forked from freeeve/pgn
-
Notifications
You must be signed in to change notification settings - Fork 0
/
position.go
201 lines (183 loc) · 2.21 KB
/
position.go
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
package pgn
import "fmt"
type Rank byte
const (
NoRank Rank = '0' + iota
Rank1
Rank2
Rank3
Rank4
Rank5
Rank6
Rank7
Rank8
)
type File byte
const (
FileA File = 'a' + iota
FileB
FileC
FileD
FileE
FileF
FileG
FileH
NoFile File = ' '
)
type Position uint64
const (
A1 Position = 1 << iota
B1
C1
D1
E1
F1
G1
H1
A2
B2
C2
D2
E2
F2
G2
H2
A3
B3
C3
D3
E3
F3
G3
H3
A4
B4
C4
D4
E4
F4
G4
H4
A5
B5
C5
D5
E5
F5
G5
H5
A6
B6
C6
D6
E6
F6
G6
H6
A7
B7
C7
D7
E7
F7
G7
H7
A8
B8
C8
D8
E8
F8
G8
H8
NoPosition Position = 0
)
func ParsePosition(pstr string) (Position, error) {
p, ok := parsePosition(pstr)
if !ok {
return 0, fmt.Errorf("pgn: invalid position string: %s", pstr)
}
return p, nil
}
func parsePosition(pstr string) (Position, bool) {
if len(pstr) != 2 {
return 0, false
}
file := File(pstr[0])
switch file {
case 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h':
case 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H':
file += 'a' - 'A' // lowercase
default:
return 0, false
}
rank := Rank(pstr[1])
switch rank {
case '1', '2', '3', '4', '5', '6', '7', '8':
default:
return 0, false
}
p := PositionFromFileRank(file, rank)
return p, true
}
func (p Position) String() string {
if NoPosition == p {
return "-"
}
f := byte(p.GetFile())
r := byte(p.GetRank())
return string([]byte{f, r})
}
func (p Position) GetRank() Rank {
switch {
case p == NoPosition:
return NoRank
case p <= H1:
return Rank1
case p <= H2:
return Rank2
case p <= H3:
return Rank3
case p <= H4:
return Rank4
case p <= H5:
return Rank5
case p <= H6:
return Rank6
case p <= H7:
return Rank7
case p <= H8:
return Rank8
}
panic("unreachable")
}
func (p Position) GetFile() File {
switch p % 255 {
case 1 << 7:
return FileH
case 1 << 6:
return FileG
case 1 << 5:
return FileF
case 1 << 4:
return FileE
case 1 << 3:
return FileD
case 1 << 2:
return FileC
case 1 << 1:
return FileB
case 1 << 0:
return FileA
}
return NoFile
}
func PositionFromFileRank(f File, r Rank) Position {
// shift ['a'..'h'] and ['1'..'8'] to [0..7]
f -= FileA
r -= Rank1
if f > 7 || r > 7 {
return NoPosition
}
return Position(1) << (uint(r*8) + uint(f))
}