Reuse buffer when scanning

entry.go

@@ -91,7 +91,7 @@ func unquoteExec(ex string) string {
 	return ex
 }
 
-func Parse(content io.Reader) (*Entry, error) {
+func Parse(content io.Reader, buf []byte) (*Entry, error) {
 	var (
 		scanner         = bufio.NewScanner(content)
 		scannedBytes    []byte
@@ -101,6 +101,8 @@ func Parse(content io.Reader) (*Entry, error) {
 		foundHeader bool
 	)
 
+	scanner.Buffer(buf, len(buf))
+
 	for scanner.Scan() {
 		scannedBytes = bytes.TrimSpace(scanner.Bytes())
 		scannedBytesLen = len(scannedBytes)

entry_test.go

@@ -20,13 +20,19 @@ var testCases = []*testData{
 }
 
 func TestParse(t *testing.T) {
+	var (
+		buf   = make([]byte, bufferSize)
+		f     *os.File
+		entry *Entry
+		err   error
+	)
 	for _, c := range testCases {
-		f, err := os.OpenFile("test/"+c.Filename, os.O_RDONLY, 0644)
+		f, err = os.OpenFile("test/"+c.Filename, os.O_RDONLY, 0644)
 		if err != nil {
 			t.Fatal(err)
 		}
 
-		entry, err := Parse(f)
+		entry, err = Parse(f, buf)
 		f.Close()
 		if err != nil {
 			t.Fatal(err)
@@ -39,33 +45,42 @@ func TestParse(t *testing.T) {
 }
 
 func BenchmarkParse(b *testing.B) {
-	var files []*os.File
+	var (
+		buf   = make([]byte, bufferSize)
+		files = make([]*os.File, len(testCases))
+		entry *Entry
+		err   error
+	)
 	defer func() {
 		for _, f := range files {
 			f.Close()
 		}
 	}()
 
-	for _, c := range testCases {
+	for i, c := range testCases {
 		f, err := os.OpenFile("test/"+c.Filename, os.O_RDONLY, 0644)
 		if err != nil {
 			b.Fatal(err)
 		}
 
-		files = append(files, f)
+		files[i] = f
 	}
 
 	b.StopTimer()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		for _, f := range files {
+		for ci, f := range files {
 			b.StartTimer()
-			_, err := Parse(f)
+			entry, err = Parse(f, buf)
 			if err != nil {
 				b.Fatal(err)
 			}
 			b.StopTimer()
 
+			if !reflect.DeepEqual(entry, testCases[ci].Entry) {
+				b.Fatalf("%s: entry incorrect: got %#v, want %#v", f.Name(), entry, testCases[ci].Entry)
+			}
+
 			_, err = f.Seek(0, io.SeekStart)
 			if err != nil {
 				b.Fatal(err)

scan.go

@@ -8,6 +8,8 @@ import (
 	"sync"
 )
 
+const bufferSize = 32 * 1024
+
 type scan struct {
 	e    map[int][]*Entry
 	errs chan error
@@ -53,13 +55,14 @@ func Scan(dirs []string) (map[int][]*Entry, error) {
 
 func scanner(s *scan) {
 	var (
+		buf       = make([]byte, bufferSize)
 		scanEntry *scanEntry
 		entry     *Entry
 		err       error
 	)
 
 	for scanEntry = range s.in {
-		entry, err = Parse(scanEntry.f)
+		entry, err = Parse(scanEntry.f, buf)
 		scanEntry.f.Close()
 		if err != nil {
 			s.errs <- err