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diff --git a/lib/isc/include/isc/pool.h b/lib/isc/include/isc/pool.h
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+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#ifndef ISC_OBJPOOL_H
+#define ISC_OBJPOOL_H 1
+
+/*****
+***** Module Info
+*****/
+
+/*! \file isc/pool.h
+ * \brief An object pool is a mechanism for sharing a small pool of
+ * fungible objects among a large number of objects that depend on them.
+ *
+ * This is useful, for example, when it causes performance problems for
+ * large number of zones to share a single memory context or task object,
+ * but it would create a different set of problems for them each to have an
+ * independent task or memory context.
+ */
+
+/***
+ *** Imports.
+ ***/
+
+#include <isc/lang.h>
+#include <isc/mem.h>
+#include <isc/types.h>
+
+ISC_LANG_BEGINDECLS
+
+/*****
+***** Types.
+*****/
+
+typedef void (*isc_pooldeallocator_t)(void **object);
+
+typedef isc_result_t (*isc_poolinitializer_t)(void **target, void *arg);
+
+typedef struct isc_pool isc_pool_t;
+
+/*****
+***** Functions.
+*****/
+
+isc_result_t
+isc_pool_create(isc_mem_t *mctx, unsigned int count, isc_pooldeallocator_t free,
+		isc_poolinitializer_t init, void *initarg, isc_pool_t **poolp);
+/*%<
+ * Create a pool of "count" object pointers. If 'free' is not NULL,
+ * it points to a function that will detach the objects.  'init'
+ * points to a function that will initialize the arguments, and
+ * 'arg' to an argument to be passed into that function (for example,
+ * a relevant manager or context object).
+ *
+ * Requires:
+ *
+ *\li	'mctx' is a valid memory context.
+ *
+ *\li	init != NULL
+ *
+ *\li	poolp != NULL && *poolp == NULL
+ *
+ * Ensures:
+ *
+ *\li	On success, '*poolp' points to the new object pool.
+ *
+ * Returns:
+ *
+ *\li	#ISC_R_SUCCESS
+ *\li	#ISC_R_NOMEMORY
+ *\li	#ISC_R_UNEXPECTED
+ */
+
+void *
+isc_pool_get(isc_pool_t *pool);
+/*%<
+ * Returns a pointer to an object from the pool. Currently the object
+ * is chosen from the pool at random.  (This may be changed in the future
+ * to something that guaratees balance.)
+ */
+
+int
+isc_pool_count(isc_pool_t *pool);
+/*%<
+ * Returns the number of objcts in the pool 'pool'.
+ */
+
+isc_result_t
+isc_pool_expand(isc_pool_t **sourcep, unsigned int count, isc_pool_t **targetp);
+
+/*%<
+ * If 'size' is larger than the number of objects in the pool pointed to by
+ * 'sourcep', then a new pool of size 'count' is allocated, the existing
+ * objects are copied into it, additional ones created to bring the
+ * total number up to 'count', and the resulting pool is attached to
+ * 'targetp'.
+ *
+ * If 'count' is less than or equal to the number of objects in 'source', then
+ * 'sourcep' is attached to 'targetp' without any other action being taken.
+ *
+ * In either case, 'sourcep' is detached.
+ *
+ * Requires:
+ *
+ * \li	'sourcep' is not NULL and '*source' is not NULL
+ * \li	'targetp' is not NULL and '*source' is NULL
+ *
+ * Ensures:
+ *
+ * \li	On success, '*targetp' points to a valid task pool.
+ * \li	On success, '*sourcep' points to NULL.
+ *
+ * Returns:
+ *
+ * \li	#ISC_R_SUCCESS
+ * \li	#ISC_R_NOMEMORY
+ */
+
+void
+isc_pool_destroy(isc_pool_t **poolp);
+/*%<
+ * Destroy a task pool.  The tasks in the pool are detached but not
+ * shut down.
+ *
+ * Requires:
+ * \li	'*poolp' is a valid task pool.
+ */
+
+ISC_LANG_ENDDECLS
+
+#endif /* ISC_OBJPOOL_H */