#include <db.h>

int
memp_fget(DB_MPOOLFILE *mpf,
    db_pgno_t *pgnoaddr, u_int32_t flags, void **pagep);

Description

The memp_fget function copies a pointer to the page with the page number specified by pgnoaddr, from the source file in the DB_MPOOLFILE, into the memory location referenced by pagep. If the page does not exist or cannot be retrieved, memp_fget will fail.

Page numbers begin at 0, i.e., the first page in the file is page number 0, not page number 1.

The returned page is size_t type aligned.

The flags value must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values.

DB_MPOOL_CREATE

If the specified page does not exist, create it. In this case, the pgin function, if specified, is called.

DB_MPOOL_LAST

Return the last page of the source file and copy its page number to the location referenced by pgnoaddr.

DB_MPOOL_NEW

Create a new page in the file and copy its page number to the location referenced by pgnoaddr. In this case, the pgin function, if specified, is not called.

The DB_MPOOL_CREATE, DB_MPOOL_LAST and DB_MPOOL_NEW flags are mutually exclusive.

Created pages have all their bytes set to 0, unless otherwise specified when the file was opened.

All pages returned by memp_fget will be retained (i.e. pinned), in the pool until a subsequent call to memp_fput.

The memp_fget function returns a non-zero error value on failure and 0 on success.

Errors

The memp_fget function may fail and return a non-zero error for the following conditions:

EAGAIN

The page reference count has overflowed. (This should never happen unless there's a bug in the application.)

EINVAL

An invalid flag value or parameter was specified.

The DB_MPOOL_NEW flag was set and the source file was not opened for writing.

More than one of DB_MPOOL_CREATE, DB_MPOOL_LAST and DB_MPOOL_NEW was set.

EIO

The requested page does not exist and DB_MPOOL_CREATE was not set.

ENOMEM

The cache is full and no more pages will fit in the pool.

The memp_fget function may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions. If a catastrophic error has occurred, the memp_fget function may fail and return DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.

See Also