<!--$Id: set_func_region_map.so,v 10.22 2008/01/17 03:26:52 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: db_env_set_func_region_map</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <table width="100%"><tr valign=top> <td> <b>db_env_set_func_region_map</b> </td> <td align=right> <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></td> </tr></table> <hr size=1 noshade> <tt> <b><pre> #include <db.h> <p> 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></b> <hr size=1 noshade> <b>Description: db_env_set_func_region_map</b> <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 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.</p> <p>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="../api_c/env_class.html">db_env_create</a> or <a href="../api_c/db_class.html">db_create</a> methods.</p> <p>The db_env_set_func_region_map method returns a non-zero error value on failure and 0 on success. </p> <b>Parameters</b> <br> <b>func_region_map</b><ul compact><li>The <b>func_region_map</b> parameter is the function which creates shared memory regions. The function takes 5 parameters: <br> <b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment handle. This handle is provided to uniquely identify a shared memory region: the <b>dbenv</b> parameter and the path are a unique identifier pair for mapping any new region, and the <b>dbenv</b> parameter and the address are a unique identifier pair for unmapping any region.</ul> <b><b>path</b></b><ul compact><li>The <b>path</b> 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> <b><b>len</b></b><ul compact><li>The <b>len</b> parameter is the length, in bytes, needed for the region.</ul> <b><b>is_create</b></b><ul compact><li>The memory referenced by the <b>is_create</b> parameter will be non-zero if flags to Berkeley DB allowed creation of the mapped region; the memory referenced by the <b>is_create</b> parameter must be set to non-zero if the region is created by the <b>func_region_map</b> 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> <b><b>addr</b></b><ul compact><li>The <b>addr</b> parameter is the memory location into which a pointer to the region or mapped file is returned.</ul> <br> <p>The <b>func_region_map</b> function must return the value of <b>errno</b> on failure and 0 on success.</p></ul> <b>func_region_unmap</b><ul compact><li>The <b>func_region_unmap</b> parameter is the function which unmaps a shared memory region. The function takes 2 parameters: <br> <b><b>dbenv</b></b><ul compact><li>The <b>dbenv</b> parameter is the enclosing database environment handle.</ul> <b><b>addr</b></b><ul compact><li>The <b>addr</b> parameter is the value returned by the <b>func_region_map</b> function when the region was mapped into memory.</ul> <br> <p>The <b>func_region_unmap</b> function must return the value of <b>errno</b> on failure and 0 on success.</p></ul> <br> <br><b>See Also</b> <a href="../ref/program/runtime.html">Run-time configuration</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <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> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>