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