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SubjectRe: [PATCH 1/1] lib: use sunday algorithm to do strstr() and strnstr()
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在 2018/7/27 18:39, Andy Shevchenko 写道:
> On Fri, Jul 27, 2018 at 8:48 AM, Zhaoxiu Zeng <zengzhaoxiu@163.com> wrote:
>> 在 2018/7/27 1:17, Zhaoxiu Zeng 写道:
>>> 在 2018/7/23 2:37, Greg Kroah-Hartman 写道:
>>>> On Mon, Jul 23, 2018 at 01:37:15AM +0800, Zhaoxiu Zeng wrote:
>
>>>>> The Sunday algorithm is a variation of Boyer-Moore algorithm, it is easy and fast.
>>>>> For the Sunday algorithm, to see
>>>>> http://www.inf.fh-flensburg.de/lang/algorithmen/pattern/sundayen.htm
>>>>
>>>> So you say, but what does this really buy us? Why make this change?
>>>> How was it tested? What is the downside of not taking this?
>
>>> I use the following program to test on fc28.
>>> Compile with O2, the new version is almost 2X faster than the original.
>
>>> The code size of the original is 0x80, the newer is 0xB0.
>
> So, output of bloat-o-meter would be good to have in commit message.
>
>>> The test result:
>
> Compact performance statistics as well.
>
>>> Thanks!
>
>> The original strnstr might has a bug too!
>> For example, assume s1 is "123\0abc...." and s2 is "abc\0",
>> call strnstr(s1, s2, 7) will return &s1[4], but the correct result is NULL.
>
> If there is a bug, send another patch to fix the bug first.
>

The bug could be fixed by this patch.

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