@nuintun/qrcode/esm/common/BitArray.js

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
 */

import { getBitMask, toBit, getBitOffset, toInt32 } from './utils.js';

/**
 * @module BitArray
 */
const LOAD_FACTOR = 0.75;
function offset(index) {
  return toInt32(index / 32);
}
function makeArray(length) {
  return new Int32Array(Math.ceil(length / 32));
}
class BitArray {
  #length;
  #bits;
  constructor(length = 0) {
    this.#length = length;
    this.#bits = makeArray(length);
  }
  #alloc(length) {
    const bits = this.#bits;
    if (length > bits.length * 32) {
      const array = makeArray(Math.ceil(length / LOAD_FACTOR));
      array.set(bits);
      this.#bits = array;
    }
    this.#length = length;
  }
  get length() {
    return this.#length;
  }
  get byteLength() {
    return Math.ceil(this.#length / 8);
  }
  set(index) {
    this.#bits[offset(index)] |= getBitMask(index);
  }
  get(index) {
    return toBit(this.#bits[offset(index)] >>> getBitOffset(index));
  }
  xor(mask) {
    const bits = this.#bits;
    const maskBits = mask.#bits;
    const length = Math.min(this.#length, mask.#length);
    for (let i = 0; i < length; i++) {
      // The last int could be incomplete (i.e. not have 32 bits in
      // it) but there is no problem since 0 XOR 0 == 0.
      bits[i] ^= maskBits[i];
    }
  }
  append(value, length = 1) {
    let index = this.#length;
    if (value instanceof BitArray) {
      length = value.#length;
      this.#alloc(index + length);
      for (let i = 0; i < length; i++) {
        if (value.get(i) !== 0) {
          this.set(index);
        }
        index++;
      }
    } else {
      this.#alloc(index + length);
      for (let i = length - 1; i >= 0; i--) {
        if (toBit(value >>> i) !== 0) {
          this.set(index);
        }
        index++;
      }
    }
  }
  writeToUint8Array(bitOffset, target, byteOffset, byteLength) {
    for (let i = 0; i < byteLength; i++) {
      let byte = 0;
      for (let j = 0; j < 8; j++) {
        if (this.get(bitOffset++) !== 0) {
          byte |= 1 << (7 - j);
        }
      }
      target[byteOffset + i] = byte;
    }
  }
  clear() {
    this.#bits.fill(0);
  }
}

export { BitArray };