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/* Copyright (C) 2001-2020 Free Software Foundation, Inc.
Written by Werner Lemberg (wl@gnu.org)
This file is part of groff.
groff 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, either version 3 of the License, or
(at your option) any later version.
groff 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, see <http://www.gnu.org/licenses/>. */
/* This file is heavily based on the function __gen_tempname() in the
file tempname.c which is part of the fileutils package. */
#include "lib.h"
#include <stddef.h>
#include <stdlib.h>
#include <errno.h>
#include <time.h>
#include "posix.h"
#include "nonposix.h"
#ifndef TMP_MAX
# define TMP_MAX 238328
#endif
#if HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#ifdef HAVE_GETTIMEOFDAY
#ifdef NEED_DECLARATION_GETTIMEOFDAY
extern "C" {
int gettimeofday(struct timeval *, void *);
}
#endif
#endif
#if HAVE_CC_INTTYPES_H
# include <inttypes.h>
#endif
/* Use the widest available unsigned type if uint64_t is not
available. The algorithm below extracts a number less than 62**6
(approximately 2**35.725) from uint64_t, so ancient hosts where
uintmax_t is only 32 bits lose about 3.725 bits of randomness,
which is better than not having mkstemp at all. */
#if !defined UINT64_MAX && !defined uint64_t
# define uint64_t uintmax_t
#endif
/* These are the characters used in temporary filenames. */
static const char letters[] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
int gen_tempname(char *tmpl, int dir)
{
static uint64_t value;
size_t len = strlen(tmpl);
if (len < 6 || strcmp(&tmpl[len - 6], "XXXXXX"))
return -1; /* EINVAL */
/* This is where the Xs start. */
char *XXXXXX = &tmpl[len - 6];
/* Get some more or less random data. */
#if HAVE_GETTIMEOFDAY
timeval tv;
gettimeofday(&tv, 0);
uint64_t random_time_bits = ((uint64_t)tv.tv_usec << 16) ^ tv.tv_sec;
#else
uint64_t random_time_bits = time(0);
#endif
value += random_time_bits ^ getpid();
for (int count = 0; count < TMP_MAX; value += 7777, ++count) {
uint64_t v = value;
/* Fill in the random bits. */
XXXXXX[0] = letters[v % 62];
v /= 62;
XXXXXX[1] = letters[v % 62];
v /= 62;
XXXXXX[2] = letters[v % 62];
v /= 62;
XXXXXX[3] = letters[v % 62];
v /= 62;
XXXXXX[4] = letters[v % 62];
v /= 62;
XXXXXX[5] = letters[v % 62];
int fd = dir ? mkdir(tmpl, S_IRUSR | S_IWUSR | S_IXUSR)
: open(tmpl,
O_RDWR | O_CREAT | O_EXCL | O_BINARY,
S_IRUSR | S_IWUSR);
if (fd >= 0)
return fd;
else if (errno != EEXIST)
return -1;
}
/* We got out of the loop because we ran out of combinations to try. */
return -1; /* EEXIST */
}
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