BitMask

Git Source

State Variables

M1

Constants used to efficiently calculate the hamming weight of a bitfield. See https://en.wikipedia.org/wiki/Hamming_weight#Efficient_implementation for an explanation of those constants.

uint256 internal constant M1 = 0x5555555555555555555555555555555555555555555555555555555555555555;

M2

uint256 internal constant M2 = 0x3333333333333333333333333333333333333333333333333333333333333333;

M4

uint256 internal constant M4 = 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f;

M8

uint256 internal constant M8 = 0x00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff00ff;

M16

uint256 internal constant M16 = 0x0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff0000ffff;

M32

uint256 internal constant M32 = 0x00000000ffffffff00000000ffffffff00000000ffffffff00000000ffffffff;

M64

uint256 internal constant M64 = 0x0000000000000000ffffffffffffffff0000000000000000ffffffffffffffff;

M128

uint256 internal constant M128 = 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff;

BITS_IN_LIMB

uint256 internal constant BITS_IN_LIMB = 256;

NNNN

uint256 internal constant NNNN = 4;

Functions

count_ones

Calculates the number of set bits by using the hamming weight of the bitfield. The algorithm below is implemented after https://en.wikipedia.org/wiki/Hamming_weight#Efficient_implementation. Further improvements are possible, see the article above.

function count_ones(Bitmask memory self) internal pure returns (uint256);

Parameters

Returns

count_ones

function count_ones(uint256 x) internal pure returns (uint256);

size

Actual size of bitmask, not including the padding.

function size(Bitmask memory self) internal pure returns (uint256);

Parameters

Returns

at

Bit at index of bitmask.

function at(Bitmask memory self, uint256 index) internal pure returns (bool);

Parameters

Returns

serialize

function serialize(Bitmask memory self) internal pure returns (bytes memory);