Merge pull request #115 from xushiwei/q

stringutil.Capitalize

Author: xushiwei

stringutil/string_test.go

@@ -22,6 +22,18 @@ import (
 	"testing"
 )
 
+func TestCapitalize(t *testing.T) {
+	if ret := Capitalize(""); ret != "" {
+		t.Fatal("Capitalize:", ret)
+	}
+	if ret := Capitalize("hello"); ret != "Hello" {
+		t.Fatal("Capitalize:", ret)
+	}
+	if ret := Capitalize("Hello"); ret != "Hello" {
+		t.Fatal("Capitalize:", ret)
+	}
+}
+
 func TestConcat(t *testing.T) {
 	if ret := Concat("1"); ret != "1" {
 		t.Fatal("Concat(1):", ret)

stringutil/transform.go

@@ -0,0 +1,35 @@
+/*
+Copyright 2025 Qiniu Limited (qiniu.com)
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package stringutil
+
+import (
+	"unicode"
+	"unicode/utf8"
+)
+
+// Capitalize returns a copy of the string str with the first letter mapped to
+// its upper case.
+func Capitalize(str string) string {
+	c, nc := utf8.DecodeRuneInString(str)
+	if unicode.IsUpper(c) || c == utf8.RuneError {
+		return str
+	}
+	ret := make([]byte, len(str))
+	nr := utf8.EncodeRune(ret, unicode.ToUpper(c))
+	ret = append(ret[:nr], str[nc:]...)
+	return String(ret)
+}