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Fixed bug #54598 (bcpowmod() may return 1 if modulus is 1)

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`x mod 1` is always zero; we have to take the scale into account,
though.
This commit is contained in:
Christoph M. Becker 2017-09-07 00:30:05 +02:00
parent dea41f3c3a
commit b2919853f8
3 changed files with 32 additions and 8 deletions
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23
ext/bcmath/libbcmath/src/raisemod.c
View file

@ -75,17 +75,24 @@ bc_raisemod (bc_num base, bc_num expo, bc_num mod, bc_num *result, int scale)
/* Do the calculation. */
rscale = MAX(scale, base->n_scale);
while ( !bc_is_zero(exponent) )
if ( !bc_compare(mod, BCG(_one_)) )
{
(void) bc_divmod (exponent, BCG(_two_), &exponent, &parity, 0);
if ( !bc_is_zero(parity) )
temp = bc_new_num (1, scale);
}
else
{
while ( !bc_is_zero(exponent) )
{
bc_multiply (temp, power, &temp, rscale);
(void) bc_modulo (temp, mod, &temp, scale);
}
(void) bc_divmod (exponent, BCG(_two_), &exponent, &parity, 0);
if ( !bc_is_zero(parity) )
{
bc_multiply (temp, power, &temp, rscale);
(void) bc_modulo (temp, mod, &temp, scale);
}
bc_multiply (power, power, &power, rscale);
(void) bc_modulo (power, mod, &power, scale);
bc_multiply (power, power, &power, rscale);
(void) bc_modulo (power, mod, &power, scale);
}
}
/* Assign the value. */