merged RC_1_1 into master

ChangeLog

@@ -82,6 +82,8 @@
 	* resume data no longer has timestamps of files
 	* require C++11 to build libtorrent
 
+	* defer truncating existing files until the first time we write to them
+	* fix issue when receiving a torrent with 0-sized padfiles as magnet link
 	* fix issue resuming 1.0.x downloads with a file priority 0
 	* fix torrent_status::next_announce
 	* fix pad-file scalability issue

simulation/test_checking.cpp

@@ -34,6 +34,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/deadline_timer.hpp"
 #include "libtorrent/address.hpp"
 #include "libtorrent/torrent_status.hpp"
+#include "libtorrent/torrent_info.hpp"
 #include "simulator/simulator.hpp"
 #include "simulator/utils.hpp"
 
@@ -42,6 +43,8 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "create_torrent.hpp"
 #include "utils.hpp"
 
+#include <fstream>
+
 template <typename Setup, typename Test>
 void run_test(Setup const& setup, Test const& test)
 {
@@ -76,6 +79,28 @@ void run_test(Setup const& setup, Test const& test)
 	sim.run();
 }
 
+TORRENT_TEST(no_truncate_checking)
+{
+	std::string filename;
+	int size = 0;
+	run_test(
+		[&](lt::add_torrent_params& atp, lt::settings_pack& p) {
+			filename = atp.save_path + "/" + atp.ti->files().file_path(lt::file_index_t{0});
+			std::ofstream f(filename);
+			// create a file that's 100 bytes larger
+			size = int(atp.ti->files().file_size(lt::file_index_t{0}) + 100);
+			std::vector<char> dummy(size);
+			f.write(dummy.data(), dummy.size());
+		},
+		[](lt::session& ses) {}
+		);
+
+	// file should not have been truncated just by checking
+	std::ifstream f(filename);
+	f.seekg(0, std::ios_base::end);
+	TEST_EQUAL(f.tellg(), std::fstream::pos_type(size));
+}
+
 TORRENT_TEST(cache_after_checking)
 {
 	run_test(

src/storage.cpp

@@ -239,9 +239,9 @@ namespace libtorrent {
 			// ignore pad files
 			if (files().pad_file_at(file_index)) continue;
 
+			// this is just to see if the file exists
 			error_code err;
-			std::int64_t size = m_stat_cache.get_filesize(file_index, files()
-				, m_save_path, err);
+			m_stat_cache.get_filesize(file_index, files(), m_save_path, err);
 
 			if (err && err != boost::system::errc::no_such_file_or_directory)
 			{
@@ -251,11 +251,12 @@ namespace libtorrent {
 				break;
 			}
 
-			// if the file already exists, but is larger than what
-			// it's supposed to be, truncate it
-			// if the file is empty, just create it either way.
-			if ((!err && size > files().file_size(file_index))
-				|| (files().file_size(file_index) == 0 && err == boost::system::errc::no_such_file_or_directory))
+			// if the file is empty and doesn't already exist, create it
+			// deliberately don't truncate files that already exist
+			// if a file is supposed to have size 0, but already exists, we will
+			// never truncate it to 0.
+			if (files().file_size(file_index) == 0
+				&& err == boost::system::errc::no_such_file_or_directory)
 			{
 				std::string file_path = files().file_path(file_index, m_save_path);
 				std::string dir = parent_path(file_path);
@@ -273,23 +274,12 @@ namespace libtorrent {
 					}
 				}
 				ec.ec.clear();
+				// just creating the file is enough to make it zero-sized. If
+				// there's a race here and some other process truncates the file,
+				// it's not a problem, we won't access empty files ever again
 				file_handle f = open_file(file_index, open_mode::read_write
 					| open_mode::random_access, ec);
-				if (ec)
-				{
-					ec.file(file_index);
-					ec.operation = operation_t::file_fallocate;
-					return;
-				}
-
-				size = files().file_size(file_index);
-				f->set_size(size, ec.ec);
-				if (ec)
-				{
-					ec.file(file_index);
-					ec.operation = operation_t::file_fallocate;
-					break;
-				}
+				if (ec) return;
 			}
 			ec.ec.clear();
 		}
@@ -617,7 +607,7 @@ namespace libtorrent {
 		}
 		TORRENT_ASSERT(h);
 
-		if (m_allocate_files && (mode & open_mode::rw_mask) != open_mode::read_only)
+		if ((mode & open_mode::rw_mask) != open_mode::read_only)
 		{
 			std::unique_lock<std::mutex> l(m_file_created_mutex);
 			if (m_file_created.size() != files().num_files())
@@ -632,9 +622,12 @@ namespace libtorrent {
 			{
 				m_file_created.set_bit(file);
 				l.unlock();
-				error_code e;
+
+				// if we're allocating files or if the file exists and is greater
+				// than what it's supposed to be, truncate it to its correct size
 				std::int64_t const size = files().file_size(file);
-				h->set_size(size, e);
+				error_code e;
+				bool const need_truncate = h->get_size(e) > size;
 				if (e)
 				{
 					ec.ec = e;
@@ -642,7 +635,19 @@ namespace libtorrent {
 					ec.operation = operation_t::file_fallocate;
 					return h;
 				}
-				m_stat_cache.set_dirty(file);
+
+				if (m_allocate_files || need_truncate)
+				{
+					h->set_size(size, e);
+					if (e)
+					{
+						ec.ec = e;
+						ec.file(file);
+						ec.operation = operation_t::file_fallocate;
+						return h;
+					}
+					m_stat_cache.set_dirty(file);
+				}
 			}
 		}
 		return h;

src/torrent.cpp

@@ -1776,6 +1776,8 @@ namespace libtorrent {
 		}
 		else
 		{
+			need_picker();
+
 			int num_pad_files = 0;
 			TORRENT_ASSERT(block_size() > 0);
 
@@ -1786,10 +1788,6 @@ namespace libtorrent {
 				if (!fs.pad_file_at(i) || fs.file_size(i) == 0) continue;
 				m_padding += std::uint32_t(fs.file_size(i));
 
-				// TODO: instead of creating the picker up front here,
-				// maybe this whole section should move to need_picker()
-				need_picker();
-
 				peer_request pr = m_torrent_file->map_file(i, 0, int(fs.file_size(i)));
 				int off = pr.start & (block_size() - 1);
 				if (off != 0) { pr.length -= block_size() - off; pr.start += block_size() - off; }

test/test_checking.cpp

@@ -243,30 +243,9 @@ void test_checking(int flags = read_only_files)
 	{
 		TEST_CHECK(!st.is_seeding);
 
-		if (flags & read_only_files)
-		{
-			// we expect our checking of the files to trigger
-			// attempts to truncate them, since the files are
-			// read-only here, we expect the checking to fail.
-			TEST_CHECK(st.errc);
-			if (st.errc)
-				std::printf("error: %s\n", st.errc.message().c_str());
-
-			// wait a while to make sure libtorrent survived the error
-			std::this_thread::sleep_for(lt::milliseconds(1000));
-
-			st = tor1.status();
-			TEST_CHECK(!st.is_seeding);
-			TEST_CHECK(st.errc);
-			if (st.errc)
-				std::printf("error: %s\n", st.errc.message().c_str());
-		}
-		else
-		{
-			TEST_CHECK(!st.errc);
-			if (st.errc)
-				std::printf("error: %s\n", st.errc.message().c_str());
-		}
+		TEST_CHECK(!st.errc);
+		if (st.errc)
+			std::printf("error: %s\n", st.errc.message().c_str());
 	}
 
 	if ((flags & (incomplete_files | corrupt_files)) == 0)