String view entry (#1147)

make entry support string_view in its interface, and make it efficient when in in C++14

ChangeLog

@@ -1,3 +1,4 @@
+	* use string_view in entry interface
 	* deprecate "send_stats" property on trackers (since lt_tracker extension has
 	  been removed)
 	* remove deprecate session_settings API (use settings_pack instead)

include/libtorrent/announce_entry.hpp

@@ -47,7 +47,7 @@ namespace libtorrent
 	struct TORRENT_EXPORT announce_entry
 	{
 		// constructs a tracker announce entry with ``u`` as the URL.
-		announce_entry(std::string const& u);
+		announce_entry(std::string u);
 		announce_entry();
 		~announce_entry();
 		announce_entry(announce_entry const&) = default;

include/libtorrent/create_torrent.hpp

@@ -240,7 +240,7 @@ namespace libtorrent
 		// tracker less torrent. It can be used by clients to bootstrap their DHT node from.
 		// The node is a hostname and a port number where there is a DHT node running.
 		// You can have any number of DHT nodes in a torrent.
-		void add_node(std::pair<std::string, int> const& node);
+		void add_node(std::pair<std::string, int> node);
 
 		// Adds a tracker to the torrent. This is not strictly required, but most torrents
 		// use a tracker as their main source of peers. The url should be an http:// or udp://

include/libtorrent/entry.hpp

@@ -72,6 +72,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/assert.hpp"
 #include "libtorrent/error_code.hpp"
 #include "libtorrent/span.hpp"
+#include "libtorrent/string_view.hpp"
 
 namespace libtorrent
 {
@@ -82,6 +83,21 @@ namespace libtorrent
 #endif
 	struct bdecode_node;
 
+#if __cplusplus > 201103
+	namespace aux
+	{
+		// this enables us to compare a string_view against the std::string that's
+		// held by the std::map
+		struct strview_less
+		{
+			using is_transparent = std::true_type;
+			template <typename T1, typename T2>
+			bool operator()(T1 const& rhs, T2 const& lhs) const
+			{ return rhs < lhs; }
+		};
+	};
+#endif
+
 	// The ``entry`` class represents one node in a bencoded hierarchy. It works as a
 	// variant type, it can be either a list, a dictionary (``std::map``), an integer
 	// or a string.
@@ -92,7 +108,11 @@ namespace libtorrent
 		// the key is always a string. If a generic entry would be allowed
 		// as a key, sorting would become a problem (e.g. to compare a string
 		// to a list). The definition doesn't mention such a limit though.
+#if __cplusplus <= 201103
 		typedef std::map<std::string, entry> dictionary_type;
+#else
+		typedef std::map<std::string, entry, aux::strview_less> dictionary_type;
+#endif
 		typedef std::string string_type;
 		typedef std::vector<entry> list_type;
 		typedef std::int64_t integer_type;
@@ -119,6 +139,7 @@ namespace libtorrent
 		entry(span<char const>);
 		template <typename U, typename Cond = typename std::enable_if<
 			std::is_same<U, entry::string_type>::value
+			|| std::is_same<U, string_view>::value
 			|| std::is_same<U, char const*>::value>::type>
 		entry(U v)
 			: m_type(undefined_t)
@@ -250,21 +271,17 @@ namespace libtorrent
 		// The const version of ``operator[]`` will only return a reference to an
 		// existing element at the given key. If the key is not found, it will
 		// throw ``system_error``.
-		entry& operator[](char const* key);
-		entry& operator[](std::string const& key);
-		const entry& operator[](char const* key) const;
-		const entry& operator[](std::string const& key) const;
+		entry& operator[](string_view key);
+		const entry& operator[](string_view key) const;
 
 		// These functions requires the entry to be a dictionary, if it isn't
 		// they will throw ``system_error``.
 		//
 		// They will look for an element at the given key in the dictionary, if
-		// the element cannot be found, they will return 0. If an element with
-		// the given key is found, the return a pointer to it.
-		entry* find_key(char const* key);
-		entry const* find_key(char const* key) const;
-		entry* find_key(std::string const& key);
-		entry const* find_key(std::string const& key) const;
+		// the element cannot be found, they will return nullptr. If an element
+		// with the given key is found, the return a pointer to it.
+		entry* find_key(string_view key);
+		entry const* find_key(string_view key) const;
 
 		// returns a pretty-printed string representation
 		// of the bencoded structure, with JSON-style syntax

include/libtorrent/kademlia/put_data.hpp

@@ -65,7 +65,7 @@ protected:
 
 	put_callback m_put_callback;
 	item m_data;
-	bool m_done;
+	bool m_done = false;
 };
 
 struct put_data_observer : traversal_observer

src/announce_entry.cpp

@@ -47,8 +47,8 @@ namespace libtorrent
 		tracker_retry_delay_max = 60 * 60
 	};
 
