bufio: fix UnreadByte
Also:
- fix error messages in tests
- make tests more symmetric
Fixes #7607.
LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/86180043
diff --git a/src/pkg/bufio/bufio.go b/src/pkg/bufio/bufio.go
index de81b4d..1e0cdae 100644
--- a/src/pkg/bufio/bufio.go
+++ b/src/pkg/bufio/bufio.go
@@ -177,7 +177,7 @@
// If no byte is available, returns an error.
func (b *Reader) ReadByte() (c byte, err error) {
b.lastRuneSize = -1
- for b.w == b.r {
+ for b.r == b.w {
if b.err != nil {
return 0, b.readErr()
}
@@ -191,19 +191,19 @@
// UnreadByte unreads the last byte. Only the most recently read byte can be unread.
func (b *Reader) UnreadByte() error {
- b.lastRuneSize = -1
- if b.r == b.w && b.lastByte >= 0 {
- b.w = 1
- b.r = 0
- b.buf[0] = byte(b.lastByte)
- b.lastByte = -1
- return nil
- }
- if b.r <= 0 {
+ if b.lastByte < 0 || b.r == 0 && b.w > 0 {
return ErrInvalidUnreadByte
}
- b.r--
+ // b.r > 0 || b.w == 0
+ if b.r > 0 {
+ b.r--
+ } else {
+ // b.r == 0 && b.w == 0
+ b.w = 1
+ }
+ b.buf[b.r] = byte(b.lastByte)
b.lastByte = -1
+ b.lastRuneSize = -1
return nil
}
@@ -233,7 +233,7 @@
// regard it is stricter than UnreadByte, which will unread the last byte
// from any read operation.)
func (b *Reader) UnreadRune() error {
- if b.lastRuneSize < 0 || b.r == 0 {
+ if b.lastRuneSize < 0 || b.r < b.lastRuneSize {
return ErrInvalidUnreadRune
}
b.r -= b.lastRuneSize
