ircd::fs: Initial asynchronous file IO support for Linux platforms.

configure.ac

@@ -511,14 +511,26 @@ AM_COND_IF(INTERIX,
 ],[])
 
 
+dnl
+dnl Linux AIO support
+dnl
+
 AM_COND_IF(LINUX,
 [
-	AC_ARG_ENABLE(aio,
-	AC_HELP_STRING([--enable-aio], [Enable AIO support on Linux platforms]),
+	AC_ARG_ENABLE(aio, AC_HELP_STRING([--disable-aio], [Disable kernel AIO support]),
 	[
-		IRCD_DEFINE(USE_AIO, [1], [Define to 1 if you want AIO support on linux])
-	],[])
-],[])
+		aio=$enableval
+	],
+	[
+		aio=yes
+	])
+], [])
+
+if test "$aio" = "yes"; then
+	IRCD_DEFINE(USE_AIO, [1], [Linux AIO is supported and will be used])
+else
+	IRCD_DEFINE(USE_AIO, [0], [Define to 1 if you want AIO support (linux only)])
+fi
 
 
 dnl ***************************************************************************
@@ -1364,6 +1376,7 @@ echo
 echo "Configured ........................ $PACKAGE_NAME $PACKAGE_VERSION"
 echo "Version ........................... $RB_VERSION"
 echo "Configuration time ................ $RB_DATESTR"
+echo "Host OS ........................... $host_os"
 echo "Compiler .......................... $CXX"
 echo "Compiler flags (CXXFLAGS) ......... $CXXFLAGS"
 echo "Building boost .................... $with_included_boost"
@@ -1375,6 +1388,7 @@ echo "SSL support........................ $SSL_TYPE"
 echo "Precompiled headers ............... $build_pch"
 echo "Developer debug ................... $debug"
 echo "IPv6 support ...................... $ipv6"
+echo "Linux AIO support ................. $aio"
 echo "Installing into ................... $prefix"
 echo
 echo "* Ready to build $PACKAGE_NAME"

include/ircd/fs/fs.h

@@ -1,23 +1,21 @@
-/*
- * Copyright (C) 2016 Charybdis Development Team
- * Copyright (C) 2016 Jason Volk <jason@zemos.net>
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice is present in all copies.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
- * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
- * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
- * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
- * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
- * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
- * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- */
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+// IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
 
 #pragma once
 #define HAVE_IRCD_FS_H
@@ -96,19 +94,18 @@ namespace ircd::fs
 	bool mkdir(const std::string &path);
 
 	// This suite of IO functions may yield your context.
-	std::string read(const std::string &name);
-	string_view read(const std::string &name, const mutable_raw_buffer &buf);
-	string_view read(const string_view &name, const mutable_raw_buffer &buf);
 	bool write(const std::string &name, const const_raw_buffer &buf);
 	bool append(const std::string &name, const const_raw_buffer &buf);
 	bool overwrite(const std::string &name, const const_raw_buffer &buf);
 	bool overwrite(const string_view &name, const const_raw_buffer &buf);
+
+	extern aio *aioctx;
 }
 
+#include "read.h"
+
 struct ircd::fs::init
 {
-	std::unique_ptr<fs::aio> aio;
-
 	init();
 	~init() noexcept;
 };

include/ircd/fs/read.h

@@ -0,0 +1,63 @@
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+// IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+#define HAVE_IRCD_FS_READ_H
+
+namespace ircd::fs
+{
+	struct read_opts extern const read_opts_default;
+	using read_callback = std::function<void (std::exception_ptr, const string_view &)>;
+
+	// Asynchronous callback-based read into buffer; callback views read portion.
+	void read(const string_view &path, const mutable_raw_buffer &, const read_opts &, read_callback);
+	void read(const string_view &path, const mutable_raw_buffer &, read_callback);
+
+	// Yields ircd::ctx for read into buffer; returns view of read portion.
+	string_view read(const string_view &path, const mutable_raw_buffer &, const read_opts & = read_opts_default);
+
+	// Yields ircd::ctx for read into allocated string; returns that string
+	std::string read(const string_view &path, const read_opts & = read_opts_default);
+}
+
+/// Options for a read operation
+struct ircd::fs::read_opts
+{
+	read_opts() = default;
+	read_opts(const off_t &);
+
+	/// Offset in the file to start the read from.
+	off_t offset {0};
+
+	/// Request priority (this option may be improved, avoid for now)
+	int16_t priority {0};
+};
+
+inline
+ircd::fs::read_opts::read_opts(const off_t &offset)
+:offset{offset}
+{}
+
+inline void
+ircd::fs::read(const string_view &path,
+               const mutable_raw_buffer &buf,
+               read_callback callback)
+{
+	return read(path, buf, read_opts_default, std::move(callback));
+}

