ACE_Shared_Memory_Pool Class Reference

Make a memory pool that is based on System V shared memory (shmget(2) etc.). This implementation allows memory to be shared between processes. If your platform doesn't support System V shared memory (e.g., Win32 and many RTOS platforms do not) then you should use ACE_MMAP_Memory_Pool instead of this class. In fact, you should probably use ACE_MMAP_Memory_Pool on platforms that do support System V shared memory since it provides more powerful features, such as persistent backing store and greatly scalability. More...

#include <Shared_Memory_Pool.h>

Inheritance diagram for ACE_Shared_Memory_Pool:

Collaboration diagram for ACE_Shared_Memory_Pool:

Classes
struct	SHM_TABLE

Public Types
typedef ACE_Shared_Memory_Pool_Options	OPTIONS
Public Types inherited from ACE_Event_Handler
enum	{   LO_PRIORITY = 0 , HI_PRIORITY = 10 , NULL_MASK = 0 , READ_MASK = (1 << 0) ,   WRITE_MASK = (1 << 1) , EXCEPT_MASK = (1 << 2) , ACCEPT_MASK = (1 << 3) , CONNECT_MASK = (1 << 4) ,   TIMER_MASK = (1 << 5) , QOS_MASK = (1 << 6) , GROUP_QOS_MASK = (1 << 7) , SIGNAL_MASK = (1 << 8) ,   ALL_EVENTS_MASK , RWE_MASK , DONT_CALL = (1 << 9) }
enum	{ ACE_EVENT_HANDLER_NOT_RESUMED = -1 , ACE_REACTOR_RESUMES_HANDLER = 0 , ACE_APPLICATION_RESUMES_HANDLER }
typedef long	Reference_Count
	Reference count type.

Public Member Functions
	ACE_Shared_Memory_Pool (const ACE_TCHAR *backing_store_name=nullptr, const OPTIONS *options=nullptr)
	Initialize the pool.
virtual	~ACE_Shared_Memory_Pool ()=default
virtual void *	init_acquire (size_t nbytes, size_t &rounded_bytes, int &first_time)
	Ask system for initial chunk of local memory.
virtual void *	acquire (size_t nbytes, size_t &rounded_bytes)
	Ask system for more shared memory.
virtual int	release (int destroy=1)
	Instruct the memory pool to release all of its resources.
virtual int	sync (ssize_t len=-1, int flags=MS_SYNC)
virtual int	sync (void *addr, size_t len, int flags=MS_SYNC)
	Sync the memory region to the backing store starting at addr.
virtual int	protect (ssize_t len=-1, int prot=PROT_RDWR)
virtual int	protect (void *addr, size_t len, int prot=PROT_RDWR)
virtual void *	base_addr () const
virtual void	dump () const
	Dump the state of an object.
Public Member Functions inherited from ACE_Event_Handler
virtual	~ACE_Event_Handler ()=default
	Destructor is virtual to enable proper cleanup.
virtual ACE_HANDLE	get_handle () const
	Get the I/O handle.
virtual void	set_handle (ACE_HANDLE)
	Set the I/O handle.
virtual int	priority () const
virtual void	priority (int priority)
	Set the priority of the Event_Handler.
virtual int	handle_input (ACE_HANDLE fd=ACE_INVALID_HANDLE)
	Called when input events occur (e.g., connection or data).
virtual int	handle_output (ACE_HANDLE fd=ACE_INVALID_HANDLE)
virtual int	handle_exception (ACE_HANDLE fd=ACE_INVALID_HANDLE)
	Called when an exceptional events occur (e.g., SIGURG).
virtual int	handle_timeout (const ACE_Time_Value &current_time, const void *act=0)
virtual int	handle_exit (ACE_Process *)
	Called when a process exits.
virtual int	handle_close (ACE_HANDLE handle, ACE_Reactor_Mask close_mask)
virtual int	resume_handler ()
virtual int	handle_qos (ACE_HANDLE=ACE_INVALID_HANDLE)
virtual int	handle_group_qos (ACE_HANDLE=ACE_INVALID_HANDLE)
virtual void	reactor (ACE_Reactor *reactor)
	Set the event demultiplexors.
virtual ACE_Reactor *	reactor () const
	Get the event demultiplexors.
virtual ACE_Reactor_Timer_Interface *	reactor_timer_interface () const
	Get only the reactor's timer related interface.
virtual Reference_Count	add_reference ()
	Increment reference count on the handler.
virtual Reference_Count	remove_reference ()
	Decrement reference count on the handler.
Reference_Counting_Policy &	reference_counting_policy ()
	Current Reference_Counting_Policy.

