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123 строки
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123 строки
5.7 KiB
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<HTML>
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<HEAD>
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<TITLE>DbLock</TITLE>
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</HEAD>
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<BODY BGCOLOR=white>
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<H1>DbLock</H1>
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<HR SIZE=1 NOSHADE>
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<PRE>
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<!-- Manpage converted by man2html 3.0.1 -->
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<B>#include</B> <B><db</B>_<B>cxx.h></B>
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<B>int</B>
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<B>DbLock::put(DbLockTab</B> <B>*lt);</B>
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<B>unsigned</B> <B>int</B>
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<B>DbLock::get</B>_<B>lock</B>_<B>id();</B>
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<B>void</B>
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<B>DbLock::set</B>_<B>lock</B>_<B>id(unsigned</B> <B>int);</B>
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<B>DBLock::DbLock(unsigned</B> <B>int);</B>
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<B>DBLock::DbLock();</B>
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<B>DBLock::DbLock(const</B> <B>DbLock</B> <B>&);</B>
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<B>DbLock</B> <B>&DBLock::operator</B> <B>=</B> <B>(const</B> <B>DbLock</B> <B>&);</B>
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</PRE>
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<H2>DESCRIPTION</H2><PRE>
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The DB library is a family of classes that provides a
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modular programming interface to transactions and record-
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oriented file access. The library includes support for
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transactions, locking, logging and file page caching, as
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well as various indexed access methods. Many of the
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classes (e.g., the file page caching class) are useful
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independent of the other DB classes, although some classes
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are explicitly based on other classes (e.g., transactions
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and logging). For a general description of the DB
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package, see <B><A HREF="db_intro.html">db_intro(3)</A></B>.
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This manual page describes the specific details of the
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locking interface. The DbLock class is used in
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conjunction with <B><A HREF="DbLockTab.html">DbLockTab(3)</A></B> to provide general-purpose
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locking. While designed to work with the other Db
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classes, these classes are also useful for more general
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locking purposes. Locks can be shared between processes.
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In most cases, when multiple threads or processes are
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using locking, the deadlock detector, <B><A HREF="db_deadlock.html">db_deadlock(1)</A></B>,
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should be run.
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DbLock::put
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The DbLock::put method is a simple interface to the
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DbLockTab::vec functionality, and is equivalent to calling
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the DbLockTab::vec method with a single element list
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array, for which the op field is DB_LOCK_PUT and the lock
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field is represented by the DbLock object. The
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DbLock::put method returns success and failure as
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described for the DbLockTab::vec method.
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DbLock::get_lock_id
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The DbLock::get_lock_id method gets the underlying
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representation of the lock id. Direct manipulation of the
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underlying representation is not recommended.
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DbLock::set_lock_id
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The DbLock::set_lock_id method sets the underlying
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representation of the lock id. Direct manipulation of the
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underlying representation is not recommended. Rather,
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DbLockTab::get should be used to initialize locks (see
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<B><A HREF="DbLockTab.html">DbLockTab(3)</A></B>), and the copy constructor and assignment
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operators can be used to assign to other DbLock objects.
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</PRE>
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<H2>ERRORS</H2><PRE>
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Methods marked as returning errno will, by default, throw
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an exception that encapsulates the error information. The
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default error behavior can be changed, see <B><A HREF="DbException.html">DbException(3)</A></B>.
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The DbLock::put method may fail and throw a <B><A HREF="DbException.html">DbException(3)</A></B>
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or return errno for any of the errors specified for the
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following DB and library functions: <B><A HREF="DbLock.html">DbLock::detect(3)</A></B>,
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<B>fcntl(2)</B>, <B>fflush(3)</B>, <B>lseek(2)</B>, <B>memcpy(3)</B>, <B>memset(3)</B>,
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<B>mmap(2)</B>, <B>munmap(2)</B>, <B>strerror(3)</B>, and <B>write(2)</B>.
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In addition, the DbLock::put method may fail and throw a
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<B><A HREF="DbException.html">DbException(3)</A></B> or return errno for the following
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conditions:
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[EACCES]
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An attempt was made to release lock held by another
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locker.
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[EINVAL]
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An invalid flag value or parameter was specified.
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</PRE>
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<H2>BUGS</H2><PRE>
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If a process dies while holding locks, those locks remain
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held and are <B>never</B> released. In this case, all processes
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should exit as quickly as possible, so that db_recover can
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be run.
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</PRE>
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<H2>SEE ALSO</H2><PRE>
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<B><A HREF="db_archive.html">db_archive(1)</A></B>, <B><A HREF="db_checkpoint.html">db_checkpoint(1)</A></B>, <B><A HREF="db_deadlock.html">db_deadlock(1)</A></B>, <B><A HREF="db_dump.html">db_dump(1)</A></B>,
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<B><A HREF="db_load.html">db_load(1)</A></B>, <B><A HREF="db_recover.html">db_recover(1)</A></B>, <B><A HREF="db_stat.html">db_stat(1)</A></B>, <B><A HREF="db_intro.html">db_intro(3)</A></B>,
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<B><A HREF="db_internal.html">db_internal(3)</A></B>, <B><A HREF="db_thread.html">db_thread(3)</A></B>, <B><A HREF="Db.html">Db(3)</A></B>, <B><A HREF="Dbc.html">Dbc(3)</A></B>, <B><A HREF="DbEnv.html">DbEnv(3)</A></B>,
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<B><A HREF="DbException.html">DbException(3)</A></B>, <B><A HREF="DbInfo.html">DbInfo(3)</A></B>, <B><A HREF="DbLock.html">DbLock(3)</A></B>, <B><A HREF="DbLockTab.html">DbLockTab(3)</A></B>, <B><A HREF="DbLog.html">DbLog(3)</A></B>,
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<B><A HREF="DbLsn.html">DbLsn(3)</A></B>, <B><A HREF="DbMpool.html">DbMpool(3)</A></B>, <B><A HREF="DbMpoolFile.html">DbMpoolFile(3)</A></B>, <B><A HREF="Dbt.html">Dbt(3)</A></B>, <B><A HREF="DbTxn.html">DbTxn(3)</A></B>,
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<B><A HREF="DbTxnMgr.html">DbTxnMgr(3)</A></B>
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</PRE>
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