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authorJohn Hawthorn <john@hawthorn.email>2019-06-26 09:52:30 -0700
committerAaron Patterson <tenderlove@ruby-lang.org>2019-08-09 16:33:53 -0700
commit9d298b9dab831f966ea4bf365c712161118dd631 (patch)
treecafabbc52374a8f11e4450d19a1cad3809d29acd
parentb1678338e545589540b1dd85dee6a18fd98aa8ed (diff)
Allow Array#join to allocate smaller strings
rb_str_buf_new always allocates at least 127 bytes of capacity, even when less is requested. > ObjectSpace.dump(%w[a b c].join) {"address":"0x7f935f06ebf0", "type":"STRING", "class":"0x7f935d8b7bb0", "bytesize":3, "capacity":127, "value":"abc", "encoding":"UTF-8", "memsize":168, "flags":{"wb_protected":true}} Instead, by using rb_str_new and then setting the length to 0, we can allocate the exact amount of memory needed, without extra capacity. > ObjectSpace.dump(%w[a b c].join) {"address":"0x7f903fcab530", "type":"STRING", "class":"0x7f903f8b7988", "embedded":true, "bytesize":3, "value":"abc", "encoding":"UTF-8", "memsize":40, "flags":{"wb_protected":true}}
-rw-r--r--array.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/array.c b/array.c
index adb3281..5443268 100644
--- a/array.c
+++ b/array.c
@@ -2368,7 +2368,9 @@ rb_ary_join(VALUE ary, VALUE sep)
len += RSTRING_LEN(tmp);
}
- result = rb_str_buf_new(len);
+ result = rb_str_new(0, len);
+ rb_str_set_len(result, 0);
+
if (taint) OBJ_TAINT(result);
ary_join_0(ary, sep, RARRAY_LEN(ary), result);