string.c: add fastpath in str_ensure_byte_pos

If the string only contain single byte characters we can skips all the costly checks. 

1 files changed, 8 insertions, 6 deletions

diff --git a/string.c b/string.c
index 5db35724e1..17a552e0de 100644
--- a/string.c
+++ b/string.c
@@ -4254,12 +4254,14 @@ rb_str_index_m(int argc, VALUE *argv, VALUE str)
 static void
 str_ensure_byte_pos(VALUE str, long pos)
 {
- const char *s = RSTRING_PTR(str);
- const char *e = RSTRING_END(str);
- const char *p = s + pos;
- if (!at_char_boundary(s, p, e, rb_enc_get(str))) {
- rb_raise(rb_eIndexError,
- "offset %ld does not land on character boundary", pos);
+ if (!single_byte_optimizable(str)) {
+ const char *s = RSTRING_PTR(str);
+ const char *e = RSTRING_END(str);
+ const char *p = s + pos;
+ if (!at_char_boundary(s, p, e, rb_enc_get(str))) {
+ rb_raise(rb_eIndexError,
+ "offset %ld does not land on character boundary", pos);
+ }
 }
 }