From d4d5022cfc6f1b826e4c644539a2c756a7499198 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Sat, 25 Apr 2015 08:19:57 -0700
Subject: [PATCH] Use ring buffer of set iterators instead of deque of copies
 in mruset

---
 src/mruset.h              | 36 ++++++++++++++++--------------------
 src/net.cpp               |  6 ++++--
 src/test/mruset_tests.cpp |  2 +-
 3 files changed, 21 insertions(+), 23 deletions(-)

diff --git a/src/mruset.h b/src/mruset.h
index 1969f419c..398aa173b 100644
--- a/src/mruset.h
+++ b/src/mruset.h
@@ -1,12 +1,12 @@
-// Copyright (c) 2012 The Bitcoin Core developers
+// Copyright (c) 2012-2015 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_MRUSET_H
 #define BITCOIN_MRUSET_H
 
-#include <deque>
 #include <set>
+#include <vector>
 #include <utility>
 
 /** STL-like set container that only keeps the most recent N elements. */
@@ -22,11 +22,13 @@ public:
 
 protected:
     std::set<T> set;
-    std::deque<T> queue;
-    size_type nMaxSize;
+    std::vector<iterator> order;
+    size_type first_used;
+    size_type first_unused;
+    const size_type nMaxSize;
 
 public:
-    mruset(size_type nMaxSizeIn = 0) { nMaxSize = nMaxSizeIn; }
+    mruset(size_type nMaxSizeIn = 1) : nMaxSize(nMaxSizeIn) { clear(); }
     iterator begin() const { return set.begin(); }
     iterator end() const { return set.end(); }
     size_type size() const { return set.size(); }
@@ -36,7 +38,9 @@ public:
     void clear()
     {
         set.clear();
-        queue.clear();
+        order.assign(nMaxSize, set.end());
+        first_used = 0;
+        first_unused = 0;
     }
     bool inline friend operator==(const mruset<T>& a, const mruset<T>& b) { return a.set == b.set; }
     bool inline friend operator==(const mruset<T>& a, const std::set<T>& b) { return a.set == b; }
@@ -45,25 +49,17 @@ public:
     {
         std::pair<iterator, bool> ret = set.insert(x);
         if (ret.second) {
-            if (nMaxSize && queue.size() == nMaxSize) {
-                set.erase(queue.front());
-                queue.pop_front();
+            if (set.size() == nMaxSize + 1) {
+                set.erase(order[first_used]);
+                order[first_used] = set.end();
+                if (++first_used == nMaxSize) first_used = 0;
             }
-            queue.push_back(x);
+            order[first_unused] = ret.first;
+            if (++first_unused == nMaxSize) first_unused = 0;
         }
         return ret;
     }
     size_type max_size() const { return nMaxSize; }
-    size_type max_size(size_type s)
-    {
-        if (s)
-            while (queue.size() > s) {
-                set.erase(queue.front());
-                queue.pop_front();
-            }
-        nMaxSize = s;
-        return nMaxSize;
-    }
 };
 
 #endif // BITCOIN_MRUSET_H
diff --git a/src/net.cpp b/src/net.cpp
index 4648dae11..2de04fc57 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -1905,7 +1905,10 @@ bool CAddrDB::Read(CAddrMan& addr)
 unsigned int ReceiveFloodSize() { return 1000*GetArg("-maxreceivebuffer", 5*1000); }
 unsigned int SendBufferSize() { return 1000*GetArg("-maxsendbuffer", 1*1000); }
 
-CNode::CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn, bool fInboundIn) : ssSend(SER_NETWORK, INIT_PROTO_VERSION), addrKnown(5000, 0.001, insecure_rand())
+CNode::CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn, bool fInboundIn) :
+    ssSend(SER_NETWORK, INIT_PROTO_VERSION),
+    addrKnown(5000, 0.001, insecure_rand()),
+    setInventoryKnown(SendBufferSize() / 1000)
 {
     nServices = 0;
     hSocket = hSocketIn;
@@ -1934,7 +1937,6 @@ CNode::CNode(SOCKET hSocketIn, CAddress addrIn, std::string addrNameIn, bool fIn
     nStartingHeight = -1;
     fGetAddr = false;
     fRelayTxes = false;
-    setInventoryKnown.max_size(SendBufferSize() / 1000);
     pfilter = new CBloomFilter();
     nPingNonceSent = 0;
     nPingUsecStart = 0;
diff --git a/src/test/mruset_tests.cpp b/src/test/mruset_tests.cpp
index bd4e9c1d3..9a9763e27 100644
--- a/src/test/mruset_tests.cpp
+++ b/src/test/mruset_tests.cpp
@@ -24,7 +24,7 @@ private:
     std::set<int> set;
 
 public:
-    mrutester() { mru.max_size(MAX_SIZE); }
+    mrutester() : mru(MAX_SIZE) {}
     int size() const { return set.size(); }
 
     void insert(int n)