io: fix Copyn EOF handling
Fixes #1383.
R=r
CC=golang-dev
https://golang.org/cl/3821044
diff --git a/src/pkg/io/io.go b/src/pkg/io/io.go
index fa1c0d2..1a6eca9 100644
--- a/src/pkg/io/io.go
+++ b/src/pkg/io/io.go
@@ -206,7 +206,12 @@
// If the writer has a ReadFrom method, use it to do the copy.
// Avoids a buffer allocation and a copy.
if rt, ok := dst.(ReaderFrom); ok {
- return rt.ReadFrom(LimitReader(src, n))
+ written, err = rt.ReadFrom(LimitReader(src, n))
+ if written < n && err == nil {
+ // rt stopped early; must have been EOF.
+ err = os.EOF
+ }
+ return
}
buf := make([]byte, 32*1024)
for written < n {
diff --git a/src/pkg/io/io_test.go b/src/pkg/io/io_test.go
index 20f240a..4fcd85e 100644
--- a/src/pkg/io/io_test.go
+++ b/src/pkg/io/io_test.go
@@ -8,6 +8,7 @@
"bytes"
. "io"
"os"
+ "strings"
"testing"
)
@@ -80,6 +81,41 @@
}
}
+type noReadFrom struct {
+ w Writer
+}
+
+func (w *noReadFrom) Write(p []byte) (n int, err os.Error) {
+ return w.w.Write(p)
+}
+
+func TestCopynEOF(t *testing.T) {
+ // Test that EOF behavior is the same regardless of whether
+ // argument to Copyn has ReadFrom.
+
+ b := new(bytes.Buffer)
+
+ n, err := Copyn(&noReadFrom{b}, strings.NewReader("foo"), 3)
+ if n != 3 || err != nil {
+ t.Errorf("Copyn(noReadFrom, foo, 3) = %d, %v; want 3, nil", n, err)
+ }
+
+ n, err = Copyn(&noReadFrom{b}, strings.NewReader("foo"), 4)
+ if n != 3 || err != os.EOF {
+ t.Errorf("Copyn(noReadFrom, foo, 4) = %d, %v; want 3, EOF", n, err)
+ }
+
+ n, err = Copyn(b, strings.NewReader("foo"), 3) // b has read from
+ if n != 3 || err != nil {
+ t.Errorf("Copyn(bytes.Buffer, foo, 3) = %d, %v; want 3, nil", n, err)
+ }
+
+ n, err = Copyn(b, strings.NewReader("foo"), 4) // b has read from
+ if n != 3 || err != os.EOF {
+ t.Errorf("Copyn(bytes.Buffer, foo, 4) = %d, %v; want 3, EOF", n, err)
+ }
+}
+
func TestReadAtLeast(t *testing.T) {
var rb bytes.Buffer
rb.Write([]byte("0123"))
