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<h1>db_env_set_func_map</h1>
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<h3><pre>
#include <db.h>
<p>
int
db_env_set_func_map(int (*func_map)(char *path,
size_t len, int is_region, int is_rdonly, void **addr));
</pre></h3>
<h1>Description</h1>
<p>The Berkeley DB library requires the ability to map a file into memory and to
create shared memory regions (which may or may not be backed by files).
The <b>func_map</b> argument must conform to the following interface:
<p><blockquote><pre>int map(char *path, size_t len,
int is_region, int is_rdonly, void **addr);</pre></blockquote>
<p>The <b>path</b> argument is the name of a file.
<p>The <b>is_region</b> argument will be zero if the intention is to map
a file into shared memory. In this case, the <b>map</b> function must
map the first <b>len</b> bytes of the file into memory and return a
pointer to the mapped location into the memory location to which the
argument <b>addr</b> refers. The <b>is_rdonly</b> argument will be
non-zero if the file is considered read-only by the caller.
<p>The <b>is_region</b> argument will be non-zero if the memory is
intended to be used as a shared memory region for synchronization
between Berkeley DB threads/processes. In this case, the returned memory may
be of any kind (for example, anonymous memory), but must be able to
support semaphores. In this case, the <b>path</b> argument may be
ignored (although future <b>map</b> calls using the same <b>path</b>
must return the same memory), and the <b>is_rdonly</b> argument will
always be zero.
<p>The <b>func_map</b> interface must return the value of <b>errno</b> on
failure and 0 on success.
<p>The db_env_set_func_map method configures all operations performed by a process and
all of its threads of control, not operations confined to a single
database environment.
<p>Although the db_env_set_func_map interface may be called at any time during the
life of the application, it should normally be called before making
calls to the <a href="../api_c/env_create.html">db_env_create</a> or <a href="../api_c/db_create.html">db_create</a> methods.
<p>The db_env_set_func_map method returns a non-zero error value on failure and 0 on success.
<h1>Errors</h1>
<p>The db_env_set_func_map method may fail and return a non-zero error for the following conditions:
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
</dl>
<p>The db_env_set_func_map method 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 db_env_set_func_map method may fail and
return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>,
in which case all subsequent Berkeley DB calls will fail in the same way.
<h1>See Also</h1>
<a href="../ref/program/runtime.html">Run-time configuration</a>
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