configure.ac: add option --enable-eventfd

Remove the runtime check for eventfd(), hard-code the feature once
it's been selected at compile time.  The class WakeFD is splitted into
EventFD and EventPipe, using WakeFD as a macro diversion.

Makefile.am

@@ -288,7 +288,9 @@ libutil_a_SOURCES = \
 # Event loop library
 
 libevent_a_SOURCES = \
-	src/event/WakeFD.cxx src/event/WakeFD.hxx \
+	src/event/EventPipe.cxx src/event/EventPipe.hxx \
+	src/event/EventFD.cxx src/event/EventFD.hxx \
+	src/event/WakeFD.hxx \
 	src/event/TimeoutMonitor.hxx src/event/TimeoutMonitor.cxx \
 	src/event/SocketMonitor.cxx src/event/SocketMonitor.hxx \
 	src/event/BufferedSocket.cxx src/event/BufferedSocket.hxx \

configure.ac

@@ -139,7 +139,8 @@ AC_SEARCH_LIBS([syslog], [bsd socket inet],
 AC_SEARCH_LIBS([socket], [socket])
 AC_SEARCH_LIBS([gethostbyname], [nsl])
 
-AC_CHECK_FUNCS(pipe2 accept4 eventfd)
+AC_CHECK_FUNCS(pipe2 accept4)
+MPD_OPTIONAL_FUNC(eventfd, USE_EVENTFD)
 
 AC_SEARCH_LIBS([exp], [m],,
 	[AC_MSG_ERROR([exp() not found])])

m4/mpd_func.m4

@@ -0,0 +1,12 @@
+dnl MPD_OPTIONAL_FUNC(func, macro)
+dnl
+dnl Allow the user to enable or disable the use of a function.  If the
+dnl option is not specified, the function is auto-detected.
+AC_DEFUN([MPD_OPTIONAL_FUNC], [
+	AC_ARG_ENABLE([$1],
+		AS_HELP_STRING([--enable-$1],
+			[use the function "$1()" (default: auto)]),
+		[test xenable_$1 = xyes && AC_DEFINE([$2], 1, [Define to use $1()])],
+		[AC_CHECK_FUNC([$1],
+			[AC_DEFINE([$2], 1, [Define to use $1()])],)])
+])

src/event/EventFD.cxx

@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#ifdef USE_EVENTFD
+#include "EventFD.hxx"
+#include "fd_util.h"
+#include "gcc.h"
+
+#include <unistd.h>
+
+#include <sys/eventfd.h>
+
+#ifdef WIN32
+static bool PoorSocketPair(int fd[2]);
+#endif
+
+bool
+EventFD::Create()
+{
+	assert(fd == -1);
+
+	fd = eventfd_cloexec_nonblock(0, 0);
+	return fd >= 0;
+}
+
+void
+EventFD::Destroy()
+{
+	close(fd);
+
+#ifndef NDEBUG
+	fd = -1;
+#endif
+}
+
+bool
+EventFD::Read()
+{
+	assert(fd >= 0);
+
+	eventfd_t value;
+	return read(fd, &value, sizeof(value)) == (ssize_t)sizeof(value);
+}
+
+void
+EventFD::Write()
+{
+	assert(fd >= 0);
+
+	static constexpr eventfd_t value = 1;
+	gcc_unused ssize_t nbytes =
+		write(fd, &value, sizeof(value));
+}
+
+#endif /* USE_EVENTFD */

src/event/EventFD.hxx

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_EVENT_FD_HXX
+#define MPD_EVENT_FD_HXX
+
+#include "check.h"
+
+#include <assert.h>
+
+/**
+ * A class that wraps eventfd().
+ *
+ * For optimization purposes, this class does not have a constructor
+ * or a destructor.
+ */
+class EventFD {
+	int fd;
+
+public:
+#ifdef NDEBUG
+	EventFD() = default;
+#else
+	EventFD():fd(-1) {}
+#endif
+
+	EventFD(const EventFD &other) = delete;
+	EventFD &operator=(const EventFD &other) = delete;
+
+	bool Create();
+	void Destroy();
+
+	int Get() const {
+		assert(fd >= 0);
+
+		return fd;
+	}
+
+	/**
+	 * Checks if Write() was called at least once since the last
+	 * Read() call.
+	 */
+	bool Read();
+
+	/**
+	 * Wakes up the reader.  Multiple calls to this function will
+	 * be combined to one wakeup.
+	 */
+	void Write();
+};
+
+#endif

