bufio: handle a "\r\n" that straddles the buffer.

Fixes #2164.

R=r, rsc
CC=golang-dev
https://golang.org/cl/4927043

src/pkg/bufio/bufio.go

@@ -54,11 +54,11 @@ type Reader struct {
 }
 
 // NewReaderSize creates a new Reader whose buffer has the specified size,
-// which must be greater than zero.  If the argument io.Reader is already a
+// which must be greater than one.  If the argument io.Reader is already a
 // Reader with large enough size, it returns the underlying Reader.
 // It returns the Reader and any error.
 func NewReaderSize(rd io.Reader, size int) (*Reader, os.Error) {
-	if size <= 0 {
+	if size <= 1 {
 		return nil, BufSizeError(size)
 	}
 	// Is it already a Reader?
@@ -298,6 +298,17 @@ func (b *Reader) ReadSlice(delim byte) (line []byte, err os.Error) {
 func (b *Reader) ReadLine() (line []byte, isPrefix bool, err os.Error) {
 	line, err = b.ReadSlice('\n')
 	if err == ErrBufferFull {
+		// Handle the case where "\r\n" straddles the buffer.
+		if len(line) > 0 && line[len(line)-1] == '\r' {
+			// Put the '\r' back on buf and drop it from line.
+			// Let the next call to ReadLine check for "\r\n".
+			if b.r == 0 {
+				// should be unreachable
+				panic("bufio: tried to rewind past start of buffer")
+			}
+			b.r--
+			line = line[:len(line)-1]
+		}
 		return line, true, nil
 	}
 
@@ -307,10 +318,11 @@ func (b *Reader) ReadLine() (line []byte, isPrefix bool, err os.Error) {
 	err = nil
 
 	if line[len(line)-1] == '\n' {
-		line = line[:len(line)-1]
-	}
-	if len(line) > 0 && line[len(line)-1] == '\r' {
-		line = line[:len(line)-1]
+		drop := 1
+		if len(line) > 1 && line[len(line)-2] == '\r' {
+			drop = 2
+		}
+		line = line[:len(line)-drop]
 	}
 	return
 }

src/pkg/bufio/bufio_test.go

@@ -137,7 +137,7 @@ var bufreaders = []bufReader{
 }
 
 var bufsizes = []int{
-	1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+	2, 3, 4, 5, 6, 7, 8, 9, 10,
 	23, 32, 46, 64, 93, 128, 1024, 4096,
 }
 
@@ -697,3 +697,71 @@ func TestLinesAfterRead(t *testing.T) {
 		t.Errorf("expected EOF from ReadLine, got '%s' %t %s", line, isPrefix, err)
 	}
 }
+
+type readLineResult struct {
+	line     []byte
+	isPrefix bool
+	err      os.Error
+}
+
+var readLineNewlinesTests = []struct {
+	input   string
+	bufSize int
+	expect  []readLineResult
+}{
+	{"h\r\nb\r\n", 2, []readLineResult{
+		{[]byte("h"), true, nil},
+		{nil, false, nil},
+		{[]byte("b"), true, nil},
+		{nil, false, nil},
+		{nil, false, os.EOF},
+	}},
+	{"hello\r\nworld\r\n", 6, []readLineResult{
+		{[]byte("hello"), true, nil},
+		{nil, false, nil},
+		{[]byte("world"), true, nil},
+		{nil, false, nil},
+		{nil, false, os.EOF},
+	}},
+	{"hello\rworld\r", 6, []readLineResult{
+		{[]byte("hello"), true, nil},
+		{[]byte("\rworld"), true, nil},
+		{[]byte("\r"), false, nil},
+		{nil, false, os.EOF},
+	}},
+	{"h\ri\r\n\r", 2, []readLineResult{
+		{[]byte("h"), true, nil},
+		{[]byte("\ri"), true, nil},
+		{nil, false, nil},
+		{[]byte("\r"), false, nil},
+		{nil, false, os.EOF},
+	}},
+}
+
+func TestReadLineNewlines(t *testing.T) {
+	for _, e := range readLineNewlinesTests {
+		testReadLineNewlines(t, e.input, e.bufSize, e.expect)
+	}
+}
+
+func testReadLineNewlines(t *testing.T, input string, bufSize int, expect []readLineResult) {
+	b, err := NewReaderSize(strings.NewReader(input), bufSize)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i, e := range expect {
+		line, isPrefix, err := b.ReadLine()
+		if bytes.Compare(line, e.line) != 0 {
+			t.Errorf("%q call %d, line == %q, want %q", input, i, line, e.line)
+			return
+		}
+		if isPrefix != e.isPrefix {
+			t.Errorf("%q call %d, isPrefix == %v, want %v", input, i, isPrefix, e.isPrefix)
+			return
+		}
+		if err != e.err {
+			t.Errorf("%q call %d, err == %v, want %v", input, i, err, e.err)
+			return
+		}
+	}
+}