diff --git a/native/jni/src/bigram_dictionary.h b/native/jni/src/bigram_dictionary.h
index d676cca63..5f11ae822 100644
--- a/native/jni/src/bigram_dictionary.h
+++ b/native/jni/src/bigram_dictionary.h
@@ -29,8 +29,6 @@ class BigramDictionary {
     BigramDictionary(const unsigned char *dict, int maxWordLength, int maxPredictions);
     int getBigrams(const int32_t *word, int length, int *inputCodes, int codesSize,
             unsigned short *outWords, int *frequencies, int *outputTypes) const;
-    int getBigramListPositionForWord(const int32_t *prevWord, const int prevWordLength,
-            const bool forceLowerCaseSearch) const;
     void fillBigramAddressToFrequencyMapAndFilter(const int32_t *prevWord, const int prevWordLength,
             std::map<int, int> *map, uint8_t *filter) const;
     bool isValidBigram(const int32_t *word1, int length1, const int32_t *word2, int length2) const;
@@ -45,6 +43,8 @@ class BigramDictionary {
     bool getFirstBitOfByte(int *pos) { return (DICT[*pos] & 0x80) > 0; }
     bool getSecondBitOfByte(int *pos) { return (DICT[*pos] & 0x40) > 0; }
     bool checkFirstCharacter(unsigned short *word, int *inputCodes) const;
+    int getBigramListPositionForWord(const int32_t *prevWord, const int prevWordLength,
+            const bool forceLowerCaseSearch) const;
 
     const unsigned char *DICT;
     const int MAX_WORD_LENGTH;
diff --git a/native/jni/src/binary_format.h b/native/jni/src/binary_format.h
index 4cabc8404..d8f3e83dd 100644
--- a/native/jni/src/binary_format.h
+++ b/native/jni/src/binary_format.h
@@ -61,13 +61,6 @@ class BinaryFormat {
     static const int FLAG_ATTRIBUTE_ADDRESS_TYPE_TWOBYTES = 0x20;
     static const int FLAG_ATTRIBUTE_ADDRESS_TYPE_THREEBYTES = 0x30;
 
- private:
-    DISALLOW_IMPLICIT_CONSTRUCTORS(BinaryFormat);
-    const static int32_t MINIMAL_ONE_BYTE_CHARACTER_VALUE = 0x20;
-    const static int32_t CHARACTER_ARRAY_TERMINATOR = 0x1F;
-    const static int MULTIPLE_BYTE_CHARACTER_ADDITIONAL_SIZE = 2;
-
- public:
     const static int UNKNOWN_FORMAT = -1;
     // Originally, format version 1 had a 16-bit magic number, then the version number `01'
     // then options that must be 0. Hence the first 32-bits of the format are always as follow
@@ -94,7 +87,6 @@ class BinaryFormat {
     static int skipFrequency(const uint8_t flags, const int pos);
     static int skipShortcuts(const uint8_t *const dict, const uint8_t flags, const int pos);
     static int skipBigrams(const uint8_t *const dict, const uint8_t flags, const int pos);
-    static int skipAllAttributes(const uint8_t *const dict, const uint8_t flags, const int pos);
     static int skipChildrenPosAndAttributes(const uint8_t *const dict, const uint8_t flags,
             const int pos);
     static int readChildrenPosition(const uint8_t *const dict, const uint8_t flags, const int pos);
@@ -118,6 +110,13 @@ class BinaryFormat {
         REQUIRES_FRENCH_LIGATURES_PROCESSING = 0x4
     };
     const static unsigned int NO_FLAGS = 0;
+
+ private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(BinaryFormat);
+    const static int32_t MINIMAL_ONE_BYTE_CHARACTER_VALUE = 0x20;
+    const static int32_t CHARACTER_ARRAY_TERMINATOR = 0x1F;
+    const static int MULTIPLE_BYTE_CHARACTER_ADDITIONAL_SIZE = 2;
+    static int skipAllAttributes(const uint8_t *const dict, const uint8_t flags, const int pos);
 };
 
 inline int BinaryFormat::detectFormat(const uint8_t *const dict) {
diff --git a/native/jni/src/char_utils.cpp b/native/jni/src/char_utils.cpp
index 223291f60..9d886da31 100644
--- a/native/jni/src/char_utils.cpp
+++ b/native/jni/src/char_utils.cpp
@@ -889,7 +889,7 @@ static int compare_pair_capital(const void *a, const void *b) {
             - static_cast<int>((static_cast<const struct LatinCapitalSmallPair *>(b))->capital);
 }
 
-unsigned short latin_tolower(unsigned short c) {
+unsigned short latin_tolower(const unsigned short c) {
     struct LatinCapitalSmallPair *p =
             static_cast<struct LatinCapitalSmallPair *>(bsearch(&c, SORTED_CHAR_MAP,
                     sizeof(SORTED_CHAR_MAP) / sizeof(SORTED_CHAR_MAP[0]),
diff --git a/native/jni/src/char_utils.h b/native/jni/src/char_utils.h
index edd96bbb0..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