added priority to disk io jobs

include/libtorrent/disk_io_thread.hpp

@@ -50,6 +50,7 @@ namespace libtorrent
 			, buffer_size(0)
 			, piece(0)
 			, offset(0)
+			, priority(0)
 		{}
 
 		enum action_t
@@ -72,6 +73,12 @@ namespace libtorrent
 		// to the error message
 		std::string str;
 
+		// priority decides whether or not this
+		// job will skip entries in the queue or
+		// not. It always skips in front of entries
+		// with lower priority
+		int priority;
+
 		// this is called when operation completes
 		boost::function<void(int, disk_io_job const&)> callback;
 	};

include/libtorrent/storage.hpp

@@ -202,7 +202,8 @@ namespace libtorrent
 		void async_read(
 			peer_request const& r
 			, boost::function<void(int, disk_io_job const&)> const& handler
-			, char* buffer = 0);
+			, char* buffer = 0
+			, int priority = 0);
 
 		void async_write(
 			peer_request const& r

src/disk_io_thread.cpp

@@ -89,8 +89,15 @@ namespace libtorrent
 	
 	namespace
 	{
+		// The semantic of this operator is:
+		// shouls lhs come before rhs in the job queue
 		bool operator<(disk_io_job const& lhs, disk_io_job const& rhs)
 		{
+			// NOTE: comparison inverted to make higher priority
+			// skip _in_front_of_ lower priority
+			if (lhs.priority > rhs.priority) return true;
+			if (lhs.priority < rhs.priority) return false;
+
 			if (lhs.storage.get() < rhs.storage.get()) return true;
 			if (lhs.storage.get() > rhs.storage.get()) return false;
 			if (lhs.piece < rhs.piece) return true;

src/storage.cpp

@@ -1084,7 +1084,8 @@ namespace libtorrent
 	void piece_manager::async_read(
 		peer_request const& r
 		, boost::function<void(int, disk_io_job const&)> const& handler
-		, char* buffer)
+		, char* buffer
+		, int priority)
 	{
 		disk_io_job j;
 		j.storage = this;
@@ -1093,6 +1094,7 @@ namespace libtorrent
 		j.offset = r.start;
 		j.buffer_size = r.length;
 		j.buffer = buffer;
+		j.priority = priority;
 		// if a buffer is not specified, only one block can be read
 		// since that is the size of the pool allocator's buffers
 		assert(r.length <= 16 * 1024 || buffer != 0);