bufio: fix bug that ReadFrom stops before EOF or error
ReadFrom should not return until it receives a non-nil error
or too many contiguous (0, nil)s from a given reader.
Currently it immediately returns if it receives one (0, nil).
Fixes #7611.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/76400048
diff --git a/src/pkg/bufio/bufio.go b/src/pkg/bufio/bufio.go
index ef74471..de81b4d 100644
--- a/src/pkg/bufio/bufio.go
+++ b/src/pkg/bufio/bufio.go
@@ -38,6 +38,7 @@
}
const minReadBufferSize = 16
+const maxConsecutiveEmptyReads = 100
// NewReaderSize returns a new Reader whose buffer has at least the specified
// size. If the argument io.Reader is already a Reader with large enough
@@ -625,9 +626,16 @@
return n, err1
}
}
- m, err = r.Read(b.buf[b.n:])
- if m == 0 {
- break
+ nr := 0
+ for nr < maxConsecutiveEmptyReads {
+ m, err = r.Read(b.buf[b.n:])
+ if m != 0 || err != nil {
+ break
+ }
+ nr++
+ }
+ if nr == maxConsecutiveEmptyReads {
+ return n, io.ErrNoProgress
}
b.n += m
n += int64(m)
diff --git a/src/pkg/bufio/bufio_test.go b/src/pkg/bufio/bufio_test.go
index 3dd5ceb..800c6d2 100644
--- a/src/pkg/bufio/bufio_test.go
+++ b/src/pkg/bufio/bufio_test.go
@@ -1060,6 +1060,60 @@
}
}
+type emptyThenNonEmptyReader struct {
+ r io.Reader
+ n int
+}
+
+func (r *emptyThenNonEmptyReader) Read(p []byte) (int, error) {
+ if r.n <= 0 {
+ return r.r.Read(p)
+ }
+ r.n--
+ return 0, nil
+}
+
+// Test for golang.org/issue/7611
+func TestWriterReadFromUntilEOF(t *testing.T) {
+ buf := new(bytes.Buffer)
+ w := NewWriterSize(buf, 5)
+
+ // Partially fill buffer
+ n, err := w.Write([]byte("0123"))
+ if n != 4 || err != nil {
+ t.Fatalf("Write returned (%v, %v), want (4, nil)", n, err)
+ }
+
+ // Use ReadFrom to read in some data.
+ r := &emptyThenNonEmptyReader{r: strings.NewReader("abcd"), n: 3}
+ n2, err := w.ReadFrom(r)
+ if n2 != 4 || err != nil {
+ t.Fatalf("ReadFrom returned (%v, %v), want (4, nil)", n2, err)
+ }
+ w.Flush()
+ if got, want := string(buf.Bytes()), "0123abcd"; got != want {
+ t.Fatalf("buf.Bytes() returned %q, want %q", got, want)
+ }
+}
+
+func TestWriterReadFromErrNoProgress(t *testing.T) {
+ buf := new(bytes.Buffer)
+ w := NewWriterSize(buf, 5)
+
+ // Partially fill buffer
+ n, err := w.Write([]byte("0123"))
+ if n != 4 || err != nil {
+ t.Fatalf("Write returned (%v, %v), want (4, nil)", n, err)
+ }
+
+ // Use ReadFrom to read in some data.
+ r := &emptyThenNonEmptyReader{r: strings.NewReader("abcd"), n: 100}
+ n2, err := w.ReadFrom(r)
+ if n2 != 0 || err != io.ErrNoProgress {
+ t.Fatalf("buf.Bytes() returned (%v, %v), want (0, io.ErrNoProgress)", n2, err)
+ }
+}
+
func TestReaderReset(t *testing.T) {
r := NewReader(strings.NewReader("foo foo"))
buf := make([]byte, 3)
diff --git a/src/pkg/bufio/scan.go b/src/pkg/bufio/scan.go
index 77b2c2a..3f8d2a8 100644
--- a/src/pkg/bufio/scan.go
+++ b/src/pkg/bufio/scan.go
@@ -172,7 +172,7 @@
break
}
loop++
- if loop > 100 {
+ if loop > maxConsecutiveEmptyReads {
s.setErr(io.ErrNoProgress)
break
}
