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diff --git a/lib/isc/include/isc/counter.h b/lib/isc/include/isc/counter.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.
+ */
+
+#pragma once
+
+/*****
+***** Module Info
+*****/
+
+/*! \file isc/counter.h
+ *
+ * \brief The isc_counter_t object is a simplified version of the
+ * isc_quota_t object; it tracks the consumption of limited
+ * resources, returning an error condition when the quota is
+ * exceeded.  However, unlike isc_quota_t, attaching and detaching
+ * from a counter object does not increment or decrement the counter.
+ */
+
+/***
+ *** Imports.
+ ***/
+
+#include <isc/lang.h>
+#include <isc/mutex.h>
+#include <isc/types.h>
+
+/*****
+***** Types.
+*****/
+
+ISC_LANG_BEGINDECLS
+
+isc_result_t
+isc_counter_create(isc_mem_t *mctx, int limit, isc_counter_t **counterp);
+/*%<
+ * Allocate and initialize a counter object.
+ */
+
+isc_result_t
+isc_counter_increment(isc_counter_t *counter);
+/*%<
+ * Increment the counter.
+ *
+ * If the counter limit is nonzero and has been reached, then
+ * return ISC_R_QUOTA, otherwise ISC_R_SUCCESS. (The counter is
+ * incremented regardless of return value.)
+ */
+
+unsigned int
+isc_counter_used(isc_counter_t *counter);
+/*%<
+ * Return the current counter value.
+ */
+
+void
+isc_counter_setlimit(isc_counter_t *counter, int limit);
+/*%<
+ * Set the counter limit.
+ */
+
+void
+isc_counter_attach(isc_counter_t *source, isc_counter_t **targetp);
+/*%<
+ * Attach to a counter object, increasing its reference counter.
+ */
+
+void
+isc_counter_detach(isc_counter_t **counterp);
+/*%<
+ * Detach (and destroy if reference counter has dropped to zero)
+ * a counter object.
+ */
+
+ISC_LANG_ENDDECLS