ircd/aio.h

@@ -0,0 +1,516 @@
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+// IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+#define HAVE_AIO_H
+
+#include <RB_INC_SYS_SYSCALL_H
+#include <RB_INC_SYS_EVENTFD_H
+#include <linux/aio_abi.h>
+
+/// AIO context instance. Right now this is a singleton with an extern
+/// instance at fs::aioctx.
+struct ircd::fs::aio
+{
+	struct request;
+
+	/// Maximum number of events we can submit to kernel
+	static constexpr const size_t &MAX_EVENTS
+	{
+		64
+	};
+
+	/// The semaphore value for the eventfd which we keep here.
+	uint64_t semval{0};
+
+	/// An eventfd which will be notified by the kernel; we integrate this with
+	/// the ircd io_service core epoll() event loop. The EFD_SEMAPHORE flag is
+	/// not used to reduce the number of triggers. We can collect multiple AIO
+	/// completions after a single trigger to this fd. With EFD_SEMAPHORE, we
+	/// would collect all the completions on the first trigger and then
+	/// continue to get polled. Because EFD_SEMAPHORE is not set, the semval
+	/// which is kept above will reflect a hint for how many AIO's are done.
+	asio::posix::stream_descriptor resfd
+	{
+		*ircd::ios, int(syscall(::eventfd, semval, EFD_NONBLOCK))
+	};
+
+	/// Handler to the io context we submit requests to the kernel with
+	aio_context_t idp
+	{
+		0
+	};
+
+	// Callback stack invoked when the sigfd is notified of completed events.
+	void handle_event(const io_event &) noexcept;
+	void handle_events() noexcept;
+	void handle(const error_code &, const size_t) noexcept;
+
+	void set_handle();
+
+	aio()
+	{
+		syscall<SYS_io_setup>(MAX_EVENTS, &idp);
+		set_handle();
+	}
+
+	~aio() noexcept
+	{
+		resfd.cancel();
+		syscall<SYS_io_destroy>(idp);
+	}
+};
+
+/// Generic request control block.
+struct ircd::fs::aio::request
+:iocb
+{
+	struct read;
+	struct write;
+
+	ssize_t retval {0};
+	ssize_t errcode {0};
+	ctx::ctx *waiter {nullptr};
+	bool close_fd {false};
+	bool free_req {false};
+
+	/// called if close_fd is true
+	void close_fildes() noexcept;
+
+	/// Overriden by types of requests
+	virtual void handle() = 0;
+
+  public:
+	// Submit a request. ctx overload will properly yield
+	size_t operator()(ctx::ctx &waiter);
+	void operator()();
+
+	void cancel();
+
+	request(const int &fd);
+	virtual ~request() noexcept;
+};
+
+ircd::fs::aio::request::request(const int &fd)
+:iocb{0}
+{
+	assert(aioctx);
+	aio_flags = IOCB_FLAG_RESFD;
+	aio_resfd = aioctx->resfd.native_handle();
+	aio_fildes = fd;
+}
+
+/// vtable base
+ircd::fs::aio::request::~request()
+noexcept
+{
+}
+
+/// Cancel a request. The handler callstack is invoked directly from here
+/// which means any callback will be invoked or ctx will be notified if
+/// appropriate.
+void
+ircd::fs::aio::request::cancel()
+{
+	io_event result {0};
+	const auto &cb{static_cast<iocb *>(this)};
+
+	assert(aioctx);
+	syscall_nointr<SYS_io_cancel>(aioctx->idp, cb, &result);
+	aioctx->handle_event(result);
+}
+
+/// Submit a request and properly yield the ircd::ctx. The ctx argument
+/// must be the currently running ctx (or ctx::current) for now; there is
+/// no other usage. When this returns the result will be available or
+/// exception will be thrown.
+size_t
+ircd::fs::aio::request::operator()(ctx::ctx &waiter)
+try
+{
+	// Cooperation strategy is to set this->waiter to the ctx and wait for
+	// notification with this->waiter set to null to ignore spurious notes.
+	assert(&waiter == ctx::current);
+	this->waiter = &waiter;
+	operator()(); do
+	{
+		ctx::wait();
+	}
+	while(this->waiter);
+
+	if(retval == -1)
+		throw_system_error(errcode);
+
+	return size_t(retval);
+}
+catch(const ctx::interrupted &e)
+{
+	// When the ctx is interrupted we're obligated to cancel the request.
+	// The handler callstack is invoked directly from here by cancel() for
+	// what it's worth but we rethrow the interrupt anyway.
+	this->waiter = nullptr;
+	cancel();
+	throw;
+}
+
+/// Submit a request.
+void
+ircd::fs::aio::request::operator()()
