1<!--$Id: logc_get.so,v 10.48 2004/08/13 03:38:57 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: DbLogc::get</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>DbLogc::get</b> 14</td> 15<td align=right> 16<a href="../api_cxx/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_cxx.h> 23<p> 24int 25DbLogc::get(DbLsn *lsn, Dbt *data, u_int32_t flags); 26</pre></b> 27<hr size=1 noshade> 28<b>Description: DbLogc::get</b> 29<p>The DbLogc::get method returns records from the log.</p> 30<p>Unless otherwise specified, the DbLogc::get method 31either returns a non-zero error value 32or throws an exception that encapsulates a non-zero error value on 33failure, and returns 0 on success. 34</p> 35<b>Parameters</b> <br> 36 <b>data</b><ul compact><li>The data field of the <b>data</b> structure is set to the record 37retrieved, and the size field indicates the number of bytes in the 38record. See <a href="../api_cxx/dbt_class.html">Dbt</a> for a description of other fields in the 39<b>data</b> structure. The <a href="../api_cxx/dbt_class.html#DB_DBT_MALLOC">DB_DBT_MALLOC</a>, 40<a href="../api_cxx/dbt_class.html#DB_DBT_REALLOC">DB_DBT_REALLOC</a> and <a href="../api_cxx/dbt_class.html#DB_DBT_USERMEM">DB_DBT_USERMEM</a> flags may be specified 41for any <a href="../api_cxx/dbt_class.html">Dbt</a> used for data retrieval.</ul> 42 <b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to one of the following values: 43<br> 44<b><a name="DB_CURRENT">DB_CURRENT</a></b><ul compact><li>Return the log record to which the log currently refers.</ul> 45<b><a name="DB_FIRST">DB_FIRST</a></b><ul compact><li>The first record from any of the log files found in the log directory 46is returned in the <b>data</b> parameter. 47The <b>lsn</b> parameter is overwritten with the <a href="../api_cxx/lsn_class.html">DbLsn</a> of the 48record returned. 49<p>The DbLogc::get method will return <a href="../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a> if DB_FIRST is set and the log is empty. 50</p></ul> 51<b><a name="DB_LAST">DB_LAST</a></b><ul compact><li>The last record in the log is returned in the <b>data</b> parameter. 52The <b>lsn</b> parameter is overwritten with the <a href="../api_cxx/lsn_class.html">DbLsn</a> of the 53record returned. 54<p>The DbLogc::get method will return <a href="../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a> if DB_LAST is set and the log is empty. 55</p></ul> 56<b><a name="DB_NEXT">DB_NEXT</a></b><ul compact><li>The current log position is advanced to the next record in the log, and 57that record is returned in the <b>data</b> parameter. The <b>lsn</b> 58parameter is overwritten with the <a href="../api_cxx/lsn_class.html">DbLsn</a> of the record returned. 59<p>If the cursor has not been initialized via DB_FIRST, DB_LAST, DB_SET, 60DB_NEXT, or DB_PREV, DbLogc::get will return the first record in 61the log.</p> 62<p>The DbLogc::get method will return <a href="../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a> if DB_NEXT is set and the last log record has already been 63returned or the log is empty. 64</p></ul> 65<b><a name="DB_PREV">DB_PREV</a></b><ul compact><li>The current log position is advanced to the previous record in the log, 66and that record is returned in the <b>data</b> parameter. The 67<b>lsn</b> parameter is overwritten with the <a href="../api_cxx/lsn_class.html">DbLsn</a> of the record 68returned. 69<p>If the cursor has not been initialized via DB_FIRST, DB_LAST, DB_SET, 70DB_NEXT, or DB_PREV, DbLogc::get will return the last record in the 71log.</p> 72<p>The DbLogc::get method will return <a href="../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a> if DB_PREV is set and the first log record has already been 73returned or the log is empty. 74</p></ul> 75<b><a name="DB_SET">DB_SET</a></b><ul compact><li>Retrieve the record specified by the <b>lsn</b> parameter.</ul> 76<br></ul> 77 <b>lsn</b><ul compact><li>When the <b>flag</b> parameter is set to DB_CURRENT, 78DB_FIRST, DB_LAST, DB_NEXT or DB_PREV, 79the <b>lsn</b> parameter is overwritten with the <a href="../api_cxx/lsn_class.html">DbLsn</a> value 80of the record retrieved. When <b>flag</b> is set to DB_SET, 81the <b>lsn</b> parameter is the <a href="../api_cxx/lsn_class.html">DbLsn</a> value of the record to 82be retrieved.</ul> 83<br> 84<br><b>Errors</b> 85<p>The DbLogc::get method 86may fail and throw 87<a href="../api_cxx/except_class.html">DbException</a>, 88encapsulating one of the following non-zero errors, or return one of 89the following non-zero errors:</p> 90<br> 91<b>EINVAL</b><ul compact><li>If the DB_CURRENT flag was set and the log cursor has not yet 92been initialized; 93the DB_CURRENT, DB_NEXT, or DB_PREV flags were 94set and the log was opened with the DB_THREAD flag set; 95the DB_SET flag was set and the specified log sequence number 96does not appear in the log; or if an 97invalid flag value or parameter was specified.</ul> 98<br> 99<hr size=1 noshade> 100<br><b>Class</b> 101<a href="../api_cxx/env_class.html">DbEnv</a>, <a href="../api_cxx/logc_class.html">DbLogc</a>, <a href="../api_cxx/lsn_class.html">DbLsn</a> 102<br><b>See Also</b> 103<a href="../api_cxx/log_list.html">Logging Subsystem and Related Methods</a> 104</tt> 105<table width="100%"><tr><td><br></td><td align=right> 106<a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> 107</td></tr></table> 108<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 109</body> 110</html> 111
