contrib/groff-1.19/src/libs/libgroff/tmpname.cpp

   1 /* Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
   2      Written by Werner Lemberg (wl@gnu.org)
   3
   4 This file is part of groff.
   5
   6 groff is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 2, or (at your option) any later
   9 version.
  10
  11 groff is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License along
  17 with groff; see the file COPYING.  If not, write to the Free Software
  18 Foundation, 51 Franklin St - Fifth Floor, Boston, MA 02110-1301, USA. */
  19
  20
  21 /* This file is heavily based on the function __gen_tempname() in the
  22    file tempname.c which is part of the fileutils package. */
  23
  24
  25 #include "lib.h"
  26
  27 #include <stddef.h>
  28 #include <stdlib.h>
  29 #include <errno.h>
  30 #include <time.h>
  31
  32 #include "posix.h"
  33 #include "nonposix.h"
  34
  35 #ifndef TMP_MAX
  36 # define TMP_MAX 238328
  37 #endif
  38
  39 #if HAVE_SYS_TIME_H
  40 # include <sys/time.h>
  41 #endif
  42
  43 #ifdef HAVE_GETTIMEOFDAY
  44 #ifdef NEED_DECLARATION_GETTIMEOFDAY
  45 extern "C" {
  46   int gettimeofday(struct timeval *, void *);
  47 }
  48 #endif
  49 #endif
  50
  51 #if HAVE_CC_INTTYPES_H
  52 # include <inttypes.h>
  53 #endif
  54
  55 /* Use the widest available unsigned type if uint64_t is not
  56    available.  The algorithm below extracts a number less than 62**6
  57    (approximately 2**35.725) from uint64_t, so ancient hosts where
  58    uintmax_t is only 32 bits lose about 3.725 bits of randomness,
  59    which is better than not having mkstemp at all.  */
  60 #if !defined UINT64_MAX && !defined uint64_t
  61 # define uint64_t uintmax_t
  62 #endif
  63
  64 /* These are the characters used in temporary filenames.  */
  65 static const char letters[] =
  66 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  67
  68 int gen_tempname(char *tmpl, int dir)
  69 {
  70   static uint64_t value;
  71
  72   size_t len = strlen(tmpl);
  73   if (len < 6 || strcmp(&tmpl[len - 6], "XXXXXX"))
  74     return -1; /* EINVAL */
  75
  76   /* This is where the Xs start.  */
  77   char *XXXXXX = &tmpl[len - 6];
  78
  79   /* Get some more or less random data.  */
  80 #if HAVE_GETTIMEOFDAY
  81   timeval tv;
  82   gettimeofday(&tv, NULL);
  83   uint64_t random_time_bits = ((uint64_t)tv.tv_usec << 16) ^ tv.tv_sec;
  84 #else
  85   uint64_t random_time_bits = time(NULL);
  86 #endif
  87   value += random_time_bits ^ getpid();
  88
  89   for (int count = 0; count < TMP_MAX; value += 7777, ++count) {
  90     uint64_t v = value;
  91
  92     /* Fill in the random bits.  */
  93     XXXXXX[0] = letters[v % 62];
  94     v /= 62;
  95     XXXXXX[1] = letters[v % 62];
  96     v /= 62;
  97     XXXXXX[2] = letters[v % 62];
  98     v /= 62;
  99     XXXXXX[3] = letters[v % 62];
 100     v /= 62;
 101     XXXXXX[4] = letters[v % 62];
 102     v /= 62;
 103     XXXXXX[5] = letters[v % 62];
 104
 105     int fd = dir ? mkdir(tmpl, S_IRUSR | S_IWUSR | S_IXUSR)
 106                  : open(tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 107
 108     if (fd >= 0)
 109       return fd;
 110     else if (errno != EEXIST)
 111       return -1;
 112   }
 113
 114   /* We got out of the loop because we ran out of combinations to try.  */
 115   return -1; /* EEXIST */
 116 }