88 lines
4.5 KiB
HTML
88 lines
4.5 KiB
HTML
<!--$Id: db_set_alloc.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
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<!--$Id: db_set_alloc.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
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<!--Copyright (c) 1997,2008 Oracle. All rights reserved.-->
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<!--See the file LICENSE for redistribution information.-->
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<html>
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<head>
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<title>Berkeley DB: DB->set_alloc</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++">
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</head>
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<body bgcolor=white>
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<table width="100%"><tr valign=top>
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<td>
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<b>DB->set_alloc</b>
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</td>
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<td align=right>
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<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a>
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<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td>
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</tr></table>
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<hr size=1 noshade>
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<tt>
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<b><pre>
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#include <db.h>
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<p>
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int
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DB->set_alloc(DB *db,
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void *(*app_malloc)(size_t),
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void *(*app_realloc)(void *, size_t),
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void (*app_free)(void *));
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</pre></b>
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<hr size=1 noshade>
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<b>Description: DB->set_alloc</b>
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<p>Set the allocation functions used by the <a href="../api_c/env_class.html">DB_ENV</a> and <a href="../api_c/db_class.html">DB</a>
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methods to allocate or free memory owned by the application.</p>
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<p>There are a number of interfaces in Berkeley DB where memory is allocated by
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the library and then given to the application. For example, the
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<a href="../api_c/dbt_class.html#DB_DBT_MALLOC">DB_DBT_MALLOC</a> flag, when specified in the <a href="../api_c/dbt_class.html">DBT</a> object,
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will cause the <a href="../api_c/db_class.html">DB</a> methods to allocate and reallocate memory
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which then becomes the responsibility of the calling application. (See
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<a href="../api_c/dbt_class.html">DBT</a> for more information.) Other examples are the Berkeley DB
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interfaces which return statistical information to the application:
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<a href="../api_c/db_stat.html">DB->stat</a>, <a href="../api_c/lock_stat.html">DB_ENV->lock_stat</a>, <a href="../api_c/log_archive.html">DB_ENV->log_archive</a>,
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<a href="../api_c/log_stat.html">DB_ENV->log_stat</a>, <a href="../api_c/memp_stat.html">DB_ENV->memp_stat</a>, and <a href="../api_c/txn_stat.html">DB_ENV->txn_stat</a>. There is one
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method in Berkeley DB where memory is allocated by the application and then
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given to the library: <a href="../api_c/db_associate.html">DB->associate</a>.</p>
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<p>On systems in which there may be multiple library versions of the
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standard allocation routines (notably Windows NT), transferring memory
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between the library and the application will fail because the Berkeley DB
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library allocates memory from a different heap than the application uses
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to free it. To avoid this problem, the <a href="../api_c/env_set_alloc.html">DB_ENV->set_alloc</a> and
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DB->set_alloc methods can be used to pass Berkeley DB references to the
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application's allocation routines.</p>
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<p>It is not an error to specify only one or two of the possible allocation
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function parameters to these interfaces; however, in that case the
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specified interfaces must be compatible with the standard library
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interfaces, as they will be used together. The functions specified must
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match the calling conventions of the ANSI C X3.159-1989 (ANSI C) library routines of
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the same name.</p>
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<p>Because databases opened within Berkeley DB environments use the allocation
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interfaces specified to the environment, it is an error to attempt to
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set those interfaces in a database created within an environment.</p>
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<p>The DB->set_alloc method may not be called after the <a href="../api_c/db_open.html">DB->open</a> method is called.
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</p>
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<p>The DB->set_alloc method
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returns a non-zero error value on failure
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and 0 on success.
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</p>
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<br><b>Errors</b>
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<p>The DB->set_alloc method
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may fail and return one of the following non-zero errors:</p>
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<br>
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<b>EINVAL</b><ul compact><li>If called in a database environment, or called after <a href="../api_c/db_open.html">DB->open</a> was
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called; or if an
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invalid flag value or parameter was specified.</ul>
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<br>
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<hr size=1 noshade>
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<br><b>Class</b>
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<a href="../api_c/db_class.html">DB</a>
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<br><b>See Also</b>
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<a href="../api_c/db_list.html">Databases and Related Methods</a>
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</tt>
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<table width="100%"><tr><td><br></td><td align=right>
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<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>
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</td></tr></table>
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<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font>
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</body>
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</html>
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