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13<b>db_env_set_func_file_map</b>
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21<b><pre>
22#include &lt;db.h&gt;
23<p>
24int
25db_env_set_func_file_map(int (*func_file_map)(DB_ENV *dbenv, char *path, size_t len, int is_rdonly, void **addr),
26    int (*func_file_unmap)(DB_ENV *dbenv, void *addr));
27</pre></b>
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29<b>Description: db_env_set_func_file_map</b>
30<p>The Berkeley DB library optionally uses the ability to map a file into memory.</p>
31<p>The db_env_set_func_file_map method configures all operations performed by a process and
32all of its threads of control, not operations confined to a single
33database environment.</p>
34<p>Although the db_env_set_func_file_map method may be called at any time during the life of
35the application, it should normally be called before making calls to the
36<a href="../api_c/env_class.html">db_env_create</a> or <a href="../api_c/db_class.html">db_create</a> methods.</p>
37<p>The db_env_set_func_file_map method
38returns a non-zero error value on failure
39and 0 on success.
40</p>
41<b>Parameters</b> <br>
42 <b>func_file_map</b><ul compact><li>The <b>func_file_map</b> parameter is the function which maps a file
43into memory.  The function takes 5 parameters:
44<br>
45<b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment handle.</ul>
46<b><b>path</b></b><ul compact><li>The <b>path</b> parameter is the name of file.  Repeated requests for
47the mapping of the same name should return a reference to the same
48memory.</ul>
49<b><b>len</b></b><ul compact><li>The <b>len</b> parameter is the length, in bytes, of the file.</ul>
50<b><b>is_rdonly</b></b><ul compact><li>The <b>is_rdonly</b> parameter will be non-zero if the mapped file is
51read-only.</ul>
52<b><b>addr</b></b><ul compact><li>The <b>addr</b> parameter is the memory location into which a pointer
53to the mapped file is returned.</ul>
54<br>
55<p>The <b>func_file_map</b> function must return the value of <b>errno</b> on
56failure and 0 on success.</p></ul>
57 <b>func_file_unmap</b><ul compact><li>The <b>func_file_unmap</b> parameter is the function which unmaps a
58file from memory.  The function takes 2 parameters:
59<br>
60<b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment handle.</ul>
61<b><b>addr</b></b><ul compact><li>The <b>addr</b> parameter is the value returned by the
62<b>func_file_map</b> function when the file or region was mapped into
63memory.</ul>
64<br>
65<p>The <b>func_file_unmap</b> function must return the value of <b>errno</b> on
66failure and 0 on success.</p></ul>
67<br>
68<br><b>See Also</b>
69<a href="../ref/program/runtime.html">Run-time configuration</a>
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