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Time#strftime: grow the buffer faster

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Use a classic doubling of capacity rather than only adding
twice as much capacity as is already known to be needed.

```
compare-ruby: ruby 3.4.0dev (2024-09-04T09:21:53Z opt-strftime-2 ae98d19cf9) +YJIT [arm64-darwin23]
built-ruby: ruby 3.4.0dev (2024-09-04T11:46:02Z opt-strftime-growth 586263d6fb) +YJIT [arm64-darwin23]
warming up...

|                            |compare-ruby|built-ruby|
|:---------------------------|-----------:|---------:|
|time.strftime("%FT%T")      |      1.754M|    1.889M|
|                            |           -|     1.08x|
|time.strftime("%FT%T.%3N")  |      1.508M|    1.749M|
|                            |           -|     1.16x|
|time.strftime("%FT%T.%6N")  |      1.488M|    1.756M|
|                            |           -|     1.18x|
compare-ruby: ruby 3.4.0dev (2024-09-04T09:21:53Z opt-strftime-2 ae98d19cf9) +YJIT [arm64-darwin23]
built-ruby: ruby 3.4.0dev (2024-09-04T09:21:53Z opt-strftime-2 ae98d19cf9) +YJIT [arm64-darwin23]
warming up...
```
This commit is contained in:
Jean Boussier 2024-09-04 12:38:30 +02:00
parent 83334ebb3c
commit a3f589640f
Notes: git 2024-09-04 12:53:14 +00:00 
Merged: https://github.com/ruby/ruby/pull/11542
2 changed files with 10 additions and 1 deletions
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7
benchmark/time_strftime.yml Normal file
View File

@ -0,0 +1,7 @@
prelude: |
# frozen_string_literal: true
time = Time.now
benchmark:
- time.strftime("%FT%T") # 19B
- time.strftime("%FT%T.%3N") # 23B
- time.strftime("%FT%T.%6N") # 26B

4
strftime.c
View File

@ -171,7 +171,9 @@ resize_buffer(VALUE ftime, char *s, const char **start, const char **endp,
ptrdiff_t n, size_t maxsize)
{
size_t len = s - *start;
size_t nlen = len + n * 2;
size_t need = len + n * 2;
size_t nlen = rb_str_capacity(ftime);
while (nlen < need) nlen <<= 1;
if (nlen < len || nlen > maxsize) {
return 0;