From e88f89028a55acf9c8b76b7f6ca284c3f9eb4cbd Mon Sep 17 00:00:00 2001 From: Joe Tsai Date: Thu, 31 Mar 2016 16:05:23 -0700 Subject: bytes, string: add Reset method to Reader Currently, there is no easy allocation-free way to turn a []byte or string into an io.Reader. Thus, we add a Reset method to bytes.Reader and strings.Reader to allow the reuse of these Readers with another []byte or string. This is consistent with the fact that many standard library io.Readers already support a Reset method of some type: bufio.Reader flate.Reader gzip.Reader zlib.Reader debug/dwarf.LineReader bytes.Buffer crypto/rc4.Cipher Fixes #15033 Change-Id: I456fd1af77af6ef0b4ac6228b058ac1458ff3d19 Reviewed-on: https://go-review.googlesource.com/21386 Reviewed-by: Brad Fitzpatrick Run-TryBot: Brad Fitzpatrick TryBot-Result: Gobot Gobot --- src/bytes/reader.go | 3 +++ src/bytes/reader_test.go | 20 ++++++++++++++++++++ 2 files changed, 23 insertions(+) (limited to 'src/bytes') diff --git a/src/bytes/reader.go b/src/bytes/reader.go index 5941ebdab4..7aa30578b3 100644 --- a/src/bytes/reader.go +++ b/src/bytes/reader.go @@ -146,5 +146,8 @@ func (r *Reader) WriteTo(w io.Writer) (n int64, err error) { return } +// Reset resets the Reader to be reading from b. +func (r *Reader) Reset(b []byte) { *r = Reader{b, 0, -1} } + // NewReader returns a new Reader reading from b. func NewReader(b []byte) *Reader { return &Reader{b, 0, -1} } diff --git a/src/bytes/reader_test.go b/src/bytes/reader_test.go index b929a28260..add985d57e 100644 --- a/src/bytes/reader_test.go +++ b/src/bytes/reader_test.go @@ -256,3 +256,23 @@ func TestReaderLenSize(t *testing.T) { t.Errorf("Size = %d; want 3", r.Size()) } } + +func TestReaderReset(t *testing.T) { + r := NewReader([]byte("世界")) + if _, _, err := r.ReadRune(); err != nil { + t.Errorf("ReadRune: unexpected error: %v", err) + } + + const want = "abcdef" + r.Reset([]byte(want)) + if err := r.UnreadRune(); err == nil { + t.Errorf("UnreadRune: expected error, got nil") + } + buf, err := ioutil.ReadAll(r) + if err != nil { + t.Errorf("ReadAll: unexpected error: %v", err) + } + if got := string(buf); got != want { + t.Errorf("ReadAll: got %q, want %q", got, want) + } +} -- cgit v1.3-5-g9baa