/**
* Contains misc static utility methods.
*/
class Utils {
/**
* Converts a single byte to a hex string.
* @param {number} byte
* @return {string}
*/
static byteToHex(byte) {
// Ensure hex string always has two chars
return ('0' + byte.toString(16)).slice(-2);
}
/**
* Converts an array of bytes to a hex string.
* @param {array} byteArray
* @return {string}
*/
static bytesToHex(byteArray) {
var hex = [];
byteArray.forEach(byte => hex.push(Utils.byteToHex(byte)));
return hex.join('');
}
/**
* Converts a hex string to a number.
* @param {string} hexString
* @return {number}
*/
static hexToNumber(hexString) {
return parseInt(hexString, 16);
}
/**
* Converts an array of bytes to a number.
* @param {array} byteArray
* @return {number}
*/
static bytesToNumber(byteArray) {
return Utils.hexToNumber(Utils.bytesToHex(byteArray));
}
/**
* Converts an array of bytes to letters.
* @param {array} byteArray
* @return {string}
*/
static bytesToLetters(byteArray) {
var letters = [];
byteArray.forEach(byte => letters.push(String.fromCharCode(byte)));
return letters.join('');
}
/**
* Converts a decimal to it's binary representation.
* @param {number} dec
* @return {string}
*/
static decToBinary(dec) {
return (dec >>> 0).toString(2);
}
/**
* Determines the length in bytes of a variable length quaantity. The first byte in given range is assumed to be beginning of var length quantity.
* @param {array} byteArray
* @return {number}
*/
static getVarIntLength(byteArray) {
// Get byte count of delta VLV
// http://www.ccarh.org/courses/253/handout/vlv/
// If byte is greater or equal to 80h (128 decimal) then the next byte
// is also part of the VLV,
// else byte is the last byte in a VLV.
let currentByte = byteArray[0];
let byteCount = 1;
while (currentByte >= 128) {
currentByte = byteArray[byteCount];
byteCount++;
}
return byteCount;
}
/**
* Reads a variable length value.
* @param {array} byteArray
* @return {number}
*/
static readVarInt(byteArray) {
var result = 0;
byteArray.forEach(number => {
var b = number;
if (b & 0x80) {
result += (b & 0x7f);
result <<= 7;
} else {
/* b is the last byte */
result += b;
}
});
return result;
}
/**
* Decodes base-64 encoded string
* @param {string} string
* @return {string}
*/
static atob(string) {
if (typeof atob === 'function') return atob(string);
return new Buffer(string, 'base64').toString('binary');
}
}
export {Utils};