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py: Implement bignum '&' with negatives on lhs and rhs. 

Needs proper coverage testing.  Doesn't implement -ve & -ve.
Addresses issue #611.
This commit is contained in:
Damien George 2014-05-29 15:01:49 +01:00
parent d1e355ea8e
commit f55cf10101
2 changed files with 78 additions and 19 deletions
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73
py/mpz.c
View File

@ -218,6 +218,38 @@ STATIC uint mpn_and(mpz_dig_t *idig, const mpz_dig_t *jdig, uint jlen, const mpz
return idig + 1 - oidig;
}
/* computes i = j & -k = j & (~k + 1)
returns number of digits in i
assumes enough memory in i; assumes normalised j, k
can have i, j, k pointing to same memory
*/
STATIC uint mpn_and_neg(mpz_dig_t *idig, const mpz_dig_t *jdig, uint jlen, const mpz_dig_t *kdig, uint klen) {
mpz_dig_t *oidig = idig;
mpz_dbl_dig_t carry = 1;
for (; jlen > 0 && klen > 0; --jlen, --klen, ++idig, ++jdig, ++kdig) {
carry += *kdig ^ DIG_MASK;
*idig = (*jdig & carry) & DIG_MASK;
carry >>= DIG_SIZE;
}
for (; jlen > 0; --jlen, ++idig, ++jdig) {
carry += DIG_MASK;
*idig = (*jdig & carry) & DIG_MASK;
carry >>= DIG_SIZE;
}
if (carry != 0) {
*idig = carry;
} else {
// remove trailing zeros
for (--idig; idig >= oidig && *idig == 0; --idig) {
}
}
return idig + 1 - oidig;
}
/* computes i = j | k
returns number of digits in i
assumes enough memory in i; assumes normalised j, k; assumes jlen >= klen
@ -896,24 +928,35 @@ void mpz_sub_inpl(mpz_t *dest, const mpz_t *lhs, const mpz_t *rhs) {
can have dest, lhs, rhs the same
*/
void mpz_and_inpl(mpz_t *dest, const mpz_t *lhs, const mpz_t *rhs) {
// make sure lhs has the most digits
if (lhs->len < rhs->len) {
const mpz_t *temp = lhs;
lhs = rhs;
rhs = temp;
}
if (lhs->neg == rhs->neg) {
mpz_need_dig(dest, rhs->len);
dest->len = mpn_and(dest->dig, lhs->dig, lhs->len, rhs->dig, rhs->len);
if (lhs->neg == 0) {
// make sure lhs has the most digits
if (lhs->len < rhs->len) {
const mpz_t *temp = lhs;
lhs = rhs;
rhs = temp;
}
// do the and'ing
mpz_need_dig(dest, rhs->len);
dest->len = mpn_and(dest->dig, lhs->dig, lhs->len, rhs->dig, rhs->len);
dest->neg = 0;
} else {
// TODO both args are negative
assert(0);
}
} else {
mpz_need_dig(dest, lhs->len);
// TODO
assert(0);
// dest->len = mpn_and_neg(dest->dig, lhs->dig, lhs->len, rhs->dig, rhs->len);
// args have different sign
// make sure lhs is the positive arg
if (rhs->neg == 0) {
const mpz_t *temp = lhs;
lhs = rhs;
rhs = temp;
}
mpz_need_dig(dest, lhs->len + 1);
dest->len = mpn_and_neg(dest->dig, lhs->dig, lhs->len, rhs->dig, rhs->len);
assert(dest->len <= dest->alloc);
dest->neg = 0;
}
dest->neg = lhs->neg;
}
/* computes dest = lhs | rhs

24
tests/basics/int-big-and.py
View File

@ -2,7 +2,23 @@ print(0 & (1 << 80))
print(0 & (1 << 80) == 0)
print(bool(0 & (1 << 80)))
#a = 0xfffffffffffffffffffffffffffff
#print(a & (1 << 80))
#print((a & (1 << 80)) >> 80)
#print((a & (1 << 80)) >> 80 == 1)
a = 0xfffffffffffffffffffffffffffff
print(a & (1 << 80))
print((a & (1 << 80)) >> 80)
print((a & (1 << 80)) >> 80 == 1)
# test negative on rhs
a = 123456789012345678901234567890
print(a & -1)
print(a & -2)
print(a & -2345678901234567890123456789)
print(a & (-a))
# test negative on lhs
a = 123456789012345678901234567890
print(-1 & a)
print(-2 & a)
print(-2345678901234567890123456789 & a)
print((-a) & a)
print((-a) & 0xffffffff)
print((-a) & 0xffffffffffffffffffffffffffffffff)