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lib/strutils: parse_size() fix frac digit calculation 

Old code:

	./test_strutils --size 0.5MiB
		0.5MiB :               512000 :     500K :      500 KiB
	./test_strutils --size 0.50MiB
		0.50MiB :              5120000 :     4.9M :      4.9 MiB

New code:
	./test_strutils --size 0.5MiB
		0.5MiB :               524288 :     512K :      512 KiB
	./test_strutils --size 0.50MiB
	       0.50MiB :               524288 :     512K :      512 KiB

Note that the new implementation also does not use float points,
because we need to support PiB and so on... it seems good enough for
things like:

        ./test_strutils --size 7.13G
                7.13G :           7656104581 :     7.1G :      7.1 GiB
        ./test_strutils --size 7.16G
                7.16G :           7690675814 :     7.2G :      7.2 GiB

to avoid situation where cfdisk creates partition with completely
crazy numbers.

Addresses: https://github.com/karelzak/util-linux/issues/782
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2019-05-13 17:07:14 +02:00
parent 482e0a0754
commit 8c368dc6d3
1 changed files with 32 additions and 10 deletions
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42
lib/strutils.c
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@ -162,17 +162,39 @@ check_suffix:
if (power)
*power = pwr;
if (frac && pwr) {
int zeros_in_pwr = frac_zeros % 3;
int frac_pwr = pwr - (frac_zeros / 3) - 1;
uintmax_t y = frac * (zeros_in_pwr == 0 ? 100 :
zeros_in_pwr == 1 ? 10 : 1);
int i;
uintmax_t frac_div = 10, frac_poz = 1, frac_base = 1;
if (frac_pwr < 0) {
rc = -EINVAL;
goto err;
}
do_scale_by_power(&y, base, frac_pwr);
x += y;
/* mega, giga, ... */
do_scale_by_power(&frac_base, base, pwr);
/* maximal divisor for last digit (e.g. for 0.05 is
* frac_div=100, for 0.054 is frac_div=1000, etc.)
*/
while (frac_div < frac)
frac_div *= 10;
/* 'frac' is without zeros (5 means 0.5 as well as 0.05) */
for (i = 0; i < frac_zeros; i++)
frac_div *= 10;
/*
* Go backwardly from last digit and add to result what the
* digit represents in the frac_base. For example 0.25G
*
* 5 means 1GiB / (100/5)
* 2 means 1GiB / (10/2)
*/
do {
unsigned int seg = frac % 10; /* last digit of the frac */
uintmax_t seg_div = frac_div / frac_poz; /* what represents the segment 1000, 100, .. */
frac /= 10; /* remove last digit from frac */
frac_poz *= 10;
if (seg)
x += frac_base / (seg_div / seg);
} while (frac);
}
done:
*res = x;