chore: initial commit

lib/character.c

@@ -0,0 +1,47 @@
+#include "character.h"
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include "string.h"
+
+void character_append(char* string, const char character) {
+  size_t length = string_get_length(string);
+  character_append_at(string, character, length);
+}
+
+void character_append_at(char* string, const char character, const size_t index) {
+  size_t length = string_get_length(string);
+  for (size_t index_string = length; index_string > index; index_string--) {
+    string[index_string] = string[index_string - 1];
+  }
+  string[index] = character;
+  string[length + 1] = '\0';
+}
+
+char character_to_upper(const char character) {
+  if (character >= 'a' && character <= 'z') {
+    return character + ('A' - 'a');
+  }
+  return character;
+}
+
+char character_to_lower(const char character) {
+  if (character >= 'A' && character <= 'Z') {
+    return character - ('A' - 'a');
+  }
+  return character;
+}
+
+bool character_get_is_digit(const char character) {
+  return character >= '0' && character <= '9';
+}
+
+unsigned char character_get_alphabet_position(const char character) {
+  const char letter = character_to_lower(character);
+  unsigned char position = 0;
+  if (letter >= 'a' && letter <= 'z') {
+    position = (letter - 'a') + 1;
+  }
+  return position;
+}