popCount
r = @popCount(a) with 2s-complement semantics. r and a may be aliases.
Assets the result fits in r. Upper bound on the number of limbs needed by
r is calcTwosCompLimbCount(bit_count).
Function parameters
Parameters
Used to indicate either limit of a 2s-complement integer.
Types
- TwosCompIntLimit
- Used to indicate either limit of a 2s-complement integer.
- Mutable
- A arbitrary-precision big integer, with a fixed set of mutable limbs.
- Const
- A arbitrary-precision big integer, with a fixed set of immutable limbs.
- Managed
- An arbitrary-precision big integer along with an allocator which manages the memory.
Returns the number of limbs needed to store `scalar`, which must be a
Functions
- calcLimbLen
- Returns the number of limbs needed to store `scalar`, which must be a
- calcSetStringLimbCount
- Assumes `string_len` doesn't account for minus signs if the number is negative.
- calcNonZeroTwosCompLimbCount
- Compute the number of limbs required to store a 2s-complement number of `bit_count` bits.
- calcTwosCompLimbCount
- Compute the number of limbs required to store a 2s-complement number of `bit_count` bits.
- addMulLimbWithCarry
- a + b * c + *carry, sets carry to the overflow bits
- llcmp
- Returns -1, 0, 1 if |a| < |b|, |a| == |b| or |a| > |b| respectively for limbs.
Source
Implementation
pub fn popCount(r: *Mutable, a: Const, bit_count: usize) void {
r.copy(a);
if (!a.positive) {
r.positive = true; // Negate.
r.bitNotWrap(r.toConst(), .unsigned, bit_count); // Bitwise NOT.
r.addScalar(r.toConst(), 1); // Add one.
}
var sum: Limb = 0;
for (r.limbs[0..r.len]) |limb| {
sum += @popCount(limb);
}
r.set(sum);
}