Cleanup and move char functions to the `char_utils.h` header.

12 files changed, 148 insertions, 96 deletions

diff --git a/core/io/http_client_tcp.cpp b/core/io/http_client_tcp.cpp
index e61833ce7c..f920799677 100644
--- a/core/io/http_client_tcp.cpp
+++ b/core/io/http_client_tcp.cpp
@@ -614,7 +614,7 @@ PackedByteArray HTTPClientTCP::read_response_body_chunk() {
 					for (int i = 0; i < chunk.size() - 2; i++) {
 						char c = chunk[i];
 						int v = 0;
-						if (c >= '0' && c <= '9') {
+						if (is_digit(c)) {
 							v = c - '0';
 						} else if (c >= 'a' && c <= 'f') {
 							v = c - 'a' + 10;
diff --git a/core/io/image.cpp b/core/io/image.cpp
index 9df2b6835c..4f72599faf 100644
--- a/core/io/image.cpp
+++ b/core/io/image.cpp
@@ -2056,7 +2056,7 @@ void Image::create(const char **p_xpm) {
 						for (int i = 0; i < 6; i++) {
 							char v = line_ptr[i];
 
-							if (v >= '0' && v <= '9') {
+							if (is_digit(v)) {
 								v -= '0';
 							} else if (v >= 'A' && v <= 'F') {
 								v = (v - 'A') + 10;
diff --git a/core/io/ip_address.cpp b/core/io/ip_address.cpp
index 38f99a08a4..d183c60798 100644
--- a/core/io/ip_address.cpp
+++ b/core/io/ip_address.cpp
@@ -71,7 +71,7 @@ static void _parse_hex(const String &p_string, int p_start, uint8_t *p_dst) {
 
 		int n = 0;
 		char32_t c = p_string[i];
-		if (c >= '0' && c <= '9') {
+		if (is_digit(c)) {
 			n = c - '0';
 		} else if (c >= 'a' && c <= 'f') {
 			n = 10 + (c - 'a');
@@ -113,7 +113,7 @@ void IPAddress::_parse_ipv6(const String &p_string) {
 		} else if (c == '.') {
 			part_ipv4 = true;
 
-		} else if ((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F')) {
+		} else if (is_hex_digit(c)) {
 			if (!part_found) {
 				parts[parts_idx++] = i;
 				part_found = true;
diff --git a/core/io/json.cpp b/core/io/json.cpp
index 7b642f6a59..4b745dff44 100644
--- a/core/io/json.cpp
+++ b/core/io/json.cpp
@@ -229,12 +229,12 @@ Error JSON::_get_token(const char32_t *p_str, int &index, int p_len, Token &r_to
 										r_err_str = "Unterminated String";
 										return ERR_PARSE_ERROR;
 									}
-									if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'))) {
+									if (!is_hex_digit(c)) {
 										r_err_str = "Malformed hex constant in string";
 										return ERR_PARSE_ERROR;
 									}
 									char32_t v;
-									if (c >= '0' && c <= '9') {
+									if (is_digit(c)) {
 										v = c - '0';
 									} else if (c >= 'a' && c <= 'f') {
 										v = c - 'a';
@@ -265,12 +265,12 @@ Error JSON::_get_token(const char32_t *p_str, int &index, int p_len, Token &r_to
 											r_err_str = "Unterminated String";
 											return ERR_PARSE_ERROR;
 										}
-										if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'))) {
+										if (!is_hex_digit(c)) {
 											r_err_str = "Malformed hex constant in string";
 											return ERR_PARSE_ERROR;
 										}
 										char32_t v;
-										if (c >= '0' && c <= '9') {
+										if (is_digit(c)) {
 											v = c - '0';
 										} else if (c >= 'a' && c <= 'f') {
 											v = c - 'a';
@@ -326,7 +326,7 @@ Error JSON::_get_token(const char32_t *p_str, int &index, int p_len, Token &r_to
 					break;
 				}
 
-				if (p_str[index] == '-' || (p_str[index] >= '0' && p_str[index] <= '9')) {
+				if (p_str[index] == '-' || is_digit(p_str[index])) {
 					//a number
 					const char32_t *rptr;
 					double number = String::to_float(&p_str[index], &rptr);
@@ -335,10 +335,10 @@ Error JSON::_get_token(const char32_t *p_str, int &index, int p_len, Token &r_to
 					r_token.value = number;
 					return OK;
 
