1package utils
2
3import (
4	"sync"
5)
6
7type ReedSolomonEncoder struct {
8	gf        *GaloisField
9	polynomes []*GFPoly
10	m         *sync.Mutex
11}
12
13func NewReedSolomonEncoder(gf *GaloisField) *ReedSolomonEncoder {
14	return &ReedSolomonEncoder{
15		gf, []*GFPoly{NewGFPoly(gf, []int{1})}, new(sync.Mutex),
16	}
17}
18
19func (rs *ReedSolomonEncoder) getPolynomial(degree int) *GFPoly {
20	rs.m.Lock()
21	defer rs.m.Unlock()
22
23	if degree >= len(rs.polynomes) {
24		last := rs.polynomes[len(rs.polynomes)-1]
25		for d := len(rs.polynomes); d <= degree; d++ {
26			next := last.Multiply(NewGFPoly(rs.gf, []int{1, rs.gf.ALogTbl[d-1+rs.gf.Base]}))
27			rs.polynomes = append(rs.polynomes, next)
28			last = next
29		}
30	}
31	return rs.polynomes[degree]
32}
33
34func (rs *ReedSolomonEncoder) Encode(data []int, eccCount int) []int {
35	generator := rs.getPolynomial(eccCount)
36	info := NewGFPoly(rs.gf, data)
37	info = info.MultByMonominal(eccCount, 1)
38	_, remainder := info.Divide(generator)
39
40	result := make([]int, eccCount)
41	numZero := int(eccCount) - len(remainder.Coefficients)
42	copy(result[numZero:], remainder.Coefficients)
43	return result
44}
45