57 lines
2.7 KiB
C
57 lines
2.7 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=2 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/rand/rand.h"
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#include "libc/rand/xorshift.h"
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#include "libc/str/str.h"
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/**
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* Fills memory with random bytes, e.g.
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*
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* char buf[1024];
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* rngset(buf, sizeof(buf), rand64, -1);
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*
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* @param seed can be rand64() and is always called at least once
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* @param reseed is bytes between seed() calls and -1 disables it
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* @return original buf
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*/
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void *rngset(void *buf, size_t size, uint64_t seed(void), size_t reseed) {
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unsigned char *p;
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uint64_t i, x, state;
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p = buf;
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state = seed();
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for (i = 0; size - i >= sizeof(x); i += sizeof(x)) {
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x = MarsagliaXorshift64(&state);
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memcpy(p + i, &x, sizeof(x));
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if (i >= reseed) {
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state = seed();
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p += i;
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size -= i;
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i = 0;
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}
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}
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if (i < size) {
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x = MarsagliaXorshift64(&state);
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for (; i < size; ++i, x >>= 8) {
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p[i] = x & 0xff;
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}
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}
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return buf;
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}
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