1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
use crate::file::File;
use crate::rank::Rank;
use crate::square::*;
use std::fmt;
use std::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Mul, Not};

/// A good old-fashioned bitboard
/// You *do* have access to the actual value, but you are probably better off
/// using the implemented operators to work with this object.
///
/// ```
/// use chess::{BitBoard, Square};
///
/// let bb = BitBoard(7); // lower-left 3 squares
///
/// let mut count = 0;
///
/// // Iterate over each square in the bitboard
/// for _ in bb {
///     count += 1;
/// }
///
/// assert_eq!(count, 3);
/// ```
///
#[derive(PartialEq, PartialOrd, Clone, Copy, Debug, Default)]
pub struct BitBoard(pub u64);

/// An empty bitboard.  It is sometimes useful to use !EMPTY to get the universe of squares.
///
/// ```
///     use chess::EMPTY;
///
///     assert_eq!(EMPTY.count(), 0);
///
///     assert_eq!((!EMPTY).count(), 64);
/// ```
pub const EMPTY: BitBoard = BitBoard(0);

// Impl BitAnd
impl BitAnd for BitBoard {
    type Output = BitBoard;

    fn bitand(self, other: BitBoard) -> BitBoard {
        BitBoard(self.0 & other.0)
    }
}

impl BitAnd for &BitBoard {
    type Output = BitBoard;
    fn bitand(self, other: &BitBoard) -> BitBoard {
        BitBoard(self.0 & other.0)
    }
}

impl BitAnd<&BitBoard> for BitBoard {
    type Output = BitBoard;
    fn bitand(self, other: &BitBoard) -> BitBoard {
        BitBoard(self.0 & other.0)
    }
}

impl BitAnd<BitBoard> for &BitBoard {
    type Output = BitBoard;
    fn bitand(self, other: BitBoard) -> BitBoard {
        BitBoard(self.0 & other.0)
    }
}

// Impl BitOr
impl BitOr for BitBoard {
    type Output = BitBoard;

    fn bitor(self, other: BitBoard) -> BitBoard {
        BitBoard(self.0 | other.0)
    }
}

impl BitOr for &BitBoard {
    type Output = BitBoard;

    fn bitor(self, other: &BitBoard) -> BitBoard {
        BitBoard(self.0 | other.0)
    }
}

impl BitOr<&BitBoard> for BitBoard {
    type Output = BitBoard;

    fn bitor(self, other: &BitBoard) -> BitBoard {
        BitBoard(self.0 | other.0)
    }
}

impl BitOr<BitBoard> for &BitBoard {
    type Output = BitBoard;
    fn bitor(self, other: BitBoard) -> BitBoard {
        BitBoard(self.0 | other.0)
    }
}

// Impl BitXor

impl BitXor for BitBoard {
    type Output = BitBoard;

    fn bitxor(self, other: BitBoard) -> BitBoard {
        BitBoard(self.0 ^ other.0)
    }
}

impl BitXor for &BitBoard {
    type Output = BitBoard;

    fn bitxor(self, other: &BitBoard) -> BitBoard {
        BitBoard(self.0 ^ other.0)
    }
}

impl BitXor<&BitBoard> for BitBoard {
    type Output = BitBoard;

    fn bitxor(self, other: &BitBoard) -> BitBoard {
        BitBoard(self.0 ^ other.0)
    }
}

impl BitXor<BitBoard> for &BitBoard {
    type Output = BitBoard;

    fn bitxor(self, other: BitBoard) -> BitBoard {
        BitBoard(self.0 ^ other.0)
    }
}

// Impl BitAndAssign

impl BitAndAssign for BitBoard {
    fn bitand_assign(&mut self, other: BitBoard) {
        self.0 &= other.0;
    }
}

impl BitAndAssign<&BitBoard> for BitBoard {
    fn bitand_assign(&mut self, other: &BitBoard) {
        self.0 &= other.0;
    }
}

