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72 lines
3.4 KiB
C
72 lines
3.4 KiB
C
/*-*- 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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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/intrin/getauxval.internal.h"
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#include "libc/nexgen32e/rdtsc.h"
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#include "libc/runtime/internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/auxv.h"
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#include "libc/thread/thread.h"
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#include "libc/thread/tls.h"
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static struct {
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int thepid;
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uint128_t thepool;
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pthread_spinlock_t lock;
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} g_rand64;
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/**
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* Returns nondeterministic random data.
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*
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* This function is similar to lemur64() except that it doesn't produce
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* the same sequences of numbers each time your program is run. This is
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* the case even across forks and threads, whose sequences will differ.
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*
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* @see rdseed(), rdrand(), rand(), random(), rngset()
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* @note this function takes 5 cycles (30 if `__threaded`)
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* @note this function is not intended for cryptography
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* @note this function passes bigcrush and practrand
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*/
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uint64_t _rand64(void) {
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void *p;
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uint128_t s;
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if (__threaded) pthread_spin_lock(&g_rand64.lock);
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if (__pid == g_rand64.thepid) {
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s = g_rand64.thepool; // normal path
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} else {
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if (!g_rand64.thepid) {
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if (AT_RANDOM && (p = (void *)__getauxval(AT_RANDOM).value)) {
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// linux / freebsd kernel supplied entropy
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memcpy(&s, p, 16);
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} else {
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// otherwise initialize w/ cheap timestamp
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s = kStartTsc;
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}
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} else {
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// blend another timestamp on fork contention
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s = g_rand64.thepool ^ rdtsc();
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}
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// blend the pid on startup and fork contention
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s ^= __pid;
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g_rand64.thepid = __pid;
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}
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g_rand64.thepool = (s *= 15750249268501108917ull); // lemur64
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pthread_spin_unlock(&g_rand64.lock);
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return s >> 64;
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}
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