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<title>Berkeley DB: DbLogc::get</title>
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<h1>DbLogc::get</h1>
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<h3><pre>
#include <db_cxx.h>
<p>
int
DbLogc::get(DbLsn *lsn, Dbt *data, u_int32_t flags);
</pre></h3>
<h1>Description</h1>
<p>The DbLogc::get method retrieve records from the log according to the
<b>lsn</b> and <b>flags</b> arguments.
<p>The data field of the <b>data</b> structure is set to the record
retrieved, and the size field indicates the number of bytes in the
record. See <a href="../api_cxx/dbt_class.html">Dbt</a> for a description of other fields in the
<b>data</b> structure. The <a href="../api_cxx/dbt_class.html#DB_DBT_MALLOC">DB_DBT_MALLOC</a>,
<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
for any <a href="../api_cxx/dbt_class.html">Dbt</a> used for data retrieval.
<p>The <b>flags</b> value must be set to one of the following values:
<p><dl compact>
<p><dt><a name="DB_FIRST">DB_FIRST</a><dd>The first record from any of the log files found in the log directory
is returned in the <b>data</b> argument.
The <b>lsn</b> argument is overwritten with the <a href="../api_cxx/lsn_class.html">DbLsn</a> of the
record returned.
<p>
If the log is empty, the DbLogc::get method will return DB_NOTFOUND.
<p><dt><a name="DB_LAST">DB_LAST</a><dd>The last record in the log is returned in the <b>data</b> argument.
The <b>lsn</b> argument is overwritten with the <a href="../api_cxx/lsn_class.html">DbLsn</a> of the
record returned.
<p>
If the log is empty, the DbLogc::get method will return DB_NOTFOUND.
<p><dt><a name="DB_NEXT">DB_NEXT</a>, <a name="DB_PREV">DB_PREV</a><dd>The current log position is advanced to the next (previous) record in
the log, and that record is returned in the <b>data</b> argument. The
<b>lsn</b> argument is overwritten with the <a href="../api_cxx/lsn_class.html">DbLsn</a> of the record
returned.
<p>If the cursor has not been initialized via DB_FIRST, DB_LAST, DB_SET,
DB_NEXT, or DB_PREV, DbLogc::get will return the first (last) record
in the log.
If the last (first) log record has already been returned or the log is
empty, the DbLogc::get method will return DB_NOTFOUND.
If the log was opened with the DB_THREAD flag set, calls to
DbLogc::get with the DB_NEXT (DB_PREV) flag set, the DbLogc::get method either returns EINVAL or throws an exception that encapsulates EINVAL.
<p><dt><a name="DB_CURRENT">DB_CURRENT</a><dd>Return the log record to which the log currently refers.
If the log cursor has not been initialized via DB_FIRST, DB_LAST,
DB_SET, DB_NEXT, or DB_PREV, or if the log was opened with the DB_THREAD
flag set, the DbLogc::get method either returns EINVAL or throws an exception that encapsulates EINVAL.
<p><dt><a name="DB_SET">DB_SET</a><dd>Retrieve the record specified by the <b>lsn</b> argument.
If the specified <a href="../api_cxx/lsn_class.html">DbLsn</a> is invalid (for example, it does not
appear in the log), the DbLogc::get method either returns EINVAL or throws an exception that encapsulates EINVAL.
</dl>
<p>
Otherwise, the DbLogc::get method either returns a non-zero error value or throws an exception that
encapsulates a non-zero error value on failure, and returns 0 on success.
<h1>Errors</h1>
<p>The DbLogc::get method may fail and throw an exception or return a non-zero error for the following conditions:
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
<p>The DB_CURRENT flag was set and the log pointer had not yet been
initialized.
<p>The DB_SET flag was set and the specified log sequence number does not
exist.
</dl>
<p>The DbLogc::get method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.
If a catastrophic error has occurred, the DbLogc::get method may fail and
either return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a> or throw a
<a href="../api_cxx/runrec_class.html">DbRunRecoveryException</a>,
in which case all subsequent Berkeley DB calls will fail in the same way.
<h1>Class</h1>
<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>
<h1>See Also</h1>
<a href="../api_cxx/log_list.html">Logging Subsystem and Related Methods</a>
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