// Impl BitOrAssign
impl BitOrAssign for BitBoard {
    fn bitor_assign(&mut self, other: BitBoard) {
        self.0 |= other.0;
    }
}

impl BitOrAssign<&BitBoard> for BitBoard {
    fn bitor_assign(&mut self, other: &BitBoard) {
        self.0 |= other.0;
    }
}

// Impl BitXor Assign
impl BitXorAssign for BitBoard {
    fn bitxor_assign(&mut self, other: BitBoard) {
        self.0 ^= other.0;
    }
}

impl BitXorAssign<&BitBoard> for BitBoard {
    fn bitxor_assign(&mut self, other: &BitBoard) {
        self.0 ^= other.0;
    }
}

// Impl Mul
impl Mul for BitBoard {
    type Output = BitBoard;

    fn mul(self, other: BitBoard) -> BitBoard {
        BitBoard(self.0.wrapping_mul(other.0))
    }
}

impl Mul for &BitBoard {
    type Output = BitBoard;

    fn mul(self, other: &BitBoard) -> BitBoard {
        BitBoard(self.0.wrapping_mul(other.0))
    }
}

impl Mul<&BitBoard> for BitBoard {
    type Output = BitBoard;

    fn mul(self, other: &BitBoard) -> BitBoard {
        BitBoard(self.0.wrapping_mul(other.0))
    }
}

impl Mul<BitBoard> for &BitBoard {
    type Output = BitBoard;

    fn mul(self, other: BitBoard) -> BitBoard {
        BitBoard(self.0.wrapping_mul(other.0))
    }
}

// Impl Not
impl Not for BitBoard {
    type Output = BitBoard;

    fn not(self) -> BitBoard {
        BitBoard(!self.0)
    }
}

impl Not for &BitBoard {
    type Output = BitBoard;

    fn not(self) -> BitBoard {
        BitBoard(!self.0)
    }
}

impl fmt::Display for BitBoard {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let mut s: String = "".to_owned();
        for x in 0..64 {
            if self.0 & (1u64 << x) == (1u64 << x) {
                s.push_str("X ");
            } else {
                s.push_str(". ");
            }
            if x % 8 == 7 {
                s.push_str("\n");
            }
        }
        write!(f, "{}", s)
    }
}

impl BitBoard {
    /// Construct a new bitboard from a u64
    pub fn new(b: u64) -> BitBoard {
        BitBoard(b)
    }

    /// Construct a new `BitBoard` with a particular `Square` set
    pub fn set(rank: Rank, file: File) -> BitBoard {
        BitBoard::from_square(Square::make_square(rank, file))
    }

    /// Construct a new `BitBoard` with a particular `Square` set
    pub fn from_square(sq: Square) -> BitBoard {
        BitBoard(1u64 << sq.to_int())
    }

    /// Convert an `Option<Square>` to an `Option<BitBoard>`
    pub fn from_maybe_square(sq: Option<Square>) -> Option<BitBoard> {
        sq.map(|s| BitBoard::from_square(s))
    }

    /// Convert a `BitBoard` to a `Square`.  This grabs the least-significant `Square`
    pub fn to_square(&self) -> Square {
        unsafe { Square::new(self.0.trailing_zeros() as u8) }
    }

    /// Count the number of `Squares` set in this `BitBoard`
    pub fn popcnt(&self) -> u32 {
        self.0.count_ones()
    }

    /// Reverse this `BitBoard`.  Look at it from the opponents perspective.
    pub fn reverse_colors(&self) -> BitBoard {
        BitBoard(self.0.swap_bytes())
    }

    /// Convert this `BitBoard` to a `usize` (for table lookups)
    pub fn to_size(&self, rightshift: u8) -> usize {
        (self.0 >> rightshift) as usize
    }
}

/// For the `BitBoard`, iterate over every `Square` set.
impl Iterator for BitBoard {
    type Item = Square;

    fn next(&mut self) -> Option<Square> {
        if self.0 == 0 {
            None
        } else {
            let result = self.to_square();
            *self ^= BitBoard::from_square(result);
            Some(result)
        }
    }
}