bufio: read from underlying reader at most once in Read
Fixes #17059.
Change-Id: I5c7ee46604399f7dc3c3c49f964cbb1aa6c0d621
Reviewed-on: https://go-review.googlesource.com/31320
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/src/bufio/bufio.go b/src/bufio/bufio.go
index 1e7872d..e1e8fb2 100644
--- a/src/bufio/bufio.go
+++ b/src/bufio/bufio.go
@@ -206,10 +206,18 @@
}
return n, b.readErr()
}
- b.fill() // buffer is empty
- if b.r == b.w {
+ // One read.
+ // Do not use b.fill, which will loop.
+ b.r = 0
+ b.w = 0
+ n, b.err = b.rd.Read(b.buf)
+ if n < 0 {
+ panic(errNegativeRead)
+ }
+ if n == 0 {
return 0, b.readErr()
}
+ b.w += n
}
// copy as much as we can
diff --git a/src/bufio/bufio_test.go b/src/bufio/bufio_test.go
index 8580486..ef0f6c8 100644
--- a/src/bufio/bufio_test.go
+++ b/src/bufio/bufio_test.go
@@ -1236,6 +1236,27 @@
}
}
+func TestReadZero(t *testing.T) {
+ for _, size := range []int{100, 2} {
+ t.Run(fmt.Sprintf("bufsize=%d", size), func(t *testing.T) {
+ r := io.MultiReader(strings.NewReader("abc"), &emptyThenNonEmptyReader{r: strings.NewReader("def"), n: 1})
+ br := NewReaderSize(r, size)
+ want := func(s string, wantErr error) {
+ p := make([]byte, 50)
+ n, err := br.Read(p)
+ if err != wantErr || n != len(s) || string(p[:n]) != s {
+ t.Fatalf("read(%d) = %q, %v, want %q, %v", len(p), string(p[:n]), err, s, wantErr)
+ }
+ t.Logf("read(%d) = %q, %v", len(p), string(p[:n]), err)
+ }
+ want("abc", nil)
+ want("", nil)
+ want("def", nil)
+ want("", io.EOF)
+ })
+ }
+}
+
func TestReaderReset(t *testing.T) {
r := NewReader(strings.NewReader("foo foo"))
buf := make([]byte, 3)
