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pobj_layout_begin - Man Page

persistent memory transactional object store layout


#include <libpmemobj.h>



libpmemobj(7) defines a set of macros for convenient declaration of a pool’s layout. The layout declaration consists of declarations of a number of used types. The declared types will be assigned consecutive type numbers. Declared types may be used in conjunction with type safety macros (see TOID_DECLARE(3)). Once created, the layout declaration must not be changed unless any new types are added at the end of the existing layout declaration. Modifying any existing declaration may lead to changes in the type numbers of declared types, which in consequence may cause data corruption.

The POBJ_LAYOUT_BEGIN() macro indicates a begin of declaration of layout. The LAYOUT argument is a name of layout. This argument must be passed to all macros related to the declaration of layout.

The POBJ_LAYOUT_TOID() macro declares a typed OID for type passed as TYPE argument inside the declaration of layout. All types declared using this macro are assigned with consecutive type numbers. This macro must be used between the POBJ_LAYOUT_BEGIN() and POBJ_LAYOUT_END() macros, with the same name passed as LAYOUT argument.

The POBJ_LAYOUT_ROOT() macro declares a typed OID for type passed as ROOT_TYPE argument inside the declaration of layout. The typed OID will be assigned with type number for root object POBJ_ROOT_TYPE_NUM.

The POBJ_LAYOUT_END() macro ends the declaration of layout.

The POBJ_LAYOUT_NAME() macro returns the name of layout as a null-terminated string.

The POBJ_LAYOUT_TYPES_NUM() macro returns number of types declared using the POBJ_LAYOUT_TOID() macro within the layout declaration.


This is an example of layout declaration:

POBJ_LAYOUT_ROOT(mylayout, struct root);
POBJ_LAYOUT_TOID(mylayout, struct node);
POBJ_LAYOUT_TOID(mylayout, struct foo);

struct root
    TOID(struct node) node;

struct node
    TOID(struct node) next;
    TOID(struct foo) foo;

The name of layout and the number of declared types can be retrieved using the following code:

const char *layout_name = POBJ_LAYOUT_NAME(mylayout);
int num_of_types = POBJ_LAYOUT_TYPES_NUM(mylayout);

See Also

TOID_DECLARE(3), libpmemobj(7) and <https://pmem.io>

Referenced By

The man pages pobj_layout_end(3), pobj_layout_name(3), pobj_layout_root(3), pobj_layout_toid(3) and pobj_layout_types_num(3) are aliases of pobj_layout_begin(3).

2024-01-25 PMDK - PMDK Programmer's Manual