denoland-deno/cli/js2/07_base64.js

// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.

// Forked from https://github.com/beatgammit/base64-js
// Copyright (c) 2014 Jameson Little. MIT License.

((window) => {
  const lookup = [];
  const revLookup = [];

  const code =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  for (let i = 0, len = code.length; i < len; ++i) {
    lookup[i] = code[i];
    revLookup[code.charCodeAt(i)] = i;
  }

  // Support decoding URL-safe base64 strings, as Node.js does.
  // See: https://en.wikipedia.org/wiki/Base64#URL_applications
  revLookup["-".charCodeAt(0)] = 62;
  revLookup["_".charCodeAt(0)] = 63;

  function getLens(b64) {
    const len = b64.length;

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

    // Trim off extra bytes after placeholder bytes are found
    // See: https://github.com/beatgammit/base64-js/issues/42
    let validLen = b64.indexOf("=");
    if (validLen === -1) validLen = len;

    const placeHoldersLen = validLen === len ? 0 : 4 - (validLen % 4);

    return [validLen, placeHoldersLen];
  }

  // base64 is 4/3 + up to two characters of the original data
  function byteLength(b64) {
    const lens = getLens(b64);
    const validLen = lens[0];
    const placeHoldersLen = lens[1];
    return ((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen;
  }

  function _byteLength(
    b64,
    validLen,
    placeHoldersLen,
  ) {
    return ((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen;
  }

  function toByteArray(b64) {
    let tmp;
    const lens = getLens(b64);
    const validLen = lens[0];
    const placeHoldersLen = lens[1];

    const arr = new Uint8Array(_byteLength(b64, validLen, placeHoldersLen));

    let curByte = 0;

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

    let i;
    for (i = 0; i < len; i += 4) {
      tmp = (revLookup[b64.charCodeAt(i)] << 18) |
        (revLookup[b64.charCodeAt(i + 1)] << 12) |
        (revLookup[b64.charCodeAt(i + 2)] << 6) |
        revLookup[b64.charCodeAt(i + 3)];
      arr[curByte++] = (tmp >> 16) & 0xff;
      arr[curByte++] = (tmp >> 8) & 0xff;
      arr[curByte++] = tmp & 0xff;
    }

    if (placeHoldersLen === 2) {
      tmp = (revLookup[b64.charCodeAt(i)] << 2) |
        (revLookup[b64.charCodeAt(i + 1)] >> 4);
      arr[curByte++] = tmp & 0xff;
    }

    if (placeHoldersLen === 1) {
      tmp = (revLookup[b64.charCodeAt(i)] << 10) |
        (revLookup[b64.charCodeAt(i + 1)] << 4) |
        (revLookup[b64.charCodeAt(i + 2)] >> 2);
      arr[curByte++] = (tmp >> 8) & 0xff;
      arr[curByte++] = 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) {
    let tmp;
    const output = [];
    for (let i = start; i < end; i += 3) {
      tmp = ((uint8[i] << 16) & 0xff0000) +
        ((uint8[i + 1] << 8) & 0xff00) +
        (uint8[i + 2] & 0xff);
      output.push(tripletToBase64(tmp));
    }
    return output.join("");
  }

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

    // go through the array every three bytes, we'll deal with trailing stuff later
    for (let 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];
      parts.push(lookup[tmp >> 2] + lookup[(tmp << 4) & 0x3f] + "==");
    } else if (extraBytes === 2) {
      tmp = (uint8[len - 2] << 8) + uint8[len - 1];
      parts.push(
        lookup[tmp >> 10] +
          lookup[(tmp >> 4) & 0x3f] +
          lookup[(tmp << 2) & 0x3f] +
          "=",
      );
    }

    return parts.join("");
  }

  window.__base64 = {
    byteLength,
    toByteArray,
    fromByteArray,
  };
})(this);