Source: coins/undocoins.js

  1. /*!
  2.  * undocoins.js - undocoins object for bcoin
  3.  * Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
  4.  * https://github.com/bcoin-org/bcoin
  5.  */
  7. 'use strict';
  9. const assert = require('bsert');
  10. const bio = require('bufio');
  11. const CoinEntry = require('../coins/coinentry');
  13. /**
  14.  * Undo Coins
  15.  * Coins need to be resurrected from somewhere
  16.  * during a reorg. The undo coins store all
  17.  * spent coins in a single record per block
  18.  * (in a compressed format).
  19.  * @alias module:coins.UndoCoins
  20.  * @property {UndoCoin[]} items
  21.  */
  23. class UndoCoins {
  24.   /**
  25.    * Create undo coins.
  26.    * @constructor
  27.    */
  29.   constructor() {
  30.     this.items = [];
  31.   }
  33.   /**
  34.    * Push coin entry onto undo coin array.
  35.    * @param {CoinEntry}
  36.    * @returns {Number}
  37.    */
  39.   push(coin) {
  40.     return this.items.push(coin);
  41.   }
  43.   /**
  44.    * Calculate undo coins size.
  45.    * @returns {Number}
  46.    */
  48.   getSize() {
  49.     let size = 0;
  51.     size += 4;
  53.     for (const coin of this.items)
  54.       size += coin.getSize();
  56.     return size;
  57.   }
  59.   /**
  60.    * Serialize all undo coins.
  61.    * @returns {Buffer}
  62.    */
  64.   toRaw() {
  65.     const size = this.getSize();
  66.     const bw = bio.write(size);
  68.     bw.writeU32(this.items.length);
  70.     for (const coin of this.items)
  71.       coin.toWriter(bw);
  73.     return bw.render();
  74.   }
  76.   /**
  77.    * Inject properties from serialized data.
  78.    * @private
  79.    * @param {Buffer} data
  80.    * @returns {UndoCoins}
  81.    */
  83.   fromRaw(data) {
  84.     const br = bio.read(data);
  85.     const count = br.readU32();
  87.     for (let i = 0; i < count; i++)
  88.       this.items.push(CoinEntry.fromReader(br));
  90.     return this;
  91.   }
  93.   /**
  94.    * Instantiate undo coins from serialized data.
  95.    * @param {Buffer} data
  96.    * @returns {UndoCoins}
  97.    */
  99.   static fromRaw(data) {
  100.     return new this().fromRaw(data);
  101.   }
  103.   /**
  104.    * Test whether the undo coins have any members.
  105.    * @returns {Boolean}
  106.    */
  108.   isEmpty() {
  109.     return this.items.length === 0;
  110.   }
  112.   /**
  113.    * Render the undo coins.
  114.    * @returns {Buffer}
  115.    */
  117.   commit() {
  118.     const raw = this.toRaw();
  119.     this.items.length = 0;
  120.     return raw;
  121.   }
  123.   /**
  124.    * Re-apply undo coins to a view, effectively unspending them.
  125.    * @param {CoinView} view
  126.    * @param {Outpoint} prevout
  127.    */
  129.   apply(view, prevout) {
  130.     const undo = this.items.pop();
  132.     assert(undo);
  134.     view.addEntry(prevout, undo);
  135.   }
  136. }
  138. /*
  139.  * Expose
  140.  */
  142. module.exports = UndoCoins;