NAME

       POBJ_LAYOUT_BEGIN(),     POBJ_LAYOUT_TOID(),    POBJ_LAYOUT_ROOT(),    POBJ_LAYOUT_NAME(),
       POBJ_LAYOUT_END(), POBJ_LAYOUT_TYPES_NUM() - persistent memory transactional object  store
       layout

SYNOPSIS

              #include <libpmemobj.h>

              POBJ_LAYOUT_BEGIN(layout)
              POBJ_LAYOUT_TOID(layout, TYPE)
              POBJ_LAYOUT_ROOT(layout, ROOT_TYPE)
              POBJ_LAYOUT_NAME(layout)
              POBJ_LAYOUT_END(layout)
              POBJ_LAYOUT_TYPES_NUM(layout)

DESCRIPTION

       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.

EXAMPLE

       This is an example of layout declaration:

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

              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>