Add utility functions for copying strings.

src/util.c

@@ -1,4 +1,5 @@
 #include "util.h"
+#include <stdlib.h>
 
 libab_result libab_convert_lex_result(liblex_result to_convert) {
     libab_result result = LIBAB_SUCCESS;
@@ -18,3 +19,20 @@ libab_result libab_convert_ds_result(libds_result to_convert) {
     }
     return result;
 }
+libab_result libab_copy_string_range(char** destination, const char* source, size_t from, size_t to) {
+    libab_result result = LIBAB_SUCCESS;
+    size_t string_length = to - from;
+    if((*destination = malloc(string_length + 1)) == NULL) {
+        result = LIBAB_MALLOC;
+    } else {
+        strncpy(*destination, source + from, string_length);
+        (*destination)[string_length] = '\0';
+    }
+    return result;
+}
+libab_result libab_copy_string_size(char** destination, const char* source, size_t length) {
+    return libab_copy_string_range(destination, source, 0, length);
+}
+libab_result libab_copy_string(char** destination, const char* source) {
+    return libab_copy_string_range(destination, source, 0, strlen(source));
+}