bufio: minor fixes
* note end-of-line and EOF behavior for ReadLine
* diagnose broken Readers
Fixes #3825.
Fixes #4276.
R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/6907060
diff --git a/src/pkg/bufio/bufio.go b/src/pkg/bufio/bufio.go
index cd51585..4b69019 100644
--- a/src/pkg/bufio/bufio.go
+++ b/src/pkg/bufio/bufio.go
@@ -64,6 +64,8 @@
return NewReaderSize(rd, defaultBufSize)
}
+var errNegativeRead = errors.New("bufio: reader returned negative count from Read")
+
// fill reads a new chunk into the buffer.
func (b *Reader) fill() {
// Slide existing data to beginning.
@@ -75,6 +77,9 @@
// Read new data.
n, e := b.rd.Read(b.buf[b.w:])
+ if n < 0 {
+ panic(errNegativeRead)
+ }
b.w += n
if e != nil {
b.err = e
@@ -282,6 +287,9 @@
// of the line. The returned buffer is only valid until the next call to
// ReadLine. ReadLine either returns a non-nil line or it returns an error,
// never both.
+//
+// The text returned from ReadLine does not include the line end ("\r\n" or "\n").
+// No indication or error is given if the input ends without a final line end.
func (b *Reader) ReadLine() (line []byte, isPrefix bool, err error) {
line, err = b.ReadSlice('\n')
if err == ErrBufferFull {
diff --git a/src/pkg/bufio/bufio_test.go b/src/pkg/bufio/bufio_test.go
index 75d9edf..5646211 100644
--- a/src/pkg/bufio/bufio_test.go
+++ b/src/pkg/bufio/bufio_test.go
@@ -939,6 +939,29 @@
return len(p), nil
}
+type negativeReader int
+
+func (r *negativeReader) Read([]byte) (int, error) { return -1, nil }
+
+func TestNegativeRead(t *testing.T) {
+ // should panic with a description pointing at the reader, not at itself.
+ // (should NOT panic with slice index error, for example.)
+ b := NewReader(new(negativeReader))
+ defer func() {
+ switch err := recover().(type) {
+ case nil:
+ t.Fatal("read did not panic")
+ case error:
+ if !strings.Contains(err.Error(), "reader returned negative count from Read") {
+ t.Fatal("wrong panic: %v", err)
+ }
+ default:
+ t.Fatalf("unexpected panic value: %T(%v)", err, err)
+ }
+ }()
+ b.Read(make([]byte, 100))
+}
+
// An onlyReader only implements io.Reader, no matter what other methods the underlying implementation may have.
type onlyReader struct {
r io.Reader
