Add stringmanip package

stringmanip/strings.go

@@ -0,0 +1,17 @@
+package stringmanip
+
+// Substring provides a safe way to extract a substring from a UTF-8 string.
+// From this discussion:
+//   https://groups.google.com/d/msg/golang-nuts/cGq1Irv_5Vs/0SKoj49BsWQJ
+func Substring(s string, p, l int) string {
+	if p < 0 || l <= 0 {
+		return ""
+	}
+	c := []rune(s)
+	if p > len(c) {
+		return ""
+	} else if p+l > len(c) || p+l < p {
+		return string(c[p:])
+	}
+	return string(c[p : p+l])
+}