1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <title>Db::set_alloc()</title> 7 <link rel="stylesheet" href="apiReference.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" /> 10 <link rel="up" href="db.html" title="Chapter 2. The Db Handle" /> 11 <link rel="prev" href="dbrename.html" title="Db::rename()" /> 12 <link rel="next" href="dbset_append_recno.html" title="Db::set_append_recno()" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Db::set_alloc()</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="dbrename.html">Prev</a> </td> 22 <th width="60%" align="center">Chapter 2. 23 The Db Handle 24 </th> 25 <td width="20%" align="right"> <a accesskey="n" href="dbset_append_recno.html">Next</a></td> 26 </tr> 27 </table> 28 <hr /> 29 </div> 30 <div class="sect1" lang="en" xml:lang="en"> 31 <div class="titlepage"> 32 <div> 33 <div> 34 <h2 class="title" style="clear: both"><a id="dbset_alloc"></a>Db::set_alloc()</h2> 35 </div> 36 </div> 37 </div> 38 <pre class="programlisting">#include <db_cxx.h> 39 40int 41Db::set_alloc(db_malloc_fcn_type app_malloc, 42 db_realloc_fcn_type app_realloc, 43 db_free_fcn_type app_free);</pre> 44 <p> 45 Set the allocation functions used by the 46 <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> and 47 <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> methods to allocate or free 48 memory owned by the application. 49 </p> 50 <p> 51 There are a number of interfaces in Berkeley DB where memory is 52 allocated by the library and then given to the application. For 53 example, the <a class="link" href="dbt.html#dbt_DB_DBT_MALLOC">DB_DBT_MALLOC</a> 54 flag, when specified in the <a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> 55 object, will cause the <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> methods to allocate and 56 reallocate memory which then becomes the responsibility of the calling 57 application. (See <a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> 58 for more information.) Other examples are the Berkeley DB interfaces 59 which return statistical information to the application: 60 <a class="xref" href="dbstat.html" title="Db::stat()">Db::stat()</a>, 61 <a class="xref" href="lockstat.html" title="DbEnv::lock_stat()">DbEnv::lock_stat()</a>, 62 <a class="xref" href="logarchive.html" title="DbEnv::log_archive()">DbEnv::log_archive()</a>, 63 <a class="xref" href="logstat.html" title="DbEnv::log_stat()">DbEnv::log_stat()</a>, 64 <a class="xref" href="mempstat.html" title="DbEnv::memp_stat()">DbEnv::memp_stat()</a>, 65 and <a class="xref" href="txnstat.html" title="DbEnv::txn_stat()">DbEnv::txn_stat()</a>. There is 66 one method in Berkeley DB where memory is allocated by the application 67 and then given to the library: <a class="xref" href="dbassociate.html" title="Db::associate()">Db::associate()</a>. 68 </p> 69 <p> 70 On systems in which there may be multiple library versions of the 71 standard allocation routines (notably Windows NT), transferring memory 72 between the library and the application will fail because the Berkeley 73 DB library allocates memory from a different heap than the application 74 uses to free it. To avoid this problem, the 75 <a class="xref" href="envset_alloc.html" title="DbEnv::set_alloc()">DbEnv::set_alloc()</a> and 76 <code class="methodname">Db::set_alloc()</code> methods can be used to pass Berkeley DB references to 77 the application's allocation routines. 78 </p> 79 <p> 80 It is not an error to specify only one or two of the possible 81 allocation function parameters to these interfaces; however, in that 82 case the specified interfaces must be compatible with the standard 83 library interfaces, as they will be used together. The functions 84 specified must match the calling conventions of the ANSI C X3.159-1989 85 (ANSI C) library routines of the same name. 86 </p> 87 <p> 88 Because databases opened within Berkeley DB environments use the 89 allocation interfaces specified to the environment, it is an error to 90 attempt to set those interfaces in a database created within an 91 environment. 92 </p> 93 <p> 94 The <code class="methodname">Db::set_alloc()</code> method may not be called after the 95 <a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a> method is called. 96 </p> 97 <p> 98 The <code class="methodname">Db::set_alloc()</code> <span> 99 100 <span> 101 method either returns a non-zero error value or throws an 102 exception that encapsulates a non-zero error value on 103 failure, and returns 0 on success. 104 </span> 105 </span> 106 </p> 107 <div class="sect2" lang="en" xml:lang="en"> 108 <div class="titlepage"> 109 <div> 110 <div> 111 <h3 class="title"><a id="id1642846"></a>Errors</h3> 112 </div> 113 </div> 114 </div> 115 <p> 116 The <code class="methodname">Db::set_alloc()</code> <span> 117 118 <span> 119 method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> 120 exception, encapsulating one of the following non-zero errors, or return one 121 of the following non-zero errors: 122 </span> 123 </span> 124 </p> 125 <div class="sect3" lang="en" xml:lang="en"> 126 <div class="titlepage"> 127 <div> 128 <div> 129 <h4 class="title"><a id="id1642993"></a>EINVAL</h4> 130 </div> 131 </div> 132 </div> 133 <p> 134 If called in a database environment, or called after 135 <a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a> was called; or if an 136 invalid flag value or parameter was specified. 137 </p> 138 </div> 139 </div> 140 <div class="sect2" lang="en" xml:lang="en"> 141 <div class="titlepage"> 142 <div> 143 <div> 144 <h3 class="title"><a id="id1643002"></a>Class</h3> 145 </div> 146 </div> 147 </div> 148 <p> 149 <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> 150 </p> 151 </div> 152 <div class="sect2" lang="en" xml:lang="en"> 153 <div class="titlepage"> 154 <div> 155 <div> 156 <h3 class="title"><a id="id1642935"></a>See Also</h3> 157 </div> 158 </div> 159 </div> 160 <p> 161 <a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a> 162 </p> 163 </div> 164 </div> 165 <div class="navfooter"> 166 <hr /> 167 <table width="100%" summary="Navigation footer"> 168 <tr> 169 <td width="40%" align="left"><a accesskey="p" href="dbrename.html">Prev</a> </td> 170 <td width="20%" align="center"> 171 <a accesskey="u" href="db.html">Up</a> 172 </td> 173 <td width="40%" align="right"> <a accesskey="n" href="dbset_append_recno.html">Next</a></td> 174 </tr> 175 <tr> 176 <td width="40%" align="left" valign="top">Db::rename() </td> 177 <td width="20%" align="center"> 178 <a accesskey="h" href="index.html">Home</a> 179 </td> 180 <td width="40%" align="right" valign="top"> Db::set_append_recno()</td> 181 </tr> 182 </table> 183 </div> 184 </body> 185</html> 186