Struct Bitboard

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pub struct Bitboard(/* private fields */);

Expand description

Bitboard is a wrapper around a u64 integer, where each bit represents some or none on its corresponding chess board square. It is used to encode a set of some arbitrary homogenous data for an entire chess board.

Implementations§

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impl Bitboard

Bitboard Constants

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pub const fn bits(&self) -> u64

Get copy of internal u64 representation of this Bitboard.

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pub const fn is_empty(&self) -> bool

Returns true if there are no squares in self, false otherwise.

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pub const fn count_squares(&self) -> u32

Returns number of squares present. Equivalent to number of bits in binary representation that are ‘1’. When compiled for targets with BMI1 popcnt instruction, should resolve to a single instruction.

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pub fn has_square<I: SquareIndexable>(&self, idx: I) -> bool

Returns true if index is populated.

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pub fn set_square<I: SquareIndexable>(&mut self, idx: I)

Sets bit index to 1.

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pub fn clear_square<I: SquareIndexable>(&mut self, idx: I)

Sets bit index to 0.

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pub fn toggle_square<I: SquareIndexable>(&mut self, idx: I)

Toggles bit index. 0 -> 1, 1 -> 0.

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pub fn clear_square_and_above<I: SquareIndexable>(&mut self, idx: I)

Clears squares including and above target square. TODO: There is a BMI2 instruction BZHI to zero high hits starting at position, however the instruction is not used with &mut self, only self. Figure out how to get get compiler to use BZHI.

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pub fn clear_square_and_below<I: SquareIndexable>(&mut self, idx: I)

Clears squares including and below target square. TODO: Find a BMI instruction, if applicable. Maybe BLSMSK.

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pub fn clear_lowest_square(&mut self)

Clears the lowest square from self. If there are no squares, does nothing. When compiled for targets that support BMI1 BLSR (reset lowest set bit), should resolve to a single instruction and a move.

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pub fn get_lowest_square(&self) -> Option<Square>

Returns the lowest square that exists in bitboard, or None if bitboard has no squares.

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pub fn remove(&mut self, other: &Bitboard)

Remove all squares in other from self.

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pub const fn contains(&self, other: &Bitboard) -> bool

Returns true if other is a subset of self. If all squares of other are in self, then other is a subset of self.

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pub const fn has_any(&self, other: &Bitboard) -> bool

Returns true if self has any squares that are in other. In other words, if there is any overlap, return true.

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pub const fn to_north(&self) -> Self

Returns new Bitboard with all squares shifted 1 square north (ex: D4 -> D5).

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pub const fn to_south(&self) -> Self

Returns new Bitboard with all squares shifted 1 square south (ex: D4 -> D3).

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pub const fn to_east(&self) -> Self

Returns new Bitboard with all squares shifted 1 square east (ex: D4 -> E4). To prevent wrapping of bit to other rank, bits are removed on FILE_A.

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pub const fn to_west(&self) -> Self

Returns new Bitboard with all squares shifted 1 square west (ex: D4 -> C4). To prevent wrapping of bit to other rank, bits are removed on FILE_H.

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pub const fn to_north_east(&self) -> Self

Returns new Bitboard with all squares shifted 1 square north east (ex: D4 -> E5). To prevent wrapping of bit to other rank, bits are removed on FILE_A.

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pub const fn to_north_west(&self) -> Self

Returns new Bitboard with all squares shifted 1 square north west (ex: D4 -> C5). To prevent wrapping of bit to other rank, bits are removed on FILE_H.

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pub const fn to_south_east(&self) -> Self

Returns new Bitboard with all squares shifted 1 square south east (ex: D4 -> E3). To prevent wrapping of bit to other rank, bits are removed on FILE_A.

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pub const fn to_south_west(&self) -> Self

Returns new Bitboard with all squares shifted 1 square south west (ex: D4 -> C3). To prevent wrapping of bit to other rank, bits are removed on FILE_H.

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pub fn squares(&self) -> Vec<Square>

Returns a vector of all the Squares represented in the Bitboard.

§Examples

let squares = vec![Square::A1, Square::D7];
let mut board = Bitboard::EMPTY;
squares.iter().for_each(|square| board.set_square(*square));
assert_eq!(board.squares(), squares);