-				} else if ((p_str[index] >= 'A' && p_str[index] <= 'Z') || (p_str[index] >= 'a' && p_str[index] <= 'z')) {
+				} else if (is_ascii_char(p_str[index])) {
 					String id;
 
-					while ((p_str[index] >= 'A' && p_str[index] <= 'Z') || (p_str[index] >= 'a' && p_str[index] <= 'z')) {
+					while (is_ascii_char(p_str[index])) {
 						id += p_str[index];
 						index++;
 					}
diff --git a/core/io/pck_packer.cpp b/core/io/pck_packer.cpp
index 221a680130..272ace3438 100644
--- a/core/io/pck_packer.cpp
+++ b/core/io/pck_packer.cpp
@@ -62,7 +62,7 @@ Error PCKPacker::pck_start(const String &p_file, int p_alignment, const String &
 		int v = 0;
 		if (i * 2 < _key.length()) {
 			char32_t ct = _key[i * 2];
-			if (ct >= '0' && ct <= '9') {
+			if (is_digit(ct)) {
 				ct = ct - '0';
 			} else if (ct >= 'a' && ct <= 'f') {
 				ct = 10 + ct - 'a';
@@ -72,7 +72,7 @@ Error PCKPacker::pck_start(const String &p_file, int p_alignment, const String &
 
 		if (i * 2 + 1 < _key.length()) {
 			char32_t ct = _key[i * 2 + 1];
-			if (ct >= '0' && ct <= '9') {
+			if (is_digit(ct)) {
 				ct = ct - '0';
 			} else if (ct >= 'a' && ct <= 'f') {
 				ct = 10 + ct - 'a';
diff --git a/core/io/resource_uid.cpp b/core/io/resource_uid.cpp
index 1a16d5b47a..776756e64e 100644
--- a/core/io/resource_uid.cpp
+++ b/core/io/resource_uid.cpp
@@ -71,9 +71,9 @@ ResourceUID::ID ResourceUID::text_to_id(const String &p_text) const {
 	for (uint32_t i = 6; i < l; i++) {
 		uid *= base;
 		uint32_t c = p_text[i];
-		if (c >= 'a' && c <= 'z') {
+		if (is_ascii_lower_case(c)) {
 			uid += c - 'a';
-		} else if (c >= '0' && c <= '9') {
+		} else if (is_digit(c)) {
 			uid += c - '0' + char_count;
 		} else {
 			return INVALID_ID;
diff --git a/core/math/expression.cpp b/core/math/expression.cpp
index 0bd8a0abb5..b447d09887 100644
--- a/core/math/expression.cpp
+++ b/core/math/expression.cpp
@@ -37,18 +37,6 @@
 #include "core/os/os.h"
 #include "core/variant/variant_parser.h"
 
-static bool _is_number(char32_t c) {
-	return (c >= '0' && c <= '9');
-}
-
-static bool _is_hex_digit(char32_t c) {
-	return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F');
-}
-
-static bool _is_binary_digit(char32_t c) {
-	return (c == '0' || c == '1');
-}
-
 Error Expression::_get_token(Token &r_token) {
 	while (true) {
 #define GET_CHAR() (str_ofs >= expression.length() ? 0 : expression[str_ofs++])
@@ -96,7 +84,7 @@ Error Expression::_get_token(Token &r_token) {
 				r_token.type = TK_INPUT;
 				int index = 0;
 				do {
-					if (!_is_number(expression[str_ofs])) {
+					if (!is_digit(expression[str_ofs])) {
 						_set_error("Expected number after '$'");
 						r_token.type = TK_ERROR;
 						return ERR_PARSE_ERROR;
@@ -105,7 +93,7 @@ Error Expression::_get_token(Token &r_token) {
 					index += expression[str_ofs] - '0';
 					str_ofs++;
 
