#include <db.h>
int
db_env_set_func_file_map(int (*func_file_map)(DB_ENV *dbenv, char *path,
size_t len, int is_rdonly, void **addr),
int (*func_file_unmap)(DB_ENV *dbenv, void *addr));
The Berkeley DB library optionally uses the ability to map a file into memory.
The db_env_set_func_file_map() function configures all operations
performed by a process and all of its threads of control, not
operations confined to a single database environment.
Although the db_env_set_func_file_map() function may be called at any time
during the life of the application, it should normally be called
before making calls to the
db_env_create
or
db_create
methods.
The db_env_set_func_file_map()
function returns a non-zero error value on failure and 0 on success.
The func_file_map parameter is the function which maps a file into memory. The function takes 5 parameters:
dbenv
The dbenv parameter is the enclosing database environment handle.
path
The path parameter is the name of file. Repeated requests for the mapping of the same name should return a reference to the same memory.
len
The len parameter is the length, in bytes, of the file.
is_rdonly
The is_rdonly parameter will be non-zero if the mapped file is read-only.
addr
The addr parameter is the memory location into which a pointer to the mapped file is returned.
The func_file_map function must return the value of errno on failure and 0 on success.
The func_file_unmap parameter is the function which unmaps a file from memory. The function takes 2 parameters:
dbenv
The dbenv parameter is the enclosing database environment handle.
addr
The addr parameter is the value returned by the func_file_map function when the file or region was mapped into memory.