go-ethereum/ethcrypto/mnemonic.go

package ethcrypto

import (
	"fmt"
	"io/ioutil"
	"os"
	"path"
	"path/filepath"
	"strconv"
	"strings"
)

func InitWords(wordsPath string) {
	filename := path.Join(wordsPath, "mnemonic.words.lst")
	if _, err := os.Stat(filename); os.IsNotExist(err) {
		fmt.Printf("reading mnemonic word list file from supplied path not found. Looked in %s. Trying next option.\n", filename)

		dir := path.Join(os.Getenv("GOPATH"), "src", "github.com", "ethereum", "eth-go", "ethcrypto")
		filename = path.Join(dir, "mnemonic.words.lst")
		if _, err := os.Stat(filename); os.IsNotExist(err) {
			fmt.Printf("reading mnemonic word list file 'mnemonic.words.lst' from source folder failed: %s.\n", filename)
			dir, err := filepath.Abs(filepath.Dir(os.Args[0]))
			if err != nil {
				panic(fmt.Errorf("problem getting current folder: ", err))
			}
			filename = path.Join(dir, "mnemonic.words.lst")
		}
	}

	content, err := ioutil.ReadFile(filename)
	if err != nil {
		panic(fmt.Errorf("All options for finding the mnemonic word list file 'mnemonic.words.lst' failed: ", err))
	}
	words = strings.Split(string(content), "\n")
}

var words []string

// TODO: See if we can refactor this into a shared util lib if we need it multiple times
func IndexOf(slice []string, value string) int64 {
	for p, v := range slice {
		if v == value {
			return int64(p)
		}
	}
	return -1
}

func MnemonicEncode(message string) []string {
	var out []string
	n := int64(len(words))

	for i := 0; i < len(message); i += (len(message) / 8) {
		x := message[i : i+8]
		bit, _ := strconv.ParseInt(x, 16, 64)
		w1 := (bit % n)
		w2 := ((bit / n) + w1) % n
		w3 := ((bit / n / n) + w2) % n
		out = append(out, words[w1], words[w2], words[w3])
	}
	return out
}

func MnemonicDecode(wordsar []string) string {
	var out string
	n := int64(len(words))

	for i := 0; i < len(wordsar); i += 3 {
		word1 := wordsar[i]
		word2 := wordsar[i+1]
		word3 := wordsar[i+2]
		w1 := IndexOf(words, word1)
		w2 := IndexOf(words, word2)
		w3 := IndexOf(words, word3)

		y := (w2 - w1) % n
		z := (w3 - w2) % n

		// Golang handles modulo with negative numbers different then most languages
		// The modulo can be negative, we don't want that.
		if z < 0 {
			z += n
		}
		if y < 0 {
			y += n
		}
		x := w1 + n*(y) + n*n*(z)
		out += fmt.Sprintf("%08x", x)
	}
	return out
}