event/SocketMonitor: wrapper class for GSource + GPollFD

Makefile.am

@@ -39,8 +39,8 @@ src_mpd_LDADD = \
 	$(FILTER_LIBS) \
 	$(ENCODER_LIBS) \
 	$(MIXER_LIBS) \
-	libutil.a \
 	libevent.a \
+	libutil.a \
 	$(SYSTEMD_DAEMON_LIBS) \
 	$(GLIB_LIBS)
 
@@ -357,6 +357,8 @@ libutil_a_SOURCES = \
 libevent_a_SOURCES = \
 	src/event/WakeFD.cxx 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 \
 	src/event/Loop.hxx
 
 # PCM library

src/event/BufferedSocket.cxx

@@ -0,0 +1,256 @@
+/*
+ * 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"
+#include "BufferedSocket.hxx"
+#include "SocketError.hxx"
+#include "util/fifo_buffer.h"
+
+#include <assert.h>
+#include <stdint.h>
+#include <string.h>
+
+#ifndef WIN32
+#include <sys/types.h>
+#include <sys/socket.h>
+#endif
+
+BufferedSocket::~BufferedSocket()
+{
+	if (input != nullptr)
+		fifo_buffer_free(input);
+}
+
+BufferedSocket::ssize_t
+BufferedSocket::DirectWrite(const void *data, size_t length)
+{
+	int flags = 0;
+#ifdef MSG_NOSIGNAL
+	flags |= MSG_NOSIGNAL;
+#endif
+#ifdef MSG_DONTWAIT
+	flags |= MSG_DONTWAIT;
+#endif
+
+	const auto nbytes = send(Get(), (const char *)data, length, flags);
+	if (gcc_unlikely(nbytes < 0)) {
+		const auto code = GetSocketError();
+		if (IsSocketErrorAgain(code))
+			return 0;
+
+		Cancel();
+
+		if (IsSocketErrorClosed(code))
+			OnSocketClosed();
+		else
+			OnSocketError(NewSocketError(code));
+	}
+
+	return nbytes;
+}
+
+ssize_t
+BufferedSocket::DirectRead(void *data, size_t length)
+{
+	int flags = 0;
+#ifdef MSG_DONTWAIT
+	flags |= MSG_DONTWAIT;
+#endif
+
+	const auto nbytes = recv(Get(), (char *)data, length, flags);
+	if (gcc_likely(nbytes > 0))
+		return nbytes;
+
+	if (nbytes == 0) {
+		OnSocketClosed();
+		return -1;
+	}
+
+	const auto code = GetSocketError();
+	if (IsSocketErrorAgain(code))
+		return 0;
+
+	if (IsSocketErrorClosed(code))
+		OnSocketClosed();
+	else
+		OnSocketError(NewSocketError(code));
+	return -1;
+}
+
+bool
+BufferedSocket::WriteFromBuffer()
+{
+	assert(IsDefined());
+
+	size_t length;
+	const void *data = output.Read(&length);
+	if (data == nullptr) {
+		CancelWrite();
+		return true;
+	}
+
+	auto nbytes = DirectWrite(data, length);
+	if (gcc_unlikely(nbytes <= 0))
+		return nbytes == 0;
+
+	output.Consume(nbytes);
+
+	if (output.IsEmpty())
+		CancelWrite();
+
+	return true;
+}
+
+bool
+BufferedSocket::ReadToBuffer()
+{
+	assert(IsDefined());
+
+	if (input == nullptr)
+		input = fifo_buffer_new(8192);
+
+	size_t length;
+	void *buffer = fifo_buffer_write(input, &length);
+	assert(buffer != nullptr);
+
+	const auto nbytes = DirectRead(buffer, length);
+	if (nbytes > 0)
+		fifo_buffer_append(input, nbytes);
+
+	return nbytes >= 0;
+}
+
+bool
+BufferedSocket::Write(const void *data, size_t length)
+{
+	assert(IsDefined());
+
+#if 0
+	/* TODO: disabled because this would add overhead on some callers (the ones that often), but it may be useful */
+
+	if (output.IsEmpty()) {
+		/* try to write it directly first */
+		const auto nbytes = DirectWrite(data, length);
+		if (gcc_likely(nbytes > 0)) {
+			data = (const uint8_t *)data + nbytes;
+			length -= nbytes;
+			if (length == 0)
+				return true;
+		} else if (nbytes < 0)
+			return false;
+	}
+#endif
+
+	if (!output.Append(data, length)) {
+		// TODO
+		OnSocketError(g_error_new_literal(g_quark_from_static_string("buffered_socket"),
+						  0, "Output buffer is full"));
+		return false;
+	}
+
+	ScheduleWrite();
+	return true;
+}
+
+bool
+BufferedSocket::ResumeInput()
+{
+	assert(IsDefined());
+
+	if (input == nullptr) {
+		ScheduleRead();
+		return true;
+	}
+
+	while (true) {
+		size_t length;
+		const void *data = fifo_buffer_read(input, &length);
+		if (data == nullptr) {
+			ScheduleRead();
+			return true;
+		}
+
+		const auto result = OnSocketInput(data, length);
+		switch (result) {
+		case InputResult::MORE:
+			if (fifo_buffer_is_full(input)) {
+				// TODO
+				OnSocketError(g_error_new_literal(g_quark_from_static_string("buffered_socket"),
+								  0, "Input buffer is full"));
+				return false;
+			}
+
+			ScheduleRead();
+			return true;
+
+		case InputResult::PAUSE:
+			CancelRead();
+			return true;
+
+		case InputResult::AGAIN:
+			continue;
+
+		case InputResult::CLOSED:
+			return false;
+		}
+	}
+}
+
+void
+BufferedSocket::ConsumeInput(size_t nbytes)
+{
+	assert(IsDefined());
+
+	fifo_buffer_consume(input, nbytes);
+}
+
+void
+BufferedSocket::OnSocketReady(unsigned flags)
+{
+	assert(IsDefined());
+
+	if (gcc_unlikely(flags & (ERROR|HANGUP))) {
+		OnSocketClosed();
+		return;
+	}
+
+	if (flags & READ) {
+		assert(input == nullptr || !fifo_buffer_is_full(input));
+
+		if (!ReadToBuffer() || !ResumeInput())
+			return;
+
+		if (input == nullptr || !fifo_buffer_is_full(input))
+			ScheduleRead();
+
+		/* just in case the OnSocketInput() method has added
+		   data to the output buffer: try to send it now
+		   instead of waiting for the next event loop
+		   iteration */
+		if (!output.IsEmpty())
+			flags |= WRITE;
+	}
+
+	if (flags & WRITE) {
+		assert(!output.IsEmpty());
+
+		if (!WriteFromBuffer())
+			return;
+	}
+}

