src/lib-roff/tmpname.cpp

   1 /*@ FIXME Consider to use our own temporary file name creation!
   2  * Copyright (c) 2014 - 2017 Steffen (Daode) Nurpmeso <steffen@sdaoden.eu>.
   3  *
   4  * Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
   5  *      Written by Werner Lemberg (wl@gnu.org)
   6  *
   7  * This is free software; you can redistribute it and/or modify it under
   8  * the terms of the GNU General Public License as published by the Free
   9  * Software Foundation; either version 2, or (at your option) any later
  10  * version.
  11  *
  12  * This is distributed in the hope that it will be useful, but WITHOUT ANY
  13  * WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15  * for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with groff; see the file COPYING.  If not, write to the Free Software
  19  * Foundation, 51 Franklin St - Fifth Floor, Boston, MA 02110-1301, USA.
  20  */
  21
  22 /* This file is heavily based on the function __gen_tempname() in the
  23    file tempname.c which is part of the fileutils package. */
  24
  25 #include "config.h"
  26 #include "lib.h"
  27
  28 #include <errno.h>
  29 #include <inttypes.h>
  30 #include <stddef.h>
  31 #include <stdlib.h>
  32 #include <time.h>
  33
  34 #if HAVE_SYS_TIME_H
  35 # include <sys/time.h>
  36 #endif
  37
  38 #include "nonposix.h"
  39 #include "posix.h"
  40
  41 #ifndef TMP_MAX
  42 # define TMP_MAX 238328 /* FIXME lib.h! */
  43 #endif
  44
  45 /* Use the widest available unsigned type if uint64_t is not
  46    available.  The algorithm below extracts a number less than 62**6
  47    (approximately 2**35.725) from uint64_t, so ancient hosts where
  48    uintmax_t is only 32 bits lose about 3.725 bits of randomness,
  49    which is better than not having mkstemp at all.  */
  50 #if !defined UINT64_MAX && !defined uint64_t /* FIXME -> lib.h!! */
  51 # define uint64_t uintmax_t
  52 #endif
  53
  54 /* These are the characters used in temporary filenames.  */
  55 static const char letters[] =
  56 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  57
  58 int gen_tempname(char *tmpl, int dir)
  59 {
  60   static uint64_t value;
  61
  62   size_t len = strlen(tmpl);
  63   if (len < 6 || strcmp(&tmpl[len - 6], "XXXXXX"))
  64     return -1; /* EINVAL */
  65
  66   /* This is where the Xs start.  */
  67   char *XXXXXX = &tmpl[len - 6];
  68
  69   /* Get some more or less random data.  */
  70 #if HAVE_GETTIMEOFDAY
  71   timeval tv;
  72   gettimeofday(&tv, NULL);
  73   uint64_t random_time_bits = ((uint64_t)tv.tv_usec << 16) ^ tv.tv_sec;
  74 #else
  75   uint64_t random_time_bits = time(NULL);
  76 #endif
  77   value += random_time_bits ^ getpid();
  78
  79   for (int count = 0; count < TMP_MAX; value += 7777, ++count) {
  80     uint64_t v = value;
  81
  82     /* Fill in the random bits.  */
  83     XXXXXX[0] = letters[v % 62];
  84     v /= 62;
  85     XXXXXX[1] = letters[v % 62];
  86     v /= 62;
  87     XXXXXX[2] = letters[v % 62];
  88     v /= 62;
  89     XXXXXX[3] = letters[v % 62];
  90     v /= 62;
  91     XXXXXX[4] = letters[v % 62];
  92     v /= 62;
  93     XXXXXX[5] = letters[v % 62];
  94
  95     int fd = dir ? mkdir(tmpl, S_IRUSR | S_IWUSR | S_IXUSR)
  96                  : open(tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
  97
  98     if (fd >= 0)
  99       return fd;
 100     else if (errno != EEXIST)
 101       return -1;
 102   }
 103
 104   /* We got out of the loop because we ran out of combinations to try.  */
 105   return -1; /* EEXIST */
 106 }
 107
 108 // s-it2-mode