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Justine Tunney 2020-06-15 07:18:57 -07:00
commit c91b3c5006
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libc/rand/devrand.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/bits/bits.h"
#include "libc/dce.h"
#include "libc/rand/rand.h"
#include "libc/str/str.h"
#include "libc/calls/internal.h"
#include "libc/calls/calls.h"
#include "libc/sysv/errfuns.h"
#include "libc/sysv/consts/at.h"
#include "libc/sysv/consts/nr.h"
#include "libc/sysv/consts/o.h"
/**
* Reads random bytes from system pseudo random number api.
* @return 0 on success or -1 w/ errno
*/
int devrand(void *buf, size_t size) {
int fd;
size_t got;
ssize_t rc;
unsigned char *p, *pe;
fd = -1;
if (IsWindows()) return enosys();
if ((fd = openat$sysv(AT_FDCWD, "/dev/urandom", O_RDONLY, 0)) == -1) {
return -1;
}
p = buf;
pe = p + size;
while (p < pe) {
if ((rc = read$sysv(fd, p, pe - p)) == -1) break;
if (!(got = (size_t)rc)) break;
p += got;
}
close$sysv(fd);
return p == pe ? 0 : -1;
}