genode/repos/ports/src/noux/vfs_io_channel.h

/*
 * \brief  I/O channel for files opened via virtual directory service
 * \author Norman Feske
 * \date   2011-02-17
 */

/*
 * Copyright (C) 2011-2017 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU Affero General Public License version 3.
 */

#ifndef _NOUX__VFS_IO_CHANNEL_H_
#define _NOUX__VFS_IO_CHANNEL_H_

/* Genode includes */
#include <timer_session/connection.h>

/* Noux includes */
#include <io_channel.h>
#include <vfs/dir_file_system.h>
#include <time_info.h>

namespace Noux {
	class Vfs_io_waiter;
	struct Vfs_handle_context;
	struct Vfs_io_channel;

	typedef Registry<Registered_no_delete<Vfs_io_waiter>>
	        Vfs_io_waiter_registry;
}

class Noux::Vfs_io_waiter
{
	private:

		Genode::Semaphore _sem { };

	public:

		void wait_for_io() { _sem.down(); }

		void wakeup() { _sem.up(); }
};

struct Noux::Vfs_handle_context : Vfs::Io_response_handler
{
	Vfs_io_waiter vfs_io_waiter { };

	void read_ready_response() override {
		vfs_io_waiter.wakeup(); }

	void io_progress_response() override {
		vfs_io_waiter.wakeup(); }
};

struct Noux::Vfs_io_channel : Io_channel
{
	Signal_handler<Vfs_io_channel> _read_avail_handler;

	void _handle_read_avail()
	{
		Io_channel::invoke_all_notifiers();
	}

	Vfs::Vfs_handle &_fh;

	Vfs_io_waiter_registry &_vfs_io_waiter_registry;

	Absolute_path _path;
	Absolute_path _leaf_path;

	bool const _dir = _fh.ds().directory(_leaf_path.base());

	Time_info   const &_time_info;
	Timer::Connection &_timer;

	void _sync()
	{
		Milliseconds const ms =
			_timer.curr_time().trunc_to_plain_ms();
		uint64_t sec   = _time_info.initial_time();
		         sec  += (ms.value / 1000);

		Vfs::Timestamp ts { .value = (long long)sec };

		Registered_no_delete<Vfs_io_waiter>
			vfs_io_waiter(_vfs_io_waiter_registry);

		for (;;) {
			if (_fh.fs().update_modification_timestamp(&_fh, ts)) {
				break;
			} else {
				Genode::error("_sync: update_modification_timestamp failed");
				vfs_io_waiter.wait_for_io();
			}
		}

		while (!_fh.fs().queue_sync(&_fh))
			vfs_io_waiter.wait_for_io();

		while (_fh.fs().complete_sync(&_fh) == Vfs::File_io_service::SYNC_QUEUED)
			vfs_io_waiter.wait_for_io();

		/* wake up threads blocking for 'queue_*()' or 'write()' */
		_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
			r.wakeup();
		});
	}

	Vfs_io_channel(char const *path, char const *leaf_path,
	               Vfs::Vfs_handle *vfs_handle,
	               Vfs_io_waiter_registry &vfs_io_waiter_registry,
	               Entrypoint &ep,
	               Time_info const &time_info,
	               Timer::Connection &timer)
	:
		_read_avail_handler(ep, *this, &Vfs_io_channel::_handle_read_avail),
		_fh(*vfs_handle), _vfs_io_waiter_registry(vfs_io_waiter_registry),
		_path(path), _leaf_path(leaf_path), _time_info(time_info), _timer(timer)
	{
		_fh.fs().register_read_ready_sigh(&_fh, _read_avail_handler);
	}

	~Vfs_io_channel()
	{
		_sync();

		_fh.ds().close(&_fh);
	}

	bool write(Sysio &sysio) override
	{
		if (_dir) {
			sysio.error.write = Vfs::File_io_service::WRITE_ERR_INVALID;
			return false;
		}

		Vfs::file_size count = sysio.write_in.count;
		Vfs::file_size out_count = 0;

		Registered_no_delete<Vfs_io_waiter>
			vfs_io_waiter(_vfs_io_waiter_registry);

		for (;;) {
			try {
				sysio.error.write = _fh.fs().write(&_fh, sysio.write_in.chunk,
				                                   count, out_count);
				break;
			} catch (Vfs::File_io_service::Insufficient_buffer) {
				vfs_io_waiter.wait_for_io();
			}
		}

		/* wake up threads blocking for 'queue_*()' or 'write()' */
		_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
			r.wakeup();
		});

		if (sysio.error.write != Vfs::File_io_service::WRITE_OK)
			return false;

		_fh.advance_seek(out_count);

		sysio.write_out.count = out_count;

		return true;
	}

	bool read(Sysio &sysio) override
	{
		if (_dir) {
			sysio.error.read = Vfs::File_io_service::READ_ERR_INVALID;
			return false;
		}

		size_t count = min(sysio.read_in.count, sizeof(sysio.read_out.chunk));

		Vfs::file_size out_count = 0;

		Registered_no_delete<Vfs_io_waiter>
			vfs_io_waiter(_vfs_io_waiter_registry);

		while (!_fh.fs().queue_read(&_fh, count))
			vfs_io_waiter.wait_for_io();

		for (;;) {

			sysio.error.read = _fh.fs().complete_read(&_fh, sysio.read_out.chunk, count, out_count);

			if (sysio.error.read != Vfs::File_io_service::READ_QUEUED)
				break;

			vfs_io_waiter.wait_for_io();
		}

		/* wake up threads blocking for 'queue_*()' or 'write()' */
		_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
			r.wakeup();
		});
	
		if (sysio.error.read != Vfs::File_io_service::READ_OK)
			return false;

		sysio.read_out.count = out_count;

