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author | Brad Fitzpatrick <bradfitz@golang.org> | 2019-01-02 18:33:31 +0000 |
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committer | Brad Fitzpatrick <bradfitz@golang.org> | 2019-01-08 23:47:27 +0000 |
commit | 9473c044f1d492a6ba49ec695042dec4365d70ca (patch) | |
tree | cbe2424090b7c4ee2083e0b9ac2109166570c6dc | |
parent | 1d2e548b428373461e92c7490edb49fc39df0c85 (diff) | |
download | go-9473c044f1d492a6ba49ec695042dec4365d70ca.tar.gz go-9473c044f1d492a6ba49ec695042dec4365d70ca.zip |
bufio: document relationship between UnreadByte/UnreadRune and Peek
Fixes #29387
Change-Id: I2d9981f63ac16630ed39d6da6692c81396f4e9ea
Reviewed-on: https://go-review.googlesource.com/c/155930
Reviewed-by: Ian Lance Taylor <iant@golang.org>
-rw-r--r-- | src/bufio/bufio.go | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/src/bufio/bufio.go b/src/bufio/bufio.go index ffb278ad9e..0125d729d1 100644 --- a/src/bufio/bufio.go +++ b/src/bufio/bufio.go @@ -33,8 +33,8 @@ type Reader struct { rd io.Reader // reader provided by the client r, w int // buf read and write positions err error - lastByte int - lastRuneSize int + lastByte int // last byte read for UnreadByte; -1 means invalid + lastRuneSize int // size of last rune read for UnreadRune; -1 means invalid } const minReadBufferSize = 16 @@ -123,6 +123,9 @@ func (b *Reader) readErr() error { // being valid at the next read call. If Peek returns fewer than n bytes, it // also returns an error explaining why the read is short. The error is // ErrBufferFull if n is larger than b's buffer size. +// +// Calling Peek prevents a UnreadByte or UnreadRune call from succeeding +// until the next read operation. func (b *Reader) Peek(n int) ([]byte, error) { if n < 0 { return nil, ErrNegativeCount @@ -252,6 +255,10 @@ func (b *Reader) ReadByte() (byte, error) { } // UnreadByte unreads the last byte. Only the most recently read byte can be unread. +// +// UnreadByte returns an error if the most recent method called on the +// Reader was not a read operation. Notably, Peek is not considered a +// read operation. func (b *Reader) UnreadByte() error { if b.lastByte < 0 || b.r == 0 && b.w > 0 { return ErrInvalidUnreadByte @@ -290,8 +297,8 @@ func (b *Reader) ReadRune() (r rune, size int, err error) { return r, 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 +// UnreadRune unreads the last rune. If the most recent method called on +// the Reader 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() error { |