src/event/BufferedSocket.hxx

@@ -0,0 +1,125 @@
+/*
+ * 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_BUFFERED_SOCKET_HXX
+#define MPD_BUFFERED_SOCKET_HXX
+
+#include "check.h"
+#include "SocketMonitor.hxx"
+#include "util/PeakBuffer.hxx"
+#include "gcc.h"
+
+#include <type_traits>
+
+#include <stddef.h>
+
+struct fifo_buffer;
+class EventLoop;
+
+class BufferedSocket : private SocketMonitor {
+	typedef std::make_signed<size_t>::type ssize_t;
+
+	fifo_buffer *input;
+	PeakBuffer output;
+
+public:
+	BufferedSocket(int _fd, EventLoop &_loop,
+		       size_t normal_size, size_t peak_size=0)
+		:SocketMonitor(_fd, _loop), input(nullptr),
+		 output(normal_size, peak_size) {
+		ScheduleRead();
+	}
+
+	~BufferedSocket();
+
+	using SocketMonitor::IsDefined;
+	using SocketMonitor::Close;
+
+private:
+	ssize_t DirectWrite(const void *data, size_t length);
+	ssize_t DirectRead(void *data, size_t length);
+
+	/**
+	 * Send data from the output buffer to the socket.
+	 *
+	 * @return false if the socket has been closed
+	 */
+	bool WriteFromBuffer();
+
+	/**
+	 * Receive data from the socket to the input buffer.
+	 *
+	 * @return false if the socket has been closed
+	 */
+	bool ReadToBuffer();
+
+protected:
+	/**
+	 * @return false if the socket has been closed
+	 */
+	bool Write(const void *data, size_t length);
+
+	/**
+	 * @return false if the socket has been closed
+	 */
+	bool ResumeInput();
+
+	/**
+	 * Mark a portion of the input buffer "consumed".  Only
+	 * allowed to be called from OnSocketInput().  This method
+	 * does not invalidate the pointer passed to OnSocketInput()
+	 * yet.
+	 */
+	void ConsumeInput(size_t nbytes);
+
+	enum class InputResult {
+		/**
+		 * The method was successful, and it is ready to
+		 * read more data.
+		 */
+		MORE,
+
+		/**
+		 * The method does not want to get more data for now.
+		 * It will call ResumeInput() when it's ready for
+		 * more.
+		 */
+		PAUSE,
+
+		/**
+		 * The method wants to be called again immediately, if
+		 * there's more data in the buffer.
+		 */
+		AGAIN,
+
+		/**
+		 * The method has closed the socket.
+		 */
+		CLOSED,
+	};
+
+	virtual InputResult OnSocketInput(const void *data, size_t length) = 0;
+	virtual void OnSocketError(GError *error) = 0;
+	virtual void OnSocketClosed() = 0;
+
+private:
+	virtual void OnSocketReady(unsigned flags) override;
+};
+
+#endif

