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

use std::sync::Once;
use std::boxed::Box;

use m4ri_rust::friendly::BinMatrix;
use m4ri_rust::friendly::BinVector;

use crate::codes::BinaryCode;

/// ``[7, 4]`` Hamming code
/// 
/// Decodes using direct lookup tables
#[derive(Debug,Serialize)]
pub struct HammingCode7_4;

static INIT: Once = Once::new();
static mut GENERATOR_MATRIX: *const BinMatrix = 0 as *const BinMatrix;
static mut PARITY_MATRIX: *const BinMatrix = 0 as *const BinMatrix;

fn init() {
    INIT.call_once(|| {
        unsafe {
            let matrix = Box::new(BinMatrix::new(vec![
                BinVector::from_bools(&[true, false, false, false, false, true, true]),
                BinVector::from_bools(&[false, true, false, false, true, false, true]),
                BinVector::from_bools(&[false, false, true, false, true, true, false]),
                BinVector::from_bools(&[false, false, false, true, true, true, true]),
                
            ]));
            GENERATOR_MATRIX = Box::into_raw(matrix);

            let matrix = Box::new(BinMatrix::new(vec![
                    BinVector::from_bools(&[true, false, true, false, true, false, true]),
                    BinVector::from_bools(&[false, true, true, false, false, true, true]),
                    BinVector::from_bools(&[false, false, false, true, true, true, true]),
                    
