mirror of
https://github.com/libretro/scummvm.git
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77 lines
2.0 KiB
C++
77 lines
2.0 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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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 General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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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 General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "common/btea.h"
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namespace Common {
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namespace BTEACrypto {
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#define DELTA 0x9e3779b9
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#define MX (((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4)) ^ ((sum ^ y) + (key[(p & 3) ^ e] ^ z)))
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// This method comes from https://en.wikipedia.org/wiki/XXTEA
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void btea(uint32 *v, int n, const uint32 *key) {
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uint32 y, z, sum;
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unsigned int p, rounds, e;
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if (n > 1) { /* Coding Part */
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rounds = 6 + 52 / n;
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sum = 0;
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z = v[n - 1];
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do {
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sum += DELTA;
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e = (sum >> 2) & 3;
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for (p = 0; p < static_cast<uint32>(n - 1); p++) {
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y = v[p + 1];
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z = v[p] += MX;
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}
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y = v[0];
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z = v[n - 1] += MX;
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} while (--rounds);
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} else if (n < -1) { /* Decoding Part */
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n = -n;
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rounds = 6 + 52 / n;
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sum = rounds * DELTA;
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y = v[0];
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do {
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e = (sum >> 2) & 3;
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for (p = n - 1; p > 0; p--) {
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z = v[p - 1];
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y = v[p] -= MX;
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}
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z = v[n - 1];
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y = v[0] -= MX;
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sum -= DELTA;
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} while (--rounds);
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}
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}
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void encrypt(uint32 *v, int n, const uint32 *key) {
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btea(v, n, key);
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}
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void decrypt(uint32 *v, int n, const uint32 *key) {
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btea(v, -n, key);
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}
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} // namespace BTEACrypto
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} // namespace Common
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