add write_torrent_file_buf() overload for generating .torrent files

ChangeLog

@@ -1,3 +1,4 @@
+	* add write_torrent_file_buf() overload for generating .torrent files
 	* add create_torrent::generate_buf() function to generate into a buffer
 	* fix copy_file when the file ends with a sparse region
 	* uTP performance, fix packet loss when sending is stalled

bindings/python/src/session.cpp

@@ -1325,6 +1325,7 @@ void bind_session()
 
     entry (*write_torrent_file0)(add_torrent_params const&, write_torrent_flags_t) = &write_torrent_file;
     def("write_torrent_file", write_torrent_file0, (arg("atp"), arg("flags") = 0));
+    def("write_torrent_file_buf", write_torrent_file_buf, (arg("atp"), arg("flags") = 0));
 
     {
         scope s = class_<dummy17>("write_flags");

include/libtorrent/write_resume_data.hpp

@@ -71,8 +71,14 @@ namespace libtorrent {
 	// * The add_torrent_params object passed to this function does not contain the
 	//   info dictionary (the ``ti`` field)
 	// * The piece layers are not complete for all files that need them
+	//
+	// The ``write_torrent_file_buf()`` overload returns the torrent file in
+	// bencoded buffer form. This overload may be faster at the expense of lost
+	// flexibility to add custom fields.
 	TORRENT_EXPORT entry write_torrent_file(add_torrent_params const& atp);
 	TORRENT_EXPORT entry write_torrent_file(add_torrent_params const& atp, write_torrent_flags_t flags);
+	TORRENT_EXPORT std::vector<char> write_torrent_file_buf(add_torrent_params const& atp
+		, write_torrent_flags_t flags);
 }
 
 #endif

src/write_resume_data.cpp

@@ -418,6 +418,15 @@ namespace {
 		return ret;
 	}
 
+	std::vector<char> write_torrent_file_buf(add_torrent_params const& atp
+		, write_torrent_flags_t flags)
+	{
+		std::vector<char> ret;
+		entry e = write_torrent_file(atp, flags);
+		bencode(std::back_inserter(ret), e);
+		return ret;
+	}
+
 	std::vector<char> write_resume_data_buf(add_torrent_params const& atp)
 	{
 		std::vector<char> ret;

test/test_torrent_info.cpp

@@ -1472,6 +1472,8 @@ TORRENT_TEST(write_torrent_file_session_roundtrip)
 			std::vector<char> out_buffer;
 			bencode(std::back_inserter(out_buffer), e);
 
+			TEST_CHECK(out_buffer == write_torrent_file_buf(p, write_flags::include_dht_nodes));
+
 			if (out_buffer != data)
 			{
 				std::cout << "GOT:\n";
@@ -1493,6 +1495,8 @@ TORRENT_TEST(write_torrent_file_session_roundtrip)
 			std::vector<char> out_buffer;
 			bencode(std::back_inserter(out_buffer), e);
 
+			TEST_CHECK(out_buffer == write_torrent_file_buf(p, write_flags::include_dht_nodes));
+
 			if (out_buffer != data)
 			{
 				std::cout << "GOT:\n";