vlink::SysSharemem Class Reference

Named cross-process shared memory backed by the OS IPC layer. More...

#include <sys_sharemem.h>

Collaboration diagram for vlink::SysSharemem:

Public Types
enum	Mode : uint8_t { kReadOnly = 0 , kReadWrite = 1 }
	Access mode for the shared memory mapping. More...

Public Member Functions
	SysSharemem ()
	Default constructor. The object is not attached until create() or attach() is called.
	~SysSharemem ()
	Destructor. Calls detach(true) if still attached.
bool	create (const std::string &name, size_t size, Mode mode=kReadWrite)
	Creates a new named shared memory region of the given size and maps it.
bool	attach (const std::string &name, Mode mode=kReadWrite)
	Attaches to an existing named shared memory region.
bool	detach (bool force=true)
	Unmaps the shared memory region and optionally unlinks the OS object.
bool	is_attached () const
	Returns true if the region is currently mapped.
void *	data ()
	Returns a writable pointer to the beginning of the shared memory region.
const void *	data () const
	Returns a read-only pointer to the beginning of the shared memory region.
size_t	size () const
	Returns the size of the mapped region in bytes.

Detailed Description

Named cross-process shared memory backed by the OS IPC layer.

Provides a typed data() pointer into a shared memory region that is accessible by any process that attaches the same name.

Member Enumeration Documentation

Mode

enum vlink::SysSharemem::Mode : uint8_t

Access mode for the shared memory mapping.

Enumerator
kReadOnly	Read-only mapping (PROT_READ).
kReadWrite	Read-write mapping (PROT_READ | PROT_WRITE).

Constructor & Destructor Documentation

SysSharemem()

vlink::SysSharemem::SysSharemem

(

)

Default constructor. The object is not attached until create() or attach() is called.

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~SysSharemem()

vlink::SysSharemem::~SysSharemem

(

)

Destructor. Calls detach(true) if still attached.

Member Function Documentation

attach()

bool vlink::SysSharemem::attach	(	const std::string &	name,
		Mode	mode = kReadWrite )

Attaches to an existing named shared memory region.

The region must have been created by another process (or an earlier call to create()) before attach() can succeed.

Parameters

name	OS name of the shared memory object.
mode	Access mode (default: kReadWrite).

Returns

true on success, false if the region does not exist or access is denied.

create()

bool vlink::SysSharemem::create	(	const std::string &	name,
		size_t	size,
		Mode	mode = kReadWrite )

Creates a new named shared memory region of the given size and maps it.

Fails if a region with the same name already exists. The region is not zero-initialised.

Parameters

name	OS name for the shared memory object (POSIX: must start with '/').
size	Size of the region in bytes.
mode	Access mode (default: kReadWrite).

Returns

true on success, false on failure.

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data() [1/2]

void * vlink::SysSharemem::data ( )

nodiscard

Returns a writable pointer to the beginning of the shared memory region.

Returns

Pointer to the mapped region, or nullptr if not attached or in read-only mode (use the const overload for read-only access).

data() [2/2]

const void * vlink::SysSharemem::data ( ) const

nodiscard

Returns a read-only pointer to the beginning of the shared memory region.

Returns

Const pointer to the mapped region, or nullptr if not attached.

detach()

bool vlink::SysSharemem::detach

(

bool

force = true

)

Unmaps the shared memory region and optionally unlinks the OS object.

After detach(), is_attached() returns false and data() returns nullptr.

Parameters

force

If true, POSIX backends unlink the backing OS object. Set false to merely unmap without destroying the object (other processes keep access). On Windows this only closes the local mapping handle. Default: true.

Returns

true on success, false if not attached or unmap failed.

is_attached()

bool vlink::SysSharemem::is_attached ( ) const

nodiscard

Returns true if the region is currently mapped.

Returns

true if attached (mapped), false otherwise.

size()

size_t vlink::SysSharemem::size ( ) const

nodiscard

Returns the size of the mapped region in bytes.

Returns

Region size in bytes, or 0 if not attached.

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

• include/vlink/base/sys_sharemem.h