boost/interprocess/shared_memory_object.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_SHARED_MEMORY_OBJECT_HPP
#define BOOST_INTERPROCESS_SHARED_MEMORY_OBJECT_HPP
#include <boost/interprocess/detail/config_begin.hpp>
#include <boost/interprocess/detail/workaround.hpp>
#include <boost/interprocess/creation_tags.hpp>
#include <boost/interprocess/exceptions.hpp>
#include <boost/move/move.hpp>
#include <boost/interprocess/interprocess_fwd.hpp>
#include <boost/interprocess/exceptions.hpp>
#include <boost/interprocess/detail/os_file_functions.hpp>
#include <boost/interprocess/detail/tmp_dir_helpers.hpp>
#include <boost/interprocess/permissions.hpp>
#include <cstddef>
#include <string>
#include <algorithm>
#if defined(BOOST_INTERPROCESS_XSI_SHARED_MEMORY_OBJECTS_ONLY)
# include <sys/shm.h> //System V shared memory...
#elif defined(BOOST_INTERPROCESS_POSIX_SHARED_MEMORY_OBJECTS)
# include <fcntl.h> //O_CREAT, O_*...
# include <sys/mman.h> //shm_xxx
# include <unistd.h> //ftruncate, close
# include <sys/stat.h> //mode_t, S_IRWXG, S_IRWXO, S_IRWXU,
# if defined(BOOST_INTERPROCESS_RUNTIME_FILESYSTEM_BASED_POSIX_SHARED_MEMORY)
# if defined(__FreeBSD__)
# include <sys/sysctl.h>
# endif
# endif
#else
//
#endif
//!\file
//!Describes a shared memory object management class.
namespace boost {
namespace interprocess {
//!A class that wraps a shared memory mapping that can be used to
//!create mapped regions from the mapped files
class shared_memory_object
{
/// @cond
//Non-copyable and non-assignable
BOOST_MOVABLE_BUT_NOT_COPYABLE(shared_memory_object)
/// @endcond
public:
//!Default constructor. Represents an empty shared_memory_object.
shared_memory_object();
//!Creates a shared memory object with name "name" and mode "mode", with the access mode "mode"
//!If the file previously exists, throws an error.*/
shared_memory_object(create_only_t, const char *name, mode_t mode, const permissions &perm = permissions())
{ this->priv_open_or_create(ipcdetail::DoCreate, name, mode, perm); }
//!Tries to create a shared memory object with name "name" and mode "mode", with the
//!access mode "mode". If the file previously exists, it tries to open it with mode "mode".
//!Otherwise throws an error.
shared_memory_object(open_or_create_t, const char *name, mode_t mode, const permissions &perm = permissions())
{ this->priv_open_or_create(ipcdetail::DoOpenOrCreate, name, mode, perm); }
//!Tries to open a shared memory object with name "name", with the access mode "mode".
//!If the file does not previously exist, it throws an error.
shared_memory_object(open_only_t, const char *name, mode_t mode)
{ this->priv_open_or_create(ipcdetail::DoOpen, name, mode, permissions()); }
//!Moves the ownership of "moved"'s shared memory object to *this.
//!After the call, "moved" does not represent any shared memory object.
//!Does not throw
shared_memory_object(BOOST_RV_REF(shared_memory_object) moved)
: m_handle(file_handle_t(ipcdetail::invalid_file()))
, m_mode(read_only)
{ this->swap(moved); }
//!Moves the ownership of "moved"'s shared memory to *this.
//!After the call, "moved" does not represent any shared memory.
//!Does not throw
shared_memory_object &operator=(BOOST_RV_REF(shared_memory_object) moved)
{
shared_memory_object tmp(boost::move(moved));
this->swap(tmp);
return *this;
}
//!Swaps the shared_memory_objects. Does not throw
void swap(shared_memory_object &moved);
//!Erases a shared memory object from the system.
//!Returns false on error. Never throws
static bool remove(const char *name);
//!Sets the size of the shared memory mapping
void truncate(offset_t length);
//!Destroys *this and indicates that the calling process is finished using
//!the resource. All mapped regions are still
//!valid after destruction. The destructor function will deallocate
//!any system resources allocated by the system for use by this process for
//!this resource. The resource can still be opened again calling
//!the open constructor overload. To erase the resource from the system
//!use remove().
