convert_smilies is very slow

[Acci]

I created a testing WordPress blog with 10 posts and I found huge performance problem in convert_smilies function. This function took at average 39 ms on my high-end PC.

Currently this function uses preg_replace and it's called 40× for each part of the post.

My solution is to use very similar function preg_replace_callback with modified regular expression. This solution is 6× faster than original (5,9 ms).

Path deleted.

Faster regexp and uses preg_replace_callback()

Patch added for this. Also, I think it should go in before 2.9.

This patch changes smilies_init and convert_smilies to make a more efficient regular expression resulting in a ~10times speedup.

This is done by:

o the search expression is built up as sub-expressions for smiley first letter (example of partial result: "8(\)\)O|O)").

o to handle the replacement preg_replace_callback() in convert_smilies.

Resulting generated search regular expression for default smilies:

"/(\s|^{)8(\)\)O|O)|\:(\!\:|\(|\)\(\)\?DPox\}

\?|\?\:|\?\?\?\:|D|P|arrow\:|cool\:|cry\:|eek\:|evil\:|grin\:|idea\:|lol\:|mad\:|mrgreen\:|neutral\:|o|oops\:|razz\:|roll\:|sad\:|shock\:|smile\:|twisted\:|wink\:|x|\|)|;(\)\))(\s|$)/e"

Load time on the site for a post with 403 comments: Original: 4.3s Modified: 2.6s

Sorry, slightly old regexp in comment above. There is no 'e' modifier on the end in patch.

Tested all smilies with trunk revision 10308 and 2.6.5

(found and fixed an error in handling smilies like :???: vs :?)

Faster regexp and uses preg_replace_callback(), tested, fixed

Faster regexp and uses preg_replace_callback(), tested, fixed, minor cleaning

Test case for smilies, for use with Wordpress Test

Added a proposed test case for smilies (use with  http://codex.wordpress.org/Automated_Testing).

Also minor clean ups of patch (removed unused global).

(In [10322]) Faster smilies. Props johanee. fixes #6464

(In [10514]) Require smilies to be surrounded by spaces or be at the beginning or end of the line, see #6464