@nuintun/qrcode/cjs/common/image/utils/Base64Stream.cjs

A pure JavaScript QRCode encode and decode library.

/**
 * @module QRCode
 * @package @nuintun/qrcode
 * @license MIT
 * @version 5.0.2
 * @author nuintun <nuintun@qq.com>
 * @description A pure JavaScript QRCode encode and decode library.
 * @see https://github.com/nuintun/qrcode#readme
 */

'use strict';

const ByteStream = require('./ByteStream.cjs');

/**
 * @module Base64Stream
 */
const { fromCharCode } = String;
function encode(byte) {
  byte &= 0x3f;
  if (byte >= 0) {
    if (byte < 26) {
      // A.
      return 0x41 + byte;
    } else if (byte < 52) {
      // a.
      return 0x61 + (byte - 26);
    } else if (byte < 62) {
      // 0.
      return 0x30 + (byte - 52);
    } else if (byte === 62) {
      // +.
      return 0x2b;
    } else if (byte === 63) {
      // /.
      return 0x2f;
    }
  }
  throw new Error(`illegal char: ${fromCharCode(byte)}`);
}
class Base64Stream {
  #bits = 0;
  #buffer = 0;
  #length = 0;
  #stream = new ByteStream.ByteStream();
  get bytes() {
    return this.#stream.bytes;
  }
  write(byte) {
    let bits = this.#bits + 8;
    const stream = this.#stream;
    const buffer = (this.#buffer << 8) | (byte & 0xff);
    while (bits >= 6) {
      stream.writeByte(encode(buffer >>> (bits - 6)));
      bits -= 6;
    }
    this.#length++;
    this.#bits = bits;
    this.#buffer = buffer;
  }
  close() {
    const bits = this.#bits;
    const stream = this.#stream;
    if (bits > 0) {
      stream.writeByte(encode(this.#buffer << (6 - bits)));
      this.#bits = 0;
      this.#buffer = 0;
    }
    const length = this.#length;
    if (length % 3 != 0) {
      // Padding.
      const pad = 3 - (length % 3);
      for (let i = 0; i < pad; i++) {
        // =.
        stream.writeByte(0x3d);
      }
    }
  }
}

exports.Base64Stream = Base64Stream;
exports.fromCharCode = fromCharCode;