m4_comment([$Id: memp_set_fileid.so,v 10.14 2005/04/14 13:08:06 sue Exp $])

define(M4PAGELOCAL, [memp_set_fileid, memp_get_fileid])
include(m4/m4.seealso)

m4_pf_header(m4_ref(memp_set_fileid),
ifelse(M4API, C_API, [dnl
int
DB_MPOOLFILE-__GT__set_fileid(DB_MPOOLFILE *mpf, u_int8_t *fileid);
m4_blank
int
DB_MPOOLFILE-__GT__get_fileid(DB_MPOOLFILE *mpf, u_int8_t *fileid);
])
ifelse(M4API, CXX_API, [dnl
int
DbMpoolFile::set(u_int8_t *fileid);
m4_blank
int DbMpoolFile::get_fileid(u_int8_t *fileid);
]))

m4_p([dnl
The m4_refT(memp_set_fileid) specifies a unique identifier for the file.
(The shared memory buffer pool functions must be able to uniquely
identify files in order that multiple processes wanting to share a file
will correctly identify it in the pool.)])

m4_p([dnl
On most UNIX/POSIX systems, the m4_arg(fileid) field will not need to
be set, and the memory pool functions will use the file's device and
inode numbers for this purpose.  On Windows systems, the memory pool
functions use the values returned by GetFileInformationByHandle() by
default -- these values are known to be constant between processes and
over reboot in the case of NTFS (in which they are the NTFS MFT
indices).])

m4_p([dnl
On other filesystems (for example, FAT or NFS), these default values
are not necessarily unique between processes or across system reboots.
m4_bold([Applications wanting to maintain a shared memory buffer pool
between processes or across system reboots, in which the pool contains
pages from files stored on such filesystems, must specify a unique file
identifier using the m4_refT(memp_set_fileid), and each process opening
the file must provide the same unique identifier.])])

m4_p([dnl
This call should not be necessary for most applications.  Specifically,
it is not necessary if the memory pool is not shared between processes
and is reinstantiated after each system reboot, if the application is
using the m4_db access methods instead of calling the pool functions
explicitly, or if the files in the memory pool are stored on filesystems
in which the default values as described previously are invariant
between process and across system reboots.])

m4_scope_mpf(memp_set_fileid)

m4_when_mpfopen(memp_set_fileid)

m4_return(memp_set_fileid, std)

m4_parambegin
m4_param(fileid, [dnl
The m4_arg(fileid) parameter is the unique identifier for the file.
Unique file identifiers must be a DB_FILE_ID_LEN length array of bytes.])
m4_paramend

m4_pf_description(m4_ref(memp_get_fileid))
m4_p([dnl
The m4_refT(memp_get_fileid) copies the file's identifier into the
memory location referenced by m4_arg(fileid).])

m4_return(memp_get_fileid, std)

m4_when_any(memp_get_fileid)

m4_seealso(DbMpool)
m4_page_footer