A POSIX shared memory class. More...

#include <gsharedmemory.h>

Classes
struct	Control
	Overload discriminator for G::SharedMemory. More...

Public Member Functions
	SharedMemory (size_t size)
	Constructor for a new anonymous segment, typically used across a fork(). More...

	SharedMemory (int fd)
	Constructor for a segment inherited via a file descriptor, typically across fork()/exec(). More...

	SharedMemory (const std::string &name)
	Constructor for an existing named segment. More...

	SharedMemory (const std::string &name, size_t size)
	Constructor for a new named segment. More...

	SharedMemory (size_t size, Control)
	Constructor overload for control segments that might contain semaphores. More...

	SharedMemory (int fd, Control)
	Constructor overload for control segments that might contain semaphores. More...

	SharedMemory (const std::string &name, Control)
	Constructor overload for control segments that might contain semaphores. More...

	SharedMemory (const std::string &name, size_t size, Control)
	Constructor overload for control segments that might contain semaphores. More...

	~SharedMemory ()
	Destructor. More...

size_t	size () const
	Returns the segment size. This is affected by remap().

void	unlink ()
	Unlinks the segment from the filesystem. More...

int	fd () const
	Returns the file descriptor. Returns -1 for anonymous segments.

void	inherit ()
	Marks fd() as inherited across exec() ie. no-close-on-exec.

void *	ptr () const
	Returns the mapped address.

bool	remap (size_t, bool may_move, bool no_throw=false)
	Resizes and remaps the shared memory. More...

Static Public Member Functions
static std::string	delete_ (const std::string &name, bool control_segment)
	Unlinks the segment from the filesystem. More...

static void	cleanup (SignalSafe, const char os_name, void(fn)(SignalSafe, void *))
	An exit handler that unlinks the named shared memory segment and calls the user's function for the memory contents. More...

static void	trap (SignalSafe, const char os_name, void(fn)(SignalSafe, void *))
	An exit handler that calls the user's function on the shared memory contents. More...

static std::string	osName (const std::string &name)
	Converts the segment name to an internal form that can be passed to cleanup() or trap(). More...

static void	help (const std::string &)
	Sets some error-message help text for the case when named shared memory cannot be created because it already exists. More...

static void	prefix (const std::string &)
	Sets a prefix for shared memory names, used by osName(). More...

static std::string	prefix ()
	Returns the prefix, as set by by a call to the other overload.

static void	filetext (const std::string &)
	Sets some help text that gets written into the placeholder files.

static std::vector< std::string >	list (bool os_names=false)
	Returns a list of possible control segment names.

Detailed Description

A POSIX shared memory class.

Anonymous shared memory can be inherited across a fork(); shared memory associated with an open file descriptor can be inherited across a fork() and exec(); and shared memory associated with a filesystem path can be shared freely by name.

Definition at line 41 of file gsharedmemory.h.

Constructor & Destructor Documentation

G::SharedMemory::SharedMemory ( size_t size )

explicit

Constructor for a new anonymous segment, typically used across a fork().

Definition at line 104 of file gsharedmemory.cpp.

G::SharedMemory::SharedMemory ( int fd )

explicit

Constructor for a segment inherited via a file descriptor, typically across fork()/exec().

The file is closed by the destructor. See also: inherit(), fd()

Definition at line 110 of file gsharedmemory.cpp.

G::SharedMemory::SharedMemory ( const std::string & name )

explicit

Constructor for an existing named segment.

Throws if it does not exist.

Definition at line 116 of file gsharedmemory.cpp.

G::SharedMemory::SharedMemory	(	const std::string &	name,
		size_t	size
	)

Constructor for a new named segment.

Throws if it already exists. The destructor will call unlink().

Definition at line 122 of file gsharedmemory.cpp.

G::SharedMemory::SharedMemory	(	size_t	size,
		Control
	)

Constructor overload for control segments that might contain semaphores.

Definition at line 130 of file gsharedmemory.cpp.

G::SharedMemory::SharedMemory	(	int	fd,
		Control
	)

Constructor overload for control segments that might contain semaphores.

Definition at line 136 of file gsharedmemory.cpp.

G::SharedMemory::SharedMemory	(	const std::string &	name,
		Control
	)

Constructor overload for control segments that might contain semaphores.

Definition at line 142 of file gsharedmemory.cpp.

G::SharedMemory::SharedMemory	(	const std::string &	name,
		size_t	size,
		Control
	)

Constructor overload for control segments that might contain semaphores.

Definition at line 148 of file gsharedmemory.cpp.

G::SharedMemory::~SharedMemory ( )

Destructor.

The memory is unmapped and, where relevant, the newly-created named segment is unlink()ed.

Definition at line 156 of file gsharedmemory.cpp.

Member Function Documentation

void G::SharedMemory::cleanup	(	SignalSafe	signal_safe,
		const char *	os_name,
		void()(SignalSafe, void )	fn
	)

static

An exit handler that unlinks the named shared memory segment and calls the user's function for the memory contents.

Use osName() for the segment name.

Definition at line 268 of file gsharedmemory.cpp.

std::string G::SharedMemory::delete_	(	const std::string &	name,
		bool	control_segment
	)

static

Unlinks the segment from the filesystem.

Typically used administratively, especially on BSD. Returns a failure reason, or the empty string on success.

Definition at line 396 of file gsharedmemory.cpp.

void G::SharedMemory::help ( const std::string & s )

static

Sets some error-message help text for the case when named shared memory cannot be created because it already exists.

Definition at line 416 of file gsharedmemory.cpp.

std::string G::SharedMemory::osName ( const std::string & name )

static

Converts the segment name to an internal form that can be passed to cleanup() or trap().

Definition at line 258 of file gsharedmemory.cpp.

void G::SharedMemory::prefix ( const std::string & s )

static

Sets a prefix for shared memory names, used by osName().

This method has to be called early and consistently (if called at all) in all cooperating programs. Does nothing if the prefix starts with a double-underscore.

Definition at line 421 of file gsharedmemory.cpp.

bool G::SharedMemory::remap	(	size_t	new_size,
		bool	may_move,
		bool	no_throw = `false`
	)

Resizes and remaps the shared memory.

Addresses may change if 'may_move' is true, but when false resizing will be less likely to succeed. Throws or returns false on error depending on 'no_throw'. Do not use this if there are semaphores inside the shared memory.

Definition at line 239 of file gsharedmemory.cpp.

void G::SharedMemory::trap	(	SignalSafe	signal_safe,
		const char *	os_name,
		void()(SignalSafe, void )	fn
	)

static

An exit handler that calls the user's function on the shared memory contents.

Use osName() for the segment name.

Definition at line 288 of file gsharedmemory.cpp.

void G::SharedMemory::unlink ( )

Unlinks the segment from the filesystem.

Typically used for early cleanup when doing fork()/exec(). Does not throw.

Definition at line 326 of file gsharedmemory.cpp.

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

/home/graeme/videotools/src/glib/gsharedmemory.h
/home/graeme/videotools/src/glib/gsharedmemory.cpp

Classes

Public Member Functions

Static Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation