add support for creating symlinks, for torrents with symlinks in them

ChangeLog

@@ -1,3 +1,4 @@
+	* support creating symlinks, for torrents with symlinks in them
 	* fix error in seed_mode flag
 	* support magnet link parameters with number siffixes
 	* consistently use "lt" namespace in examples and documentation

bindings/python/src/alert.cpp

@@ -345,6 +345,7 @@ void bind_alert()
        .value("partfile_read", operation_t::partfile_read)
        .value("partfile_write", operation_t::partfile_write)
        .value("hostname_lookup", operation_t::hostname_lookup)
+       .value("symlink", operation_t::symlink)
        ;
 
     def("operation_name", static_cast<char const*(*)(operation_t)>(&lt::operation_name));

include/libtorrent/config.hpp

@@ -166,6 +166,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #endif
 #endif // __APPLE__
 
+#define TORRENT_HAS_SYMLINK 1
 #define TORRENT_USE_DEV_RANDOM 1
 #define TORRENT_HAVE_MMAP 1
 
@@ -188,6 +189,7 @@ POSSIBILITY OF SUCH DAMAGE.
 # define TORRENT_USE_PREAD 1
 #endif
 
+#define TORRENT_HAS_SYMLINK 1
 #define TORRENT_HAVE_MMAP 1
 #define TORRENT_USE_NETLINK 1
 #define TORRENT_USE_IFADDRS 0
@@ -308,6 +310,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #define TORRENT_HAS_SALEN 0
 #define TORRENT_HAS_SEM_RELTIMEDWAIT 1
 #define TORRENT_HAVE_MMAP 1
+#define TORRENT_HAS_SYMLINK 1
 
 // ==== BEOS ===
 #elif defined __BEOS__ || defined __HAIKU__
@@ -323,6 +326,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #define TORRENT_HURD
 #define TORRENT_USE_IFADDRS 1
 #define TORRENT_USE_IFCONF 1
+#define TORRENT_HAS_SYMLINK 1
 
 // ==== eCS(OS/2) ===
 #elif defined __OS2__
@@ -505,6 +509,10 @@ constexpr std::size_t TORRENT_WRITE_HANDLER_MAX_SIZE = 342;
 # endif
 #endif
 
+#ifndef TORRENT_HAS_SYMLINK
+#define TORRENT_HAS_SYMLINK 0
+#endif
+
 // debug builds have asserts enabled by default, release
 // builds have asserts if they are explicitly enabled by
 // the release_asserts macro.

include/libtorrent/create_torrent.hpp

@@ -465,6 +465,8 @@ namespace detail {
 	}
 #endif // TORRENT_ABI_VERSION
 
+	TORRENT_EXTRA_EXPORT file_flags_t get_file_attributes(std::string const& p);
+	TORRENT_EXTRA_EXPORT std::string get_symlink_path(std::string const& p);
 }
 
 #endif

include/libtorrent/operations.hpp

@@ -134,6 +134,7 @@ namespace libtorrent {
 		partfile_read,
 		partfile_write,
 		hostname_lookup,
+		symlink,
 	};
 
 	// maps an operation id (from peer_error_alert and peer_disconnected_alert)

src/alert.cpp

@@ -894,6 +894,7 @@ namespace {
 			case o::partfile_read: return -1;
 			case o::partfile_write: return -1;
 			case o::hostname_lookup: return -1;
+			case o::symlink: return -1;
 		};
 		return -1;
 	}
@@ -1558,7 +1559,8 @@ namespace {
 			"partfile_move",
 			"partfile_read",
 			"partfile_write",
-			"hostname_lookup"
+			"hostname_lookup",
+			"symlink"
 		};
 
 		int const idx = static_cast<int>(op);

src/create_torrent.cpp

@@ -66,28 +66,6 @@ namespace {
 	bool ignore_subdir(std::string const& leaf)
 	{ return leaf == ".." || leaf == "."; }
 
-	file_flags_t get_file_attributes(std::string const& p)
-	{
-		auto const path = convert_to_native_path_string(p);
-
-#ifdef TORRENT_WINDOWS
-		WIN32_FILE_ATTRIBUTE_DATA attr;
-		GetFileAttributesExW(path.c_str(), GetFileExInfoStandard, &attr);
-		if (attr.dwFileAttributes == INVALID_FILE_ATTRIBUTES) return {};
-		if (attr.dwFileAttributes & FILE_ATTRIBUTE_HIDDEN) return file_storage::flag_hidden;
-		return {};
-#else
-		struct ::stat s;
-		if (::lstat(path.c_str(), &s) < 0) return {};
-		file_flags_t file_attr = {};
-		if (s.st_mode & S_IXUSR)
-			file_attr |= file_storage::flag_executable;
-		if (S_ISLNK(s.st_mode))
-			file_attr |= file_storage::flag_symlink;
-		return file_attr;
-#endif
-	}
-
 #ifndef TORRENT_WINDOWS
 	std::string get_symlink_path_impl(char const* path)
 	{
@@ -103,16 +81,6 @@ namespace {
 	}
 #endif
 
-	std::string get_symlink_path(std::string const& p)
-	{
-#if defined TORRENT_WINDOWS
-		TORRENT_UNUSED(p);
-		return "";
-#else
-		return get_symlink_path_impl(p.c_str());
-#endif
-	}
-
 	void add_files_impl(file_storage& fs, std::string const& p
 		, std::string const& l, std::function<bool(std::string)> const& pred
 		, create_flags_t const flags)
@@ -202,6 +170,39 @@ namespace {
 
