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155b378a39
The organization of the source files is now much more rational. Old experiments that didn't work out are now deleted. Naming of things like files is now more intuitive.
75 lines
3.5 KiB
C
75 lines
3.5 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/calls/_getauxval.internal.h"
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#include "libc/thread/thread.h"
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#include "libc/nexgen32e/rdtsc.h"
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#include "libc/thread/tls.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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static struct {
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int thepid;
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uint128_t thepool;
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pthread_mutex_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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* @asyncsignalsafe
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* @threadsafe
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* @vforksafe
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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_mutex_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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if (__threaded) pthread_mutex_unlock(&g_rand64.lock);
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return s >> 64;
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}
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