80 lines
2.5 KiB
C
80 lines
2.5 KiB
C
/****************************************************************************
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* libs/libc/misc/lib_xorshift128.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy 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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****************************************************************************/
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/* This random number generator is simple, fast and portable.
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* Ref: https://en.wikipedia.org/wiki/Xorshift
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*/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <stdint.h>
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#include <assert.h>
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#include <nuttx/lib/xorshift128.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: xorshift128
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*
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* Description:
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* Generate one 32-bit pseudo-random number.
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*
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* NOTE: Because the PRNG state is passed as a parameter, this function is
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* fully re-entrant and may be called from an interrupt handler.
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*
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* The downside to this is that users of the PRNG might not get as much
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* entropy as if it were a common state structure.
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*
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* Input Parameters:
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* state - The current XorShift128 state.
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*
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* Returned Value:
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* The generated pseudo-random number
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*
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****************************************************************************/
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uint32_t xorshift128(FAR struct xorshift128_state_s *state)
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{
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uint32_t t;
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DEBUGASSERT(state != NULL);
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t = state->x;
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t ^= t << 11;
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t ^= t >> 8;
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state->x = state->y;
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state->y = state->z;
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state->z = state->w;
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state->w ^= state->w >> 19;
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state->w ^= t;
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return state->w;
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}
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