@node-dlc/bitcoin/lib/LockTime.ts

DLC bitcoin

import { BufferWriter, StreamReader } from '@node-dlc/bufio';

import { ICloneable } from './ICloneable';
import { TimeLockMode } from './TimeLockMode';

const DEFAULT_LOCKTIME = 0xffff_ffff;
const TIME_THRESHOLD = 500_000_000;

/**
 * Specifies the absolute lock time for a transaction referred in the
 * reference implementation as nLocktime. An absolute locktime is only
 * active when its value is less than 0xffff_ffff and at least one
 * transaction input has a non-0xffff_ffff nSequence.
 */
export class LockTime implements ICloneable<LockTime> {
  /**
   * Parses a locktime from a reader
   * @param reader
   */
  public static parse(reader: StreamReader): LockTime {
    return new LockTime(reader.readUInt32LE());
  }

  /**
   * Creates an nLockTime of zero which enforces finality for the
   * transaction.
   */
  public static zero(): LockTime {
    return new LockTime(0);
  }

  /**
   * Gets or sets the value of the timelock. The value must be less than
   * the maximum allowed value of 0xffff_ffff. When set to the max
   * value, the locktime is disabled.
   */
  public get value(): number {
    return this._value;
  }

  public set value(val: number) {
    if (val > DEFAULT_LOCKTIME || val < 0) throw new Error('Invalid nLocktime');
    this._value = val;
  }

  private _value: number;

  /**
   * Creates a new locktime instance
   * @param value defaults to 0xffff_ffff
   */
  constructor(value: number = DEFAULT_LOCKTIME) {
    this.value = value;
  }

  /**
   * True when a non-default is configured. This flag has no
   * knowledge if the locktime is fully enabled with the requirement
   * that at least one tx input has an nSequence value that non-default.
   */
  public get isEnabled(): boolean {
    return this.value < DEFAULT_LOCKTIME;
  }

  /**
   * Gets the type of lock time: Block or Time based
   */
  public get type(): TimeLockMode {
    if (this.value < TIME_THRESHOLD) return TimeLockMode.Block;
    else return TimeLockMode.Time;
  }

  /**
   * Returns the string value
   */
  public toString(): string {
    return this.value.toString();
  }

  /**
   * Returns the JSON serialized value
   */
  public toJSON(): number {
    return this.value;
  }

  /**
   * Serializes the locktime into a Buffer
   */
  public serialize(): Buffer {
    const writer = new BufferWriter(Buffer.alloc(4));
    writer.writeUInt32LE(this.value);
    return writer.toBuffer();
  }

  /**
   * Clone via deep copy
   */
  public clone(): LockTime {
    return new LockTime(this._value);
  }
}