-				} while (_is_number(expression[str_ofs]));
+				} while (is_digit(expression[str_ofs]));
 
 				r_token.value = index;
 				return OK;
@@ -255,13 +243,13 @@ Error Expression::_get_token(Token &r_token) {
 										r_token.type = TK_ERROR;
 										return ERR_PARSE_ERROR;
 									}
-									if (!(_is_number(c) || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'))) {
+									if (!is_hex_digit(c)) {
 										_set_error("Malformed hex constant in string");
 										r_token.type = TK_ERROR;
 										return ERR_PARSE_ERROR;
 									}
 									char32_t v;
-									if (_is_number(c)) {
+									if (is_digit(c)) {
 										v = c - '0';
 									} else if (c >= 'a' && c <= 'f') {
 										v = c - 'a';
@@ -336,7 +324,7 @@ Error Expression::_get_token(Token &r_token) {
 				}
 
 				char32_t next_char = (str_ofs >= expression.length()) ? 0 : expression[str_ofs];
-				if (_is_number(cchar) || (cchar == '.' && _is_number(next_char))) {
+				if (is_digit(cchar) || (cchar == '.' && is_digit(next_char))) {
 					//a number
 
 					String num;
@@ -360,7 +348,7 @@ Error Expression::_get_token(Token &r_token) {
 					while (true) {
 						switch (reading) {
 							case READING_INT: {
-								if (_is_number(c)) {
+								if (is_digit(c)) {
 									if (is_first_char && c == '0') {
 										if (next_char == 'b') {
 											reading = READING_BIN;
@@ -379,7 +367,7 @@ Error Expression::_get_token(Token &r_token) {
 
 							} break;
 							case READING_BIN: {
-								if (bin_beg && !_is_binary_digit(c)) {
+								if (bin_beg && !is_binary_digit(c)) {
 									reading = READING_DONE;
 								} else if (c == 'b') {
 									bin_beg = true;
@@ -387,7 +375,7 @@ Error Expression::_get_token(Token &r_token) {
 
 							} break;
 							case READING_HEX: {
-								if (hex_beg && !_is_hex_digit(c)) {
+								if (hex_beg && !is_hex_digit(c)) {
 									reading = READING_DONE;
 								} else if (c == 'x') {
 									hex_beg = true;
@@ -395,7 +383,7 @@ Error Expression::_get_token(Token &r_token) {
 
 							} break;
 							case READING_DEC: {
-								if (_is_number(c)) {
+								if (is_digit(c)) {
 								} else if (c == 'e') {
 									reading = READING_EXP;
 
@@ -405,7 +393,7 @@ Error Expression::_get_token(Token &r_token) {
 
 							} break;
 							case READING_EXP: {
-								if (_is_number(c)) {
+								if (is_digit(c)) {
 									exp_beg = true;
 
 								} else if ((c == '-' || c == '+') && !exp_sign && !exp_beg) {
@@ -443,11 +431,11 @@ Error Expression::_get_token(Token &r_token) {
 					}
 					return OK;
 
-				} else if ((cchar >= 'A' && cchar <= 'Z') || (cchar >= 'a' && cchar <= 'z') || cchar == '_') {
+				} else if (is_ascii_char(cchar) || is_underscore(cchar)) {
 					String id;
 					bool first = true;
 
