feat: add string concat

include/tstd/string.h

@@ -63,4 +63,13 @@ void str_to_upper(char* str);
  */
 void str_to_lower(char* str);
 
+/**
+ * @brief Concatenate two null-terminated strings into a newly allocated string.
+ * @param str1 First input string (must not be NULL).
+ * @param str2 Second input string (must not be NULL).
+ * @return Pointer to a newly allocated null-terminated string containing the concatenated result of str1 and str2.
+ *         Caller is responsible for freeing the allocated memory.
+ */
+char* str_concat(const char* str1, const char* str2);
+
 #endif //TSTD_STRING_H

string.c

@@ -98,4 +98,15 @@ void str_to_lower(char* str) {
             str[i] += 'a' - 'A';
         }
     }
+}
+
+char* str_concat(const char* str1, const char* str2) {
+    const size_t len1 = strlen(str1);
+    const size_t len2 = strlen(str2);
+
+    char* result = malloc(sizeof(char) * (len1 + len2 + 1));
+    memcpy(result, str1, len1);
+    memcpy(&result[len1], str2, len2);
+    result[len1 + len2] = '\0';
+    return result;
 }

test/test_main.c

@@ -94,6 +94,14 @@ int test_string_to_lower() {
     return 0;
 }
 
+int test_string_concat() {
+    char* test_str = str_concat("Hello", "World");
+    assert(strcmp(test_str, "HelloWorld") == 0);
+    free(test_str);
+
+    return 0;
+}
+
 int test_string_functions() {
     int result = 0;
 
@@ -103,6 +111,7 @@ int test_string_functions() {
     result += test_split_function_by_substring();
     result += test_string_to_upper();
     result += test_string_to_lower();
+    result += test_string_concat();
 
     return result;
 }