Code generator

codes.go

package main

import (
	"github.com/lazybeaver/xorshift"
	"log"
	"os"
	"strconv"
	"time"
)

const (
	possibleChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
)

var totalCode, possibleCharsLength, lengthCode int
var outputFile string
var randomValue uint64

func init() {
	// Default values
	totalCode = 10
	lengthCode = 5
	outputFile = "output.txt"

	if len(os.Args) >= 2 {
		totalCode, _ = strconv.Atoi(os.Args[1])
	}
	if len(os.Args) >= 3 {
		lengthCode, _ = strconv.Atoi(os.Args[2])
	}
	if len(os.Args) >= 4 {
		outputFile = os.Args[3]
	}

	possibleCharsLength = len(possibleChars)
}

func main() {
	start := time.Now()

	writeContent(generateCodes(totalCode), outputFile)

	elapsed := time.Since(start)
	log.Printf("Total time %s", elapsed)
}

func generateCodes(totalCodes int) (codes map[string]int) {
	count := 0
	codes = make(map[string]int)

	seed := uint64(time.Now().Nanosecond())
	xor64s := xorshift.NewXorShift64Star(seed)

	for count < totalCode {

		randomValueString := ""

		for len(randomValueString) < (lengthCode * 2) {
			randomValue = xor64s.Next()
			randomValueString += strconv.FormatUint(randomValue, 10)
		}

		s := []int{}
		for i := 0; i < len(randomValueString)-1; i += 2 {
			tow_num, _ := strconv.Atoi(string(randomValueString[i]) + string(randomValueString[i+1]))
			s = append(s, tow_num%possibleCharsLength)
		}
		var code string
		for i := 0; i < lengthCode; i++ {
			code += string(possibleChars[s[i]])
		}

		code += "\n"

		codes[code]++
		if len(codes) == count+1 {
			count++
		}
	}

	return
}

func writeContent(content map[string]int, output string) {
	os.Remove(output)
	os.Create(output)
	f, err := os.OpenFile(output, os.O_APPEND|os.O_WRONLY, 0600)
	if err != nil {
		panic(err)
	}

	defer f.Close()
	for code, _ := range content {
		if _, err = f.WriteString(code); err != nil {
			panic(err)
		}
	}
}