//
// mp::fdnotify
//
// Copyright (C) 2008 FURUHASHI Sadayuki
//
//    Licensed under the Apache License, Version 2.0 (the "License");
//    you may not use this file except in compliance with the License.
//    You may obtain a copy of the License at
//
//        http://www.apache.org/licenses/LICENSE-2.0
//
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS,
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//    See the License for the specific language governing permissions and
//    limitations under the License.
//

#ifndef MP_FDNOTIFY_IMPL_H__
#define MP_FDNOTIFY_IMPL_H__

#include <fcntl.h>
#include <errno.h>

namespace mp {


template <typename NotifyObject>
fdnotify<NotifyObject>::fdnotify() : m_head(m_buffer), m_tail(m_buffer)
{
	if( ::pipe(m_pipe) < 0 ) {
		throw fdnotify_exception("can't create pipe");
	}
	if( ::fcntl(m_pipe[0], F_SETFL, O_NONBLOCK) < 0 ) {
		close(m_pipe[0]);
		close(m_pipe[1]);
		throw fdnotify_exception("can't set non-blocking mode");
	}
}

template <typename NotifyObject>
fdnotify<NotifyObject>::~fdnotify()
{
	close(m_pipe[0]);
	close(m_pipe[1]);
}

template <typename NotifyObject>
inline bool fdnotify<NotifyObject>::try_receive(NotifyObject* result)
{
	if(m_tail - m_head >= static_cast<ptrdiff_t>(sizeof(NotifyObject))) {
		*result = *((NotifyObject*)m_head);
		m_head += sizeof(NotifyObject);
		return true;
	} else {
		return receive_next(result);
	}
}

template <typename NotifyObject>
inline void fdnotify<NotifyObject>::send(const NotifyObject& obj)
{
	ssize_t len;
	while(1) {
		len = ::write(m_pipe[1], (void*)&obj, sizeof(NotifyObject));
		if(len >= static_cast<ssize_t>(sizeof(NotifyObject))) {
			return;
		}
		if(len < 0) {
			if(errno != EAGAIN && errno != EINTR) {
				throw fdnotify_exception("write-side pipe is broken");
			}
		}
	}
}

template <typename NotifyObject>
bool fdnotify<NotifyObject>::receive_next(NotifyObject* result)
{
	size_t carry = m_tail - m_head;

	std::memcpy(m_buffer, m_head, carry);
	m_head = m_buffer;
	m_tail = m_buffer + carry;

	ssize_t len = ::read(m_pipe[0], m_tail, sizeof(m_buffer)-carry);
	if(len < 0) {
		if(errno == EAGAIN || errno == EINTR) {
			return false;
		} else {
			throw fdnotify_exception("read-side pipe is broken");
		}
	} else if(len == 0) {
		throw fdnotify_exception("read-side pipe is closed");
	}

	m_tail += len;
	if(m_tail - m_head >= static_cast<ptrdiff_t>(sizeof(NotifyObject))) {
		*result = *((NotifyObject*)m_head);
		m_head += sizeof(NotifyObject);
		return true;
	} else {
		return false;
	}
}


}  // namespace mp

#endif /* mp/fdnotify_impl.h */