ugcs::vsm::Shared_memory Class Reference

Platform independent implementation of system-wide named shared memory used for interprocess communications. More...

#include <shared_memory.h>

Inheritance diagram for ugcs::vsm::Shared_memory:

Public Types
enum	Open_result { OPEN_RESULT_OK, OPEN_RESULT_CREATED, OPEN_RESULT_ERROR }
	Possible return codes from Open() call.
typedef std::shared_ptr < Shared_memory >	Ptr
	Pointer type.
typedef std::weak_ptr < Shared_memory >	Weak_ptr
	Pointer type.

Public Member Functions
	Shared_memory ()
	Constructor should not be called explicitly. More...
virtual Open_result	Open (const std::string &name, const size_t size)=0
	Open/create shared memory. More...
virtual void	Close ()=0
	Closes previously opened memory.
virtual void *	Get ()
	Returns the pointer to shared memory. More...

Static Public Member Functions
template<typename... Args>
static Ptr	Create (Args &&...args)
	Create an instance. More...
static bool	Delete (const std::string &name)
	Deletes the named memory. More...
static Ptr	Create ()
	Creates Platform specific class instance. More...

Protected Attributes
void *	memory
	pointer to shared memory

Detailed Description

Platform independent implementation of system-wide named shared memory used for interprocess communications.

Workflow: 1) Call Shared_memory::Create() to create class instance. 2) Call Shared_memory::Open() to open or create shared memory. 3) Call Shared_memory::Get() to Get the pointer to shared memory.

The pointer is valid until object is closed. Object is closed:

• explicitly via call to Close()
• implicitly when calling Open() on the same instance.
• in destructor.

User must be aware of the following platform specific differences in shared memory semantics: Windows: 1) When the last handle to memory is closed the OS destroys the memory. (Note: OS closes all open handles on application termination/crash) 2) By default the memory is created in Session Kernel object namespace. 3) Shared memory cannot be explicitly deleted. Implemented via CreateFileMapping() and friends.

Linux: 1) Shared memory persists in the system until explicitly deleted or system restarted. 2) It is accessible from any session of its creator user. Implemented via shm_open() and friends.

Constructor & Destructor Documentation

ugcs::vsm::Shared_memory::Shared_memory ( )

inline

Constructor should not be called explicitly.

Use Create() function to instantiate the object.

Member Function Documentation

template<typename... Args>

static Ptr ugcs::vsm::Shared_memory::Create ( Args &&...  args )

inlinestatic

Create an instance.

static Ptr ugcs::vsm::Shared_memory::Create ( )

static

Creates Platform specific class instance.

This does not create the memory itself, you should call Open() to create the named memory.

Returns

shared_ptr<Shared_memory> of newly created instance

static bool ugcs::vsm::Shared_memory::Delete ( const std::string &  name )

static

Deletes the named memory.

(Linux-only) Does not affect any opened memory with this name.

Parameters

name	Shared memory name.

Returns

true Shared memory deleted. false error occurred.

virtual void* ugcs::vsm::Shared_memory::Get ( )

inlinevirtual

Returns the pointer to shared memory.

Returns

pointer to shared memory. Returns nullptr if not opened.

virtual Open_result ugcs::vsm::Shared_memory::Open ( const std::string &  name, const size_t  size  )

pure virtual

Open/create shared memory.

Closes previously opened memory if any.

Parameters

name	Name of memory object
size	size in bytes. Will return error if size==0

Returns

OPEN_RESULT_OK Opened existing shared memory. OPEN_RESULT_CREATED Created new shared memory. OPEN_RESULT_ERROR Error while creating shared memory. Previously opened memory is closed.

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

• shared_memory.h