            ]));
            PARITY_MATRIX = Box::into_raw(matrix);
        }
    });
}

static SYNDROME: [[bool; 4]; 128] = [
     [false, false, false, false], // (0, 0, 0, 0)
     [false, false, false, false], // (0, 0, 0, 0)
     [false, false, false, false], // (0, 0, 0, 0)
     [true, true, true, false], // (1, 1, 1, 0)
     [false, false, false, false], // (0, 0, 0, 0)
     [true, true, true, false], // (1, 1, 1, 0)
     [true, true, true, false], // (1, 1, 1, 0)
     [true, true, true, false], // (1, 1, 1, 0)
     [false, false, false, false], // (0, 0, 0, 0)
     [true, false, false, true], // (1, 0, 0, 1)
     [false, true, false, true], // (0, 1, 0, 1)
     [true, true, false, true], // (1, 1, 0, 1)
     [false, false, true, true], // (0, 0, 1, 1)
     [true, false, true, true], // (1, 0, 1, 1)
     [false, true, true, true], // (0, 1, 1, 1)
     [true, true, true, false], // (1, 1, 1, 0)
     [false, false, false, false], // (0, 0, 0, 0)
     [true, false, false, true], // (1, 0, 0, 1)
     [false, true, false, false], // (0, 1, 0, 0)
     [true, true, false, false], // (1, 1, 0, 0)
     [false, false, true, false], // (0, 0, 1, 0)
     [true, false, true, false], // (1, 0, 1, 0)
     [false, true, true, true], // (0, 1, 1, 1)
     [true, true, true, false], // (1, 1, 1, 0)
     [true, false, false, true], // (1, 0, 0, 1)
     [true, false, false, true], // (1, 0, 0, 1)
     [false, true, true, true], // (0, 1, 1, 1)
     [true, false, false, true], // (1, 0, 0, 1)
     [false, true, true, true], // (0, 1, 1, 1)
     [true, false, false, true], // (1, 0, 0, 1)
     [false, true, true, true], // (0, 1, 1, 1)
     [false, true, true, true], // (0, 1, 1, 1)
     [false, false, false, false], // (0, 0, 0, 0)
     [true, false, false, false], // (1, 0, 0, 0)
     [false, true, false, true], // (0, 1, 0, 1)
     [true, true, false, false], // (1, 1, 0, 0)
     [false, false, true, false], // (0, 0, 1, 0)
     [true, false, true, true], // (1, 0, 1, 1)
     [false, true, true, false], // (0, 1, 1, 0)
     [true, true, true, false], // (1, 1, 1, 0)
     [false, true, false, true], // (0, 1, 0, 1)
     [true, false, true, true], // (1, 0, 1, 1)
     [false, true, false, true], // (0, 1, 0, 1)
     [false, true, false, true], // (0, 1, 0, 1)
     [true, false, true, true], // (1, 0, 1, 1)
     [true, false, true, true], // (1, 0, 1, 1)
     [false, true, false, true], // (0, 1, 0, 1)
     [true, false, true, true], // (1, 0, 1, 1)
     [false, false, true, false], // (0, 0, 1, 0)
     [true, true, false, false], // (1, 1, 0, 0)
     [true, true, false, false], // (1, 1, 0, 0)
     [true, true, false, false], // (1, 1, 0, 0)
     [false, false, true, false], // (0, 0, 1, 0)
     [false, false, true, false], // (0, 0, 1, 0)
     [false, false, true, false], // (0, 0, 1, 0)
     [true, true, false, false], // (1, 1, 0, 0)
     [false, false, false, true], // (0, 0, 0, 1)
     [true, false, false, true], // (1, 0, 0, 1)
     [false, true, false, true], // (0, 1, 0, 1)
     [true, true, false, false], // (1, 1, 0, 0)
     [false, false, true, false], // (0, 0, 1, 0)
     [true, false, true, true], // (1, 0, 1, 1)
     [false, true, true, true], // (0, 1, 1, 1)
     [true, true, true, true], // (1, 1, 1, 1)
     [false, false, false, false], // (0, 0, 0, 0)
     [true, false, false, false], // (1, 0, 0, 0)
     [false, true, false, false], // (0, 1, 0, 0)
     [true, true, false, true], // (1, 1, 0, 1)
     [false, false, true, true], // (0, 0, 1, 1)
     [true, false, true, false], // (1, 0, 1, 0)
     [false, true, true, false], // (0, 1, 1, 0)
     [true, true, true, false], // (1, 1, 1, 0)
     [false, false, true, true], // (0, 0, 1, 1)
     [true, true, false, true], // (1, 1, 0, 1)
     [true, true, false, true], // (1, 1, 0, 1)
     [true, true, false, true], // (1, 1, 0, 1)
     [false, false, true, true], // (0, 0, 1, 1)
     [false, false, true, true], // (0, 0, 1, 1)
     [false, false, true, true], // (0, 0, 1, 1)
     [true, true, false, true], // (1, 1, 0, 1)
     [false, true, false, false], // (0, 1, 0, 0)
     [true, false, true, false], // (1, 0, 1, 0)
     [false, true, false, false], // (0, 1, 0, 0)
     [false, true, false, false], // (0, 1, 0, 0)
     [true, false, true, false], // (1, 0, 1, 0)
     [true, false, true, false], // (1, 0, 1, 0)
     [false, true, false, false], // (0, 1, 0, 0)
     [true, false, true, false], // (1, 0, 1, 0)
     [false, false, false, true], // (0, 0, 0, 1)
     [true, false, false, true], // (1, 0, 0, 1)
     [false, true, false, false], // (0, 1, 0, 0)
     [true, true, false, true], // (1, 1, 0, 1)
     [false, false, true, true], // (0, 0, 1, 1)
     [true, false, true, false], // (1, 0, 1, 0)
     [false, true, true, true], // (0, 1, 1, 1)
     [true, true, true, true], // (1, 1, 1, 1)
     [true, false, false, false], // (1, 0, 0, 0)
     [true, false, false, false], // (1, 0, 0, 0)
     [false, true, true, false], // (0, 1, 1, 0)
     [true, false, false, false], // (1, 0, 0, 0)
     [false, true, true, false], // (0, 1, 1, 0)
     [true, false, false, false], // (1, 0, 0, 0)
     [false, true, true, false], // (0, 1, 1, 0)
     [false, true, true, false], // (0, 1, 1, 0)
     [false, false, false, true], // (0, 0, 0, 1)
     [true, false, false, false], // (1, 0, 0, 0)
     [false, true, false, true], // (0, 1, 0, 1)
     [true, true, false, true], // (1, 1, 0, 1)
     [false, false, true, true], // (0, 0, 1, 1)
     [true, false, true, true], // (1, 0, 1, 1)
     [false, true, true, false], // (0, 1, 1, 0)
     [true, true, true, true], // (1, 1, 1, 1)
     [false, false, false, true], // (0, 0, 0, 1)
     [true, false, false, false], // (1, 0, 0, 0)
     [false, true, false, false], // (0, 1, 0, 0)
     [true, true, false, false], // (1, 1, 0, 0)
     [false, false, true, false], // (0, 0, 1, 0)
     [true, false, true, false], // (1, 0, 1, 0)
     [false, true, true, false], // (0, 1, 1, 0)
     [true, true, true, true], // (1, 1, 1, 1)
     [false, false, false, true], // (0, 0, 0, 1)
     [false, false, false, true], // (0, 0, 0, 1)
     [false, false, false, true], // (0, 0, 0, 1)
     [true, true, true, true], // (1, 1, 1, 1)
     [false, false, false, true], // (0, 0, 0, 1)
     [true, true, true, true], // (1, 1, 1, 1)
     [true, true, true, true], // (1, 1, 1, 1)
     [true, true, true, true], // (1, 1, 1, 1)
];

