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diff --git a/lib/isccc/include/isccc/symtab.h b/lib/isccc/include/isccc/symtab.h
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+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0 AND ISC
+ *
+ * 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.
+ */
+
+/*
+ * Copyright (C) 2001 Nominum, Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC AND NOMINUM DISCLAIMS ALL
+ * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#pragma once
+
+/*****
+***** Module Info
+*****/
+
+/*! \file isccc/symtab.h
+ * \brief
+ * Provides a simple memory-based symbol table.
+ *
+ * Keys are C strings.  A type may be specified when looking up,
+ * defining, or undefining.  A type value of 0 means "match any type";
+ * any other value will only match the given type.
+ *
+ * It's possible that a client will attempt to define a <key, type,
+ * value> tuple when a tuple with the given key and type already
+ * exists in the table.  What to do in this case is specified by the
+ * client.  Possible policies are:
+ *
+ *\li	isccc_symexists_reject	Disallow the define, returning #ISC_R_EXISTS
+ *\li	isccc_symexists_replace	Replace the old value with the new.  The
+ *				undefine action (if provided) will be called
+ *				with the old <key, type, value> tuple.
+ *\li	isccc_symexists_add	Add the new tuple, leaving the old tuple in
+ *				the table.  Subsequent lookups will retrieve
+ *				the most-recently-defined tuple.
+ *
+ * A lookup of a key using type 0 will return the most-recently
+ * defined symbol with that key.  An undefine of a key using type 0
+ * will undefine the most-recently defined symbol with that key.
+ * Trying to define a key with type 0 is illegal.
+ *
+ * The symbol table library does not make a copy the key field, so the
+ * caller must ensure that any key it passes to isccc_symtab_define()
+ * will not change until it calls isccc_symtab_undefine() or
+ * isccc_symtab_destroy().
+ *
+ * A user-specified action will be called (if provided) when a symbol
+ * is undefined.  It can be used to free memory associated with keys
+ * and/or values.
+ */
+
+/***
+ *** Imports.
+ ***/
+
+#include <stdbool.h>
+
+#include <isc/lang.h>
+
+#include <isccc/types.h>
+
+/***
+ *** Symbol Tables.
+ ***/
+
+typedef union isccc_symvalue {
+	void	    *as_pointer;
+	int	     as_integer;
+	unsigned int as_uinteger;
+} isccc_symvalue_t;
+
+typedef void (*isccc_symtabundefaction_t)(char *key, unsigned int type,
+					  isccc_symvalue_t value,
+					  void		  *userarg);
+
+typedef bool (*isccc_symtabforeachaction_t)(char *key, unsigned int type,
+					    isccc_symvalue_t value,
+					    void	    *userarg);
+
+typedef enum {
+	isccc_symexists_reject = 0,
+	isccc_symexists_replace = 1,
+	isccc_symexists_add = 2
+} isccc_symexists_t;
+
+ISC_LANG_BEGINDECLS
+
+isc_result_t
+isccc_symtab_create(unsigned int	      size,
+		    isccc_symtabundefaction_t undefine_action,
+		    void *undefine_arg, bool case_sensitive,
+		    isccc_symtab_t **symtabp);
+
+void
+isccc_symtab_destroy(isccc_symtab_t **symtabp);
+
+isc_result_t
+isccc_symtab_lookup(isccc_symtab_t *symtab, const char *key, unsigned int type,
+		    isccc_symvalue_t *value);
+
+isc_result_t
+isccc_symtab_define(isccc_symtab_t *symtab, char *key, unsigned int type,
+		    isccc_symvalue_t value, isccc_symexists_t exists_policy);
+
+isc_result_t
+isccc_symtab_undefine(isccc_symtab_t *symtab, const char *key,
+		      unsigned int type);
+
+void
+isccc_symtab_foreach(isccc_symtab_t *symtab, isccc_symtabforeachaction_t action,
+		     void *arg);
+
+ISC_LANG_ENDDECLS