mirror of
https://github.com/OpenVPN/openvpn3.git
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78 lines
2.1 KiB
C++
78 lines
2.1 KiB
C++
// OpenVPN -- An application to securely tunnel IP networks
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// over a single port, with support for SSL/TLS-based
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// session authentication and key exchange,
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// packet encryption, packet authentication, and
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// packet compression.
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//
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// Copyright (C) 2012-2015 OpenVPN Technologies, Inc.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License Version 3
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// as published by the Free Software Foundation.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program in the COPYING file.
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// If not, see <http://www.gnu.org/licenses/>.
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#ifndef OPENVPN_COMMON_FFS_H
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#define OPENVPN_COMMON_FFS_H
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// find_first_set: find the one-based position of the first 1 bit in
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// a word (scanning from least significant bit to most significant)
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// find_last_set: find the one-based position of the last 1 bit in
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// a word (scanning from most significant bit to least significant)
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namespace openvpn {
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#if defined(__GNUC__)
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inline int find_first_set(unsigned int v)
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{
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if (!v)
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return 0;
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return __builtin_ffs(v);
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}
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inline int find_last_set(unsigned int v)
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{
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if (!v)
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return 0;
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return 32 - __builtin_clz(v);
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}
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#elif defined(_MSC_VER)
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#include <intrin.h>
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inline int find_first_set(unsigned int x)
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{
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if (!x)
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return 0;
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unsigned int r = 0;
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_BitScanForward((unsigned long *)&r, x);
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return r + 1;
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}
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inline int find_last_set(unsigned int x)
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{
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if (!x)
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return 0;
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unsigned int r = 0;
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_BitScanReverse((unsigned long *)&r, x);
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return r + 1;
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}
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#else
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#error no find_first_set / find_last_set implementation for this platform
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#endif
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} // namespace openvpn
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#endif // OPENVPN_COMMON_FFS_H
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