-	announce_entry::announce_entry(std::string const& u)
-		: url(u)
+	announce_entry::announce_entry(std::string u)
+		: url(std::move(u))
 		, fails(0)
 		, updating(false)
 		, source(0)

src/create_torrent.cpp

@@ -705,9 +705,9 @@ namespace libtorrent
 		m_filehashes[index] = h;
 	}
 
-	void create_torrent::add_node(std::pair<std::string, int> const& node)
+	void create_torrent::add_node(std::pair<std::string, int> node)
 	{
-		m_nodes.push_back(node);
+		m_nodes.emplace_back(std::move(node));
 	}
 
 	void create_torrent::add_url_seed(string_view url)

src/entry.cpp

@@ -89,64 +89,52 @@ namespace libtorrent
 		}
 	}
 
-	entry& entry::operator[](char const* key)
+	entry& entry::operator[](string_view key)
 	{
+#if __cplusplus <= 201103
+		dictionary_type::iterator i = dict().find(key.to_string());
+#else
 		dictionary_type::iterator i = dict().find(key);
+#endif
 		if (i != dict().end()) return i->second;
 		dictionary_type::iterator ret = dict().insert(
-			std::pair<const std::string, entry>(key, entry())).first;
+			std::make_pair(key.to_string(), entry())).first;
 		return ret->second;
 	}
 
-	entry& entry::operator[](std::string const& key)
-	{
-		dictionary_type::iterator i = dict().find(key);
-		if (i != dict().end()) return i->second;
-		dictionary_type::iterator ret = dict().insert(
-			std::make_pair(key, entry())).first;
-		return ret->second;
-	}
-
-	entry* entry::find_key(char const* key)
-	{
-		dictionary_type::iterator i = dict().find(key);
-		if (i == dict().end()) return nullptr;
-		return &i->second;
-	}
-
-	entry const* entry::find_key(char const* key) const
-	{
-		dictionary_type::const_iterator i = dict().find(key);
-		if (i == dict().end()) return nullptr;
-		return &i->second;
-	}
-
-	entry* entry::find_key(std::string const& key)
-	{
-		dictionary_type::iterator i = dict().find(key);
-		if (i == dict().end()) return nullptr;
-		return &i->second;
-	}
-
-	entry const* entry::find_key(std::string const& key) const
-	{
-		dictionary_type::const_iterator i = dict().find(key);
-		if (i == dict().end()) return nullptr;
-		return &i->second;
-	}
-
-	const entry& entry::operator[](char const* key) const
-	{
-		return (*this)[std::string(key)];
-	}
-
-	const entry& entry::operator[](std::string const& key) const
+	const entry& entry::operator[](string_view key) const
 	{
+#if __cplusplus <= 201103
+		dictionary_type::const_iterator i = dict().find(key.to_string());
+#else
 		dictionary_type::const_iterator i = dict().find(key);
+#endif
 		if (i == dict().end()) throw_error();
 		return i->second;
 	}
 
+	entry* entry::find_key(string_view key)
+	{
+#if __cplusplus <= 201103
+		dictionary_type::iterator i = dict().find(key.to_string());
+#else
+		dictionary_type::iterator i = dict().find(key);
+#endif
+		if (i == dict().end()) return nullptr;
+		return &i->second;
+	}
+
+	entry const* entry::find_key(string_view key) const
+	{
+#if __cplusplus <= 201103
+		dictionary_type::const_iterator i = dict().find(key.to_string());
+#else
+		dictionary_type::const_iterator i = dict().find(key);
+#endif
+		if (i == dict().end()) return nullptr;
+		return &i->second;
+	}
+
 	entry::data_type entry::type() const
 	{
 #if TORRENT_USE_ASSERTS

src/kademlia/put_data.cpp

@@ -41,9 +41,7 @@ namespace libtorrent { namespace dht
 put_data::put_data(node& dht_node, put_callback const& callback)
 	: traversal_algorithm(dht_node, (node_id::min)())
 	, m_put_callback(callback)
-	, m_done(false)
-{
-}
+{}
 
 char const* put_data::name() const { return "put_data"; }
 
@@ -51,7 +49,7 @@ void put_data::start()
 {
 	// router nodes must not be added to puts
 	init();
-	bool is_done = add_requests();
+	bool const is_done = add_requests();
 	if (is_done) done();
 }
 
@@ -66,7 +64,7 @@ void put_data::set_targets(std::vector<std::pair<node_entry, std::string>> const
 	#if TORRENT_USE_ASSERTS
 		o->m_in_constructor = false;
 	#endif
-		m_results.push_back(o);
+		m_results.push_back(std::move(o));
 	}
 }
 

test/test_bdecode.cpp

@@ -32,6 +32,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 #include "test.hpp"
 #include "libtorrent/bdecode.hpp"
+#include "libtorrent/entry.hpp"
 
 using namespace libtorrent;
 
@@ -51,6 +52,31 @@ TORRENT_TEST(integer)
 	TEST_EQUAL(e.int_value(), 12453);
 }
 
+TORRENT_TEST(construct_string)
+{
+	entry e(std::string("abc123"));
+	TEST_EQUAL(e.string(), "abc123");
+}
+
+TORRENT_TEST(construct_string_literal)
+{
+	entry e("abc123");
+	TEST_EQUAL(e.string(), "abc123");
+}
+
+
+TORRENT_TEST(construct_string_view)
+{
+	entry e(string_view("abc123"));
+	TEST_EQUAL(e.string(), "abc123");
+}
+
+TORRENT_TEST(construct_integer)
+{
+	entry e(4);
+	TEST_EQUAL(e.integer(), 4);
+}
+
 // test string
 TORRENT_TEST(string)
 {