git.sr.ht/~pingoo/stdx@v0.0.0-20240218134121-094174641f6e/barcode/utils/reedsolomon.go (about)

     1  package utils
     2  
     3  import (
     4  	"sync"
     5  )
     6  
     7  type ReedSolomonEncoder struct {
     8  	gf        *GaloisField
     9  	polynomes []*GFPoly
    10  	m         *sync.Mutex
    11  }
    12  
    13  func NewReedSolomonEncoder(gf *GaloisField) *ReedSolomonEncoder {
    14  	return &ReedSolomonEncoder{
    15  		gf, []*GFPoly{NewGFPoly(gf, []int{1})}, new(sync.Mutex),
    16  	}
    17  }
    18  
    19  func (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  
    34  func (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  }