honor pieces with priority 7 in sequential download mode

ChangeLog

@@ -1,3 +1,4 @@
+	* honor pieces with priority 7 in sequential download mode
 	* simplified building python bindings
 	* make ignore_non_routers more forgiving in the case there are no UPnP
 	  devices at a known router. Should improve UPnP compatibility.

include/libtorrent/torrent_handle.hpp

@@ -1020,7 +1020,9 @@ namespace libtorrent
 
 		// ``set_sequential_download()`` enables or disables *sequential
 		// download*. When enabled, the piece picker will pick pieces in sequence
-		// instead of rarest first.
+		// instead of rarest first. In this mode, piece priorities are ignored,
+		// with the exception of priority 7, which are still preferred over the
+		// sequential piece order.
 		// 
 		// Enabling sequential download will affect the piece distribution
 		// negatively in the swarm. It should be used sparingly.

src/piece_picker.cpp

@@ -1585,11 +1585,28 @@ namespace libtorrent
 
 		if (options & sequential)
 		{
+			if (m_dirty) update_pieces();
+			TORRENT_ASSERT(!m_dirty);
+
+			for (std::vector<int>::const_iterator i = m_pieces.begin();
+				i != m_pieces.end() && piece_priority(*i) == 7; ++i)
+			{
+				if (!is_piece_free(*i, pieces)) continue;
+				num_blocks = add_blocks(*i, pieces
+					, interesting_blocks, backup_blocks
+					, backup_blocks2, num_blocks
+					, prefer_whole_pieces, peer, suggested_pieces
+					, speed, options);
+				if (num_blocks <= 0) return;
+			}
+
 			if (options & reverse)
 			{
 				for (int i = m_reverse_cursor - 1; i >= m_cursor; --i)
 				{	
 					if (!is_piece_free(i, pieces)) continue;
+					// we've already added prio 7 pieces
+					if (piece_priority(i) == 7) continue;
 					num_blocks = add_blocks(i, pieces
 						, interesting_blocks, backup_blocks
 						, backup_blocks2, num_blocks
@@ -1603,6 +1620,8 @@ namespace libtorrent
 				for (int i = m_cursor; i < m_reverse_cursor; ++i)
 				{	
 					if (!is_piece_free(i, pieces)) continue;
+					// we've already added prio 7 pieces
+					if (piece_priority(i) == 7) continue;
 					num_blocks = add_blocks(i, pieces
 						, interesting_blocks, backup_blocks
 						, backup_blocks2, num_blocks

test/test_piece_picker.cpp

@@ -550,6 +550,25 @@ int test_main()
 	for (int i = 0; i < int(picked.size()); ++i)
 		TEST_CHECK(picked[i] == piece_block(6 - (i / blocks_per_piece), i % blocks_per_piece));
 
+// ========================================================
+
+	// test priority sequential download
+	print_title("test priority sequential download");
+	p = setup_picker("7654321", "       ", "1117071", "");
+	picked = pick_pieces(p, "*******", 7 * blocks_per_piece, 0, 0, piece_picker::fast
+		, piece_picker::sequential, empty_vector);
+
+	// the piece with priority 0 was not picked
+	TEST_CHECK(int(picked.size()) == 6 * blocks_per_piece);
+
+	// the first two pieces picked should be 3 and 5 since those have priority 7
+	for (int i = 0; i < 2 * blocks_per_piece; ++i)
+		TEST_CHECK(picked[i].piece_index == 3 || picked[i].piece_index == 5);
+
+	int expected[] = {-1, -1, 0, 1, 2, 6};
+	for (int i = 2 * blocks_per_piece; i < int(picked.size()); ++i)
+		TEST_CHECK(picked[i].piece_index == expected[i / blocks_per_piece]);
+
 // ========================================================
 
 	// test cursors