+{
+	struct iocb *const cbs[]
+	{
+		static_cast<iocb *>(this)
+	};
+
+	assert(aioctx);
+	syscall<SYS_io_submit>(aioctx->idp, 1, &cbs);
+/*
+	log::debug("AIO request(%p) fd:%u op:%d bytes:%lu off:%ld prio:%d ctx:%p submit",
+	           this,
+	           this->aio_fildes,
+	           this->aio_lio_opcode,
+	           this->aio_nbytes,
+	           this->aio_offset,
+	           this->aio_reqprio,
+	           this->waiter);
+*/
+}
+
+void
+ircd::fs::aio::set_handle()
+{
+	semval = 0;
+	const asio::mutable_buffers_1 bufs(&semval, sizeof(semval));
+	auto handler{std::bind(&aio::handle, this, ph::_1, ph::_2)};
+	asio::async_read(resfd, bufs, std::move(handler));
+}
+
+/// Handle notifications that requests are complete.
+void
+ircd::fs::aio::handle(const error_code &ec,
+                      const size_t bytes)
+noexcept
+{
+	assert((bytes == 8 && !ec && semval >= 1) || (bytes == 0 && ec));
+	assert(!ec || ec.category() == asio::error::get_system_category());
+
+	switch(ec.value())
+	{
+		case boost::system::errc::success:
+			handle_events();
+			break;
+
+		case boost::system::errc::operation_canceled:
+			return;
+
+		default:
+			throw boost::system::system_error(ec);
+	}
+
+	set_handle();
+}
+
+void
+ircd::fs::aio::handle_events()
+noexcept try
+{
+	std::array<io_event, MAX_EVENTS> event;
+
+	// The number of completed requests available in events[]. This syscall
+	// is restarted on EINTR. After restart, it may or may not find any ready
+	// events but it never blocks to do so.
+	const auto count
+	{
+		syscall_nointr<SYS_io_getevents>(idp, 0, event.size(), event.data(), nullptr)
+	};
+
+	// The count should be at least 1 event. The only reason to return 0 might
+	// be related to an INTR; this assert will find out and may be commented.
+	assert(count > 0);
+
+	for(ssize_t i(0); i < count; ++i)
+		handle_event(event[i]);
+}
+catch(const std::exception &e)
+{
+	log::error("AIO(%p) handle_events: %s",
+	           this,
+	           e.what());
+}
+
+void
+ircd::fs::aio::handle_event(const io_event &event)
+noexcept try
+{
+	// Our extended control block is passed in event.data
+	auto *const request
+	{
+		reinterpret_cast<aio::request *>(event.data)
+	};
+
+	// The relevant iocb is repeated back to us in the result; we assert
+	// some basic sanity here about the layout of the request conglomerate.
+	assert(reinterpret_cast<iocb *>(event.obj) == static_cast<iocb *>(request));
+
+	// error conventions are like so
+	assert(event.res >= -1);  // unix syscall return value semantic
+	assert(event.res2 >= 0);  // errno code semantic
+	assert(event.res == -1 || event.res2 == 0);
+
+	// Set result indicators
+	request->retval = event.res;
+	request->errcode = event.res2;
+/*
+	log::debug("AIO request(%p) fd:%d op:%d bytes:%lu off:%ld prio:%d ctx:%p result: bytes:%ld errno:%ld",
+	           request,
+	           request->aio_fildes,
+	           request->aio_lio_opcode,
+	           request->aio_nbytes,
+	           request->aio_offset,
+	           request->aio_reqprio,
+	           request->waiter,
+	           request->retval,
+	           request->errcode);
+*/
+	const unwind cleanup{[&request]
+	{
+		// The user might want us to cleanup their fd after this event
+		if(request->close_fd)
+			request->close_fildes();
+
+		// The user might want us to free a dynamically allocated request struct
+		// to simplify their callback sequence. The noexcept guarantees h
+		if(request->free_req)
+			delete request;
+	}};
+
+	// virtual dispatch based on the request type. Alternatively, we could
+	// switch() on the iocb lio_opcode and downcast... but that's what vtable
+	// does for us right here.
+	request->handle();
+}
+catch(const std::exception &e)
+{
+	log::critical("Unhandled request(%lu) event(%p) error: %s",
+	              event.data,
+	              &event,
+	              e.what());
+}
+
+/// If requested, close the file descriptor. Errors here can be logged but
+/// must be otherwise ignored.
+void