-					while ((cchar >= 'A' && cchar <= 'Z') || (cchar >= 'a' && cchar <= 'z') || cchar == '_' || (!first && _is_number(cchar))) {
+					while (is_ascii_char(cchar) || is_underscore(cchar) || (!first && is_digit(cchar))) {
 						id += String::chr(cchar);
 						cchar = GET_CHAR();
 						first = false;
diff --git a/core/string/char_utils.h b/core/string/char_utils.h
new file mode 100644
index 0000000000..0afd058f01
--- /dev/null
+++ b/core/string/char_utils.h
@@ -0,0 +1,92 @@
+/*************************************************************************/
+/*  char_utils.h                                                         */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef CHAR_UTILS_H
+#define CHAR_UTILS_H
+
+#include "core/typedefs.h"
+
+static _FORCE_INLINE_ bool is_ascii_upper_case(char32_t c) {
+	return (c >= 'A' && c <= 'Z');
+}
+
+static _FORCE_INLINE_ bool is_ascii_lower_case(char32_t c) {
+	return (c >= 'a' && c <= 'z');
+}
+
+static _FORCE_INLINE_ bool is_digit(char32_t c) {
+	return (c >= '0' && c <= '9');
+}
+
+static _FORCE_INLINE_ bool is_hex_digit(char32_t c) {
+	return (is_digit(c) || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'));
+}
+
+static _FORCE_INLINE_ bool is_binary_digit(char32_t c) {
+	return (c == '0' || c == '1');
+}
+
+static _FORCE_INLINE_ bool is_ascii_char(char32_t c) {
+	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
+}
+
+static _FORCE_INLINE_ bool is_ascii_alphanumeric_char(char32_t c) {
+	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9');
+}
+
+static _FORCE_INLINE_ bool is_ascii_identifier_char(char32_t c) {
+	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '_';
+}
+
+static _FORCE_INLINE_ bool is_symbol(char32_t c) {
+	return c != '_' && ((c >= '!' && c <= '/') || (c >= ':' && c <= '@') || (c >= '[' && c <= '`') || (c >= '{' && c <= '~') || c == '\t' || c == ' ');
+}
+
+static _FORCE_INLINE_ bool is_control(char32_t p_char) {
+	return (p_char <= 0x001f) || (p_char >= 0x007f && p_char <= 0x009f);
+}
+
+static _FORCE_INLINE_ bool is_whitespace(char32_t p_char) {
+	return (p_char == ' ') || (p_char == 0x00a0) || (p_char == 0x1680) || (p_char >= 0x2000 && p_char <= 0x200a) || (p_char == 0x202f) || (p_char == 0x205f) || (p_char == 0x3000) || (p_char == 0x2028) || (p_char == 0x2029) || (p_char >= 0x0009 && p_char <= 0x000d) || (p_char == 0x0085);
+}
+
+static _FORCE_INLINE_ bool is_linebreak(char32_t p_char) {
+	return (p_char >= 0x000a && p_char <= 0x000d) || (p_char == 0x0085) || (p_char == 0x2028) || (p_char == 0x2029);
+}
+
+static _FORCE_INLINE_ bool is_punct(char32_t p_char) {
+	return (p_char >= ' ' && p_char <= '/') || (p_char >= ':' && p_char <= '@') || (p_char >= '[' && p_char <= '^') || (p_char == '`') || (p_char >= '{' && p_char <= '~') || (p_char >= 0x2000 && p_char <= 0x206f) || (p_char >= 0x3000 && p_char <= 0x303f);
+}
+
+static _FORCE_INLINE_ bool is_underscore(char32_t p_char) {
+	return (p_char == '_');
+}
+
+#endif // CHAR_UTILS_H
diff --git a/core/string/translation.cpp b/core/string/translation.cpp
index 355ee238e8..7cc41df9ef 100644
--- a/core/string/translation.cpp
+++ b/core/string/translation.cpp
@@ -213,14 +213,6 @@ static _character_accent_pair _character_to_accented[] = {
 	{ 'z', U"ź" },
 };
 
-static _FORCE_INLINE_ bool is_upper_case(char32_t c) {
-	return (c >= 'A' && c <= 'Z');
-}
-
-static _FORCE_INLINE_ bool is_lower_case(char32_t c) {
-	return (c >= 'a' && c <= 'z');
-}
-
 Vector<TranslationServer::LocaleScriptInfo> TranslationServer::locale_script_info;
 
