fus-ext/target/base64.js

FutureScript Extension

'use strict';

exports.toByteArray = toByteArray;
exports.fromByteArray = fromByteArray;

var lookup = [];
var revLookup = [];
var Arr = typeof Uint8Array !== 'undefined' ? Uint8Array : Array;

function init() {
  var code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
  for (var i = 0, len = code.length; i < len; ++i) {
    lookup[i] = code[i];
    revLookup[code.charCodeAt(i)] = i;
  }

  revLookup['-'.charCodeAt(0)] = 62;
  revLookup['_'.charCodeAt(0)] = 63;
}

init();

function toByteArray(b64) {
  var i, j, l, tmp, placeHolders, arr;
  var len = b64.length;

  if (len % 4 > 0) {
    throw new Error('Invalid string. Length must be a multiple of 4');
  }

  // the number of equal signs (place holders)
  // if there are two placeholders, than the two characters before it
  // represent one byte
  // if there is only one, then the three characters before it represent 2 bytes
  // this is just a cheap hack to not do indexOf twice
  placeHolders = b64[len - 2] === '=' ? 2 : b64[len - 1] === '=' ? 1 : 0;

  // base64 is 4/3 + up to two characters of the original data
  arr = new Arr(len * 3 / 4 - placeHolders);

  // if there are placeholders, only get up to the last complete 4 chars
  l = placeHolders > 0 ? len - 4 : len;

  var L = 0;

  for (i = 0, j = 0; i < l; i += 4, j += 3) {
    tmp = revLookup[b64.charCodeAt(i)] << 18 | revLookup[b64.charCodeAt(i + 1)] << 12 | revLookup[b64.charCodeAt(i + 2)] << 6 | revLookup[b64.charCodeAt(i + 3)];
    arr[L++] = tmp >> 16 & 0xFF;
    arr[L++] = tmp >> 8 & 0xFF;
    arr[L++] = tmp & 0xFF;
  }

  if (placeHolders === 2) {
    tmp = revLookup[b64.charCodeAt(i)] << 2 | revLookup[b64.charCodeAt(i + 1)] >> 4;
    arr[L++] = tmp & 0xFF;
  } else if (placeHolders === 1) {
    tmp = revLookup[b64.charCodeAt(i)] << 10 | revLookup[b64.charCodeAt(i + 1)] << 4 | revLookup[b64.charCodeAt(i + 2)] >> 2;
    arr[L++] = tmp >> 8 & 0xFF;
    arr[L++] = tmp & 0xFF;
  }

  return arr;
}

function tripletToBase64(num) {
  return lookup[num >> 18 & 0x3F] + lookup[num >> 12 & 0x3F] + lookup[num >> 6 & 0x3F] + lookup[num & 0x3F];
}

function encodeChunk(uint8, start, end) {
  var tmp;
  var output = [];
  for (var i = start; i < end; i += 3) {
    tmp = (uint8[i] << 16) + (uint8[i + 1] << 8) + uint8[i + 2];
    output.push(tripletToBase64(tmp));
  }
  return output.join('');
}

function fromByteArray(uint8) {
  var tmp;
  var len = uint8.length;
  var extraBytes = len % 3; // if we have 1 byte left, pad 2 bytes
  var output = '';
  var parts = [];
  var maxChunkLength = 16383; // must be multiple of 3

  // go through the array every three bytes, we'll deal with trailing stuff later
  for (var i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
    parts.push(encodeChunk(uint8, i, i + maxChunkLength > len2 ? len2 : i + maxChunkLength));
  }

  // pad the end with zeros, but make sure to not forget the extra bytes
  if (extraBytes === 1) {
    tmp = uint8[len - 1];
    output += lookup[tmp >> 2];
    output += lookup[tmp << 4 & 0x3F];
    output += '==';
  } else if (extraBytes === 2) {
    tmp = (uint8[len - 2] << 8) + uint8[len - 1];
    output += lookup[tmp >> 10];
    output += lookup[tmp >> 4 & 0x3F];
    output += lookup[tmp << 2 & 0x3F];
    output += '=';
  }

  parts.push(output);

  return parts.join('');
}