+ircd::fs::aio::request::close_fildes()
+noexcept try
+{
+	syscall(::close, aio_fildes);
+}
+catch(const std::exception &e)
+{
+	log::error("Failed to close request(%p) fd:%d: %s",
+	           this,
+	           aio_fildes);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// fs/read.h
+//
+
+namespace ircd::fs
+{
+	void read__aio(const string_view &path, const mutable_raw_buffer &, const read_opts &, read_callback);
+	string_view read__aio(const string_view &path, const mutable_raw_buffer &, const read_opts &);
+	std::string read__aio(const string_view &path, const read_opts &);
+}
+
+/// Read request control block
+struct ircd::fs::aio::request::read
+:request
+{
+	read_callback callback;
+
+	virtual void handle() final override;
+
+	read(const int &fd, const mutable_raw_buffer &buf, const read_opts &opts, read_callback callback);
+};
+
+ircd::fs::aio::request::read::read(const int &fd,
+                                   const mutable_raw_buffer &buf,
+                                   const read_opts &opts,
+                                   read_callback callback)
+:request{fd}
+,callback{std::move(callback)}
+{
+	aio_data = uintptr_t(this);
+	aio_reqprio = opts.priority;
+	aio_lio_opcode = IOCB_CMD_PREAD;
+
+	aio_buf = uintptr_t(buffer::data(buf));
+	aio_nbytes = buffer::size(buf);
+	aio_offset = opts.offset;
+}
+
+void
+ircd::fs::aio::request::read::handle()
+{
+	if(waiter)
+	{
+		ircd::ctx::notify(*waiter);
+		waiter = nullptr;
+	}
+
+	if(callback)
+	{
+		const size_t bytes
+		{
+			retval >= 0? size_t(retval) : 0
+		};
+
+		const string_view view
+		{
+			reinterpret_cast<const char *>(aio_buf), bytes
+		};
+
+		std::exception_ptr eptr
+		{
+			errcode != 0? make_system_error(errcode) : std::exception_ptr{}
+		};
+
+		callback(std::move(eptr), view);
+	}
+}
+
+//
+// Interface
+//
+
+std::string
+ircd::fs::read__aio(const string_view &path,
+                    const read_opts &opts)
+{
+	// Path to open(2) must be null terminated;
+	static thread_local char pathstr[2048];
+	strlcpy(pathstr, path, sizeof(pathstr));
+
+	const auto fd
+	{
+		syscall(::open, pathstr, O_CLOEXEC, O_RDONLY)
+	};
+
+	const unwind cfd{[&fd]
+	{
+		syscall(::close, fd);
+	}};
+
+	// This fstat may be defeating; to be sure, don't use this overload
+	// and progressively buffer chunks into your application.
+	struct stat stat;
+	syscall(::fstat, fd, &stat);
+	const auto &size
+	{
+		stat.st_size
+	};
+
+	std::string ret(size, char{});
+	const mutable_buffer buf
+	{
+		const_cast<char *>(ret.data()), ret.size()
+	};
+
+	aio::request::read request
+	{
+		int(fd), buf, opts, nullptr
+	};
+
+	const size_t bytes
+	{
+		request(ctx::cur())
+	};
+
+	ret.resize(bytes);
+	return ret;
+}
+
+ircd::string_view
+ircd::fs::read__aio(const string_view &path,
+                    const mutable_raw_buffer &buf,
+                    const read_opts &opts)
+{
+	// Path to open(2) must be null terminated;
+	static thread_local char pathstr[2048];
+	strlcpy(pathstr, path, sizeof(pathstr));
+
+	const auto fd
+	{
+		syscall(::open, pathstr, O_CLOEXEC, O_RDONLY)
+	};
+
+	const unwind cfd{[&fd]
+	{
+		syscall(::close, fd);
+	}};
+
+	aio::request::read request
+	{
+		int(fd), buf, opts, nullptr
+	};
+
+	const size_t bytes
+	{
+		request(ctx::cur())
+	};
+
+	const string_view view
+	{
+		reinterpret_cast<const char *>(data(buf)), bytes
+	};
+
+	return view;
+}
+
+void
+ircd::fs::read__aio(const string_view &path,
+                    const mutable_raw_buffer &buf,
+                    const read_opts &opts,
+                    read_callback callback)
+{
+	static thread_local char pathstr[2048];
+	strlcpy(pathstr, path, sizeof(pathstr));
+
+	const auto fd
+	{
+		syscall(::open, pathstr, O_CLOEXEC, O_RDONLY)
+	};
+
+	const unwind::exceptional cfd{[&fd]
+	{
+		syscall(::close, fd);
+	}};
+
+	auto request
+	{
+		std::make_unique<aio::request::read>(int(fd), buf, opts, std::move(callback))
+	};
+
+	request->close_fd = true;
+	request->free_req = true;
+	(*request)();
+	request.release();
+}

