1<!--$Id: set_func_region_map.so,v 10.22 2008/01/17 03:26:52 bostic Exp $--> 2<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 3<!--See the file LICENSE for redistribution information.--> 4<html> 5<head> 6<title>Berkeley DB: db_env_set_func_region_map</title> 7<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 8<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 9</head> 10<body bgcolor=white> 11<table width="100%"><tr valign=top> 12<td> 13<b>db_env_set_func_region_map</b> 14</td> 15<td align=right> 16<a href="/api_c/api_core.html"><img src="/images/api.gif" alt="API"></a> 17<a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a></td> 18</tr></table> 19<hr size=1 noshade> 20<tt> 21<b><pre> 22#include <db.h> 23<p> 24int 25db_env_set_func_region_map(int (*func_region_map)(DB_ENV *dbenv, char *path, size_t len, int *is_create, void **addr), 26 int (*func_region_unmap)(DB_ENV *dbenv, void *addr)); 27</pre></b> 28<hr size=1 noshade> 29<b>Description: db_env_set_func_region_map</b> 30<p>The Berkeley DB library optionally uses the ability to create shared memory 31regions (which may or may not be backed by physical files). The memory 32will be used as a shared memory region for synchronization between Berkeley DB 33threads/processes; while the returned memory may be of any kind (for 34example, anonymous memory), it must be able to support semaphores.</p> 35<p>The db_env_set_func_region_map method configures all operations performed by a process and 36all of its threads of control, not operations confined to a single 37database environment.</p> 38<p>Although the db_env_set_func_region_map method may be called at any time during the life of 39the application, it should normally be called before making calls to the 40<a href="/api_c/env_class.html">db_env_create</a> or <a href="/api_c/db_class.html">db_create</a> methods.</p> 41<p>The db_env_set_func_region_map method 42returns a non-zero error value on failure 43and 0 on success. 44</p> 45<b>Parameters</b> <br> 46 <b>func_region_map</b><ul compact><li>The <b>func_region_map</b> parameter is the function which creates 47shared memory regions. The function takes 5 parameters: 48<br> 49<b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment 50handle. This handle is provided to uniquely identify a shared memory 51region: the <b>dbenv</b> parameter and the path are a unique identifier 52pair for mapping any new region, and the <b>dbenv</b> parameter and the 53address are a unique identifier pair for unmapping any region.</ul> 54<b><b>path</b></b><ul compact><li>The <b>path</b> parameter is the name of the region. Repeated requests 55for the shared regions of the same name, in the same database 56environment, should return a reference to the same memory.</ul> 57<b><b>len</b></b><ul compact><li>The <b>len</b> parameter is the length, in bytes, needed for the 58region.</ul> 59<b><b>is_create</b></b><ul compact><li>The memory referenced by the <b>is_create</b> parameter will be 60non-zero if flags to Berkeley DB allowed creation of the mapped region; the 61memory referenced by the <b>is_create</b> parameter must be set to 62non-zero if the region is created by the <b>func_region_map</b> function, and 63set to zero if the region is not created by the function. This returned 64information will determine if the region is subsequently initialized by 65Berkeley DB.</ul> 66<b><b>addr</b></b><ul compact><li>The <b>addr</b> parameter is the memory location into which a pointer 67to the region or mapped file is returned.</ul> 68<br> 69<p>The <b>func_region_map</b> function must return the value of <b>errno</b> on 70failure and 0 on success.</p></ul> 71 <b>func_region_unmap</b><ul compact><li>The <b>func_region_unmap</b> parameter is the function which unmaps a 72shared memory region. The function takes 2 parameters: 73<br> 74<b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment handle.</ul> 75<b><b>addr</b></b><ul compact><li>The <b>addr</b> parameter is the value returned by the 76<b>func_region_map</b> function when the region was mapped into 77memory.</ul> 78<br> 79<p>The <b>func_region_unmap</b> function must return the value of <b>errno</b> on 80failure and 0 on success.</p></ul> 81<br> 82<br><b>See Also</b> 83<a href="/ref/program/runtime.html">Run-time configuration</a> 84</tt> 85<table width="100%"><tr><td><br></td><td align=right> 86<a href="/api_c/api_core.html"><img src="/images/api.gif" alt="API"></a><a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a> 87</td></tr></table> 88<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 89</body> 90</html> 91
