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bc: shrink zbc_num_ulong()

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2018-12-22 21:37:46 +01:00
parent ec74a9c145
commit 1557b76edd
1 changed files with 11 additions and 10 deletions
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21
miscutils/bc.c
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@ -1442,20 +1442,21 @@ static void bc_num_copy(BcNum *d, BcNum *s)
static BC_STATUS zbc_num_ulong(BcNum *n, unsigned long *result_p) static BC_STATUS zbc_num_ulong(BcNum *n, unsigned long *result_p)
{ {
size_t i; size_t i;
unsigned long pow, result; unsigned long result;
if (n->neg) RETURN_STATUS(bc_error("negative number")); if (n->neg) RETURN_STATUS(bc_error("negative number"));
for (result = 0, pow = 1, i = n->rdx; i < n->len; ++i) { result = 0;
unsigned long prev = result, powprev = pow; i = n->len;
while (i > n->rdx) {
result += ((unsigned long) n->num[i]) * pow; unsigned long prev = result;
pow *= 10; result = result * 10 + n->num[--i];
// Even overflowed N*10 can still satisfy N*10>=N. For example,
if (result < prev || pow < powprev) // 0x1ff00000 * 10 is 0x13f600000,
// or 0x3f600000 truncated to 32 bits. Which is larger.
// However, (N*10)/8 < N check is always correct.
if ((result / 8) < prev)
RETURN_STATUS(bc_error("overflow")); RETURN_STATUS(bc_error("overflow"));
prev = result;
powprev = pow;
} }
*result_p = result; *result_p = result;