ircd/fs.cc

@@ -1,50 +1,43 @@
-/*
- *  charybdis: A slightly useful ircd.
- *  ircd.c: Starts up and runs the ircd.
- *
- *  Copyright (C) 1990 Jarkko Oikarinen and University of Oulu, Co Center
- *  Copyright (C) 1996-2002 Hybrid Development Team
- *  Copyright (C) 2002-2008 ircd-ratbox development team
- *  Copyright (C) 2005-2013 charybdis development team
- *
- *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307
- *  USA
- */
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+// IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
 
-#undef linux
-#include <RB_INC_UNISTD_H
-#include <RB_INC_SYS_SYSCALL_H
-#include <RB_INC_SYS_EVENTFD_H
-#include <RB_INC_LINUX_AIO_ABI_H
 #include <RB_INC_BOOST_FILESYSTEM_HPP
 #include <ircd/asio.h>
 
+#ifdef IRCD_USE_AIO
+	#include "aio.h"
+#endif
+
 namespace ircd::fs
 {
 	using namespace boost::filesystem;
 
-	enum
-	{
-		NAME  = 0,
-		PATH  = 1,
-	};
-
+	enum { NAME, PATH };
 	using ent = std::pair<std::string, std::string>;
 	extern const std::array<ent, num_of<index>()> paths;
 }
 
+/// Non-null when aio is available for use
+decltype(ircd::fs::aioctx)
+ircd::fs::aioctx
+{};
+
 decltype(ircd::fs::paths)
 ircd::fs::paths
 {{
@@ -60,15 +53,147 @@ ircd::fs::paths
 }};
 
 ircd::fs::init::init()
-:aio{std::make_unique<fs::aio>()}
 {
+	#ifdef IRCD_USE_AIO
+		assert(!aioctx);
+		aioctx = new aio{};
+	#endif
 }
 
 ircd::fs::init::~init()
 noexcept
 {
+	#ifdef IRCD_USE_AIO
+		delete aioctx;
+		aioctx = nullptr;
+	#endif
+
+	assert(!aioctx);
 }
 
