Initial commit

common/btea.cpp

@@ -0,0 +1,76 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "common/btea.h"
+
+namespace Common {
+
+namespace BTEACrypto {
+
+#define DELTA 0x9e3779b9
+#define MX (((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4)) ^ ((sum ^ y) + (key[(p & 3) ^ e] ^ z)))
+
+// This method comes from https://en.wikipedia.org/wiki/XXTEA
+void btea(uint32 *v, int n, const uint32 *key) {
+	uint32 y, z, sum;
+	unsigned int p, rounds, e;
+	if (n > 1) { /* Coding Part */
+		rounds = 6 + 52 / n;
+		sum = 0;
+		z = v[n - 1];
+		do {
+			sum += DELTA;
+			e = (sum >> 2) & 3;
+			for (p = 0; p < static_cast<uint32>(n - 1); p++) {
+				y = v[p + 1];
+				z = v[p] += MX;
+			}
+			y = v[0];
+			z = v[n - 1] += MX;
+		} while (--rounds);
+	} else if (n < -1) { /* Decoding Part */
+		n = -n;
+		rounds = 6 + 52 / n;
+		sum = rounds * DELTA;
+		y = v[0];
+		do {
+			e = (sum >> 2) & 3;
+			for (p = n - 1; p > 0; p--) {
+				z = v[p - 1];
+				y = v[p] -= MX;
+			}
+			z = v[n - 1];
+			y = v[0] -= MX;
+			sum -= DELTA;
+		} while (--rounds);
+	}
+}
+
+void encrypt(uint32 *v, int n, const uint32 *key) {
+	btea(v, n, key);
+}
+
+void decrypt(uint32 *v, int n, const uint32 *key) {
+	btea(v, -n, key);
+}
+
+} // namespace BTEACrypto
+} // namespace Common