Public Attributes
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks.

Protected Member Functions
virtual size_t	round_up (size_t nbytes)
virtual int	commit_backing_store_name (size_t rounded_bytes, ACE_OFF_T &offset)
virtual int	find_seg (const void *const searchPtr, ACE_OFF_T &offset, size_t &counter)
	Find the segment that contains the searchPtr.
virtual int	in_use (ACE_OFF_T &offset, size_t &counter)
	Determine how much memory is currently in use.
virtual int	handle_signal (int, siginfo_t *siginfo, ucontext_t *)
	Handle SIGSEGV and SIGBUS signals to remap shared memory properly.
Protected Member Functions inherited from ACE_Event_Handler
	ACE_Event_Handler (ACE_Reactor *=nullptr, int priority=ACE_Event_Handler::LO_PRIORITY)
	Force ACE_Event_Handler to be an abstract base class.

Protected Attributes
size_t const	file_perms_
	File permissions to use when creating/opening a segment.
size_t const	max_segments_
	Number of shared memory segments in the SHM_TABLE table.
ACE_OFF_T const	minimum_bytes_
	What the minimum bytes of the initial segment should be.
size_t const	segment_size_
	Shared memory segment size.
key_t	base_shm_key_
	Base shared memory key for the segment.
std::unique_ptr< void *[]> const	shm_addr_table_
ACE_Sig_Handler	signal_handler_
	Handles SIGSEGV.
Protected Attributes inherited from ACE_Event_Handler
Atomic_Reference_Count	reference_count_
	Reference count.

Additional Inherited Members
Static Public Member Functions inherited from ACE_Event_Handler
static ACE_THR_FUNC_RETURN	read_adapter (void *event_handler)
static int	register_stdin_handler (ACE_Event_Handler *eh, ACE_Reactor *reactor, ACE_Thread_Manager *thr_mgr, int flags=THR_DETACHED)
static int	remove_stdin_handler (ACE_Reactor *reactor, ACE_Thread_Manager *thr_mgr)
	Performs the inverse of the register_stdin_handler() method.
Protected Types inherited from ACE_Event_Handler
typedef std::atomic< Reference_Count >	Atomic_Reference_Count
	Typedef for implementation of reference counting.

Detailed Description

Make a memory pool that is based on System V shared memory (shmget(2) etc.). This implementation allows memory to be shared between processes. If your platform doesn't support System V shared memory (e.g., Win32 and many RTOS platforms do not) then you should use ACE_MMAP_Memory_Pool instead of this class. In fact, you should probably use ACE_MMAP_Memory_Pool on platforms that do support System V shared memory since it provides more powerful features, such as persistent backing store and greatly scalability.

Member Typedef Documentation

OPTIONS

typedef ACE_Shared_Memory_Pool_Options ACE_Shared_Memory_Pool::OPTIONS

Constructor & Destructor Documentation

ACE_Shared_Memory_Pool()

ACE_Shared_Memory_Pool::ACE_Shared_Memory_Pool	(	const ACE_TCHAR *	backing_store_name = nullptr,
		const OPTIONS *	options = nullptr )

Initialize the pool.

~ACE_Shared_Memory_Pool()

virtual ACE_Shared_Memory_Pool::~ACE_Shared_Memory_Pool ( )

virtualdefault

Member Function Documentation

acquire()

void * ACE_Shared_Memory_Pool::acquire ( size_t nbytes, size_t & rounded_bytes )

virtual

Ask system for more shared memory.