src/event/SocketMonitor.cxx

@@ -0,0 +1,108 @@
+/*
+ * 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"
+#include "SocketMonitor.hxx"
+#include "Loop.hxx"
+#include "fd_util.h"
+#include "gcc.h"
+
+#include <assert.h>
+
+/*
+ * GSource methods
+ *
+ */
+
+gboolean
+SocketMonitor::Prepare(gcc_unused GSource *source, gcc_unused gint *timeout_r)
+{
+	return false;
+}
+
+gboolean
+SocketMonitor::Check(GSource *_source)
+{
+	const Source &source = *(const Source *)_source;
+	const SocketMonitor &monitor = *source.monitor;
+	assert(_source == &monitor.source->base);
+
+	return monitor.Check();
+}
+
+gboolean
+SocketMonitor::Dispatch(GSource *_source,
+			gcc_unused GSourceFunc callback,
+			gcc_unused gpointer user_data)
+{
+	Source &source = *(Source *)_source;
+	SocketMonitor &monitor = *source.monitor;
+	assert(_source == &monitor.source->base);
+
+	monitor.Dispatch();
+	return true;
+}
+
+/**
+ * The vtable for our GSource implementation.  Unfortunately, we
+ * cannot declare it "const", because g_source_new() takes a non-const
+ * pointer, for whatever reason.
+ */
+static GSourceFuncs socket_monitor_source_funcs = {
+	SocketMonitor::Prepare,
+	SocketMonitor::Check,
+	SocketMonitor::Dispatch,
+	nullptr,
+	nullptr,
+	nullptr,
+};
+
+SocketMonitor::SocketMonitor(int _fd, EventLoop &_loop)
+	:fd(_fd), loop(_loop),
+	 source((Source *)g_source_new(&socket_monitor_source_funcs,
+				       sizeof(*source))),
+	 poll{fd, 0, 0} {
+	assert(fd >= 0);
+
+	source->monitor = this;
+
+	g_source_attach(&source->base, loop.GetContext());
+	g_source_add_poll(&source->base, &poll);
+}
+
+SocketMonitor::~SocketMonitor()
+{
+	if (IsDefined())
+		Close();
+}
+
+void
+SocketMonitor::Close()
+{
+	assert(IsDefined());
+
+	Cancel();
+
+	close_socket(fd);
+	fd = -1;
+
+	g_source_destroy(&source->base);
+	g_source_unref(&source->base);
+	source = nullptr;
+}

src/event/SocketMonitor.hxx

@@ -0,0 +1,118 @@
+/*
+ * 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_SOCKET_MONITOR_HXX
+#define MPD_SOCKET_MONITOR_HXX
+
+#include "check.h"
+
+#include <glib.h>
+
+#include <assert.h>
+
+#ifdef WIN32
+/* ERRORis a WIN32 macro that poisons our namespace; this is a
+   kludge to allow us to use it anyway */
+#ifdef ERROR
+#undef ERROR
+#endif
+#endif
+
+class EventLoop;
+
+class SocketMonitor {
+	struct Source {
+		GSource base;
+
+		SocketMonitor *monitor;
+	};
+
+	int fd;
+	EventLoop &loop;
+	Source *source;
+	GPollFD poll;
+
+public:
+	static constexpr unsigned READ = G_IO_IN;
+	static constexpr unsigned WRITE = G_IO_OUT;
+	static constexpr unsigned ERROR = G_IO_ERR;
+	static constexpr unsigned HANGUP = G_IO_HUP;
+
+	SocketMonitor(int _fd, EventLoop &_loop);
+
+	~SocketMonitor();
+
+	bool IsDefined() const {
+		return fd >= 0;
+	}
+
+	int Get() const {
+		assert(IsDefined());
+
+		return fd;
+	}
+
+	void Close();
+
+	void Schedule(unsigned flags) {
+		poll.events = flags;
+		poll.revents &= flags;
+	}
+
+	void Cancel() {
+		poll.events = 0;
+	}
+
+	void ScheduleRead() {
+		poll.events |= READ|HANGUP|ERROR;
+	}
+
+	void ScheduleWrite() {
+		poll.events |= WRITE;
+	}
+
+	void CancelRead() {
+		poll.events &= ~(READ|HANGUP|ERROR);
+	}
+
+	void CancelWrite() {
+		poll.events &= ~WRITE;
+	}
+
+protected:
+	virtual void OnSocketReady(unsigned flags) = 0;
+
+public:
+	/* GSource callbacks */
+	static gboolean Prepare(GSource *source, gint *timeout_r);
+	static gboolean Check(GSource *source);
+	static gboolean Dispatch(GSource *source, GSourceFunc callback,
+				 gpointer user_data);
+
+private:
+	bool Check() const {
+		return (poll.revents & poll.events) != 0;
+	}
+
+	void Dispatch() {
+		OnSocketReady(poll.revents & poll.events);
+	}
+};
+
+#endif