static ENCODE: [[bool; 7]; 16] = [
       [false, false, false, false, false, false, false], // (0, 0, 0, 0, 0, 0, 0)
       [true, false, false, false, false, true, true], // (1, 0, 0, 0, 0, 1, 1)
       [false, true, false, false, true, false, true], // (0, 1, 0, 0, 1, 0, 1)
       [true, true, false, false, true, true, false], // (1, 1, 0, 0, 1, 1, 0)
       [false, false, true, false, true, true, false], // (0, 0, 1, 0, 1, 1, 0)
       [true, false, true, false, true, false, true], // (1, 0, 1, 0, 1, 0, 1)
       [false, true, true, false, false, true, true], // (0, 1, 1, 0, 0, 1, 1)
       [true, true, true, false, false, false, false], // (1, 1, 1, 0, 0, 0, 0)
       [false, false, false, true, true, true, true], // (0, 0, 0, 1, 1, 1, 1)
       [true, false, false, true, true, false, false], // (1, 0, 0, 1, 1, 0, 0)
       [false, true, false, true, false, true, false], // (0, 1, 0, 1, 0, 1, 0)
       [true, true, false, true, false, false, true], // (1, 1, 0, 1, 0, 0, 1)
       [false, false, true, true, false, false, true], // (0, 0, 1, 1, 0, 0, 1)
       [true, false, true, true, false, true, false], // (1, 0, 1, 1, 0, 1, 0)
       [false, true, true, true, true, false, false], // (0, 1, 1, 1, 1, 0, 0)
       [true, true, true, true, true, true, true], // (1, 1, 1, 1, 1, 1, 1)
];


impl BinaryCode for HammingCode7_4 {
    fn name(&self) -> String {
        "[7, 4] Hamming code".to_owned()
    }

    fn length(&self) -> usize {
        7
    }

    fn dimension(&self) -> usize {
        4
    }

    fn generator_matrix(&self) -> &BinMatrix {
        init();
        unsafe {
            GENERATOR_MATRIX.as_ref().unwrap()
        }
    }

    fn parity_check_matrix(&self) -> &BinMatrix {
        init();
        unsafe {
            PARITY_MATRIX.as_ref().unwrap()
        }
    }

    fn decode_to_message(&self, c: &BinVector) -> Result<BinVector, &str> {
        debug_assert_eq!(c.len(), self.length());
        Ok(BinVector::from_bools(&SYNDROME[c.as_u32() as usize]))
    }

    /// Encode using lookup table
    fn encode(&self, c: &BinVector) -> BinVector {
        debug_assert_eq!(c.len(), self.dimension());
        BinVector::from_bools(&ENCODE[c.as_u32() as usize])
    }

    // for hamming codes
    fn bias(&self, delta: f64) -> f64 {
        (1f64 + f64::from(7) * delta) / f64::from(7 + 1)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use m4ri_rust::friendly::BinVector;

    #[test]
    fn size() {
        let code = HammingCode7_4.generator_matrix();
        assert_eq!(code.ncols(), 7);
        assert_eq!(code.nrows(), 4);
    }

    #[test]
    fn decode() {
        let code = HammingCode7_4;

        let codeword = code.decode_to_message(&BinVector::from_elem(7, true)).unwrap();
        assert_eq!(codeword, BinVector::from_elem(4, true));

        let mut vec = BinVector::from_elem(7, true);
        vec.set(0, false);
        let codeword = code.decode_to_message(&vec).unwrap();
        assert_eq!(codeword, BinVector::from_elem(4, true));

        let vec = code.decode_to_code(&BinVector::from_elem(7, false)).unwrap();
        assert_eq!(vec, BinVector::from_elem(7, false));
    }

}