bit-matrix.js

/**
 * Helper class to handle QR Code symbol modules
 *
 * @param {Number} size Symbol size
 */
function BitMatrix (size) {
  if (!size || size < 1) {
    throw new Error('BitMatrix size must be defined and greater than 0')
  }

  this.size = size
  this.data = new Uint8Array(size * size)
  this.reservedBit = new Uint8Array(size * size)
}

/**
 * Set bit value at specified location
 * If reserved flag is set, this bit will be ignored during masking process
 *
 * @param {Number}  row
 * @param {Number}  col
 * @param {Boolean} value
 * @param {Boolean} reserved
 */
BitMatrix.prototype.set = function (row, col, value, reserved) {
  const index = row * this.size + col
  this.data[index] = value
  if (reserved) this.reservedBit[index] = true
}

/**
 * Returns bit value at specified location
 *
 * @param  {Number}  row
 * @param  {Number}  col
 * @return {Boolean}
 */
BitMatrix.prototype.get = function (row, col) {
  return this.data[row * this.size + col]
}

/**
 * Applies xor operator at specified location
 * (used during masking process)
 *
 * @param {Number}  row
 * @param {Number}  col
 * @param {Boolean} value
 */
BitMatrix.prototype.xor = function (row, col, value) {
  this.data[row * this.size + col] ^= value
}

/**
 * Check if bit at specified location is reserved
 *
 * @param {Number}   row
 * @param {Number}   col
 * @return {Boolean}
 */
BitMatrix.prototype.isReserved = function (row, col) {
  return this.reservedBit[row * this.size + col]
}

module.exports = BitMatrix