report errors in read_piece_alert

ChangeLog

@@ -1,3 +1,4 @@
+	* report errors in read_piece_alert
 	* DHT memory optimization
 	* improve DHT lookup speed
 	* improve support for windows XP and earlier

docs/manual.rst

@@ -6314,6 +6314,10 @@ e.g::
 		case read_piece_alert::alert_type:
 		{
 			read_piece_alert* p = (read_piece_alert*)a.get();
+			if (p->ec) {
+				// read_piece failed
+				break;
+			}
 			// use p
 			break;
 		}
@@ -6432,11 +6436,14 @@ is 0. If successful, ``buffer`` points to a buffer containing all the data
 of the piece. ``piece`` is the piece index that was read. ``size`` is the
 number of bytes that was read.
 
+If the operation fails, ec will indicat what went wrong.
+
 ::
 
 	struct read_piece_alert: torrent_alert
 	{
 		// ...
+		error_code ec;
 		boost::shared_ptr<char> buffer;
 		int piece;
 		int size;

include/libtorrent/alert_types.hpp

@@ -145,12 +145,20 @@ namespace libtorrent
 			, size(s)
 		{}
 
+		read_piece_alert(torrent_handle h, int p, error_code e)
+			: torrent_alert(h)
+			, ec(e)
+			, piece(p)
+			, size(0)
+		{}
+
 		TORRENT_DEFINE_ALERT(read_piece_alert);
 
 		const static int static_category = alert::storage_notification;
 		virtual std::string message() const;
 		virtual bool discardable() const { return false; }
 
+		error_code ec;
 		boost::shared_array<char> buffer;
 		int piece;
 		int size;

include/libtorrent/torrent.hpp

@@ -191,6 +191,7 @@ namespace libtorrent
 			boost::shared_array<char> piece_data;
 			int blocks_left;
 			bool fail;
+			error_code error;
 		};
 		void read_piece(int piece);
 		void on_disk_read_complete(int ret, disk_io_job const& j, peer_request r, read_piece_struct* rp);

src/alert.cpp

@@ -79,8 +79,16 @@ namespace libtorrent {
 	std::string read_piece_alert::message() const
 	{
 		char msg[200];
-		snprintf(msg, sizeof(msg), "%s: piece %s %u", torrent_alert::message().c_str()
-			, buffer ? "successful" : "failed", piece);
+		if (ec)
+		{
+			snprintf(msg, sizeof(msg), "%s: read_piece %u failed: %s"
+				, torrent_alert::message().c_str() , piece, ec.message().c_str());
+		}
+		else
+		{
+			snprintf(msg, sizeof(msg), "%s: read_piece %u successful"
+				, torrent_alert::message().c_str() , piece);
+		}
 		return msg;
 	}
 

src/torrent.cpp

@@ -939,13 +939,8 @@ namespace libtorrent
 		if (m_abort)
 		{
 			// failed
-			// TODO: 3 add an error code to the read_piece alert
-			// to indicate what went wrong. operation_aborted in this
-			// case. It also has to be included in the cases where
-			// a time_critical_piece is aborted by setting its priority
-			// to zero.
 			m_ses.m_alerts.post_alert(read_piece_alert(
-				get_handle(), piece, boost::shared_array<char>(), 0));
+				get_handle(), piece, error_code(boost::system::errc::operation_canceled, get_system_category())));
 			return;
 		}
 
@@ -1137,6 +1132,7 @@ namespace libtorrent
 		if (ret != r.length)
 		{
 			rp->fail = true;
+			rp->error = j.error;
 			handle_disk_error(j);
 		}
 		else
@@ -1149,12 +1145,14 @@ namespace libtorrent
 			int size = m_torrent_file->piece_size(r.piece);
 			if (rp->fail)
 			{
-				rp->piece_data.reset();
-				size = 0;
+				m_ses.m_alerts.post_alert(read_piece_alert(
+					get_handle(), r.piece, rp->error));
 			}
-
+			else
+			{
 				m_ses.m_alerts.post_alert(read_piece_alert(
 					get_handle(), r.piece, rp->piece_data, size));
+			}
 			delete rp;
 		}
 	}
@@ -3705,7 +3703,7 @@ namespace libtorrent
 			if (flags & torrent_handle::alert_when_available)
 			{
 				m_ses.m_alerts.post_alert(read_piece_alert(
-					get_handle(), piece, boost::shared_array<char>(), 0));
+					get_handle(), piece, error_code(boost::system::errc::operation_canceled, get_system_category())));
 			}
 			return;
 		}
@@ -3821,7 +3819,7 @@ namespace libtorrent
 			{
 				// post an empty read_piece_alert to indicate it failed
 				m_ses.m_alerts.post_alert(read_piece_alert(
-					get_handle(), piece, boost::shared_array<char>(), 0));
+					get_handle(), piece, error_code(boost::system::errc::operation_canceled, get_system_category())));
 			}
 			m_time_critical_pieces.erase(i);
 			return;
@@ -3840,7 +3838,7 @@ namespace libtorrent
 				{
 					// post an empty read_piece_alert to indicate it failed
 					m_ses.m_alerts.post_alert(read_piece_alert(
-						get_handle(), i->piece, boost::shared_array<char>(), 0));
+						get_handle(), i->piece, error_code(boost::system::errc::operation_canceled, get_system_category())));
 				}
 				i = m_time_critical_pieces.erase(i);
 				continue;