Reduce allocation on string multiplication

itchyny · May 26, 2020 · 6306ac8 · 6306ac8
1 parent 9163e09
commit 6306ac8
Showing 1 changed file with 9 additions and 11 deletions.
diff --git a/src/builtin.c b/src/builtin.c
@@ -320,19 +320,17 @@ static jv f_multiply(jq_state *jq, jv input, jv a, jv b) {
  str = b;
  num = a;
  }
- int n;
- size_t alen = jv_string_length_bytes(jv_copy(str));
- jv res = jv_copy(str);
-
- for (n = jv_number_value(num) - 1; n > 0; n--)
- res = jv_string_append_buf(res, jv_string_value(str), alen);
-
+ jv res = jv_null();
+ int n = jv_number_value(num);
+ if (n > 0) {
+ size_t alen = jv_string_length_bytes(jv_copy(str));
+ res = jv_string_empty(alen * n);
+ for (; n > 0; n--) {
+ res = jv_string_append_buf(res, jv_string_value(str), alen);
+ }
+ }
  jv_free(str);
  jv_free(num);
- if (n < 0) {
- jv_free(res);
- return jv_null();
- }
  return res;
  } else if (ak == JV_KIND_OBJECT && bk == JV_KIND_OBJECT) {
  return jv_object_merge_recursive(a, b);