		parser.ParseLine(line, func(label []byte, value []byte) error {
+			return nil
+		})
+	}
+}

static.go

@@ -8,7 +8,7 @@ func ParseField(field []byte) (label []byte, value []byte, err error) {
 
 // ParseLine parse one line of LTSV-encoded data and call callback.
 // The callback function will be called for each field.
-func ParseLine(line []byte, callback func(label []byte, value []byte)) error {
+func ParseLine(line []byte, callback func(label []byte, value []byte) error) error {
 	return DefaultParser.ParseLine(line, callback)
 }