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db_env_set_func_region_map
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#include &lt;db.h&gt;

int
db_env_set_func_region_map(int (*func_region_map)(DB_ENV *dbenv, char *path, size_t len, int *is_create, void **addr),
 int (*func_region_unmap)(DB_ENV *dbenv, void *addr));
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Description: db_env_set_func_region_map
The Berkeley DB library optionally uses the ability to create shared memory
regions (which may or may not be backed by physical files). The memory
will be used as a shared memory region for synchronization between Berkeley DB
threads/processes; while the returned memory may be of any kind (for
example, anonymous memory), it must be able to support semaphores.
The db_env_set_func_region_map method 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_region_map method may be called at any time during the life of
the application, it should normally be called before making calls to the
<a href="../../db4-devel-4.7.25/api_c/env_class.html">db_env_create</a> or <a href="../../db4-devel-4.7.25/api_c/db_class.html">db_create</a> methods.
The db_env_set_func_region_map method
returns a non-zero error value on failure
and 0 on success.

Parameters 
 func_region_map<ul compact><li>The func_region_map parameter is the function which creates
shared memory regions. The function takes 5 parameters:
 
dbenv<ul compact><li>The dbenv parameter is the enclosing database environment
handle. This handle is provided to uniquely identify a shared memory
region: the dbenv parameter and the path are a unique identifier
pair for mapping any new region, and the dbenv parameter and the
address are a unique identifier pair for unmapping any region.</ul>
path<ul compact><li>The path parameter is the name of the region. Repeated requests
for the shared regions of the same name, in the same database
environment, should return a reference to the same memory.</ul>
len<ul compact><li>The len parameter is the length, in bytes, needed for the
region.</ul>
is_create<ul compact><li>The memory referenced by the is_create parameter will be
non-zero if flags to Berkeley DB allowed creation of the mapped region; the
memory referenced by the is_create parameter must be set to
non-zero if the region is created by the func_region_map function, and
set to zero if the region is not created by the function. This returned
information will determine if the region is subsequently initialized by
Berkeley DB.</ul>
addr<ul compact><li>The addr parameter is the memory location into which a pointer
to the region or mapped file is returned.</ul>
 
The func_region_map function must return the value of errno on
failure and 0 on success.</ul>
 func_region_unmap<ul compact><li>The func_region_unmap parameter is the function which unmaps a
shared memory region. The function takes 2 parameters:
 
dbenv<ul compact><li>The dbenv parameter is the enclosing database environment handle.</ul>
addr<ul compact><li>The addr parameter is the value returned by the
func_region_map function when the region was mapped into
memory.</ul>
 
The func_region_unmap function must return the value of errno on
failure and 0 on success.</ul>
 
 See Also
<a href="../../db4-devel-4.7.25/ref/program/runtime.html">Run-time configuration</a>
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