 Map<String, String> TranslationServer::language_map;
@@ -309,15 +301,15 @@ String TranslationServer::standardize_locale(const String &p_locale) const {
 	Vector<String> locale_elements = univ_locale.get_slice("@", 0).split("_");
 	lang = locale_elements[0];
 	if (locale_elements.size() >= 2) {
-		if (locale_elements[1].length() == 4 && is_upper_case(locale_elements[1][0]) && is_lower_case(locale_elements[1][1]) && is_lower_case(locale_elements[1][2]) && is_lower_case(locale_elements[1][3])) {
+		if (locale_elements[1].length() == 4 && is_ascii_upper_case(locale_elements[1][0]) && is_ascii_lower_case(locale_elements[1][1]) && is_ascii_lower_case(locale_elements[1][2]) && is_ascii_lower_case(locale_elements[1][3])) {
 			script = locale_elements[1];
 		}
-		if (locale_elements[1].length() == 2 && is_upper_case(locale_elements[1][0]) && is_upper_case(locale_elements[1][1])) {
+		if (locale_elements[1].length() == 2 && is_ascii_upper_case(locale_elements[1][0]) && is_ascii_upper_case(locale_elements[1][1])) {
 			country = locale_elements[1];
 		}
 	}
 	if (locale_elements.size() >= 3) {
-		if (locale_elements[2].length() == 2 && is_upper_case(locale_elements[2][0]) && is_upper_case(locale_elements[2][1])) {
+		if (locale_elements[2].length() == 2 && is_ascii_upper_case(locale_elements[2][0]) && is_ascii_upper_case(locale_elements[2][1])) {
 			country = locale_elements[2];
 		} else if (variant_map.has(locale_elements[2].to_lower()) && variant_map[locale_elements[2].to_lower()] == lang) {
 			variant = locale_elements[2].to_lower();
@@ -434,15 +426,15 @@ String TranslationServer::get_locale_name(const String &p_locale) const {
 	Vector<String> locale_elements = locale.split("_");
 	lang = locale_elements[0];
 	if (locale_elements.size() >= 2) {
-		if (locale_elements[1].length() == 4 && is_upper_case(locale_elements[1][0]) && is_lower_case(locale_elements[1][1]) && is_lower_case(locale_elements[1][2]) && is_lower_case(locale_elements[1][3])) {
+		if (locale_elements[1].length() == 4 && is_ascii_upper_case(locale_elements[1][0]) && is_ascii_lower_case(locale_elements[1][1]) && is_ascii_lower_case(locale_elements[1][2]) && is_ascii_lower_case(locale_elements[1][3])) {
 			script = locale_elements[1];
 		}
-		if (locale_elements[1].length() == 2 && is_upper_case(locale_elements[1][0]) && is_upper_case(locale_elements[1][1])) {
+		if (locale_elements[1].length() == 2 && is_ascii_upper_case(locale_elements[1][0]) && is_ascii_upper_case(locale_elements[1][1])) {
 			country = locale_elements[1];
 		}
 	}
 	if (locale_elements.size() >= 3) {
-		if (locale_elements[2].length() == 2 && is_upper_case(locale_elements[2][0]) && is_upper_case(locale_elements[2][1])) {
+		if (locale_elements[2].length() == 2 && is_ascii_upper_case(locale_elements[2][0]) && is_ascii_upper_case(locale_elements[2][1])) {
 			country = locale_elements[2];
 		}
 	}
@@ -911,7 +903,7 @@ String TranslationServer::add_padding(String &p_message, int p_length) const {
 }
 
 const char32_t *TranslationServer::get_accented_version(char32_t p_character) const {
-	if (!((p_character >= 'a' && p_character <= 'z') || (p_character >= 'A' && p_character <= 'Z'))) {
+	if (!is_ascii_char(p_character)) {
 		return nullptr;
 	}
 
diff --git a/core/string/ustring.cpp b/core/string/ustring.cpp
index 6e0a7c7022..c4edc8c086 100644
--- a/core/string/ustring.cpp
+++ b/core/string/ustring.cpp
@@ -54,34 +54,14 @@
 
 static const int MAX_DECIMALS = 32;
 
-static _FORCE_INLINE_ bool is_digit(char32_t c) {
-	return (c >= '0' && c <= '9');
-}
-
-static _FORCE_INLINE_ bool is_hex_digit(char32_t c) {
-	return (is_digit(c) || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'));
-}
-
-static _FORCE_INLINE_ bool is_upper_case(char32_t c) {
-	return (c >= 'A' && c <= 'Z');
-}
-
-static _FORCE_INLINE_ bool is_lower_case(char32_t c) {
-	return (c >= 'a' && c <= 'z');
-}
-
 static _FORCE_INLINE_ char32_t lower_case(char32_t c) {
-	return (is_upper_case(c) ? (c + ('a' - 'A')) : c);
+	return (is_ascii_upper_case(c) ? (c + ('a' - 'A')) : c);
 }
 
 const char CharString::_null = 0;
 const char16_t Char16String::_null = 0;
 const char32_t String::_null = 0;
 
