From 9e1428a8d5bd80e769301e64780b698f0932a4e2 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Thu, 17 Nov 2016 23:21:01 -0800
Subject: [PATCH] mempool: better ancestor and descendant traversal.

---
 lib/mempool/mempool.js | 160 +++++++++++++++++++++++++++++------------
 1 file changed, 116 insertions(+), 44 deletions(-)

diff --git a/lib/mempool/mempool.js b/lib/mempool/mempool.js
index 889ab2f6..b8b2c7b5 100644
--- a/lib/mempool/mempool.js
+++ b/lib/mempool/mempool.js
@@ -384,6 +384,17 @@ Mempool.prototype.getCoin = function getCoin(hash, index) {
  */
 
 Mempool.prototype.isSpent = function isSpent(hash, index) {
+  return this.spents[hash + index] != null;
+};
+
+/**
+ * Get an output's spender transaction.
+ * @param {Hash} hash
+ * @param {Number} index
+ * @returns {MempoolEntry}
+ */
+
+Mempool.prototype.getSpent = function getSpent(hash, index) {
   return this.spents[hash + index];
 };
 
@@ -1076,24 +1087,44 @@ Mempool.prototype.checkInputs = co(function* checkInputs(tx, flags) {
  */
 
 Mempool.prototype.countAncestors = function countAncestors(tx) {
-  var max = 0;
-  var i, input, count, prev;
+  return this._countAncestors(tx, {}, 0);
+};
+
+/**
+ * Traverse ancestors and count.
+ * @private
+ * @param {TX} tx
+ * @param {Object} set
+ * @param {Number} count
+ */
+
+Mempool.prototype._countAncestors = function countAncestors(tx, set, count) {
+  var i, input, hash, prev;
 
   for (i = 0; i < tx.inputs.length; i++) {
     input = tx.inputs[i];
-    prev = this.getTX(input.prevout.hash);
+    hash = input.prevout.hash;
+    prev = this.getTX(hash);
 
     if (!prev)
       continue;
 
-    count = 1;
-    count += this.countAncestors(prev);
+    if (set[hash])
+      continue;
 
-    if (count > max)
-      max = count;
+    set[hash] = true;
+    count += 1;
+
+    if (count > constants.mempool.ANCESTOR_LIMIT)
+      break;
+
+    count = this._countAncestors(prev, set, count);
+
+    if (count > constants.mempool.ANCESTOR_LIMIT)
+      break;
   }
 
-  return max;
+  return count;
 };
 
 /**
@@ -1104,24 +1135,40 @@ Mempool.prototype.countAncestors = function countAncestors(tx) {
  */
 
 Mempool.prototype.countDescendants = function countDescendants(tx) {
-  var max = 0;
+  return this._countDescendants(tx, {}, 0);
+};
+
+/**
+ * Count the highest number of
+ * descendants a transaction may have.
+ * @private
+ * @param {TX} tx
+ * @returns {Number}
+ */
+
+Mempool.prototype._countDescendants = function countDescendants(tx, set, count) {
   var hash = tx.hash('hex');
-  var i, count, next;
+  var i, entry, next, nhash;
 
   for (i = 0; i < tx.outputs.length; i++) {
-    next = this.isSpent(hash, i);
+    entry = this.getSpent(hash, i);
 
-    if (!next)
+    if (!entry)
       continue;
 
-    count = 1;
-    count += this.countDescendants(next.tx);
+    next = entry.tx;
+    nhash = next.hash('hex');
 
-    if (count > max)
-      max = count;
+    if (set[nhash])
+      continue;
+
+    set[nhash] = true;
+    count += 1;
+
+    count = this._countDescendants(next, set, count);
   }
 
-  return max;
+  return count;
 };
 
 /**
@@ -1131,23 +1178,35 @@ Mempool.prototype.countDescendants = function countDescendants(tx) {
  */
 
 Mempool.prototype.getAncestors = function getAncestors(tx) {
-  var self = this;
-  var entries = [];
+  return this._getAncestors(tx, [], {});
+};
 
-  (function traverse(tx) {
-    var i, input, prev;
+/**
+ * Get all transaction ancestors.
+ * @private
+ * @param {TX} tx
+ * @returns {MempoolEntry[]}
+ */
 
-    for (i = 0; i < tx.inputs.length; i++) {
-      input = tx.inputs[i];
-      prev = self.getTX(input.prevout.hash);
+Mempool.prototype._getAncestors = function getAncestors(tx, entries, set) {
+  var i, hash, input, prev;
 
-      if (!prev)
-        continue;
+  for (i = 0; i < tx.inputs.length; i++) {
+    input = tx.inputs[i];
+    hash = input.prevout.hash;
+    prev = this.getTX(hash);
 
-      entries.push(prev);
-      traverse(prev);
-    }
-  })(tx);
+    if (!prev)
+      continue;
+
+    if (set[hash])
+      continue;
+
+    set[hash] = true;
+    entries.push(prev);
+
+    this._getAncestors(prev, entries, set);
+  }
 
   return entries;
 };
@@ -1159,23 +1218,36 @@ Mempool.prototype.getAncestors = function getAncestors(tx) {
  */
 
 Mempool.prototype.getDescendants = function getDescendants(tx) {
-  var self = this;
-  var entries = [];
+  return this._getDescendants(tx, [], {});
+};
 
-  (function traverse(tx) {
-    var hash = tx.hash('hex');
-    var i, next;
+/**
+ * Get all a transaction descendants.
+ * @param {TX} tx
+ * @returns {MempoolEntry[]}
+ */
 
-    for (i = 0; i < tx.outputs.length; i++) {
-      next = self.isSpent(hash, i);
+Mempool.prototype._getDescendants = function getDescendants(tx, entries, set) {
+  var hash = tx.hash('hex');
+  var i, entry, next, nhash;
 
-      if (!next)
-        continue;
+  for (i = 0; i < tx.outputs.length; i++) {
+    entry = this.getSpent(hash, i);
 
-      entries.push(next);
-      traverse(next.tx);
-    }
-  })(tx);
+    if (!entry)
+      continue;
+
+    next = entry.tx;
+    nhash = next.hash('hex');
+
+    if (set[nhash])
+      continue;
+
+    set[nhash] = true;
+    entries.push(next);
+
+    this._getDescendants(next, entries, set);
+  }
 
   return entries;
 };
@@ -1671,7 +1743,7 @@ Mempool.prototype.removeSpenders = function removeSpenders(entry) {
   var i, spender;
 
   for (i = 0; i < tx.outputs.length; i++) {
-    spender = this.isSpent(hash, i);
+    spender = this.getSpent(hash, i);
 
     if (!spender)
       continue;