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Make secp256k1_i128_check_pow2 support -(2^n)

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This commit is contained in:
Pieter Wuille
2022-12-10 15:13:43 -05:00
parent cbd2555934
commit 5fffb2c7af
5 changed files with 43 additions and 15 deletions
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38
src/tests.c
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@@ -2022,30 +2022,56 @@ static void run_int128_test_case(void) {
}
CHECK(secp256k1_i128_eq_var(&swa, &swz) == expect);
}
/* test secp256k1_i128_check_pow2 */
/* test secp256k1_i128_check_pow2 (sign == 1) */
{
int expect = (uc & 1);
int pos = ub % 127;
if (expect) {
/* If expect==1, set swz to exactly (2 << pos). */
/* If expect==1, set swz to exactly 2^pos. */
uint64_t hi = 0;
uint64_t lo = 0;
if (pos & 64) {
if (pos >= 64) {
hi = (((uint64_t)1) << (pos & 63));
} else {
lo = (((uint64_t)1) << (pos & 63));
}
secp256k1_i128_load(&swz, hi, lo);
} else {
/* If expect==0, set swz = swa, but update expect=1 if swa happens to equal (2 << pos). */
if (pos & 64) {
/* If expect==0, set swz = swa, but update expect=1 if swa happens to equal 2^pos. */
if (pos >= 64) {
if ((v[1] == (((uint64_t)1) << (pos & 63))) && v[0] == 0) expect = 1;
} else {
if ((v[0] == (((uint64_t)1) << (pos & 63))) && v[1] == 0) expect = 1;
}
swz = swa;
}
CHECK(secp256k1_i128_check_pow2(&swz, pos) == expect);
CHECK(secp256k1_i128_check_pow2(&swz, pos, 1) == expect);
}
/* test secp256k1_i128_check_pow2 (sign == -1) */
{
int expect = (uc & 1);
int pos = ub % 127;
if (expect) {
/* If expect==1, set swz to exactly -2^pos. */
uint64_t hi = ~(uint64_t)0;
uint64_t lo = ~(uint64_t)0;
if (pos >= 64) {
hi <<= (pos & 63);
lo = 0;
} else {
lo <<= (pos & 63);
}
secp256k1_i128_load(&swz, hi, lo);
} else {
/* If expect==0, set swz = swa, but update expect=1 if swa happens to equal -2^pos. */
if (pos >= 64) {
if ((v[1] == ((~(uint64_t)0) << (pos & 63))) && v[0] == 0) expect = 1;
} else {
if ((v[0] == ((~(uint64_t)0) << (pos & 63))) && v[1] == ~(uint64_t)0) expect = 1;
}
swz = swa;
}
CHECK(secp256k1_i128_check_pow2(&swz, pos, -1) == expect);
}
}