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database/apache/include/apr_global_mutex.h

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+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef APR_GLOBAL_MUTEX_H
+#define APR_GLOBAL_MUTEX_H
+
+/**
+ * @file apr_global_mutex.h
+ * @brief APR Global Locking Routines
+ */
+
+#include "apr.h"
+#include "apr_proc_mutex.h"    /* only for apr_lockmech_e */
+#include "apr_pools.h"
+#include "apr_errno.h"
+#if APR_PROC_MUTEX_IS_GLOBAL
+#include "apr_proc_mutex.h"
+#endif
+#include "apr_time.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+/**
+ * @defgroup APR_GlobalMutex Global Locking Routines
+ * @ingroup APR 
+ * @{
+ */
+
+#if !APR_PROC_MUTEX_IS_GLOBAL || defined(DOXYGEN)
+
+/** Opaque global mutex structure. */
+typedef struct apr_global_mutex_t apr_global_mutex_t;
+
+/*   Function definitions */
+
+/**
+ * Create and initialize a mutex that can be used to synchronize both
+ * processes and threads. Note: There is considerable overhead in using
+ * this API if only cross-process or cross-thread mutual exclusion is
+ * required. See apr_proc_mutex.h and apr_thread_mutex.h for more
+ * specialized lock routines.
+ * @param mutex the memory address where the newly created mutex will be
+ *        stored.
+ * @param fname A file name to use if the lock mechanism requires one.  This
+ *        argument should always be provided.  The lock code itself will
+ *        determine if it should be used.
+ * @param mech The mechanism to use for the interprocess lock, if any; one of
+ * <PRE>
+ *            APR_LOCK_FCNTL
+ *            APR_LOCK_FLOCK
+ *            APR_LOCK_SYSVSEM
+ *            APR_LOCK_POSIXSEM
+ *            APR_LOCK_PROC_PTHREAD
+ *            APR_LOCK_DEFAULT     pick the default mechanism for the platform
+ *            APR_LOCK_DEFAULT_TIMED pick the default timed mechanism
+ * </PRE>
+ * @param pool the pool from which to allocate the mutex.
+ * @warning Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
+ *          APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
+ */
+APR_DECLARE(apr_status_t) apr_global_mutex_create(apr_global_mutex_t **mutex,
+                                                  const char *fname,
+                                                  apr_lockmech_e mech,
+                                                  apr_pool_t *pool);
+
+/**
+ * Re-open a mutex in a child process.
+ * @param mutex The newly re-opened mutex structure.
+ * @param fname A file name to use if the mutex mechanism requires one.  This
+ *              argument should always be provided.  The mutex code itself will
+ *              determine if it should be used.  This filename should be the 
+ *              same one that was passed to apr_global_mutex_create().
+ * @param pool The pool to operate on.
+ * @remark This function must be called to maintain portability, even
+ *         if the underlying lock mechanism does not require it.
+ */
+APR_DECLARE(apr_status_t) apr_global_mutex_child_init(
+                              apr_global_mutex_t **mutex,
+                              const char *fname,
+                              apr_pool_t *pool);
+
+/**
+ * Acquire the lock for the given mutex. If the mutex is already locked,
+ * the current thread will be put to sleep until the lock becomes available.
+ * @param mutex the mutex on which to acquire the lock.
+ */
+APR_DECLARE(apr_status_t) apr_global_mutex_lock(apr_global_mutex_t *mutex);
+
+/**
+ * Attempt to acquire the lock for the given mutex. If the mutex has already
+ * been acquired, the call returns immediately with APR_EBUSY. Note: it
+ * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
+ * if the return value was APR_EBUSY, for portability reasons.
+ * @param mutex the mutex on which to attempt the lock acquiring.
+ */
+APR_DECLARE(apr_status_t) apr_global_mutex_trylock(apr_global_mutex_t *mutex);
+
+/**
+ * Attempt to acquire the lock for the given mutex until timeout expires.
+ * If the acquisition time outs, the call returns with APR_TIMEUP.
+ * @param mutex the mutex on which to attempt the lock acquiring.
+ * @param timeout the relative timeout (microseconds).
+ * @note A negative or nul timeout means immediate attempt, returning
+ *       APR_TIMEUP without blocking if it the lock is already acquired.
+ */
+APR_DECLARE(apr_status_t) apr_global_mutex_timedlock(apr_global_mutex_t *mutex,
+                                                 apr_interval_time_t timeout);
+
+/**
+ * Release the lock for the given mutex.
+ * @param mutex the mutex from which to release the lock.
+ */
+APR_DECLARE(apr_status_t) apr_global_mutex_unlock(apr_global_mutex_t *mutex);
+
+/**
+ * Destroy the mutex and free the memory associated with the lock.
+ * @param mutex the mutex to destroy.
+ */
+APR_DECLARE(apr_status_t) apr_global_mutex_destroy(apr_global_mutex_t *mutex);
+
+/**
+ * Return the name of the lockfile for the mutex, or NULL
+ * if the mutex doesn't use a lock file
+ */
+APR_DECLARE(const char *) apr_global_mutex_lockfile(apr_global_mutex_t *mutex);
+
+/**
+ * Get the mechanism of the mutex, as it relates to the actual method
+ * used for the underlying apr_proc_mutex_t.
+ * @param mutex the mutex to get the mechanism from.
+ */
+APR_DECLARE(apr_lockmech_e) apr_global_mutex_mech(apr_global_mutex_t *mutex);
+
+/**
+ * Get the mechanism's name of the mutex, as it relates to the actual method
+ * used for the underlying apr_proc_mutex_t.
+ * @param mutex the mutex to get the mechanism's name from.
+ */
+APR_DECLARE(const char *) apr_global_mutex_name(apr_global_mutex_t *mutex);
+
+/**
+ * Set mutex permissions.
+ */
+APR_PERMS_SET_IMPLEMENT(global_mutex);
+
+/**
+ * Get the pool used by this global_mutex.
+ * @return apr_pool_t the pool
+ */
+APR_POOL_DECLARE_ACCESSOR(global_mutex);
+
+#else /* APR_PROC_MUTEX_IS_GLOBAL */
+
+/* Some platforms [e.g. Win32] have cross process locks that are truly
+ * global locks, since there isn't the concept of cross-process locks.
+ * Define these platforms in terms of an apr_proc_mutex_t.
+ */
+
+#define apr_global_mutex_t          apr_proc_mutex_t
+#define apr_global_mutex_create     apr_proc_mutex_create
+#define apr_global_mutex_child_init apr_proc_mutex_child_init
+#define apr_global_mutex_lock       apr_proc_mutex_lock
+#define apr_global_mutex_trylock    apr_proc_mutex_trylock
+#define apr_global_mutex_unlock     apr_proc_mutex_unlock
+#define apr_global_mutex_destroy    apr_proc_mutex_destroy
+#define apr_global_mutex_lockfile   apr_proc_mutex_lockfile
+#define apr_global_mutex_mech       apr_proc_mutex_mech
+#define apr_global_mutex_name       apr_proc_mutex_name
+#define apr_global_mutex_perms_set  apr_proc_mutex_perms_set
+#define apr_global_mutex_pool_get   apr_proc_mutex_pool_get
+
+#endif
+
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  /* ndef APR_GLOBAL_MUTEX_H */