-bool is_symbol(char32_t c) {
-	return c != '_' && ((c >= '!' && c <= '/') || (c >= ':' && c <= '@') || (c >= '[' && c <= '`') || (c >= '{' && c <= '~') || c == '\t' || c == ' ');
-}
-
 bool select_word(const String &p_s, int p_col, int &r_beg, int &r_end) {
 	const String &s = p_s;
 	int beg = CLAMP(p_col, 0, s.length());
@@ -974,21 +954,21 @@ String String::camelcase_to_underscore(bool lowercase) const {
 	int start_index = 0;
 
 	for (int i = 1; i < this->size(); i++) {
-		bool is_upper = is_upper_case(cstr[i]);
+		bool is_upper = is_ascii_upper_case(cstr[i]);
 		bool is_number = is_digit(cstr[i]);
 
 		bool are_next_2_lower = false;
 		bool is_next_lower = false;
 		bool is_next_number = false;
-		bool was_precedent_upper = is_upper_case(cstr[i - 1]);
+		bool was_precedent_upper = is_ascii_upper_case(cstr[i - 1]);
 		bool was_precedent_number = is_digit(cstr[i - 1]);
 
 		if (i + 2 < this->size()) {
-			are_next_2_lower = is_lower_case(cstr[i + 1]) && is_lower_case(cstr[i + 2]);
+			are_next_2_lower = is_ascii_lower_case(cstr[i + 1]) && is_ascii_lower_case(cstr[i + 2]);
 		}
 
 		if (i + 1 < this->size()) {
-			is_next_lower = is_lower_case(cstr[i + 1]);
+			is_next_lower = is_ascii_lower_case(cstr[i + 1]);
 			is_next_number = is_digit(cstr[i + 1]);
 		}
 
@@ -2212,7 +2192,7 @@ bool String::is_numeric() const {
 				return false;
 			}
 			dot = true;
-		} else if (c < '0' || c > '9') {
+		} else if (!is_digit(c)) {
 			return false;
 		}
 	}
@@ -3691,7 +3671,7 @@ bool String::is_valid_identifier() const {
 			}
 		}
 
-		bool valid_char = is_digit(str[i]) || is_lower_case(str[i]) || is_upper_case(str[i]) || str[i] == '_';
+		bool valid_char = is_ascii_identifier_char(str[i]);
 
 		if (!valid_char) {
 			return false;
@@ -3716,7 +3696,7 @@ String String::uri_encode() const {
 	String res;
 	for (int i = 0; i < temp.length(); ++i) {
 		char ord = temp[i];
-		if (ord == '.' || ord == '-' || ord == '_' || ord == '~' || is_lower_case(ord) || is_upper_case(ord) || is_digit(ord)) {
+		if (ord == '.' || ord == '-' || ord == '~' || is_ascii_identifier_char(ord)) {
 			res += ord;
 		} else {
 			char h_Val[3];
@@ -3738,9 +3718,9 @@ String String::uri_decode() const {
 	for (int i = 0; i < src.length(); ++i) {
 		if (src[i] == '%' && i + 2 < src.length()) {
 			char ord1 = src[i + 1];
-			if (is_digit(ord1) || is_upper_case(ord1)) {
+			if (is_digit(ord1) || is_ascii_upper_case(ord1)) {
 				char ord2 = src[i + 2];
-				if (is_digit(ord2) || is_upper_case(ord2)) {
+				if (is_digit(ord2) || is_ascii_upper_case(ord2)) {
 					char bytes[3] = { (char)ord1, (char)ord2, 0 };
 					res += (char)strtol(bytes, nullptr, 16);
 					i += 2;
@@ -3867,7 +3847,7 @@ static _FORCE_INLINE_ int _xml_unescape(const char32_t *p_src, int p_src_len, ch
 					for (int i = 2; i < p_src_len; i++) {
 						eat = i + 1;
 						char32_t ct = p_src[i];
-						if (ct == ';' || ct < '0' || ct > '9') {
+						if (ct == ';' || !is_digit(ct)) {
 							break;
 						}
 					}
@@ -3997,7 +3977,7 @@ String String::pad_zeros(int p_digits) const {
 
 	int begin = 0;
 
-	while (begin < end && (s[begin] < '0' || s[begin] > '9')) {
+	while (begin < end && !is_digit(s[begin])) {
 		begin++;
 	}
 
@@ -4042,7 +4022,7 @@ bool String::is_valid_int() const {
 	}
 
 	for (int i = from; i < len; i++) {
-		if (operator[](i) < '0' || operator[](i) > '9') {
+		if (!is_digit(operator[](i))) {
 			return false; // no start with number plz
 		}
 	}
diff --git a/core/string/ustring.h b/core/string/ustring.h
index b685e3929f..1d302b65a7 100644
--- a/core/string/ustring.h
+++ b/core/string/ustring.h
@@ -32,6 +32,7 @@
 #define USTRING_GODOT_H
 // Note: Renamed to avoid conflict with ICU header with the same name.
 
