01eb5e9da
Denys Vlasenko
2018-12-22
Subject
bc: shrink modular exponentiation code
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miscutils/bc.c+5 -3
| @@ -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); | |