		_fh.advance_seek(out_count);

		return true;
	}

	bool fstat(Sysio &sysio) override
	{
		_sync();

		/*
		 * 'sysio.stat_in' is not used in '_fh.ds().stat()',
		 * so no 'sysio' member translation is needed here
		 */

		Vfs::Directory_service::Stat stat;
		sysio.error.stat = _fh.ds().stat(_leaf_path.base(), stat);
		sysio.fstat_out.st = stat;

		return (sysio.error.stat == Vfs::Directory_service::STAT_OK);
	}

	bool ftruncate(Sysio &sysio) override
	{
		_sync();

		sysio.error.ftruncate = _fh.fs().ftruncate(&_fh, sysio.ftruncate_in.length);

		return (sysio.error.ftruncate == Vfs::File_io_service::FTRUNCATE_OK);
	}

	bool fcntl(Sysio &sysio) override
	{
		switch (sysio.fcntl_in.cmd) {

		case Sysio::FCNTL_CMD_GET_FILE_STATUS_FLAGS:

			sysio.fcntl_out.result = _fh.status_flags();
			return true;

		case Sysio::FCNTL_CMD_SET_FILE_STATUS_FLAGS:
			_fh.status_flags(sysio.fcntl_in.long_arg);
			return true;

		default:

			warning("invalid fcntl command ", (int)sysio.fcntl_in.cmd);
			sysio.error.fcntl = Sysio::FCNTL_ERR_CMD_INVALID;
			return false;
		};
	}

	/*
	 * The 'dirent' function for the root directory only (the
	 * 'Dir_file_system::open()' function handles all requests referring
	 * to directories). Hence, '_path' is the absolute path of the
	 * directory to inspect.
	 */
	bool dirent(Sysio &sysio) override
	{
		/*
		 * Return artificial dir entries for "." and ".."
		 */
		unsigned const index = _fh.seek() / sizeof(Sysio::Dirent);
		if (index < 2) {
			sysio.dirent_out.entry.type = Vfs::Directory_service::Dirent_type::DIRECTORY;
			strncpy(sysio.dirent_out.entry.name,
			        index ? ".." : ".",
			        sizeof(sysio.dirent_out.entry.name));

			sysio.dirent_out.entry.fileno = 1;
			_fh.advance_seek(sizeof(Sysio::Dirent));
			return true;
		}

		/*
		 * Delegate remaining dir-entry request to the actual file system.
		 * Align index range to zero when calling the directory service.
		 */

		Vfs::file_size noux_dirent_seek = _fh.seek();
		_fh.seek((index - 2) * sizeof(Vfs::Directory_service::Dirent));

		Vfs::file_size const count = sizeof(Vfs::Directory_service::Dirent);

		Registered_no_delete<Vfs_io_waiter>
			vfs_io_waiter(_vfs_io_waiter_registry);

		while (!_fh.fs().queue_read(&_fh, count))
			vfs_io_waiter.wait_for_io();

		Vfs::File_io_service::Read_result read_result;
		Vfs::file_size                    out_count = 0;
		Vfs::Directory_service::Dirent    dirent { };

		for (;;) {
			read_result = _fh.fs().complete_read(&_fh, (char*)&dirent,
			                                     count, out_count);

			if (read_result != Vfs::File_io_service::READ_QUEUED)
				break;

			vfs_io_waiter.wait_for_io();
		}

		/* wake up threads blocking for 'queue_*()' or 'write()' */
		_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
			r.wakeup();
		});

		if ((read_result != Vfs::File_io_service::READ_OK) ||
		    (out_count != sizeof(dirent))) {
		    dirent = { };
		}

		_fh.seek(noux_dirent_seek);

		sysio.dirent_out.entry = dirent;

		_fh.advance_seek(sizeof(Sysio::Dirent));
		return true;
	}

	/**
	 * Return size of file that the I/O channel refers to
	 *
	 * Note that this function overwrites the 'sysio' argument. Do not
	 * call it prior saving all input arguments from the original sysio
	 * structure.
	 */
	size_t size(Sysio &sysio)
	{
		if (fstat(sysio))
			return sysio.fstat_out.st.size;

		return 0;
	}

	bool ioctl(Sysio &sysio) override
	{
		Vfs::File_system::Ioctl_arg arg = (Vfs::File_system::Ioctl_arg)sysio.ioctl_in.argp;

		sysio.error.ioctl = _fh.fs().ioctl(&_fh, sysio.ioctl_in.request, arg, sysio.ioctl_out);

		return (sysio.error.ioctl == Vfs::File_io_service::IOCTL_OK);
	}

	bool lseek(Sysio &sysio) override
	{
		switch (sysio.lseek_in.whence) {
		case Sysio::LSEEK_SET: _fh.seek(sysio.lseek_in.offset); break;
		case Sysio::LSEEK_CUR: _fh.advance_seek(sysio.lseek_in.offset); break;
		case Sysio::LSEEK_END:
			off_t offset = sysio.lseek_in.offset;
			sysio.fstat_in.fd = sysio.lseek_in.fd;
			_fh.seek(size(sysio) + offset);
			break;
		}
		sysio.lseek_out.offset = _fh.seek();
		return true;
	}

	bool check_unblock(bool rd, bool wr, bool ex) const override
	{
		return _fh.fs().check_unblock(&_fh, rd, wr, ex);
	}

	bool path(char *path, size_t len) override
	{
		strncpy(path, _path.base(), len);
		path[len - 1] = '\0';

		return true;
	}
};

#endif /* _NOUX__VFS_IO_CHANNEL_H_ */