~shared_memory_object();
//!Returns the name of the shared memory object.
const char *get_name() const;
//!Returns true if the size of the shared memory object
//!can be obtained and writes the size in the passed reference
bool get_size(offset_t &size) const;
//!Returns access mode
mode_t get_mode() const;
//!Returns mapping handle. Never throws.
mapping_handle_t get_mapping_handle() const;
/// @cond
private:
//!Closes a previously opened file mapping. Never throws.
void priv_close();
//!Closes a previously opened file mapping. Never throws.
bool priv_open_or_create(ipcdetail::create_enum_t type, const char *filename, mode_t mode, const permissions &perm);
file_handle_t m_handle;
mode_t m_mode;
std::string m_filename;
/// @endcond
};
/// @cond
inline shared_memory_object::shared_memory_object()
: m_handle(file_handle_t(ipcdetail::invalid_file()))
, m_mode(read_only)
{}
inline shared_memory_object::~shared_memory_object()
{ this->priv_close(); }
inline const char *shared_memory_object::get_name() const
{ return m_filename.c_str(); }
inline bool shared_memory_object::get_size(offset_t &size) const
{ return ipcdetail::get_file_size((file_handle_t)m_handle, size); }
inline void shared_memory_object::swap(shared_memory_object &other)
{
std::swap(m_handle, other.m_handle);
std::swap(m_mode, other.m_mode);
m_filename.swap(other.m_filename);
}
inline mapping_handle_t shared_memory_object::get_mapping_handle() const
{
return ipcdetail::mapping_handle_from_file_handle(m_handle);
}
inline mode_t shared_memory_object::get_mode() const
{ return m_mode; }
#if !defined(BOOST_INTERPROCESS_POSIX_SHARED_MEMORY_OBJECTS)
inline bool shared_memory_object::priv_open_or_create
(ipcdetail::create_enum_t type, const char *filename, mode_t mode, const permissions &perm)
{
m_filename = filename;
std::string shmfile;
ipcdetail::create_tmp_and_clean_old_and_get_filename(filename, shmfile);
//Set accesses
if (mode != read_write && mode != read_only){
error_info err = other_error;
throw interprocess_exception(err);
}
switch(type){
case ipcdetail::DoOpen:
m_handle = ipcdetail::open_existing_file(shmfile.c_str(), mode, true);
break;
case ipcdetail::DoCreate:
m_handle = ipcdetail::create_new_file(shmfile.c_str(), mode, perm, true);
break;
case ipcdetail::DoOpenOrCreate:
m_handle = ipcdetail::create_or_open_file(shmfile.c_str(), mode, perm, true);
break;
default:
{
error_info err = other_error;
throw interprocess_exception(err);
}
}
//Check for error
if(m_handle == ipcdetail::invalid_file()){
error_info err = system_error_code();
this->priv_close();
throw interprocess_exception(err);
}
m_mode = mode;
return true;
}
inline bool shared_memory_object::remove(const char *filename)
{
try{
//Make sure a temporary path is created for shared memory
std::string shmfile;
ipcdetail::tmp_filename(filename, shmfile);
return ipcdetail::delete_file(shmfile.c_str());
}
catch(...){
return false;
}
}
inline void shared_memory_object::truncate(offset_t length)
{
if(!ipcdetail::truncate_file(m_handle, length)){
error_info err = system_error_code();
throw interprocess_exception(err);
}
}
inline void shared_memory_object::priv_close()
{
if(m_handle != ipcdetail::invalid_file()){
ipcdetail::close_file(m_handle);
m_handle = ipcdetail::invalid_file();
}
}
#else //!defined(BOOST_INTERPROCESS_POSIX_SHARED_MEMORY_OBJECTS)
namespace shared_memory_object_detail {
#ifdef BOOST_INTERPROCESS_RUNTIME_FILESYSTEM_BASED_POSIX_SHARED_MEMORY
#if defined(__FreeBSD__)
inline bool use_filesystem_based_posix()
{
int jailed = 0;
std::size_t len = sizeof(jailed);
::sysctlbyname("security.jail.jailed", &jailed, &len, NULL, 0);
return jailed != 0;
}
#else
#error "Not supported platform for BOOST_INTERPROCESS_RUNTIME_FILESYSTEM_BASED_POSIX_SHARED_MEMORY"