+///////////////////////////////////////////////////////////////////////////////
+//
+// fs/read.h
+//
+
+namespace ircd::fs
+{
+	void read__std(const string_view &path, const mutable_raw_buffer &, const read_opts &, read_callback);
+	string_view read__std(const string_view &path, const mutable_raw_buffer &, const read_opts &);
+	std::string read__std(const string_view &path, const read_opts &);
+}
+
+ircd::fs::read_opts
+const ircd::fs::read_opts_default
+{};
+
+//
+// ircd::fs interface linkage
+//
+
+std::string
+ircd::fs::read(const string_view &path,
+               const read_opts &opts)
+{
+	#ifdef IRCD_USE_AIO
+	if(likely(aioctx))
+		return read__aio(path, opts);
+	#endif
+
+	return read__std(path, opts);
+}
+
+ircd::string_view
+ircd::fs::read(const string_view &path,
+               const mutable_raw_buffer &buf,
+               const read_opts &opts)
+{
+	#ifdef IRCD_USE_AIO
+	if(likely(aioctx))
+		return read__aio(path, buf, opts);
+	#endif
+
+	return read__std(path, buf, opts);
+}
+
+void
+ircd::fs::read(const string_view &path,
+               const mutable_raw_buffer &buf,
+               const read_opts &opts,
+               read_callback callback)
+{
+	#ifdef IRCD_USE_AIO
+	if(likely(aioctx))
+		return read__aio(path, buf, opts, std::move(callback));
+	#endif
+
+	return read__std(path, buf, opts, std::move(callback));
+}
+
+//
+// std read
+//
+
+std::string
+ircd::fs::read__std(const string_view &path,
+                    const read_opts &opts)
+{
+	std::ifstream file{std::string{path}};
+	std::noskipws(file);
+	std::istream_iterator<char> b{file};
+	std::istream_iterator<char> e{};
+	return std::string{b, e};
+}
+
+ircd::string_view
+ircd::fs::read__std(const string_view &path,
+                    const mutable_raw_buffer &buf,
+                    const read_opts &opts)
+{
+	string_view ret;
+	std::exception_ptr reptr;
+	read(path, buf, opts, [&reptr, &ret]
+	(std::exception_ptr eptr, const string_view &view)
+	{
+		reptr = std::move(eptr);
+		ret = view;
+	});
+
+	if(reptr)
+		std::rethrow_exception(reptr);
+
+	return ret;
+}
+
+void
+ircd::fs::read__std(const string_view &path,
+                    const mutable_raw_buffer &buf,
+                    const read_opts &opts,
+                    read_callback callback)
+try
+{
+	std::ifstream file{std::string{path}};
+	file.exceptions(file.failbit | file.badbit);
+	file.seekg(opts.offset, file.beg);
+	file.read(reinterpret_cast<char *>(data(buf)), size(buf));
+	const string_view view
+	{
+		reinterpret_cast<const char *>(data(buf)), size_t(file.gcount())
+	};
+
+	callback(std::exception_ptr{}, view);
+}
+catch(...)
+{
+	callback(std::make_exception_ptr(std::current_exception()), string_view{});
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// fs/write.h
+//
+
 bool
 ircd::fs::write(const std::string &path,
                 const const_raw_buffer &buf)
@@ -104,35 +229,6 @@ ircd::fs::append(const std::string &path,
 	return true;
 }
 
