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Re: [RFC] diff-optimizations-bytes branch: avoiding function call overhead (?)

From: Johan Corveleyn <jcorvel_at_gmail.com>
Date: Mon, 20 Dec 2010 14:16:05 +0100

On Mon, Dec 20, 2010 at 11:03 AM, Julian Foad <julian.foad_at_wandisco.com> wrote:
> On Mon, 2010-12-20, Johan Corveleyn wrote:
>> New macro version (increment only, decrement is similar):
>> [[[
>> /* For all files in the FILE array, increment the curp pointer.  If a file
>>  * points before the beginning of file, let it point at the first byte again.
>>  * If the end of the current chunk is reached, read the next chunk in the
>>  * buffer and point curp to the start of the chunk.  If EOF is reached, set
>>  * curp equal to endp to indicate EOF. */
>> #define increment_pointers(all_files, files_len, pool)                       \
>>   do {                                                                       \
>>     int i;                                                                   \
>>                                                                              \
>>     for (i = 0; i < files_len; i++)                                          \
>>     {                                                                        \
>>       if (all_files[i]->chunk == -1) /* indicates before beginning of file */\
>>         all_files[i]->chunk = 0;     /* point to beginning of file again */  \
>>       else if (all_files[i]->curp != all_files[i]->endp - 1)                 \
>>         all_files[i]->curp++;                                                \
>
> Hi Johan.
>
> Here you are having to test for two special cases every time: chunk==-1
> and curp==endp-1.  I would suggest changing the specification of "before
> beginning of file" to include the promise that curp==endp-1, so that you
> don't have to use a separate test here and can instead test for this
> special case within increment_chunk().

Good idea. I'll try this tonight ...

Cheers,

-- 
Johan
Received on 2010-12-20 14:17:03 CET

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