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<h2 class="title" style="clear: both"><a id="db_env_set_func_region_map"></a>db_env_set_func_region_map</h2>
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<pre class="programlisting">#include <db.h>
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)); </pre>
<p>
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.
</p>
<p>
The <code class="function">db_env_set_func_region_map()</code> function configures all operations
performed by a process and all of its threads of control, not
operations confined to a single database environment.
</p>
<p>
Although the <code class="function">db_env_set_func_region_map()</code> function may be called at any
time during the life of the application, it should normally be called
before making calls to the <a class="xref" href="envcreate.html" title="db_env_create">db_env_create</a> or
<a class="xref" href="dbcreate.html" title="db_create">db_create</a> methods.
</p>
<p>
The <code class="function">db_env_set_func_region_map()</code> <span>
function returns a non-zero error value on failure and 0 on success.
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp5587984"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5588176"></a>func_region_map</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>func_region_map</strong></span> parameter is the
function which creates shared memory regions. The function takes 5
parameters:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<span class="bold"><strong>dbenv</strong></span>
</p>
<p>
The <span class="bold"><strong>dbenv</strong></span> parameter is the enclosing
database environment handle. This handle is provided to uniquely
identify a shared memory region: the <span class="bold"><strong>dbenv</strong></span> parameter and the path are a unique
identifier pair for mapping any new region, and the <span class="bold"><strong>dbenv</strong></span> parameter and the address are a unique
identifier pair for unmapping any region.
</p>
</li>
<li>
<p>
<span class="bold"><strong>path</strong></span>
</p>
<p>
The <span class="bold"><strong>path</strong></span> 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.
</p>
</li>
<li>
<p>
<span class="bold"><strong>len</strong></span>
</p>
<p>
The <span class="bold"><strong>len</strong></span> parameter is the length, in
bytes, needed for the region.
</p>
</li>
<li>
<p>
<span class="bold"><strong>is_create</strong></span>
</p>
<p>
The memory referenced by the <span class="bold"><strong>is_create</strong></span> parameter will be non-zero if flags
to Berkeley DB allowed creation of the mapped region; the memory
referenced by the <span class="bold"><strong>is_create</strong></span> parameter
must be set to non-zero if the region is created by the <span class="bold"><strong>func_region_map</strong></span> 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.
</p>
</li>
<li>
<p>
<span class="bold"><strong>addr</strong></span>
</p>
<p>
The <span class="bold"><strong>addr</strong></span> parameter is the memory
location into which a pointer to the region or mapped file is
returned.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5595048"></a>func_region_unmap</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>func_region_unmap</strong></span> parameter is
the function which unmaps a shared memory region. The function takes
2 parameters:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<span class="bold"><strong>dbenv</strong></span>
</p>
<p>
The <span class="bold"><strong>dbenv</strong></span> parameter is the enclosing
database environment handle.
</p>
</li>
<li>
<p>
<span class="bold"><strong>addr</strong></span>
</p>
<p>
The <span class="bold"><strong>addr</strong></span> parameter is the value
returned by the <span class="bold"><strong>func_region_map</strong></span>
function when the region was mapped into memory.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp5593104"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a href="../../programmer_reference/program_runtime.html" class="olink">Run-time configuration</a>
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