errorcorrection.go

package mode

import (
	"errors"
	"github.com/KangSpace/gqrcode/core/cons"
	"github.com/KangSpace/gqrcode/util"
	"github.com/KangSpace/gqrcode/util/reedsolomon"
	"strconv"
)

// Define Error Correction here

// ErrorCorrection :QRCode Error Correction(Reed-Solomon codes)
// (referred to as L,M,Q and H increasing order of capacity)
// L 7%
// M 15%
// L 25%
// H 30%
type ErrorCorrection struct {
	Level cons.ErrorCorrectionLevel
	// Name in (L, M, Q, H)
	Name string `json:"name"`
	// Capacity in 0.07, 0.15, 0.25, 0.30
	RecoveryRate    float32 `json:"recoveryRate"`
	RecoveryPercent string  `json:"recoveryPercent"`
	rs              *reedsolomon.ReedSolomonEncoder
}

// NewErrorCorrection : Create a new error correction
func NewErrorCorrection(level cons.ErrorCorrectionLevel) *ErrorCorrection {
	var ec *ErrorCorrection
	rs := newReedSolomonEncoder()
	switch level {
	case cons.L:
		ec = &ErrorCorrection{cons.L, "L", 0.07, "7%", rs}
	case cons.M:
		ec = &ErrorCorrection{cons.M, "M", 0.15, "15%", rs}
	case cons.Q:
		ec = &ErrorCorrection{cons.Q, "Q", 0.25, "25%", rs}
	case cons.H:
		ec = &ErrorCorrection{cons.H, "H", 0.30, "30%", rs}
	case cons.NONE:
		// NONE_EC : None Error Correction for Micro QRCode M1
		ec = &ErrorCorrection{cons.NONE, "-", 0, "0", rs}
	default:
		panic(errors.New("specified level:" + strconv.Itoa(level) + " is not support"))
	}
	return ec
}

func newReedSolomonEncoder() *reedsolomon.ReedSolomonEncoder {
	return reedsolomon.NewReedSolomonEncoder(reedsolomon.NewGaloisField(285, 256, 0))
}

// CalcECCodewords :Get Error Correction Codewords by Reed-Solomon algorithms
func (ec *ErrorCorrection) CalcECCodewords(data []byte, ecCodewordsCount int) []byte {
	dataIntArray := util.ByteArrayToIntArray(data)
	eccIntArray := ec.rs.Encode(dataIntArray, ecCodewordsCount)
	return util.IntArrayToByteArray(eccIntArray)
}