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+// Copyright (C) 2012-2023 Internet Systems Consortium, Inc. ("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 http://mozilla.org/MPL/2.0/.
+
+#ifndef ADDR_UTILITIES_H
+#define ADDR_UTILITIES_H
+
+#include <asiolink/io_address.h>
+#include <util/bigints.h>
+
+namespace isc {
+namespace asiolink {
+
+/// This code is based on similar code from the Dibbler project. I, Tomasz Mrugalski,
+/// as a sole creator of that code hereby release it under BSD license for the benefit
+/// of the Kea project.
+
+/// @brief returns a first address in a given prefix
+///
+/// Example: For 2001:db8:1\::deaf:beef and length /120 the function will return
+/// 2001:db8:1\::dead:be00. See also @ref lastAddrInPrefix.
+///
+/// @param prefix and address that belongs to a prefix
+/// @param len prefix length
+///
+/// @return first address from a prefix
+IOAddress firstAddrInPrefix(const IOAddress& prefix, uint8_t len);
+
+/// @brief returns a last address in a given prefix
+///
+/// Example: For 2001:db8:1\::deaf:beef and length /112 the function will return
+/// 2001:db8:1\::dead:ffff. See also @ref firstAddrInPrefix.
+///
+/// @param prefix and address that belongs to a prefix
+/// @param len prefix length
+///
+/// @return first address from a prefix
+IOAddress lastAddrInPrefix(const IOAddress& prefix, uint8_t len);
+
+/// @brief Generates an IPv4 netmask of specified length
+/// @throw BadValue if len is greater than 32
+/// @return netmask
+IOAddress getNetmask4(uint8_t len);
+
+
+/// @brief Returns number of available addresses in the specified range (min - max).
+///
+/// Note that for min equal max case, the number of addresses is one.
+///
+/// @throw BadValue if min and max are not of the same family (both must be
+///        either IPv4 or IPv6) or if max < min.
+///
+/// @param min the first address in range
+/// @param max the last address in range
+/// @return number of addresses in range
+isc::util::uint128_t addrsInRange(const IOAddress& min, const IOAddress& max);
+
+/// @brief Returns prefix length from the specified range (min - max).
+///
+/// This can be considered as log2(addrsInRange)
+///
+/// @throw BadValue if min and max do not define a prefix.
+///
+/// @param min the first address in range
+/// @param max the last address in range
+/// @return the prefix length or -1 if the range is not from a prefix
+int prefixLengthFromRange(const IOAddress& min, const IOAddress& max);
+
+/// @brief Returns number of available IPv6 prefixes in the specified prefix.
+///
+/// Note that if the answer is bigger than uint64_t can hold, it will return
+/// the max value of uint64_t type.
+///
+/// Example: prefixesInRange(48, 64) returns 65536, as there are /48 pool
+/// can be split into 65536 prefixes, each /64 large.
+///
+/// @param pool_len length of the pool in bits
+/// @param delegated_len length of the prefixes to be delegated from the pool
+/// @return number of prefixes in range
+isc::util::uint128_t prefixesInRange(const uint8_t pool_len, const uint8_t delegated_len);
+
+/// @brief Finds the address increased by offset.
+///
+/// Adds offset to the IPv4 or iPv6 address and finds the resulting address.
+/// Note that the current limitation is the maximum value of the offset,
+/// i.e. max uint64_t. If the sum of the IPv4 address and the offset exceeds
+/// the maximum value of uint32_t type, the 255.255.255.255 is returned.
+///
+/// @param addr input address
+/// @param offset distance of the returned address from the input address.
+/// @return address being offset greater than the input address
+IOAddress offsetAddress(const IOAddress& addr, isc::util::uint128_t offset);
+
+}  // namespace asiolink
+}  // namespace isc
+
+#endif // ADDR_UTILITIES_H