chess/
castle_rights.rs

1use std::hint::unreachable_unchecked;
2
3use crate::bitboard::{BitBoard, EMPTY};
4use crate::color::Color;
5use crate::file::File;
6use crate::square::Square;
7
8use crate::magic::{KINGSIDE_CASTLE_SQUARES, QUEENSIDE_CASTLE_SQUARES};
9
10/// What castle rights does a particular player have?
11#[repr(u8)]
12#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Debug, Hash)]
13pub enum CastleRights {
14	NoRights = 0,
15	KingSide = 1,
16	QueenSide = 2,
17	Both = 3,
18}
19
20/// How many different types of `CastleRights` are there?
21pub const NUM_CASTLE_RIGHTS: usize = 4;
22
23/// Enumerate all castle rights.
24pub const ALL_CASTLE_RIGHTS: [CastleRights; NUM_CASTLE_RIGHTS] = [CastleRights::NoRights, CastleRights::KingSide, CastleRights::QueenSide, CastleRights::Both];
25
26const CASTLES_PER_SQUARE: [[u8; 64]; 2] = [
27	[
28		2, 0, 0, 0, 3, 0, 0, 1, // 1
29		0, 0, 0, 0, 0, 0, 0, 0, // 2
30		0, 0, 0, 0, 0, 0, 0, 0, // 3
31		0, 0, 0, 0, 0, 0, 0, 0, // 4
32		0, 0, 0, 0, 0, 0, 0, 0, // 5
33		0, 0, 0, 0, 0, 0, 0, 0, // 6
34		0, 0, 0, 0, 0, 0, 0, 0, // 7
35		0, 0, 0, 0, 0, 0, 0, 0, // 8
36	],
37	[
38		0, 0, 0, 0, 0, 0, 0, 0, // 1
39		0, 0, 0, 0, 0, 0, 0, 0, // 2
40		0, 0, 0, 0, 0, 0, 0, 0, // 3
41		0, 0, 0, 0, 0, 0, 0, 0, // 4
42		0, 0, 0, 0, 0, 0, 0, 0, // 5
43		0, 0, 0, 0, 0, 0, 0, 0, // 6
44		0, 0, 0, 0, 0, 0, 0, 0, // 7
45		2, 0, 0, 0, 3, 0, 0, 1,
46	],
47];
48
49impl CastleRights {
50	/// Can I castle kingside?
51	pub fn has_kingside(&self) -> bool {
52		self.to_index() & 1 == 1
53	}
54
55	/// Can I castle queenside?
56	pub fn has_queenside(&self) -> bool {
57		self.to_index() & 2 == 2
58	}
59
60	pub fn square_to_castle_rights(color: Color, sq: Square) -> CastleRights {
61		CastleRights::from_index(unsafe { *CASTLES_PER_SQUARE.get_unchecked(color.to_index()).get_unchecked(sq.to_index()) } as usize)
62	}
63
64	/// What squares need to be empty to castle kingside?
65	pub fn kingside_squares(&self, color: Color) -> BitBoard {
66		unsafe { *KINGSIDE_CASTLE_SQUARES.get_unchecked(color.to_index()) }
67	}
68
69	/// What squares need to be empty to castle queenside?
70	pub fn queenside_squares(&self, color: Color) -> BitBoard {
71		unsafe { *QUEENSIDE_CASTLE_SQUARES.get_unchecked(color.to_index()) }
72	}
73
74	/// Remove castle rights, and return a new `CastleRights`.
75	pub fn remove(&self, remove: CastleRights) -> CastleRights {
76		CastleRights::from_index(self.to_index() & !remove.to_index())
77	}
78
79	/// Add some castle rights, and return a new `CastleRights`.
80	pub fn add(&self, add: CastleRights) -> CastleRights {
81		CastleRights::from_index(self.to_index() | add.to_index())
82	}
83
84	/// Convert `CastleRights` to `usize` for table lookups
85	pub fn to_index(&self) -> usize {
86		*self as usize
87	}
88
89	/// Convert `usize` to `CastleRights`.
90	pub fn from_index(i: usize) -> CastleRights {
91		match i & 3 {
92			0 => CastleRights::NoRights,
93			1 => CastleRights::KingSide,
94			2 => CastleRights::QueenSide,
95			3 => CastleRights::Both,
96			_ => unsafe { unreachable_unchecked() },
97		}
98	}
99
100	/// Which rooks can we "guarantee" we haven't moved yet?
101	pub fn unmoved_rooks(&self, color: Color) -> BitBoard {
102		match *self {
103			CastleRights::NoRights => EMPTY,
104			CastleRights::KingSide => BitBoard::set(color.to_my_backrank(), File::H),
105			CastleRights::QueenSide => BitBoard::set(color.to_my_backrank(), File::A),
106			CastleRights::Both => BitBoard::set(color.to_my_backrank(), File::A) ^ BitBoard::set(color.to_my_backrank(), File::H),
107		}
108	}
109
110	/// Convert the castle rights to an FEN compatible string.
111	///
112	/// ```
113	/// use chess::{CastleRights, Color};
114	///
115	/// assert_eq!(CastleRights::NoRights.to_string(Color::White), "");
116	/// assert_eq!(CastleRights::Both.to_string(Color::Black), "kq");
117	/// assert_eq!(CastleRights::KingSide.to_string(Color::White), "K");
118	/// assert_eq!(CastleRights::QueenSide.to_string(Color::Black), "q");
119	/// ```
120	pub fn to_string(&self, color: Color) -> String {
121		let result = match *self {
122			CastleRights::NoRights => "",
123			CastleRights::KingSide => "k",
124			CastleRights::QueenSide => "q",
125			CastleRights::Both => "kq",
126		};
127
128		if color == Color::White { result.to_uppercase() } else { result.to_string() }
129	}
130
131	/// Given a square of a rook, which side is it on?
132	pub fn rook_square_to_castle_rights(square: Square) -> CastleRights {
133		match square.get_file() {
134			File::A => CastleRights::QueenSide,
135			File::H => CastleRights::KingSide,
136			_ => CastleRights::NoRights,
137		}
138	}
139}
chess/castle_rights.rs

chess/
castle_rights.rs
