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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_RESLIST_H
+#define APR_RESLIST_H
+
+/**
+ * @file apr_reslist.h
+ * @brief APR-UTIL Resource List Routines
+ */
+
+#include "apr.h"
+#include "apu.h"
+#include "apr_pools.h"
+#include "apr_errno.h"
+#include "apr_time.h"
+
+/**
+ * @defgroup APR_Util_RL Resource List Routines
+ * @ingroup APR_Util
+ * @{
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+/** Opaque resource list object */
+typedef struct apr_reslist_t apr_reslist_t;
+
+/* Generic constructor called by resource list when it needs to create a
+ * resource.
+ * @param resource opaque resource
+ * @param params flags
+ * @param pool Pool
+ */
+typedef apr_status_t (*apr_reslist_constructor)(void **resource, void *params,
+ apr_pool_t *pool);
+
+/* Generic destructor called by resource list when it needs to destroy a
+ * resource.
+ * @param resource opaque resource
+ * @param params flags
+ * @param pool Pool
+ */
+typedef apr_status_t (*apr_reslist_destructor)(void *resource, void *params,
+ apr_pool_t *pool);
+
+/* Cleanup order modes */
+#define APR_RESLIST_CLEANUP_DEFAULT 0 /**< default pool cleanup */
+#define APR_RESLIST_CLEANUP_FIRST 1 /**< use pool pre cleanup */
+
+/**
+ * Create a new resource list with the following parameters:
+ * @param reslist An address where the pointer to the new resource
+ * list will be stored.
+ * @param min Allowed minimum number of available resources. Zero
+ * creates new resources only when needed.
+ * @param smax Resources will be destroyed during reslist maintenance to
+ * meet this maximum restriction as they expire (reach their ttl).
+ * @param hmax Absolute maximum limit on the number of total resources.
+ * @param ttl If non-zero, sets the maximum amount of time in microseconds an
+ * unused resource is valid. Any resource which has exceeded this
+ * time will be destroyed, either when encountered by
+ * apr_reslist_acquire() or during reslist maintenance.
+ * @param con Constructor routine that is called to create a new resource.
+ * @param de Destructor routine that is called to destroy an expired resource.
+ * @param params Passed to constructor and deconstructor
+ * @param pool The pool from which to create this resource list. Also the
+ * same pool that is passed to the constructor and destructor
+ * routines.
+ * @remark If APR has been compiled without thread support, hmax will be
+ * automatically set to 1 and values of min and smax will be forced to
+ * 1 for any non-zero value.
+ */
+APU_DECLARE(apr_status_t) apr_reslist_create(apr_reslist_t **reslist,
+ int min, int smax, int hmax,
+ apr_interval_time_t ttl,
+ apr_reslist_constructor con,
+ apr_reslist_destructor de,
+ void *params,
+ apr_pool_t *pool);
+
+/**
+ * Destroy the given resource list and all resources controlled by
+ * this list.
+ * FIXME: Should this block until all resources become available,
+ * or maybe just destroy all the free ones, or maybe destroy
+ * them even though they might be in use by something else?
+ * Currently it will abort if there are resources that haven't
+ * been released, so there is an assumption that all resources
+ * have been released to the list before calling this function.
+ * @param reslist The reslist to destroy
+ */
+APU_DECLARE(apr_status_t) apr_reslist_destroy(apr_reslist_t *reslist);
+
+/**
+ * Retrieve a resource from the list, creating a new one if necessary.
+ * If we have met our maximum number of resources, we will block
+ * until one becomes available.
+ * @param reslist The resource list.
+ * @param resource An address where the pointer to the resource
+ * will be stored.
+ */
+APU_DECLARE(apr_status_t) apr_reslist_acquire(apr_reslist_t *reslist,
+ void **resource);
+
+/**
+ * Return a resource back to the list of available resources.
+ * @param reslist The resource list.
+ * @param resource The resource to return to the list.
+ */
+APU_DECLARE(apr_status_t) apr_reslist_release(apr_reslist_t *reslist,
+ void *resource);
+
+/**
+ * Set the timeout the acquire will wait for a free resource
+ * when the maximum number of resources is exceeded.
+ * @param reslist The resource list.
+ * @param timeout Timeout to wait. The zero waits forever.
+ */
+APU_DECLARE(void) apr_reslist_timeout_set(apr_reslist_t *reslist,
+ apr_interval_time_t timeout);
+
+/**
+ * Return the number of outstanding resources.
+ * @param reslist The resource list.
+ */
+APU_DECLARE(apr_uint32_t) apr_reslist_acquired_count(apr_reslist_t *reslist);
+
+/**
+ * Invalidate a resource in the pool - e.g. a database connection
+ * that returns a "lost connection" error and can't be restored.
+ * Use this instead of apr_reslist_release if the resource is bad.
+ * @param reslist The resource list.
+ * @param resource The resource to invalidate.
+ */
+APU_DECLARE(apr_status_t) apr_reslist_invalidate(apr_reslist_t *reslist,
+ void *resource);
+
+/**
+ * Perform routine maintenance on the resource list. This call
+ * may instantiate new resources or expire old resources.
+ * @param reslist The resource list.
+ */
+APU_DECLARE(apr_status_t) apr_reslist_maintain(apr_reslist_t *reslist);
+
+/**
+ * Set reslist cleanup order.
+ * @param reslist The resource list.
+ * @param mode Cleanup order mode
+ * <PRE>
+ * APR_RESLIST_CLEANUP_DEFAULT default pool cleanup order
+ * APR_RESLIST_CLEANUP_FIRST use pool pre cleanup
+ * </PRE>
+ * @remark If APR_RESLIST_CLEANUP_FIRST is used the destructors will
+ * be called before child pools of the pool used to create the reslist
+ * are destroyed. This allows to explicitly destroy the child pools
+ * inside reslist destructors.
+ */
+APU_DECLARE(void) apr_reslist_cleanup_order_set(apr_reslist_t *reslist,
+ apr_uint32_t mode);
+
+#ifdef __cplusplus
+}
+#endif
+
+/** @} */
+
+#endif /* ! APR_RESLIST_H */