1 files changed, 11 insertions, 8 deletions
diff --git a/native/jni/src/char_utils.h b/native/jni/src/char_utils.h
index 607dc5195..b30677fa7 100644
--- a/native/jni/src/char_utils.h
+++ b/native/jni/src/char_utils.h
@@ -17,21 +17,23 @@
 #ifndef LATINIME_CHAR_UTILS_H
 #define LATINIME_CHAR_UTILS_H
 
+#include <cctype>
+
 namespace latinime {
 
-inline static int isAsciiUpper(unsigned short c) {
-    return c >= 'A' && c <= 'Z';
+inline static bool isAsciiUpper(unsigned short c) {
+    return isupper(static_cast<int>(c)) != 0;
 }
 
 inline static unsigned short toAsciiLower(unsigned short c) {
     return c - 'A' + 'a';
 }
 
-inline static int isAscii(unsigned short c) {
-    return c <= 127;
+inline static bool isAscii(unsigned short c) {
+    return isascii(static_cast<int>(c)) != 0;
 }
 
-unsigned short latin_tolower(unsigned short c);
+unsigned short latin_tolower(const unsigned short c);
 
 /**
  * Table mapping most combined Latin, Greek, and Cyrillic characters
@@ -50,8 +52,7 @@ inline static unsigned short toBaseChar(unsigned short c) {
     return c;
 }
 
-inline static unsigned short toBaseLowerCase(unsigned short c) {
-    c = toBaseChar(c);
+inline static unsigned short toLowerCase(const unsigned short c) {
     if (isAsciiUpper(c)) {
         return toAsciiLower(c);
     } else if (isAscii(c)) {
@@ -60,6 +61,8 @@ inline static unsigned short toBaseLowerCase(unsigned short c) {
     return latin_tolower(c);
 }
 
+inline static unsigned short toBaseLowerCase(const unsigned short c) {
+    return toLowerCase(toBaseChar(c));
+}
 } // namespace latinime
-
 #endif // LATINIME_CHAR_UTILS_H