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bc: shrink modular exponentiation code

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function                                             old     new   delta
zdc_program_modexp                                   721     694     -27

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2018-12-22 23:59:21 +01:00
parent 1acac7f9c5
commit 01eb5e9da1
1 changed files with 5 additions and 3 deletions
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8
miscutils/bc.c
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@ -2503,6 +2503,7 @@ static BC_STATUS zdc_num_modexp(BcNum *a, BcNum *b, BcNum *c, BcNum *restrict d)
{
BcStatus s;
BcNum base, exp, two, temp;
BcDig two_digs[2];
if (c->len == 0)
RETURN_STATUS(bc_error("divide by zero"));
@ -2514,11 +2515,13 @@ static BC_STATUS zdc_num_modexp(BcNum *a, BcNum *b, BcNum *c, BcNum *restrict d)
bc_num_expand(d, c->len);
bc_num_init(&base, c->len);
bc_num_init(&exp, b->len);
bc_num_init_DEF_SIZE(&two);
bc_num_init(&temp, b->len);
two.cap = ARRAY_SIZE(two_digs);
two.num = two_digs;
bc_num_one(&two);
two.num[0] = 2;
two_digs[0] = 2;
bc_num_one(d);
s = zbc_num_rem(a, c, &base, 0);
@ -2543,7 +2546,6 @@ static BC_STATUS zdc_num_modexp(BcNum *a, BcNum *b, BcNum *c, BcNum *restrict d)
}
err:
bc_num_free(&temp);
bc_num_free(&two);
bc_num_free(&exp);
bc_num_free(&base);
RETURN_STATUS(s);