Add the new thread read/write API to APR. This doesn't change any

API, just adds a new one.

Submitted by:	Aaron Bannert <aaron@clove.org>


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@62295 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 149 insertions, 0 deletions

diff --git a/include/apr_thread_rwlock.h b/include/apr_thread_rwlock.h
new file mode 100644
index 000000000..d43a13e31
--- /dev/null
+++ b/include/apr_thread_rwlock.h
@@ -0,0 +1,149 @@
+/* ====================================================================
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2000-2001 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution,
+ *    if any, must include the following acknowledgment:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowledgment may appear in the software itself,
+ *    if and wherever such third-party acknowledgments normally appear.
+ *
+ * 4. The names "Apache" and "Apache Software Foundation" must
+ *    not be used to endorse or promote products derived from this
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+ *
+ * 5. Products derived from this software may not be called "Apache",
+ *    nor may "Apache" appear in their name, without prior written
+ *    permission of the Apache Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
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+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+#ifndef APR_THREAD_RWLOCK_H
+#define APR_THREAD_RWLOCK_H
+
+#include "apr.h"
+#include "apr_pools.h"
+#include "apr_errno.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+#if APR_HAS_THREADS
+
+/**
+ * @file apr_lock.h
+ * @brief APR Thread RWLock Routines
+ */
+
+/**
+ * @defgroup APR_ThreadRWLock Thread RWLock Routines
+ * @ingroup APR
+ * @{
+ */
+
+typedef struct apr_thread_rwlock_t apr_thread_rwlock_t;
+
+/**
+ * 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 shread-read lock on the given read-write lock. This
+ * is the same as apr_thread_rwlock_rdlock(), only that the funtion fails
+ * if there is another thread holding the write lock, or if there are any
+ * write threads blocking on the lock. If the function failes 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 thee 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 funtion 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 rom which to release the lock.
+ */
+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);
+
+#endif  /* APR_HAS_THREADS */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  /* ! APR_THREAD_RWLOCK_H */