1<!--$Id: db_set_alloc.so,v 10.3 2002/08/18 21:15:51 bostic Exp $--> 2<!--$Id: env_set_alloc.so,v 1.24 2008/01/19 14:12:57 bostic Exp $--> 3<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 4<!--See the file LICENSE for redistribution information.--> 5<html> 6<head> 7<title>Berkeley DB: DB->set_alloc</title> 8<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 9<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 10</head> 11<body bgcolor=white> 12<table width="100%"><tr valign=top> 13<td> 14<b>DB->set_alloc</b> 15</td> 16<td align=right> 17<a href="/api_c/api_core.html"><img src="/images/api.gif" alt="API"></a> 18<a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a></td> 19</tr></table> 20<hr size=1 noshade> 21<tt> 22<b><pre> 23#include <db.h> 24<p> 25int 26DB->set_alloc(DB *db, 27 void *(*app_malloc)(size_t), 28 void *(*app_realloc)(void *, size_t), 29 void (*app_free)(void *)); 30</pre></b> 31<hr size=1 noshade> 32<b>Description: DB->set_alloc</b> 33<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> 34methods to allocate or free memory owned by the application.</p> 35<p>There are a number of interfaces in Berkeley DB where memory is allocated by 36the library and then given to the application. For example, the 37<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, 38will cause the <a href="/api_c/db_class.html">DB</a> methods to allocate and reallocate memory 39which then becomes the responsibility of the calling application. (See 40<a href="/api_c/dbt_class.html">DBT</a> for more information.) Other examples are the Berkeley DB 41interfaces which return statistical information to the application: 42<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>, 43<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 44method in Berkeley DB where memory is allocated by the application and then 45given to the library: <a href="/api_c/db_associate.html">DB->associate</a>.</p> 46<p>On systems in which there may be multiple library versions of the 47standard allocation routines (notably Windows NT), transferring memory 48between the library and the application will fail because the Berkeley DB 49library allocates memory from a different heap than the application uses 50to free it. To avoid this problem, the <a href="/api_c/env_set_alloc.html">DB_ENV->set_alloc</a> and 51DB->set_alloc methods can be used to pass Berkeley DB references to the 52application's allocation routines.</p> 53<p>It is not an error to specify only one or two of the possible allocation 54function parameters to these interfaces; however, in that case the 55specified interfaces must be compatible with the standard library 56interfaces, as they will be used together. The functions specified must 57match the calling conventions of the ANSI C X3.159-1989 (ANSI C) library routines of 58the same name.</p> 59<p>Because databases opened within Berkeley DB environments use the allocation 60interfaces specified to the environment, it is an error to attempt to 61set those interfaces in a database created within an environment.</p> 62<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. 63</p> 64<p>The DB->set_alloc method 65returns a non-zero error value on failure 66and 0 on success. 67</p> 68<br><b>Errors</b> 69<p>The DB->set_alloc method 70may fail and return one of the following non-zero errors:</p> 71<br> 72<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 73called; or if an 74invalid flag value or parameter was specified.</ul> 75<br> 76<hr size=1 noshade> 77<br><b>Class</b> 78<a href="/api_c/db_class.html">DB</a> 79<br><b>See Also</b> 80<a href="/api_c/db_list.html">Databases and Related Methods</a> 81</tt> 82<table width="100%"><tr><td><br></td><td align=right> 83<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> 84</td></tr></table> 85<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 86</body> 87</html> 88
