On 2/5/12 5:44 PM, Michael Tokarev wrote:
> On 05.02.2012 00:10, Eric Sandeen wrote:
> []
>
> Just a very quick look:
>
>> * sparsify - utility to punch out blocks of 0s in a file
>> int main(int argc, char **argv)
>> {
> []
>> if (optind == argc) {
>> printf("Error: no filename specified\n");
>> usage();
>> }
>>
>> fname = argv[optind++];
>
> There's no handling of the case when there are more than one file
> specified on the command line.
ok
>
>> /*
>> * Normalize to blocksize-aligned range:
>> * round start down, round end up - get all blocks including the range specified
>> */
>>
>> punch_range_start = round_down(punch_range_start, blocksize);
>> punch_range_end = round_up(punch_range_end, blocksize);
>> min_hole = round_up(min_hole, blocksize);
>> if (!min_hole)
>> min_hole = blocksize;
>
> I think this deserves some bold warning if punch_range_start
> or punch_hole_end is not a multiple of blocksize.
well, we can only punch on block boundaries. But I suppose I should swap
round_up and round_down, so that we never punch anything that isn't *inside*
the specified range.
> []
>> /*
>> * Read through the file, finding block-aligned regions of 0s.
>> * If the region is at least min_hole, punch it out.
>> * This should be starting at a block-aligned offset
>> */
>>
>> while ((ret = read(fd, readbuf, min_hole)) > 0) {
>>
>> if (!memcmp(readbuf, zerobuf, min_hole)) {
>
> Now this is interesting. Can ret be < min_hole? Can a read
> in a middle of a file be shorter than specified?
yes, and yes (but unlikely i think)...
> How it will work together with some other operation being done
> at the same file -- ftruncate anyone?
I probably have some boundary condition & error checking to do yet :)
Thanks for the review,
-Eric
> Thanks!
>
> /mjt
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