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bufio: add UnreadRune.

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R=rsc
CC=golang-dev
https://golang.org/cl/2103046
This commit is contained in:
Rob Pike 2010-09-12 17:40:27 +10:00
parent b155a76a40
commit acb695f421
2 changed files with 129 additions and 14 deletions
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50
src/pkg/bufio/bufio.go
View File

@ -27,6 +27,7 @@ type Error struct {
var (
ErrInvalidUnreadByte os.Error = &Error{"bufio: invalid use of UnreadByte"}
ErrInvalidUnreadRune os.Error = &Error{"bufio: invalid use of UnreadRune"}
ErrBufferFull os.Error = &Error{"bufio: buffer full"}
ErrNegativeCount os.Error = &Error{"bufio: negative count"}
errInternal os.Error = &Error{"bufio: internal error"}
@ -44,11 +45,12 @@ func (b BufSizeError) String() string {
// Reader implements buffering for an io.Reader object.
type Reader struct {
buf []byte
rd io.Reader
r, w int
err os.Error
lastbyte int
buf []byte
rd io.Reader
r, w int
err os.Error
lastByte int
lastRuneSize int
}
// NewReaderSize creates a new Reader whose buffer has the specified size,
@ -67,7 +69,8 @@ func NewReaderSize(rd io.Reader, size int) (*Reader, os.Error) {
b = new(Reader)
b.buf = make([]byte, size)
b.rd = rd
b.lastbyte = -1
b.lastByte = -1
b.lastRuneSize = -1
return b, nil
}
@ -141,7 +144,8 @@ func (b *Reader) Read(p []byte) (nn int, err os.Error) {
// Read directly into p to avoid copy.
n, b.err = b.rd.Read(p)
if n > 0 {
b.lastbyte = int(p[n-1])
b.lastByte = int(p[n-1])
b.lastRuneSize = -1
}
p = p[n:]
nn += n
@ -156,7 +160,8 @@ func (b *Reader) Read(p []byte) (nn int, err os.Error) {
copy(p[0:n], b.buf[b.r:])
p = p[n:]
b.r += n
b.lastbyte = int(b.buf[b.r-1])
b.lastByte = int(b.buf[b.r-1])
b.lastRuneSize = -1
nn += n
}
return nn, nil
@ -165,6 +170,7 @@ func (b *Reader) Read(p []byte) (nn int, err os.Error) {
// ReadByte reads and returns a single byte.
// If no byte is available, returns an error.
func (b *Reader) ReadByte() (c byte, err os.Error) {
b.lastRuneSize = -1
for b.w == b.r {
if b.err != nil {
return 0, b.err
@ -173,24 +179,25 @@ func (b *Reader) ReadByte() (c byte, err os.Error) {
}
c = b.buf[b.r]
b.r++
b.lastbyte = int(c)
b.lastByte = int(c)
return c, nil
}
// UnreadByte unreads the last byte. Only the most recently read byte can be unread.
func (b *Reader) UnreadByte() os.Error {
if b.r == b.w && b.lastbyte >= 0 {
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
b.buf[0] = byte(b.lastByte)
b.lastByte = -1
return nil
}
if b.r <= 0 {
return ErrInvalidUnreadByte
}
b.r--
b.lastbyte = -1
b.lastByte = -1
return nil
}
@ -208,10 +215,25 @@ func (b *Reader) ReadRune() (rune int, size int, err os.Error) {
rune, size = utf8.DecodeRune(b.buf[b.r:b.w])
}
b.r += size
b.lastbyte = int(b.buf[b.r-1])
b.lastByte = int(b.buf[b.r-1])
b.lastRuneSize = size
return rune, size, nil
}
// UnreadRune unreads the last rune. If the most recent read operation on
// the buffer was not a ReadRune, UnreadRune returns an error. (In this
// regard it is stricter than UnreadByte, which will unread the last byte
// from any read operation.)
func (b *Reader) UnreadRune() os.Error {
if b.lastRuneSize < 0 {
return ErrInvalidUnreadRune
}
b.r -= b.lastRuneSize
b.lastByte = -1
b.lastRuneSize = -1
return nil
}
// Buffered returns the number of bytes that can be read from the current buffer.
func (b *Reader) Buffered() int { return b.w - b.r }

93
src/pkg/bufio/bufio_test.go
View File

@ -226,6 +226,99 @@ func TestReadRune(t *testing.T) {
}
}
func TestUnreadRune(t *testing.T) {
got := ""
segments := []string{"Hello, world:", "日本語"}
data := strings.Join(segments, "")
r := NewReader(&StringReader{data: segments})
// Normal execution.
for {
rune, _, err := r.ReadRune()
if err != nil {
if err != os.EOF {
t.Error("unexpected EOF")
}
break
}
got += string(rune)
// Put it back and read it again
if err = r.UnreadRune(); err != nil {
t.Error("unexpected error on UnreadRune:", err)
}
rune1, _, err := r.ReadRune()
if err != nil {
t.Error("unexpected error reading after unreading:", err)
}
if rune != rune1 {
t.Error("incorrect rune after unread: got %c wanted %c", rune1, rune)
}
}
if got != data {
t.Errorf("want=%q got=%q", data, got)
}
}
// Test that UnreadRune fails if the preceding operation was not a ReadRune.
func TestUnreadRuneError(t *testing.T) {
buf := make([]byte, 3) // All runes in this test are 3 bytes long
r := NewReader(&StringReader{data: []string{"日本語日本語日本語"}})
if r.UnreadRune() == nil {
t.Error("expected error on UnreadRune from fresh buffer")
}
_, _, err := r.ReadRune()
if err != nil {
t.Error("unexpected error on ReadRune (1):", err)
}
if err = r.UnreadRune(); err != nil {
t.Error("unexpected error on UnreadRune (1):", err)
}
if r.UnreadRune() == nil {
t.Error("expected error after UnreadRune (1)")
}
// Test error after Read.
_, _, err = r.ReadRune() // reset state
if err != nil {
t.Error("unexpected error on ReadRune (2):", err)
}
_, err = r.Read(buf)
if err != nil {
t.Error("unexpected error on Read (2):", err)
}
if r.UnreadRune() == nil {
t.Error("expected error after Read (2)")
}
// Test error after ReadByte.
_, _, err = r.ReadRune() // reset state
if err != nil {
t.Error("unexpected error on ReadRune (2):", err)
}
for _ = range buf {
_, err = r.ReadByte()
if err != nil {
t.Error("unexpected error on ReadByte (2):", err)
}
}
if r.UnreadRune() == nil {
t.Error("expected error after ReadByte")
}
// Test error after UnreadByte.
_, _, err = r.ReadRune() // reset state
if err != nil {
t.Error("unexpected error on ReadRune (3):", err)
}
_, err = r.ReadByte()
if err != nil {
t.Error("unexpected error on ReadByte (3):", err)
}
err = r.UnreadByte()
if err != nil {
t.Error("unexpected error on UnreadByte (3):", err)
}
if r.UnreadRune() == nil {
t.Error("expected error after UnreadByte (3)")
}
}
func TestReadWriteRune(t *testing.T) {
const NRune = 1000
byteBuf := new(bytes.Buffer)