+#include "core/string/char_utils.h"
 #include "core/templates/cowdata.h"
 #include "core/templates/vector.h"
 #include "core/typedefs.h"
@@ -533,7 +534,6 @@ String DTRN(const String &p_text, const String &p_text_plural, int p_n, const St
 String RTR(const String &p_text, const String &p_context = "");
 String RTRN(const String &p_text, const String &p_text_plural, int p_n, const String &p_context = "");
 
-bool is_symbol(char32_t c);
 bool select_word(const String &p_s, int p_col, int &r_beg, int &r_end);
 
 _FORCE_INLINE_ void sarray_add_str(Vector<String> &arr) {
diff --git a/core/variant/variant_parser.cpp b/core/variant/variant_parser.cpp
index 55fc9212b7..e889a1bb40 100644
--- a/core/variant/variant_parser.cpp
+++ b/core/variant/variant_parser.cpp
@@ -188,7 +188,7 @@ Error VariantParser::get_token(Stream *p_stream, Token &r_token, int &line, Stri
 					if (p_stream->is_eof()) {
 						r_token.type = TK_EOF;
 						return OK;
-					} else if ((ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f') || (ch >= 'A' && ch <= 'F')) {
+					} else if (is_hex_digit(ch)) {
 						color_str += ch;
 
 					} else {
@@ -265,13 +265,13 @@ Error VariantParser::get_token(Stream *p_stream, Token &r_token, int &line, Stri
 										r_token.type = TK_ERROR;
 										return ERR_PARSE_ERROR;
 									}
-									if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'))) {
+									if (!is_hex_digit(c)) {
 										r_err_str = "Malformed hex constant in string";
 										r_token.type = TK_ERROR;
 										return ERR_PARSE_ERROR;
 									}
 									char32_t v;
-									if (c >= '0' && c <= '9') {
+									if (is_digit(c)) {
 										v = c - '0';
 									} else if (c >= 'a' && c <= 'f') {
 										v = c - 'a';
@@ -381,7 +381,7 @@ Error VariantParser::get_token(Stream *p_stream, Token &r_token, int &line, Stri
 					while (true) {
 						switch (reading) {
 							case READING_INT: {
-								if (c >= '0' && c <= '9') {
+								if (is_digit(c)) {
 									//pass
 								} else if (c == '.') {
 									reading = READING_DEC;
@@ -395,7 +395,7 @@ Error VariantParser::get_token(Stream *p_stream, Token &r_token, int &line, Stri
 
 							} break;
 							case READING_DEC: {
-								if (c >= '0' && c <= '9') {
+								if (is_digit(c)) {
 								} else if (c == 'e') {
 									reading = READING_EXP;
 								} else {
@@ -404,7 +404,7 @@ Error VariantParser::get_token(Stream *p_stream, Token &r_token, int &line, Stri
 
 							} break;
 							case READING_EXP: {
-								if (c >= '0' && c <= '9') {
+								if (is_digit(c)) {
 									exp_beg = true;
 
 								} else if ((c == '-' || c == '+') && !exp_sign && !exp_beg) {
@@ -433,11 +433,11 @@ Error VariantParser::get_token(Stream *p_stream, Token &r_token, int &line, Stri
 						r_token.value = num.as_int();
 					}
 					return OK;
-				} else if ((cchar >= 'A' && cchar <= 'Z') || (cchar >= 'a' && cchar <= 'z') || cchar == '_') {
+				} else if (is_ascii_char(cchar) || is_underscore(cchar)) {
 					StringBuffer<> id;
 					bool first = true;
 
-					while ((cchar >= 'A' && cchar <= 'Z') || (cchar >= 'a' && cchar <= 'z') || cchar == '_' || (!first && cchar >= '0' && cchar <= '9')) {
+					while (is_ascii_char(cchar) || is_underscore(cchar) || (!first && is_digit(cchar))) {
 						id += cchar;
 						cchar = p_stream->get_char();
 						first = false;