-std::string
-ircd::fs::read(const std::string &path)
-{
-	std::ifstream file{path};
-	std::noskipws(file);
-	std::istream_iterator<char> b{file};
-	std::istream_iterator<char> e{};
-	return std::string{b, e};
-}
-
-ircd::string_view
-ircd::fs::read(const string_view &path,
-               const mutable_raw_buffer &buf)
-{
-	return ircd::fs::read(std::string{path}, buf);
-}
-
-ircd::string_view
-ircd::fs::read(const std::string &path,
-               const mutable_raw_buffer &buf)
-{
-	std::ifstream file{path};
-	if(!file.good())
-		return {};
-
-	file.read(reinterpret_cast<char *>(data(buf)), size(buf));
-	return { reinterpret_cast<const char *>(data(buf)), size_t(file.gcount()) };
-}
-
 void
 ircd::fs::chdir(const std::string &path)
 try
@@ -284,142 +380,3 @@ catch(const std::out_of_range &e)
 {
 	return nullptr;
 }
-
-///////////////////////////////////////////////////////////////////////////////
-//
-// linux aio
-//
-
-#ifndef IRCD_USE_AIO
-
-struct ircd::fs::aio
-{
-	aio() {}
-	~aio() noexcept {}
-};
-
-#else
-
-struct ircd::fs::aio
-{
-	static constexpr const size_t &MAX_EVENTS
-	{
-		64
-	};
-
-	asio::posix::stream_descriptor resfd
-	{
-		*ircd::ios, int(syscall(::eventfd, 0, EFD_NONBLOCK))
-	};
-
-	aio_context_t idp
-	{
-		0
-	};
-
-	void handle_ready(const error_code &ec)
-	noexcept
-	{
-		std::array<io_event, MAX_EVENTS> events;
-
-		const auto nr
-		{
-			syscall<SYS_io_getevents>(idp, 0, events.size(), events.data(), nullptr)
-		};
-
-		for(ssize_t i(0); i < nr; ++i)
-		{
-			auto &event{events[i]};
-			auto &ctx{*reinterpret_cast<ctx::ctx *>(event.data)};
-			auto &cb{*reinterpret_cast<iocb *>(event.obj)};
-			cb.aio_data = event.res;
-			ircd::ctx::notify(ctx);
-		}
-	}
-
-	std::string read(const std::string &path);
-
-	aio();
-	~aio() noexcept;
-};
-
-ircd::fs::aio::aio()
-{
-	syscall<SYS_io_setup>(MAX_EVENTS, &idp);
-	resfd.async_wait(resfd.wait_read, std::bind(&aio::handle_ready, this, ph::_1));
-
-	auto test{[this]
-	{
-		const auto got{this->read("/etc/passwd")};
-		std::cout << "got: " << got << std::endl;
-	}};
-
-	ircd::context
-	{
-		"aiotest", context::POST | context::DETACH, test
-	};
-}
-
-ircd::fs::aio::~aio()
-noexcept
-{
-	syscall<SYS_io_destroy>(idp);
-}
-
-/// Reads the file at path into a string; yields your ircd::ctx.
-///
-std::string
-ircd::fs::aio::read(const std::string &path)
-{
-	const auto fd
-	{
-		syscall(::open, path.c_str(), O_CLOEXEC, O_RDONLY)
-	};
-
-	const unwind close{[&fd]
-	{
-		syscall(::close, fd);
-	}};
-
-	struct stat stat;
-	syscall(::fstat, fd, &stat);
-	const auto &size{stat.st_size};
-
-	std::string ret(size, char{});
-	const mutable_buffer buf
-	{
-		const_cast<char *>(ret.data()), ret.size()
-	};
-
-	struct iocb cb{0};
-	cb.aio_flags = IOCB_FLAG_RESFD;
-	cb.aio_reqprio = 0;
-	cb.aio_resfd = resfd.native_handle();
-	cb.aio_data = uintptr_t(ctx::current);
-
-	cb.aio_lio_opcode = IOCB_CMD_PREAD;
-	cb.aio_fildes = fd;
-	cb.aio_buf = uintptr_t(buffer::data(buf));
-	cb.aio_nbytes = buffer::size(buf);
-	cb.aio_offset = 0;
-
-	struct iocb *cbs[]
-	{
-		&cb
-	};
-
-	syscall<SYS_io_submit>(idp, 1, &cbs);  // there
-	ctx::wait();                           // back
-
-	const ssize_t &bytes
-	{
-		reinterpret_cast<const ssize_t &>(cb.aio_data)
-	};
-
-	assert(bytes >= 0);
-	ret.resize(size_t(bytes));
-
-	return ret;
-}
-
-#endif