boost/interprocess/sync/file_lock.hpp
//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2005-2012. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////
#ifndef BOOST_INTERPROCESS_FILE_LOCK_HPP
#define BOOST_INTERPROCESS_FILE_LOCK_HPP
#if (defined _MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif
#include <boost/interprocess/detail/config_begin.hpp>
#include <boost/interprocess/detail/workaround.hpp>
#include <boost/interprocess/exceptions.hpp>
#include <boost/interprocess/detail/os_file_functions.hpp>
#include <boost/interprocess/detail/os_thread_functions.hpp>
#include <boost/interprocess/detail/posix_time_types_wrk.hpp>
#include <boost/interprocess/sync/spin/wait.hpp>
#include <boost/move/move.hpp>
//!\file
//!Describes a class that wraps file locking capabilities.
namespace boost {
namespace interprocess {
//!A file lock, is a mutual exclusion utility similar to a mutex using a
//!file. A file lock has sharable and exclusive locking capabilities and
//!can be used with scoped_lock and sharable_lock classes.
//!A file lock can't guarantee synchronization between threads of the same
//!process so just use file locks to synchronize threads from different processes.
class file_lock
{
/// @cond
//Non-copyable
BOOST_MOVABLE_BUT_NOT_COPYABLE(file_lock)
/// @endcond
public:
//!Constructs an empty file mapping.
//!Does not throw
file_lock()
: m_file_hnd(file_handle_t(ipcdetail::invalid_file()))
{}
//!Opens a file lock. Throws interprocess_exception if the file does not
//!exist or there are no operating system resources.
file_lock(const char *name);
//!Moves the ownership of "moved"'s file mapping object to *this.
//!After the call, "moved" does not represent any file mapping object.
//!Does not throw
file_lock(BOOST_RV_REF(file_lock) moved)
: m_file_hnd(file_handle_t(ipcdetail::invalid_file()))
{ this->swap(moved); }
//!Moves the ownership of "moved"'s file mapping to *this.
//!After the call, "moved" does not represent any file mapping.
//!Does not throw
file_lock &operator=(BOOST_RV_REF(file_lock) moved)
{
file_lock tmp(boost::move(moved));
this->swap(tmp);
return *this;
}
//!Closes a file lock. Does not throw.
~file_lock();
//!Swaps two file_locks.
//!Does not throw.
void swap(file_lock &other)
{
file_handle_t tmp = m_file_hnd;
m_file_hnd = other.m_file_hnd;
other.m_file_hnd = tmp;
}
//Exclusive locking
//!Effects: The calling thread tries to obtain exclusive ownership of the mutex,
//! and if another thread has exclusive, or sharable ownership of
//! the mutex, it waits until it can obtain the ownership.
//!Throws: interprocess_exception on error.
void lock();
//!Effects: The calling thread tries to acquire exclusive ownership of the mutex
//! without waiting. If no other thread has exclusive, or sharable
//! ownership of the mutex this succeeds.
//!Returns: If it can acquire exclusive ownership immediately returns true.
//! If it has to wait, returns false.
//!Throws: interprocess_exception on error.
bool try_lock();
//!Effects: The calling thread tries to acquire exclusive ownership of the mutex
//! waiting if necessary until no other thread has exclusive, or sharable
//! ownership of the mutex or abs_time is reached.
//!Returns: If acquires exclusive ownership, returns true. Otherwise returns false.
//!Throws: interprocess_exception on error.
bool timed_lock(const boost::posix_time::ptime &abs_time);
//!Precondition: The thread must have exclusive ownership of the mutex.
//!Effects: The calling thread releases the exclusive ownership of the mutex.
//!Throws: An exception derived from interprocess_exception on error.
void unlock();
//Sharable locking
//!Effects: The calling thread tries to obtain sharable ownership of the mutex,
//! and if another thread has exclusive ownership of the mutex, waits until
//! it can obtain the ownership.
//!Throws: interprocess_exception on error.
void lock_sharable();
//!Effects: The calling thread tries to acquire sharable ownership of the mutex
//! without waiting. If no other thread has exclusive ownership of the
//! mutex this succeeds.
