Messages in this thread | | | Date | Mon, 9 Sep 2019 13:06:08 +0300 | From | Andy Shevchenko <> | Subject | Re: [PATCH 5/7] lib: rework bitmap_parse() |
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On Sun, Sep 08, 2019 at 08:30:19PM -0700, Yury Norov wrote: > bitmap_parse() is ineffective and full of opaque variables and opencoded > parts. It leads to hard understanding and usage of it. This rework > includes: > - remove bitmap_shift_left() call from the cycle. Now it makes the > complexity of the algorithm as O(nbits^2). In the suggested approach > the input string is parsed in reverse direction, so no shifts needed; > - relax requirement on a single comma and no white spaces between chunks. > It is considered useful in scripting, and it aligns with > bitmap_parselist(); > - split bitmap_parse() to small readable helpers; > - make an explicit calculation of the end of input line at the > beginning, so users of the bitmap_parse() won't bother doing this.
> +static const char *bitmap_get_x32_reverse(const char *start, > + const char *end, u32 *num) > +{ > + u32 ret = 0; > + int c, i; > +
> + if (!isxdigit(*end)) > + return ERR_PTR(-EINVAL);
This seems redundant...
> + > + for (i = 0; i < 32; i += 4) {
> + c = hex_to_bin(*end--); > + if (c < 0) > + return ERR_PTR(-EINVAL);
...because this will do the same check.
Am I right?
> + > + ret |= c << i; > + > + if (start > end || __end_of_region(*end)) > + goto out; > + } > +
> + if (isxdigit(*end)) > + return ERR_PTR(-EOVERFLOW);
hex_to_bin() doesn't rely on ctype array, won't drain caches. I guess it's not a fast path, so, either will work.
> +out: > + *num = ret; > + return end; > +}
-- With Best Regards, Andy Shevchenko
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