Acquire at least nbytes from the memory pool. rounded_byes is the actual number of bytes allocated. Also acquires an internal semaphore that ensures proper serialization of Memory_Pool initialization across processes.

base_addr()

void * ACE_Shared_Memory_Pool::base_addr ( ) const

virtual

Return the base address of this memory pool, nullptr if shm_addr_table_[0] never changes.

commit_backing_store_name()

int ACE_Shared_Memory_Pool::commit_backing_store_name ( size_t rounded_bytes, ACE_OFF_T & offset )

protectedvirtual

Commits a new shared memory segment if necessary after an acquire() or a signal. offset is set to the new offset into the backing store.

dump()

void ACE_Shared_Memory_Pool::dump ( ) const

virtual

Dump the state of an object.

find_seg()

int ACE_Shared_Memory_Pool::find_seg ( const void *const searchPtr, ACE_OFF_T & offset, size_t & counter )

protectedvirtual

Find the segment that contains the searchPtr.

handle_signal()

int ACE_Shared_Memory_Pool::handle_signal ( int , siginfo_t * siginfo, ucontext_t *  )

protectedvirtual

Handle SIGSEGV and SIGBUS signals to remap shared memory properly.

Handle SIGSEGV and SIGBUS signals to remap shared memory properly.

Reimplemented from ACE_Event_Handler.

in_use()

int ACE_Shared_Memory_Pool::in_use ( ACE_OFF_T & offset, size_t & counter )

protectedvirtual

Determine how much memory is currently in use.

init_acquire()

void * ACE_Shared_Memory_Pool::init_acquire ( size_t nbytes, size_t & rounded_bytes, int & first_time )

virtual

Ask system for initial chunk of local memory.

Ask system for initial chunk of shared memory.

protect() [1/2]

int ACE_Shared_Memory_Pool::protect ( ssize_t len = -1, int prot = PROT_RDWR )

virtual

Change the protection of the pages of the mapped region to prot starting at shm_addr_table_[0] up to len bytes. If len == -1 then change protection of all pages in the mapped region.

protect() [2/2]

int ACE_Shared_Memory_Pool::protect ( void * addr, size_t len, int prot = PROT_RDWR )

virtual

Change the protection of the pages of the mapped region to prot starting at addr up to len bytes.

release()

int ACE_Shared_Memory_Pool::release ( int destroy = 1 )

virtual

Instruct the memory pool to release all of its resources.

round_up()

size_t ACE_Shared_Memory_Pool::round_up ( size_t nbytes )

protectedvirtual

Implement the algorithm for rounding up the request to an appropriate chunksize.

sync() [1/2]

int ACE_Shared_Memory_Pool::sync ( ssize_t len = -1, int flags = MS_SYNC )

virtual

Sync the memory region to the backing store starting at shm_addr_table_[0].

sync() [2/2]

int ACE_Shared_Memory_Pool::sync ( void * addr, size_t len, int flags = MS_SYNC )

virtual

Sync the memory region to the backing store starting at addr.

Member Data Documentation

ACE_ALLOC_HOOK_DECLARE

ACE_Shared_Memory_Pool::ACE_ALLOC_HOOK_DECLARE

Declare the dynamic allocation hooks.

base_shm_key_

key_t ACE_Shared_Memory_Pool::base_shm_key_

protected

Base shared memory key for the segment.

file_perms_

size_t const ACE_Shared_Memory_Pool::file_perms_

protected

File permissions to use when creating/opening a segment.

max_segments_

size_t const ACE_Shared_Memory_Pool::max_segments_

protected

Number of shared memory segments in the SHM_TABLE table.

minimum_bytes_

ACE_OFF_T const ACE_Shared_Memory_Pool::minimum_bytes_

protected

What the minimum bytes of the initial segment should be.

segment_size_

size_t const ACE_Shared_Memory_Pool::segment_size_

protected

Shared memory segment size.

shm_addr_table_

std::unique_ptr<void *[]> const ACE_Shared_Memory_Pool::shm_addr_table_

protected

Small table with the addresses of the shared memory segments mapped into this address space. We need these addresses to call shmdt at the release.

signal_handler_

ACE_Sig_Handler ACE_Shared_Memory_Pool::signal_handler_

protected

Handles SIGSEGV.

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The documentation for this class was generated from the following files:

• Shared_Memory_Pool.h
• Shared_Memory_Pool.cpp