fcoin/lib/primitives/memblock.js

/*!
 * memblock.js - memblock block object for bcoin
 * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
 * Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
 * https://github.com/bcoin-org/bcoin
 */

'use strict';

var util = require('../utils/util');
var AbstractBlock = require('./abstractblock');
var Block = require('./block');
var Script = require('../script/script');
var Headers = require('./headers');
var BufferReader = require('../utils/reader');
var DUMMY = new Buffer(0);

/**
 * A block object which is essentially a "placeholder"
 * for a full {@link Block} object. The v8 garbage
 * collector's head will explode if there is too much
 * data on the javascript heap. Blocks can currently
 * be up to 1mb in size. In the future, they may be
 * 2mb, 8mb, or maybe 20mb, who knows? A MemBlock
 * is an optimization in Bcoin which defers parsing of
 * the serialized transactions (the block Buffer) until
 * the block has passed through the chain queue and
 * is about to enter the chain. This keeps a lot data
 * off of the javascript heap for most of the time a
 * block even exists in memory, and manages to keep a
 * lot of strain off of the garbage collector. Having
 * 500mb of blocks on the js heap would not be a good
 * thing.
 * @alias module:primitives.MemBlock
 * @constructor
 * @param {NakedBlock} options
 */

function MemBlock() {
  if (!(this instanceof MemBlock))
    return new MemBlock();

  this._raw = DUMMY;
}

util.inherits(MemBlock, AbstractBlock);

/**
 * Memory flag.
 * @const {Boolean}
 * @default
 * @memberof MemBlock#
 */

MemBlock.prototype.memory = true;

/**
 * Serialize the block headers.
 * @returns {Buffer}
 */

MemBlock.prototype.abbr = function abbr() {
  return this._raw.slice(0, 80);
};

/**
 * Get the full block size.
 * @returns {Number}
 */

MemBlock.prototype.getSize = function getSize() {
  return this._raw.length;
};

/**
 * Verify the block.
 * @param {Object?} ret - Return object, may be
 * set with properties `reason` and `score`.
 * @returns {Boolean}
 */

MemBlock.prototype.verifyBody = function verifyBody(ret) {
  return true;
};

/**
 * Retrieve the coinbase height
 * from the coinbase input script.
 * @returns {Number} height (-1 if not present).
 */

MemBlock.prototype.getCoinbaseHeight = function getCoinbaseHeight() {
  if (this.version < 2)
    return -1;

  try {
    return this.parseCoinbaseHeight();
  } catch (e) {
    return -1;
  }
};

/**
 * Parse the coinbase height
 * from the coinbase input script.
 * @private
 * @returns {Number} height (-1 if not present).
 */

MemBlock.prototype.parseCoinbaseHeight = function parseCoinbaseHeight() {
  var br = new BufferReader(this._raw, true);
  var count, script;

  br.seek(80);

  count = br.readVarint();

  if (count === 0)
    return -1;

  br.seek(4);

  count = br.readVarint();

  if (count === 0) {
    if (br.readU8() !== 0)
      count = br.readVarint();
  }

  if (count === 0)
    return -1;

  br.seek(36);

  script = br.readVarBytes();

  return Script.getCoinbaseHeight(script);
};

/**
 * Inject properties from serialized data.
 * @private
 * @param {Buffer} data
 */

MemBlock.prototype.fromRaw = function fromRaw(data) {
  var br = new BufferReader(data, true);

  this.parseAbbr(br);

  this._raw = br.data;

  return this;
};

/**
 * Insantiate a memblock from serialized data.
 * @param {Buffer} data
 * @returns {MemBlock}
 */

MemBlock.fromRaw = function fromRaw(data) {
  return new MemBlock().fromRaw(data);
};

/**
 * Return serialized block data.
 * @returns {Buffer}
 */

MemBlock.prototype.toRaw = function toRaw() {
  return this._raw;
};

/**
 * Return serialized block data.
 * @returns {Buffer}
 */

MemBlock.prototype.toNormal = function toNormal() {
  return this._raw;
};

/**
 * Parse the serialized block data
 * and create an actual {@link Block}.
 * @returns {Block}
 * @throws Parse error
 */

MemBlock.prototype.toBlock = function toBlock() {
  var block = Block.fromRaw(this._raw);

  block._hash = this._hash;
  block._hhash = this._hhash;

  return block;
};

/**
 * Convert the block to a headers object.
 * @returns {Headers}
 */

MemBlock.prototype.toHeaders = function toHeaders() {
  return Headers.fromBlock(this);
};

/**
 * Test whether an object is a MemBlock.
 * @param {Object} obj
 * @returns {Boolean}
 */

MemBlock.isMemBlock = function isMemBlock(obj) {
  return obj && obj.memory && typeof obj.toBlock === 'function';
};

/*
 * Expose
 */

module.exports = MemBlock;