utf8: add Valid and ValidString
R=r, rsc, alex.brainman
CC=golang-dev
https://golang.org/cl/5234041
diff --git a/src/pkg/utf8/utf8.go b/src/pkg/utf8/utf8.go
index 8910e17..3cd919d 100644
--- a/src/pkg/utf8/utf8.go
+++ b/src/pkg/utf8/utf8.go
@@ -354,3 +354,40 @@
// an encoded rune. Second and subsequent bytes always have the top
// two bits set to 10.
func RuneStart(b byte) bool { return b&0xC0 != 0x80 }
+
+// Valid reports whether p consists entirely of valid UTF-8-encoded runes.
+func Valid(p []byte) bool {
+ i := 0
+ for i < len(p) {
+ if p[i] < RuneSelf {
+ i++
+ } else {
+ _, size := DecodeRune(p[i:])
+ if size == 1 {
+ // All valid runes of size of 1 (those
+ // below RuneSelf) were handled above.
+ // This must be a RuneError.
+ return false
+ }
+ i += size
+ }
+ }
+ return true
+}
+
+// ValidString reports whether s consists entirely of valid UTF-8-encoded runes.
+func ValidString(s string) bool {
+ for i, r := range s {
+ if r == RuneError {
+ // The RuneError value can be an error
+ // sentinel value (if it's size 1) or the same
+ // value encoded properly. Decode it to see if
+ // it's the 1 byte sentinel value.
+ _, size := DecodeRuneInString(s[i:])
+ if size == 1 {
+ return false
+ }
+ }
+ }
+ return true
+}
diff --git a/src/pkg/utf8/utf8_test.go b/src/pkg/utf8/utf8_test.go
index 7a1db93..6cbbebc 100644
--- a/src/pkg/utf8/utf8_test.go
+++ b/src/pkg/utf8/utf8_test.go
@@ -274,6 +274,35 @@
}
}
+type ValidTest struct {
+ in string
+ out bool
+}
+
+var validTests = []ValidTest{
+ {"", true},
+ {"a", true},
+ {"abc", true},
+ {"Ж", true},
+ {"ЖЖ", true},
+ {"брэд-ЛГТМ", true},
+ {"☺☻☹", true},
+ {string([]byte{66, 250}), false},
+ {string([]byte{66, 250, 67}), false},
+ {"a\uFFFDb", true},
+}
+
+func TestValid(t *testing.T) {
+ for i, tt := range validTests {
+ if Valid([]byte(tt.in)) != tt.out {
+ t.Errorf("%d. Valid(%q) = %v; want %v", i, tt.in, !tt.out, tt.out)
+ }
+ if ValidString(tt.in) != tt.out {
+ t.Errorf("%d. ValidString(%q) = %v; want %v", i, tt.in, !tt.out, tt.out)
+ }
+ }
+}
+
func BenchmarkRuneCountTenASCIIChars(b *testing.B) {
for i := 0; i < b.N; i++ {
RuneCountInString("0123456789")
