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| author | Denys Vlasenko | 2018-12-22 23:59:21 +0100 |
|---|---|---|
| committer | Denys Vlasenko | 2018-12-22 23:59:21 +0100 |
| commit | 01eb5e9da1546f5410831d3a5a8d268d630d2653 (patch) | |
| tree | cf5ce1b670b4e5be10640a3752a584ff7bfa2f4b /miscutils | |
| parent | 1acac7f9c596cd447d197039216f7b55c9ee3ab3 (diff) | |
| download | busybox-01eb5e9da1546f5410831d3a5a8d268d630d2653.zip busybox-01eb5e9da1546f5410831d3a5a8d268d630d2653.tar.gz | |
bc: shrink modular exponentiation code
function old new delta
zdc_program_modexp 721 694 -27
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'miscutils')
| -rw-r--r-- | miscutils/bc.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/miscutils/bc.c b/miscutils/bc.c index 8cd67b0..25150a9 100644 --- a/miscutils/bc.c +++ b/miscutils/bc.c @@ -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); |