sctp/lib/serial.js

SCTP network protocol (RFC4960) in plain Javascript

/*

 RFC 1982 Serial Number Arithmetic

 Taken from serial-arithmetic module and modified

*/

// TODO valueOf()

class SerialNumber {
  constructor (value, size) {
    value = value || 0
    size = size || 32
    this.serialBits = size
    this.serialBytes = size / 8
    this._value = value
    this._max = Math.pow(2, this.serialBits)
    this._half = Math.pow(2, this.serialBits - 1)
    this._maxAdd = this._half - 1
    this.number = this._value % this._max
  }

  toString () {
    return `<number=${this.number}, bits=${this.serialBits}>`
    // Return '' + this.number
  }

  getNumber (options) {
    options = options || {}
    options.radix = options.radix || 10
    options.string = options.string || true

    let number = this.number.toString(options.radix)

    if (options.encoding === 'BE') {
      const buf = Buffer.from(this.serialBytes)
      buf.writeUIntLE(this.number, 0, this.serialBytes)
      number = buf.readUIntBE(0, this.serialBytes).toString(options.radix)
    }

    if (options.string) {
      return number
    }
    console.log(number)
    return parseInt(number, options.radix)
  }

  eq (that) {
    return this.number === that.number
  }

  ne (that) {
    return this.number !== that.number
  }

  lt (that) {
    return (
      (this.number < that.number && that.number - this.number < this._half) ||
      (this.number > that.number && this.number - that.number > this._half)
    )
  }

  gt (that) {
    return (
      (this.number < that.number && that.number - this.number > this._half) ||
      (this.number > that.number && this.number - that.number < this._half)
    )
  }

  le (that) {
    return this.eq(that) || this.lt(that)
  }

  ge (that) {
    return this.eq(that) || this.gt(that)
  }

  delta (that) {
    let result = this.number - that.number
    if (result < 0 && result < -this._half) {
      result += this._max
    }
    return result
  }

  inc (delta = 1) {
    this.number = (this.number + delta) % this._max
    return this
  }

  copy () {
    return new SerialNumber(this.number, this.serialBits)
  }

  prev () {
    return new SerialNumber(
      this.number === 0 ? this._max : this.number - 1,
      this.serialBits
    )
  }

  next () {
    return new SerialNumber(
      this.number === this._max ? 0 : this.number + 1,
      this.serialBits
    )
  }
}

module.exports = SerialNumber