Initial Commit

database/apache/include/apr_thread_rwlock.h

@@ -0,0 +1,129 @@
+/* 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_THREAD_RWLOCK_H
+#define APR_THREAD_RWLOCK_H
+
+/**
+ * @file apr_thread_rwlock.h
+ * @brief APR Reader/Writer Lock Routines
+ */
+
+#include "apr.h"
+#include "apr_pools.h"
+#include "apr_errno.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+#if APR_HAS_THREADS
+
+/**
+ * @defgroup apr_thread_rwlock Reader/Writer Lock Routines
+ * @ingroup APR 
+ * @{
+ */
+
+/** Opaque read-write thread-safe lock. */
+typedef struct apr_thread_rwlock_t apr_thread_rwlock_t;
+
+/**
+ * Note: The following operations have undefined results: unlocking a
+ * read-write lock which is not locked in the calling thread; write
+ * locking a read-write lock which is already locked by the calling
+ * thread; destroying a read-write lock more than once; clearing or
+ * destroying the pool from which a <b>locked</b> read-write lock is
+ * allocated.
+ */
+
+/**
+ * Create and initialize a read-write lock that can be used to synchronize
+ * threads.
+ * @param rwlock the memory address where the newly created readwrite lock
+ *        will be stored.
+ * @param pool the pool from which to allocate the mutex.
+ */
+APR_DECLARE(apr_status_t) apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock,
+                                                   apr_pool_t *pool);
+/**
+ * Acquire a shared-read lock on the given read-write lock. This will allow
+ * multiple threads to enter the same critical section while they have acquired
+ * the read lock.
+ * @param rwlock the read-write lock on which to acquire the shared read.
+ */
+APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock);
+
+/**
+ * Attempt to acquire the shared-read lock on the given read-write lock. This
+ * is the same as apr_thread_rwlock_rdlock(), only that the function fails
+ * if there is another thread holding the write lock, or if there are any
+ * write threads blocking on the lock. If the function fails for this case,
+ * APR_EBUSY will be returned. 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 rwlock the rwlock on which to attempt the shared read.
+ */
+APR_DECLARE(apr_status_t) apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock);
+
+/**
+ * Acquire an exclusive-write lock on the given read-write lock. This will
+ * allow only one single thread to enter the critical sections. If there
+ * are any threads currently holding the read-lock, this thread is put to
+ * sleep until it can have exclusive access to the lock.
+ * @param rwlock the read-write lock on which to acquire the exclusive write.
+ */
+APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock);
+
+/**
+ * Attempt to acquire the exclusive-write lock on the given read-write lock. 
+ * This is the same as apr_thread_rwlock_wrlock(), only that the function fails
+ * if there is any other thread holding the lock (for reading or writing),
+ * in which case the function will return 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 rwlock the rwlock on which to attempt the exclusive write.
+ */
+APR_DECLARE(apr_status_t) apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock);
+
+/**
+ * Release either the read or write lock currently held by the calling thread
+ * associated with the given read-write lock.
+ * @param rwlock the read-write lock to be released (unlocked).
+ */
+APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock);
+
+/**
+ * Destroy the read-write lock and free the associated memory.
+ * @param rwlock the rwlock to destroy.
+ */
+APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock);
+
+/**
+ * Get the pool used by this thread_rwlock.
+ * @return apr_pool_t the pool
+ */
+APR_POOL_DECLARE_ACCESSOR(thread_rwlock);
+
+#endif  /* APR_HAS_THREADS */
+
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  /* ! APR_THREAD_RWLOCK_H */