bc: shrink modular exponentiation code

function                                             old     new   delta
zdc_program_modexp                                   721     694     -27

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/miscutils/bc.c b/miscutils/bc.c
index 8cd67b0f5..25150a9eb 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);