strings: add ReadRune to Reader
R=rsc
CC=golang-dev
https://golang.org/cl/940041
diff --git a/src/pkg/strings/reader.go b/src/pkg/strings/reader.go
index 7cefbd2..914faa0 100644
--- a/src/pkg/strings/reader.go
+++ b/src/pkg/strings/reader.go
@@ -4,9 +4,12 @@
package strings
-import "os"
+import (
+ "os"
+ "utf8"
+)
-// A Reader satisfies calls to Read and ReadByte by
+// A Reader satisfies calls to Read, ReadByte, and ReadRune by
// reading from a string.
type Reader string
@@ -33,6 +36,26 @@
return
}
+// ReadRune reads and returns the next UTF-8-encoded
+// Unicode code point from the buffer.
+// If no bytes are available, the error returned is os.EOF.
+// If the bytes are an erroneous UTF-8 encoding, it
+// consumes one byte and returns U+FFFD, 1.
+func (r *Reader) ReadRune() (rune int, size int, err os.Error) {
+ s := *r
+ if len(s) == 0 {
+ return 0, 0, os.EOF
+ }
+ c := s[0]
+ if c < utf8.RuneSelf {
+ *r = s[1:]
+ return int(c), 1, nil
+ }
+ rune, size = utf8.DecodeRuneInString(string(s))
+ *r = s[size:]
+ return
+}
+
// NewReader returns a new Reader reading from s.
// It is similar to bytes.NewBufferString but more efficient and read-only.
func NewReader(s string) *Reader { return (*Reader)(&s) }
