Implement a simple map + array to reduce memory allocations via Array creation

lib/services/block/index.js

@@ -209,13 +209,13 @@ BlockService.prototype._detectInitialChainState = function(headers) {
   }
 
   var index = this._tip.height - 1;
-  var record = Array.from(headers)[index];
+  var record = headers.getIndex(index);
 
-  if (record[0] !== this._tip.hash) {
+  if (record.hash !== this._tip.hash) {
     // reorg! we don't yet have the blocks to reorg to, so we'll rewind the chain back to
     // to common ancestor, set the tip to the common ancestor and start the sync
-    this._chainTips.push(record[0]);
+    this._chainTips.push(record.hash);
-    this._handleReorg(record[0]);
+    this._handleReorg(record.hash);
   }
 };
 
@@ -413,7 +413,7 @@ BlockService.prototype._getHash = function(blockArg) {
   var headers = this._header.getAllHeaders();
 
   if (utils.isHeight(blockArg)) {
-    return Array.from(headers)[blockArg];
+    return headers.getIndex(blockArg).hash;
   }
 
 };
@@ -439,7 +439,7 @@ BlockService.prototype._getOldBlocks = function(currentHash, commonAncestorHash)
   var oldBlocks;
   var headers = this._header.getAllHeaders();
   for(var i = headers.length - 1; i > 0; --i) {
-    var item = headers[i];
+    var item = headers.getIndex(i);
     if (item.hash === currentHash) {
       oldBlocks = [this._blockQueue.get(currentHash)];
       continue;
@@ -695,7 +695,7 @@ BlockService.prototype._sync = function() {
     log.info('Blocks download progress: ' + this._tip.height + '/' +
       this._numNeeded + '  (' + (this._tip.height / this._numNeeded*100).toFixed(2) + '%)');
 
-    var endHash = Array.from(headers)[ Math.min(this._tip.height + BlockService.MAX_BLOCKS, size) ][0];
+    var endHash = headers.getIndex( Math.min(this._tip.height + BlockService.MAX_BLOCKS, size) ).hash;
 
     this._p2p.getBlocks({ startHash: this._tip.hash, endHash: endHash });
     return;

lib/services/header/index.js

@@ -17,7 +17,7 @@ var HeaderService = function(options) {
   this._tip = null;
   this._p2p = this.node.services.p2p;
   this._db = this.node.services.db;
-  this._headers = new Map();
+  this._headers = new utils.SimpleMap();
 };
 
 inherits(HeaderService, BaseService);
@@ -43,8 +43,8 @@ HeaderService.prototype.getAPIMethods = function() {
 HeaderService.prototype.getBlockHeader = function(arg) {
 
   if (utils.isHeight(arg)) {
-    var header = Array.from(this._headers)[arg];
+    var header = this._headers.getIndex(arg);
-    return header ? header[1] : null;
+    return header ? header : null;
   }
 
   return this._headers.get(arg);
@@ -133,7 +133,7 @@ HeaderService.prototype._onHeaders = function(headers, convert) {
   }
 
   var runningHeight = this._tip.height;
-  var prevHeader = Array.from(this._headers)[this._headers.length - 1];
+  var prevHeader = this._headers.getLastIndex();
 
   for(var i = 0; i < headers.length; i++) {
     var header = headers[i];

lib/utils.js

@@ -199,9 +199,36 @@ utils.encodeTip = function(tip, name) {
 
 };
 
-utils.isHeight = function(arg) {
+utils.isHeight = function(blockArg) {
   return _.isNumber(blockArg) || (blockArg.length < 40 && /^[0-9]+$/.test(blockArg))
 };
 
+utils.SimpleMap = function SimpleMap() {
+  var object = {};
+  var array = [];
+
+  this.size = 0;
+  this.length = 0;
+
+  this.get = function (key) {
+    return array[object[key]];
+  };
+
+  this.set = function (key, value) {
+    object[key] = array.length;
+    array.push(value);
+
+    this.size = array.length;
+    this.length = array.length;
+  };
+
+  this.getIndex = function (index) {
+    return array[index];
+  };
+
+  this.getLastIndex = function () {
+    return array[array.length - 1];
+  };
+};
 
 module.exports = utils;