src/event/EventPipe.cxx

@@ -18,7 +18,7 @@
  */
 
 #include "config.h"
-#include "WakeFD.hxx"
+#include "EventPipe.hxx"
 #include "fd_util.h"
 #include "gcc.h"
 
@@ -30,16 +30,12 @@
 #include <cstring> /* for memset() */
 #endif
 
-#ifdef HAVE_EVENTFD
-#include <sys/eventfd.h>
-#endif
-
 #ifdef WIN32
 static bool PoorSocketPair(int fd[2]);
 #endif
 
 bool
-WakeFD::Create()
+EventPipe::Create()
 {
 	assert(fds[0] == -1);
 	assert(fds[1] == -1);
@@ -47,85 +43,50 @@ WakeFD::Create()
 #ifdef WIN32
 	return PoorSocketPair(fds);
 #else
-#ifdef HAVE_EVENTFD
-	fds[0] = eventfd_cloexec_nonblock(0, 0);
-	if (fds[0] >= 0) {
-		fds[1] = -2;
-		return true;
-	}
-#endif
 	return pipe_cloexec_nonblock(fds) >= 0;
 #endif
 }
 
 void
-WakeFD::Destroy()
+EventPipe::Destroy()
 {
 #ifdef WIN32
 	closesocket(fds[0]);
 	closesocket(fds[1]);
 #else
 	close(fds[0]);
-#ifdef HAVE_EVENTFD
+	close(fds[1]);
-	if (!IsEventFD())
-#endif
-		close(fds[1]);
-#endif
 
 #ifndef NDEBUG
 	fds[0] = -1;
 	fds[1] = -1;
 #endif
+#endif
 }
 
 bool
-WakeFD::Read()
+EventPipe::Read()
 {
 	assert(fds[0] >= 0);
-
-#ifdef WIN32
 	assert(fds[1] >= 0);
+
 	char buffer[256];
+#ifdef WIN32
 	return recv(fds[0], buffer, sizeof(buffer), 0) > 0;
 #else
-
-#ifdef HAVE_EVENTFD
-	if (IsEventFD()) {
-		eventfd_t value;
-		return read(fds[0], &value,
-			    sizeof(value)) == (ssize_t)sizeof(value);
-	}
-#endif
-
-	assert(fds[1] >= 0);
-
-	char buffer[256];
 	return read(fds[0], buffer, sizeof(buffer)) > 0;
 #endif
 }
 
 void
-WakeFD::Write()
+EventPipe::Write()
 {
 	assert(fds[0] >= 0);
+	assert(fds[1] >= 0);
 
 #ifdef WIN32
-	assert(fds[1] >= 0);
-
 	send(fds[1], "", 1, 0);
 #else
-
-#ifdef HAVE_EVENTFD
-	if (IsEventFD()) {
-		static constexpr eventfd_t value = 1;
-		gcc_unused ssize_t nbytes =
-			write(fds[0], &value, sizeof(value));
-		return;
-	}
-#endif
-
-	assert(fds[1] >= 0);
-
 	gcc_unused ssize_t nbytes = write(fds[1], "", 1);
 #endif
 }
@@ -141,7 +102,7 @@ static void SafeCloseSocket(SOCKET s)
 