//!Returns: If it can acquire sharable ownership immediately returns true. If it
//! has to wait, returns false.
//!Throws: interprocess_exception on error.
bool try_lock_sharable();
//!Effects: The calling thread tries to acquire sharable ownership of the mutex
//! waiting if necessary until no other thread has exclusive ownership of
//! the mutex or abs_time is reached.
//!Returns: If acquires sharable ownership, returns true. Otherwise returns false.
//!Throws: interprocess_exception on error.
bool timed_lock_sharable(const boost::posix_time::ptime &abs_time);
//!Precondition: The thread must have sharable ownership of the mutex.
//!Effects: The calling thread releases the sharable ownership of the mutex.
//!Throws: An exception derived from interprocess_exception on error.
void unlock_sharable();
/// @cond
private:
file_handle_t m_file_hnd;
bool timed_acquire_file_lock
(file_handle_t hnd, bool &acquired, const boost::posix_time::ptime &abs_time)
{
//Obtain current count and target time
boost::posix_time::ptime now = microsec_clock::universal_time();
using namespace boost::detail;
if(now >= abs_time) return false;
spin_wait swait;
do{
if(!ipcdetail::try_acquire_file_lock(hnd, acquired))
return false;
if(acquired)
return true;
else{
now = microsec_clock::universal_time();
if(now >= abs_time){
acquired = false;
return true;
}
// relinquish current time slice
swait.yield();
}
}while (true);
}
bool timed_acquire_file_lock_sharable
(file_handle_t hnd, bool &acquired, const boost::posix_time::ptime &abs_time)
{
//Obtain current count and target time
boost::posix_time::ptime now = microsec_clock::universal_time();
using namespace boost::detail;
if(now >= abs_time) return false;
spin_wait swait;
do{
if(!ipcdetail::try_acquire_file_lock_sharable(hnd, acquired))
return false;
if(acquired)
return true;
else{
now = microsec_clock::universal_time();
if(now >= abs_time){
acquired = false;
return true;
}
// relinquish current time slice
swait.yield();
}
}while (true);
}
/// @endcond
};
inline file_lock::file_lock(const char *name)
{
m_file_hnd = ipcdetail::open_existing_file(name, read_write);
if(m_file_hnd == ipcdetail::invalid_file()){
error_info err(system_error_code());
throw interprocess_exception(err);
}
}
inline file_lock::~file_lock()
{
if(m_file_hnd != ipcdetail::invalid_file()){
ipcdetail::close_file(m_file_hnd);
m_file_hnd = ipcdetail::invalid_file();
}
}
inline void file_lock::lock()
{
if(!ipcdetail::acquire_file_lock(m_file_hnd)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
}
inline bool file_lock::try_lock()
{
bool result;
if(!ipcdetail::try_acquire_file_lock(m_file_hnd, result)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
return result;
}
inline bool file_lock::timed_lock(const boost::posix_time::ptime &abs_time)
{
if(abs_time == boost::posix_time::pos_infin){
this->lock();
return true;
}
bool result;
if(!this->timed_acquire_file_lock(m_file_hnd, result, abs_time)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
return result;
}
inline void file_lock::unlock()
{
if(!ipcdetail::release_file_lock(m_file_hnd)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
}
inline void file_lock::lock_sharable()
{
if(!ipcdetail::acquire_file_lock_sharable(m_file_hnd)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
}
inline bool file_lock::try_lock_sharable()
{
bool result;
if(!ipcdetail::try_acquire_file_lock_sharable(m_file_hnd, result)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
return result;
}
inline bool file_lock::timed_lock_sharable(const boost::posix_time::ptime &abs_time)
{
if(abs_time == boost::posix_time::pos_infin){
this->lock_sharable();
return true;
}
bool result;
if(!this->timed_acquire_file_lock_sharable(m_file_hnd, result, abs_time)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
return result;
}
inline void file_lock::unlock_sharable()
{
if(!ipcdetail::release_file_lock_sharable(m_file_hnd)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
}
} //namespace interprocess {
} //namespace boost {
#include <boost/interprocess/detail/config_end.hpp>
#endif //BOOST_INTERPROCESS_FILE_LOCK_HPP