50 lines
2.6 KiB
C
50 lines
2.6 KiB
C
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=8 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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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; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ 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, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/dce.h"
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#include "libc/nexgen32e/x86feature.h"
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#include "libc/rand/rand.h"
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#include "libc/rand/xorshift.h"
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/**
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* Returns nondeterministic random number.
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*
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* This function uses a good random source if it's available, which
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* takes ~400 cycles (~99ns). Otherwise it's seeded at program start
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* with the system provided random value and may perform a few
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* microseconds worth of system calls to get a good value.
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*
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* @see rngset()
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*/
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nodebuginfo uint64_t(rand64)(void) {
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uint64_t res;
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if (X86_HAVE(RDRND)) {
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res = rdrand();
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} else {
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if (IsWindows()) {
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res = winrandish();
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} else {
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devrand(&res, sizeof(res));
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}
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hidden extern uint64_t g_rando64;
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res ^= MarsagliaXorshift64(&g_rando64);
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}
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return res;
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}
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