 /* Our poor man's socketpair() implementation
  * Due to limited protocol/address family support and primitive error handling
- * it's better to keep this as a private implementation detail of WakeFD
+ * it's better to keep this as a private implementation detail of EventPipe
  * rather than wide-available API.
  */
 static bool PoorSocketPair(int fd[2])
@@ -160,14 +121,14 @@ static bool PoorSocketPair(int fd[2])
 	int ret = bind(listen_socket,
 		       reinterpret_cast<sockaddr*>(&address),
 		       sizeof(address));
-	
+
 	if (ret < 0) {
 		SafeCloseSocket(listen_socket);
 		return false;
 	}
 
 	ret = listen(listen_socket, 1);
-	
+
 	if (ret < 0) {
 		SafeCloseSocket(listen_socket);
 		return false;

src/event/EventPipe.hxx

@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_EVENT_PIPE_HXX
+#define MPD_EVENT_PIPE_HXX
+
+#include "check.h"
+
+#include <assert.h>
+
+/**
+ * A pipe that can be used to trigger an event to the read side.
+ *
+ * For optimization purposes, this class does not have a constructor
+ * or a destructor.
+ */
+class EventPipe {
+	int fds[2];
+
+public:
+#ifdef NDEBUG
+	EventPipe() = default;
+#else
+	EventPipe():fds{-1, -1} {};
+#endif
+
+	EventPipe(const EventPipe &other) = delete;
+	EventPipe &operator=(const EventPipe &other) = delete;
+
+	bool Create();
+	void Destroy();
+
+	int Get() const {
+		assert(fds[0] >= 0);
+		assert(fds[1] >= 0);
+
+		return fds[0];
+	}
+
+	/**
+	 * Checks if Write() was called at least once since the last
+	 * Read() call.
+	 */
+	bool Read();
+
+	/**
+	 * Wakes up the reader.  Multiple calls to this function will
+	 * be combined to one wakeup.
+	 */
+	void Write();
+};
+
+#endif /* MAIN_NOTIFY_H */

src/event/WakeFD.hxx

@@ -24,57 +24,12 @@
 
 #include <assert.h>
 
-/**
+#ifdef USE_EVENTFD
- * This class can be used to wake up an I/O event loop.
+#include "EventFD.hxx"
- *
+#define WakeFD EventFD
- * For optimization purposes, this class does not have a constructor
- * or a destructor.
- */
-class WakeFD {
-	int fds[2];
-
-public:
-#ifdef NDEBUG
-	WakeFD() = default;
 #else
-	WakeFD():fds{-1, -1} {};
+#include "EventPipe.hxx"
+#define WakeFD EventPipe
 #endif
 
-	WakeFD(const WakeFD &other) = delete;
-	WakeFD &operator=(const WakeFD &other) = delete;
-
-	bool Create();
-	void Destroy();
-
-	int Get() const {
-		assert(fds[0] >= 0);
-#ifndef HAVE_EVENTFD
-		assert(fds[1] >= 0);
-#endif
-
-		return fds[0];
-	}
-
-	/**
-	 * Checks if Write() was called at least once since the last
-	 * Read() call.
-	 */
-	bool Read();
-
-	/**
-	 * Wakes up the reader.  Multiple calls to this function will
-	 * be combined to one wakeup.
-	 */
-	void Write();
-
-private:
-#ifdef HAVE_EVENTFD
-	bool IsEventFD() {
-		assert(fds[0] >= 0);
-
-		return fds[1] == -2;
-	}
-#endif
-};
-
 #endif /* MAIN_NOTIFY_H */

src/fd_util.c

@@ -49,7 +49,7 @@
 #include <sys/inotify.h>
 #endif
 
-#ifdef HAVE_EVENTFD
+#ifdef USE_EVENTFD
 #include <sys/eventfd.h>
 #endif
 
@@ -332,7 +332,7 @@ inotify_init_cloexec(void)
 
 #endif
 
-#ifdef HAVE_EVENTFD
+#ifdef USE_EVENTFD
 
 int
 eventfd_cloexec_nonblock(unsigned initval, int flags)

src/fd_util.h

@@ -144,7 +144,7 @@ inotify_init_cloexec(void);
 
 #endif
 
-#ifdef HAVE_EVENTFD
+#ifdef USE_EVENTFD
 
 /**
  * Wrapper for eventfd() which sets the flags CLOEXEC and NONBLOCK