iota.lib.js/lib/crypto/converter/converter.js

Javascript Library for IOTA

/**
 *
 *   Conversion functions
 *
 **/

var RADIX = 3;
var RADIX_BYTES = 256;
var MAX_TRIT_VALUE = 1;
var MIN_TRIT_VALUE = -1;
var BYTE_HASH_LENGTH = 48;

// All possible tryte values
var trytesAlphabet = "9ABCDEFGHIJKLMNOPQRSTUVWXYZ"

// map of all trits representations
var trytesTrits = [
    [ 0,  0,  0],
    [ 1,  0,  0],
    [-1,  1,  0],
    [ 0,  1,  0],
    [ 1,  1,  0],
    [-1, -1,  1],
    [ 0, -1,  1],
    [ 1, -1,  1],
    [-1,  0,  1],
    [ 0,  0,  1],
    [ 1,  0,  1],
    [-1,  1,  1],
    [ 0,  1,  1],
    [ 1,  1,  1],
    [-1, -1, -1],
    [ 0, -1, -1],
    [ 1, -1, -1],
    [-1,  0, -1],
    [ 0,  0, -1],
    [ 1,  0, -1],
    [-1,  1, -1],
    [ 0,  1, -1],
    [ 1,  1, -1],
    [-1, -1,  0],
    [ 0, -1,  0],
    [ 1, -1,  0],
    [-1,  0,  0]
];

/**
 *   Converts trytes into trits
 *
 *   @method trits
 *   @param {String|Int} input Tryte value to be converted. Can either be string or int
 *   @param {Array} state (optional) state to be modified
 *   @returns {Array} trits
 **/
var trits = function( input, state ) {

    var trits = state || [];

    if (Number.isInteger(input)) {

        var absoluteValue = input < 0 ? -input : input;

        while (absoluteValue > 0) {

            var remainder = absoluteValue % 3;
            absoluteValue = Math.floor(absoluteValue / 3);

            if (remainder > 1) {
                remainder = -1;
                absoluteValue++;
            }

            trits[trits.length] = remainder;
        }
        if (input < 0) {

            for (var i = 0; i < trits.length; i++) {

                trits[i] = -trits[i];
            }
        }
    } else {

        for (var i = 0; i < input.length; i++) {

            var index = trytesAlphabet.indexOf(input.charAt(i));
            trits[i * 3] = trytesTrits[index][0];
            trits[i * 3 + 1] = trytesTrits[index][1];
            trits[i * 3 + 2] = trytesTrits[index][2];
        }
    }

    return trits;
}

/**
 *   Converts trits into trytes
 *
 *   @method trytes
 *   @param {Array} trits
 *   @returns {String} trytes
 **/
var trytes = function(trits) {

    var trytes = "";

    for ( var i = 0; i < trits.length; i += 3 ) {

        // Iterate over all possible tryte values to find correct trit representation
        for ( var j = 0; j < trytesAlphabet.length; j++ ) {

            if ( trytesTrits[ j ][ 0 ] === trits[ i ] && trytesTrits[ j ][ 1 ] === trits[ i + 1 ] && trytesTrits[ j ][ 2 ] === trits[ i + 2 ] ) {

                trytes += trytesAlphabet.charAt( j );
                break;

            }

        }

    }

    return trytes;
}

/**
 *   Converts trits into an integer value
 *
 *   @method value
 *   @param {Array} trits
 *   @returns {int} value
 **/
var value = function(trits) {

    var returnValue = 0;

    for ( var i = trits.length; i-- > 0; ) {

        returnValue = returnValue * 3 + trits[ i ];
    }

    return returnValue;
}

/**
 *   Converts an integer value to trits
 *
 *   @method value
 *   @param {Int} value
 *   @returns {Array} trits
 **/
var fromValue = function(value) {

    var destination = [];
    var absoluteValue = value < 0 ? -value : value;
    var i = 0;

    while( absoluteValue > 0 ) {

        var remainder = ( absoluteValue % RADIX );
        absoluteValue = Math.floor( absoluteValue / RADIX );

        if ( remainder > MAX_TRIT_VALUE ) {

            remainder = MIN_TRIT_VALUE;
            absoluteValue++;

        }

        destination[ i ] = remainder;
        i++;

    }

    if ( value < 0 ) {

        for ( var j = 0; j < destination.length; j++ ) {

            // switch values
            destination[ j ] = destination[ j ] === 0 ? 0: -destination[ j ];

        }

    }

    return destination;
}

module.exports = {
    trits           : trits,
    trytes          : trytes,
    value           : value,
    fromValue       : fromValue
};