#endif
#endif
} //shared_memory_object_detail
inline bool shared_memory_object::priv_open_or_create
(ipcdetail::create_enum_t type,
const char *filename,
mode_t mode, const permissions &perm)
{
#if defined(BOOST_INTERPROCESS_FILESYSTEM_BASED_POSIX_SHARED_MEMORY)
const bool add_leading_slash = false;
#elif defined(BOOST_INTERPROCESS_RUNTIME_FILESYSTEM_BASED_POSIX_SHARED_MEMORY)
const bool add_leading_slash = !shared_memory_object_detail::use_filesystem_based_posix();
#else
const bool add_leading_slash = true;
#endif
if(add_leading_slash){
ipcdetail::add_leading_slash(filename, m_filename);
}
else{
ipcdetail::create_tmp_and_clean_old_and_get_filename(filename, m_filename);
}
//Create new mapping
int oflag = 0;
if(mode == read_only){
oflag |= O_RDONLY;
}
else if(mode == read_write){
oflag |= O_RDWR;
}
else{
error_info err(mode_error);
throw interprocess_exception(err);
}
int unix_perm = perm.get_permissions();
switch(type){
case ipcdetail::DoOpen:
{
//No oflag addition
m_handle = shm_open(m_filename.c_str(), oflag, unix_perm);
}
break;
case ipcdetail::DoCreate:
{
oflag |= (O_CREAT | O_EXCL);
m_handle = shm_open(m_filename.c_str(), oflag, unix_perm);
if(m_handle >= 0){
::fchmod(m_handle, unix_perm);
}
}
break;
case ipcdetail::DoOpenOrCreate:
{
//We need a create/open loop to change permissions correctly using fchmod, since
//with "O_CREAT" only we don't know if we've created or opened the shm.
while(1){
//Try to create shared memory
m_handle = shm_open(m_filename.c_str(), oflag | (O_CREAT | O_EXCL), unix_perm);
//If successful change real permissions
if(m_handle >= 0){
::fchmod(m_handle, unix_perm);
}
//If already exists, try to open
else if(errno == EEXIST){
m_handle = shm_open(m_filename.c_str(), oflag, unix_perm);
//If open fails and errno tells the file does not exist
//(shm was removed between creation and opening tries), just retry
if(m_handle < 0 && errno == ENOENT){
continue;
}
}
//Exit retries
break;
}
}
break;
default:
{
error_info err = other_error;
throw interprocess_exception(err);
}
}
//Check for error
if(m_handle < 0){
error_info err = errno;
this->priv_close();
throw interprocess_exception(err);
}
m_filename = filename;
m_mode = mode;
return true;
}
inline bool shared_memory_object::remove(const char *filename)
{
try{
std::string file_str;
#if defined(BOOST_INTERPROCESS_FILESYSTEM_BASED_POSIX_SHARED_MEMORY)
const bool add_leading_slash = false;
#elif defined(BOOST_INTERPROCESS_RUNTIME_FILESYSTEM_BASED_POSIX_SHARED_MEMORY)
const bool add_leading_slash = !shared_memory_object_detail::use_filesystem_based_posix();
#else
const bool add_leading_slash = true;
#endif
if(add_leading_slash){
ipcdetail::add_leading_slash(filename, file_str);
}
else{
ipcdetail::tmp_filename(filename, file_str);
}
return 0 == shm_unlink(file_str.c_str());
}
catch(...){
return false;
}
}
inline void shared_memory_object::truncate(offset_t length)
{
if(0 != ftruncate(m_handle, length)){
error_info err(system_error_code());
throw interprocess_exception(err);
}
}
inline void shared_memory_object::priv_close()
{
if(m_handle != -1){
::close(m_handle);
m_handle = -1;
}
}
#endif
///@endcond
//!A class that stores the name of a shared memory
//!and calls shared_memory_object::remove(name) in its destructor
//!Useful to remove temporary shared memory objects in the presence
//!of exceptions
class remove_shared_memory_on_destroy
{
const char * m_name;
public:
remove_shared_memory_on_destroy(const char *name)
: m_name(name)
{}
~remove_shared_memory_on_destroy()
{ shared_memory_object::remove(m_name); }
};
} //namespace interprocess {
} //namespace boost {
#include <boost/interprocess/detail/config_end.hpp>
#endif //BOOST_INTERPROCESS_SHARED_MEMORY_OBJECT_HPP