(svn r25345) -Add: implementation of SharesMap and FlowStatMap

1 files changed, 83 insertions, 0 deletions

diff --git a/src/station_base.h b/src/station_base.h
index 974caa063..200d97a97 100644
--- a/src/station_base.h
+++ b/src/station_base.h
@@ -12,12 +12,14 @@
 #ifndef STATION_BASE_H
 #define STATION_BASE_H
 
+#include "core/random_func.hpp"
 #include "base_station_base.h"
 #include "newgrf_airport.h"
 #include "cargopacket.h"
 #include "industry_type.h"
 #include "linkgraph/linkgraph_type.h"
 #include "newgrf_storage.h"
+#include <map>
 
 typedef Pool<BaseStation, StationID, 32, 64000> StationPool;
 extern StationPool _station_pool;
@@ -25,6 +27,87 @@ extern StationPool _station_pool;
 static const byte INITIAL_STATION_RATING = 175;
 
 /**
+ * Flow statistics telling how much flow should be sent along a link. This is
+ * done by creating "flow shares" and using std::map's upper_bound() method to
+ * look them up with a random number. A flow share is the difference between a
+ * key in a map and the previous key. So one key in the map doesn't actually
+ * mean anything by itself.
+ */
+class FlowStat {
+public:
+	typedef std::map<uint32, StationID> SharesMap;
+
+	/**
+	 * Invalid constructor. This can't be called as a FlowStat must not be
+	 * empty. However, the constructor must be defined and reachable for
+	 * FlwoStat to be used in a std::map.
+	 */
+	inline FlowStat() {NOT_REACHED();}
+
+	/**
+	 * Create a FlowStat with an initial entry.
+	 * @param st Station the initial entry refers to.
+	 * @param flow Amount of flow for the initial entry.
+	 */
+	inline FlowStat(StationID st, uint flow)
+	{
+		assert(flow > 0);
+		this->shares[flow] = st;
+	}
+
+	/**
+	 * Add some flow to the end of the shares map. Only do that if you know
+	 * that the station isn't in the map yet. Anything else may lead to
+	 * inconsistencies.
+	 * @param st Remote station.
+	 * @param flow Amount of flow to be added.
+	 */
+	inline void AppendShare(StationID st, uint flow)
+	{
+		assert(flow > 0);
+		this->shares[(--this->shares.end())->first + flow] = st;
+	}
+
+	uint GetShare(StationID st) const;
+
+	void ChangeShare(StationID st, int flow);
+
+	/**
+	 * Get the actual shares as a const pointer so that they can be iterated
+	 * over.
+	 * @return Actual shares.
+	 */
+	inline const SharesMap *GetShares() const { return &this->shares; }
+
+	/**
+	 * Get a station a package can be routed to. This done by drawing a
+	 * random number between 0 and sum_shares and then looking that up in
+	 * the map with lower_bound. So each share gets selected with a
+	 * probability dependent on its flow.
+	 * @return A station ID from the shares map.
+	 */
+	inline StationID GetVia() const
+	{
+		assert(!this->shares.empty());
+		return this->shares.upper_bound(RandomRange((--this->shares.end())->first - 1))->second;
+	}
+
+	StationID GetVia(StationID excluded, StationID excluded2 = INVALID_STATION) const;
+
+private:
+	SharesMap shares;  ///< Shares of flow to be sent via specified station (or consumed locally).
+};
+
+/** Flow descriptions by origin stations. */
+class FlowStatMap : public std::map<StationID, FlowStat> {
+public:
+	void AddFlow(StationID origin, StationID via, uint amount);
+	void PassOnFlow(StationID origin, StationID via, uint amount);
+	void DeleteFlows(StationID via);
+	void FinalizeLocalConsumption(StationID self);
+};
+
+/**
  * Stores station stats for a single cargo.
  */
 struct GoodsEntry {