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6.3 KiB
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<!--$Id: lock_vec.so,v 10.31 2000/12/04 18:05:39 bostic Exp $-->
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<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.-->
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<!--All rights reserved.-->
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<html>
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<head>
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<title>Berkeley DB: lock_vec</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
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</head>
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<body bgcolor=white>
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<a name="2"><!--meow--></a>
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<table><tr valign=top>
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<td>
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<h1>lock_vec</h1>
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</td>
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<td width="1%">
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<hr size=1 noshade>
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<tt>
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<h3><pre>
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#include <db.h>
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<p>
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int
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lock_vec(DB_ENV *env, u_int32_t locker, u_int32_t flags,
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DB_LOCKREQ list[], int nlist, DB_LOCKREQ **elistp);
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</pre></h3>
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<h1>Description</h1>
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<p>The lock_vec function atomically obtains and releases one or more locks
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from the lock table. The lock_vec function is intended to support
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acquisition or trading of multiple locks under one lock table semaphore,
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as is needed for lock coupling or in multigranularity locking for lock
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escalation.
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<p>The <b>locker</b> argument specified to lock_vec is an unsigned
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32-bit integer quantity. It represents the entity requesting or releasing
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the lock.
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<p>The <b>flags</b> value must be set to 0 or the following value:
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<p><dl compact>
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<p><dt><a name="DB_LOCK_NOWAIT">DB_LOCK_NOWAIT</a><dd>If a lock cannot be immediately granted because the requested lock
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conflicts with an existing lock, return instead of waiting for the lock
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to become available.
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</dl>
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<p>The <b>list</b> array provided to lock_vec is typedef'd as
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DB_LOCKREQ. A DB_LOCKREQ structure has at least the following fields,
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which must be initialized before calling lock_vec:
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<p><dl compact>
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<p><dt>lockop_t <a name="op">op</a>;<dd>The operation to be performed, which must be set to one of the
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following values:
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<p><dl compact>
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<p><dt><a name="DB_LOCK_GET">DB_LOCK_GET</a><dd>Get a lock, as defined by the values of <b>locker</b>, <b>obj</b>,
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and <b>mode</b>. Upon return from lock_vec, if the
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<b>lock</b> field is non-NULL, a reference to the acquired lock is
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stored there. (This reference is invalidated by any call to
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lock_vec or <a href="../api_c/lock_put.html">lock_put</a> that releases the lock.)
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<p><dt><a name="DB_LOCK_PUT">DB_LOCK_PUT</a><dd>The lock referenced by the contents of the <b>lock</b> field is released.
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<p><dt><a name="DB_LOCK_PUT_ALL">DB_LOCK_PUT_ALL</a><dd>All locks held by the <b>locker</b> are released. (Any locks acquired
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as a part of the current call to lock_vec that appear after the
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DB_LOCK_PUT_ALL entry are not considered for this
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operation).
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<p><dt><a name="DB_LOCK_PUT_OBJ">DB_LOCK_PUT_OBJ</a><dd>All locks held on the object <b>obj</b> are released. The <b>mode</b>
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and <b>locker</b> parameters are ignored. Note that any locks acquired
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as a part of the current call to lock_vec that occur before the
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DB_LOCK_PUT_OBJ will also be released; those acquired afterwards
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will not be released.
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</dl>
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<p><dt>const DBT <a name="obj">obj</a>;<dd>An untyped byte string that specifies the object to be locked or released.
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<p><dt>const lockmode_t <a name="mode">mode</a>;<dd>The lock mode, used as an index into the environment's lock conflict array.
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See <a href="../api_c/env_set_lk_conflicts.html">DBENV->set_lk_conflicts</a> and <a href="../ref/lock/stdmode.html">Standard Lock Modes</a> for a description of that array.
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<p><dt>DB_LOCK <a name="lock">lock</a>;<dd>A lock reference.
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</dl>
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<p>The <b>nlist</b> argument specifies the number of elements in the
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<b>list</b> array.
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<p>If any of the requested locks cannot be acquired, or any of the locks to
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be released cannot be released, the operations before the failing
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operation are guaranteed to have completed successfully, and
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lock_vec returns a non-zero value. In addition, if <b>elistp</b>
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is not NULL, it is set to point to the DB_LOCKREQ entry that was being
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processed when the error occurred.
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<p>The lock_vec function may
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return
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one of the following values:
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<p><dl compact>
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<p><dt><a name="DB_LOCK_NOTGRANTED">DB_LOCK_NOTGRANTED</a><dd>A lock was requested that could not be immediately granted and the
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<b>flag</b> parameter was set to DB_LOCK_NOWAIT. In this case, if
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non-NULL, <b>elistp</b> identifies the request that was not granted.
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</dl>
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<p>Otherwise, the lock_vec function returns a non-zero error value on failure and 0 on success.
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<h1>Errors</h1>
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<p>The lock_vec function may fail and return a non-zero error for the following conditions:
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<p><dl compact>
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<p><dt>DB_LOCK_DEADLOCK<dd>The operation was selected to resolve a deadlock.
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</dl>
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<p><dl compact>
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<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
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</dl>
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<p><dl compact>
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<p><dt>ENOMEM<dd>The maximum number of locks has been reached.
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</dl>
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<p>The lock_vec function may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
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If a catastrophic error has occurred, the lock_vec function may fail and return
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<a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>, in which case all subsequent Berkeley DB calls will fail
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in the same way.
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<h1>See Also</h1>
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<a href="../api_c/env_set_lk_conflicts.html">DBENV->set_lk_conflicts</a>,
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<a href="../api_c/env_set_lk_detect.html">DBENV->set_lk_detect</a>,
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<a href="../api_c/env_set_lk_max_locks.html">DBENV->set_lk_max_locks</a>,
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<a href="../api_c/env_set_lk_max_lockers.html">DBENV->set_lk_max_lockers</a>,
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<a href="../api_c/env_set_lk_max_objects.html">DBENV->set_lk_max_objects</a>,
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<a href="../api_c/env_set_lk_max.html">DBENV->set_lk_max</a>,
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<a href="../api_c/lock_detect.html">lock_detect</a>,
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<a href="../api_c/lock_get.html">lock_get</a>,
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<a href="../api_c/lock_id.html">lock_id</a>,
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<a href="../api_c/lock_put.html">lock_put</a>,
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<a href="../api_c/lock_stat.html">lock_stat</a>
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and
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<a href="../api_c/lock_vec.html">lock_vec</a>.
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</tt>
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<table><tr><td><br></td><td width="1%">
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font>
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