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Add secp256k1_scalar_mul_shift_var

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This commit is contained in:
Pieter Wuille
2014-12-01 17:11:59 +01:00
parent bd313f7d6e
commit ff8746d457
6 changed files with 105 additions and 49 deletions
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23
src/num_gmp_impl.h
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@@ -225,12 +225,23 @@ static void secp256k1_num_div(secp256k1_num_t *r, const secp256k1_num_t *a, cons
r->neg = a->neg ^ b->neg;
}
static int secp256k1_num_shift(secp256k1_num_t *r, int bits) {
VERIFY_CHECK(bits <= GMP_NUMB_BITS);
mp_limb_t ret = mpn_rshift(r->data, r->data, r->limbs, bits);
if (r->limbs>1 && r->data[r->limbs-1]==0) r->limbs--;
ret >>= (GMP_NUMB_BITS - bits);
return ret;
static void secp256k1_num_shift(secp256k1_num_t *r, int bits) {
if (bits % GMP_NUMB_BITS) {
// Shift within limbs.
mpn_rshift(r->data, r->data, r->limbs, bits % GMP_NUMB_BITS);
}
if (bits >= GMP_NUMB_BITS) {
// Shift full limbs.
for (int i = 0; i < r->limbs; i++) {
int index = i + (bits / GMP_NUMB_BITS);
if (index < r->limbs && index < 2*NUM_LIMBS) {
r->data[i] = r->data[index];
} else {
r->data[i] = 0;
}
}
}
while (r->limbs>1 && r->data[r->limbs-1]==0) r->limbs--;
}
static void secp256k1_num_negate(secp256k1_num_t *r) {