Move mapAlreadyAskedFor to limitedmap

This will result in re-requesting invs if we are under heavy inv
load, however as long as we get no more than 16,000 invs in two
minutes, this should have no effect on runtime behavior.

src/net.cpp

@@ -63,7 +63,7 @@ CCriticalSection cs_vNodes;
 map<CInv, CDataStream> mapRelay;
 deque<pair<int64, CInv> > vRelayExpiration;
 CCriticalSection cs_mapRelay;
-map<CInv, int64> mapAlreadyAskedFor;
+limitedmap<CInv, int64> mapAlreadyAskedFor(MAX_INV_SZ);
 
 static deque<string> vOneShots;
 CCriticalSection cs_vOneShots;

src/net.h

@@ -15,6 +15,7 @@
 #endif
 
 #include "mruset.h"
+#include "limitedmap.h"
 #include "netbase.h"
 #include "protocol.h"
 #include "addrman.h"
@@ -100,7 +101,7 @@ extern CCriticalSection cs_vNodes;
 extern std::map<CInv, CDataStream> mapRelay;
 extern std::deque<std::pair<int64, CInv> > vRelayExpiration;
 extern CCriticalSection cs_mapRelay;
-extern std::map<CInv, int64> mapAlreadyAskedFor;
+extern limitedmap<CInv, int64> mapAlreadyAskedFor;
 
 extern std::vector<std::string> vAddedNodes;
 extern CCriticalSection cs_vAddedNodes;
@@ -367,7 +368,12 @@ public:
     {
         // We're using mapAskFor as a priority queue,
         // the key is the earliest time the request can be sent
-        int64& nRequestTime = mapAlreadyAskedFor[inv];
+        int64 nRequestTime;
+        limitedmap<CInv, int64>::const_iterator it = mapAlreadyAskedFor.find(inv);
+        if (it != mapAlreadyAskedFor.end())
+            nRequestTime = it->second;
+        else
+            nRequestTime = 0;
         if (fDebugNet)
             printf("askfor %s   %"PRI64d" (%s)\n", inv.ToString().c_str(), nRequestTime, DateTimeStrFormat("%H:%M:%S", nRequestTime/1000000).c_str());
 
@@ -380,6 +386,10 @@ public:
 
         // Each retry is 2 minutes after the last
         nRequestTime = std::max(nRequestTime + 2 * 60 * 1000000, nNow);
+        if (it != mapAlreadyAskedFor.end())
+            mapAlreadyAskedFor.update(it, nRequestTime);
+        else
+            mapAlreadyAskedFor.insert(std::make_pair(inv, nRequestTime));
         mapAskFor.insert(std::make_pair(nRequestTime, inv));
     }