 } // anonymous namespace
 
+	file_flags_t get_file_attributes(std::string const& p)
+	{
+		auto const path = convert_to_native_path_string(p);
+
+#ifdef TORRENT_WINDOWS
+		WIN32_FILE_ATTRIBUTE_DATA attr;
+		GetFileAttributesExW(path.c_str(), GetFileExInfoStandard, &attr);
+		if (attr.dwFileAttributes == INVALID_FILE_ATTRIBUTES) return {};
+		if (attr.dwFileAttributes & FILE_ATTRIBUTE_HIDDEN) return file_storage::flag_hidden;
+		return {};
+#else
+		struct ::stat s;
+		if (::lstat(path.c_str(), &s) < 0) return {};
+		file_flags_t file_attr = {};
+		if (s.st_mode & S_IXUSR)
+			file_attr |= file_storage::flag_executable;
+		if (S_ISLNK(s.st_mode))
+			file_attr |= file_storage::flag_symlink;
+		return file_attr;
+#endif
+	}
+
+	std::string get_symlink_path(std::string const& p)
+	{
+#if defined TORRENT_WINDOWS
+		TORRENT_UNUSED(p);
+		return "";
+#else
+		return get_symlink_path_impl(p.c_str());
+#endif
+	}
+
+
 #if TORRENT_ABI_VERSION == 1
 
 	void add_files(file_storage& fs, std::wstring const& wfile

src/storage.cpp

@@ -62,6 +62,10 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <sys/mount.h>
 #endif
 
+#if TORRENT_HAS_SYMLINK
+#include <unistd.h> // for symlink()
+#endif
+
 #include "libtorrent/aux_/disable_warnings_pop.hpp"
 
 #include "libtorrent/storage.hpp"
@@ -294,6 +298,7 @@ namespace libtorrent {
 				break;
 			}
 
+
 			// 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
@@ -301,8 +306,7 @@ namespace libtorrent {
 			if (fs.file_size(file_index) == 0
 				&& err == boost::system::errc::no_such_file_or_directory)
 			{
-				std::string file_path = fs.file_path(file_index, m_save_path);
+				std::string dir = parent_path(fs.file_path(file_index, m_save_path));
-				std::string dir = parent_path(file_path);
 
 				if (dir != last_path)
 				{
@@ -317,12 +321,30 @@ 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,
+#if TORRENT_HAS_SYMLINK
-				// it's not a problem, we won't access empty files ever again
+				// create symlinks
-				file_handle f = open_file(file_index, open_mode::read_write
+				if (fs.file_flags(file_index) & file_storage::flag_symlink)
-					| open_mode::random_access, ec);
+				{
-				if (ec) return;
+					if (::symlink(fs.symlink(file_index).c_str()
+							, fs.file_path(file_index, m_save_path).c_str()) != 0)
+					{
+						ec.ec = error_code(errno, generic_category());
+						ec.file(file_index);
+						ec.operation = operation_t::symlink;
+						break;
+					}
+				}
+				else
+#endif
+				{
+					// 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) return;
+				}
 			}
 			ec.ec.clear();
 		}

test/test_torrent.cpp

@@ -739,3 +739,26 @@ TORRENT_TEST(test_calc_bytes_all_pieces_two_pad)
 	auto const fs = test_fs();
 	TEST_EQUAL(calc_bytes(fs, piece_count{fs.num_pieces(), 2, true}), fs.total_size() - 2 * 0x4000);
 }
+
+#if TORRENT_HAS_SYMLINK
+TORRENT_TEST(symlinks_restore)
+{
+	// downloading test torrent with symlinks
+	std::string const work_dir = current_working_directory();
+	lt::add_torrent_params p;
+	p.ti = std::make_shared<lt::torrent_info>(combine_path(
+		combine_path(parent_path(work_dir), "test_torrents"), "symlink2.torrent"));
+	p.flags &= ~lt::torrent_flags::paused;
+	p.save_path = work_dir;
+	settings_pack pack = settings();
+	pack.set_int(libtorrent::settings_pack::alert_mask, libtorrent::alert::status_notification | libtorrent::alert::error_notification);
+	lt::session ses(std::move(pack));
+	ses.add_torrent(p);
+
+	wait_for_alert(ses, torrent_checked_alert::alert_type, "torrent_checked_alert");
+
+	std::string const f = combine_path(combine_path(work_dir, "Some.framework"), "SDL2");
+	TEST_CHECK(get_file_attributes(f) & file_storage::flag_symlink);
+	TEST_CHECK(get_symlink_path(f) == "Versions/A/SDL2");
+}
+#endif

test/test_torrents/symlink2.torrent

@@ -0,0 +1 @@
+d7:comment13:Symlinks test4:infod5:filesld4:attr2:xl6:lengthi0e4:pathl4:SDL2e12:symlink pathl8:Versions1:A4:SDL2eed6:lengthi2514e4:pathl8:Versions1:A14:_CodeSignature13:CodeResourceseed6:lengthi1310e4:pathl8:Versions1:A9:Resources10:Info.plisteed6:lengthi0e4:pathl8:Versions1:A4:SDL2eed4:attr2:xl6:lengthi0e4:pathl8:Versions7:Currente12:symlink pathl1:Aeee4:name14:Some.framework12:piece lengthi16384e6:pieces20:¤ÎIÝ¡Ú‹<eõîÌ[›דÍee