add util::length_utf8

src/util/stringutil.cpp

@@ -128,7 +128,7 @@ inline uint utf8_len(ubyte cp) {
     if ((cp & 0xF8) == 0xF0) {
         return 4;
     }
-    return 0;
+    throw std::runtime_error("utf8 decode error");
 }
 
 uint32_t util::decode_utf8(uint& size, const char* chr) {
@@ -156,6 +156,16 @@ size_t util::crop_utf8(std::string_view s, size_t maxSize) {
     return pos;
 }
 
+size_t util::length_utf8(std::string_view s) {
+    size_t length = 0;
+    size_t pos = 0;
+    while (pos < s.length()) {
+        pos += utf8_len(s[pos]);
+        length++;
+    }
+    return length;
+}
+
 template<class C>
 std::string xstr2str_utf8(const std::basic_string<C>& xs) {
     std::vector<char> chars;

src/util/stringutil.hpp

@@ -44,6 +44,11 @@ namespace util {
     /// @param maxSize max encoded string length after crop
     /// @return cropped string size (less or equal to maxSize)
     size_t crop_utf8(std::string_view s, size_t maxSize);
+
+    /// @brief Measure utf8-encoded string length
+    /// @param s source encoded string
+    /// @return unicode string length (number of codepoints)
+    size_t length_utf8(std::string_view s);
     
     bool is_integer(const std::string& text);
     bool is_integer(const std::wstring& text);