initial commit, 4.5 stable

thirdparty/astcenc/astcenc_mathlib.cpp

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: Apache-2.0
+// ----------------------------------------------------------------------------
+// Copyright 2011-2021 Arm Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy
+// of the License at:
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+// ----------------------------------------------------------------------------
+
+#include "astcenc_mathlib.h"
+
+/**
+ * @brief 64-bit rotate left.
+ *
+ * @param val   The value to rotate.
+ * @param count The rotation, in bits.
+ */
+static inline uint64_t rotl(uint64_t val, int count)
+{
+	return (val << count) | (val >> (64 - count));
+}
+
+/* See header for documentation. */
+void astc::rand_init(uint64_t state[2])
+{
+	state[0] = 0xfaf9e171cea1ec6bULL;
+	state[1] = 0xf1b318cc06af5d71ULL;
+}
+
+/* See header for documentation. */
+uint64_t astc::rand(uint64_t state[2])
+{
+	uint64_t s0 = state[0];
+	uint64_t s1 = state[1];
+	uint64_t res = s0 + s1;
+	s1 ^= s0;
+	state[0] = rotl(s0, 24) ^ s1 ^ (s1 << 16);
+	state[1] = rotl(s1, 37);
+	return res;
+}