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https://github.com/jart/cosmopolitan.git
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50 lines
2.8 KiB
C
50 lines
2.8 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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│ 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/bits/safemacros.internal.h"
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#include "libc/calls/internal.h"
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#include "libc/errno.h"
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#include "libc/rand/rand.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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/**
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* Returns random bytes appropriate for random seeding.
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*
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* @param size should be the smallest value that meets your requirements
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* @param flags may be GRND_{RANDOM,NONBLOCK}
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* @return number of bytes copied on success; or -1 w/ errno, which
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* indicates only that the request couldn't be serviced by the host
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* kernel; this wrapper will still fill the buffer with random bytes
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* from fallback sources no matter what
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*/
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ssize_t getrandom(void *buf, size_t size, unsigned flags) {
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ssize_t rc = sys_getrandom(buf, size, flags);
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size_t i = rc == -1 ? 0 : (size_t)rc;
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if (i > size) abort();
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if (i < size) {
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unsigned char *p = buf;
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int olderr = errno;
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do {
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uint64_t i64 = rand64();
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memcpy(&p[i], &i64, min(sizeof(i64), size - i));
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} while ((i += sizeof(uint64_t)) < size);
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errno = olderr;
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}
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return rc;
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}
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