gnu/dist/groff/src/libs/libgroff/tmpname.cpp

   1 /*      $NetBSD$        */
   2
   3 /* Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
   4      Written by Werner Lemberg (wl@gnu.org)
   5
   6 This file is part of groff.
   7
   8 groff is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 2, or (at your option) any later
  11 version.
  12
  13 groff is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License along
  19 with groff; see the file COPYING.  If not, write to the Free Software
  20 Foundation, 51 Franklin St - Fifth Floor, Boston, MA 02110-1301, USA. */
  21
  22
  23 /* This file is heavily based on the function __gen_tempname() in the
  24    file tempname.c which is part of the fileutils package. */
  25
  26
  27 #include "lib.h"
  28
  29 #include <stddef.h>
  30 #include <stdlib.h>
  31 #include <errno.h>
  32 #include <time.h>
  33
  34 #include "posix.h"
  35 #include "nonposix.h"
  36
  37 #ifndef TMP_MAX
  38 # define TMP_MAX 238328
  39 #endif
  40
  41 #if HAVE_SYS_TIME_H
  42 # include <sys/time.h>
  43 #endif
  44
  45 #ifdef HAVE_GETTIMEOFDAY
  46 #ifdef NEED_DECLARATION_GETTIMEOFDAY
  47 extern "C" {
  48   int gettimeofday(struct timeval *, void *);
  49 }
  50 #endif
  51 #endif
  52
  53 #if HAVE_CC_INTTYPES_H
  54 # include <inttypes.h>
  55 #endif
  56
  57 /* Use the widest available unsigned type if uint64_t is not
  58    available.  The algorithm below extracts a number less than 62**6
  59    (approximately 2**35.725) from uint64_t, so ancient hosts where
  60    uintmax_t is only 32 bits lose about 3.725 bits of randomness,
  61    which is better than not having mkstemp at all.  */
  62 #if !defined UINT64_MAX && !defined uint64_t
  63 # define uint64_t uintmax_t
  64 #endif
  65
  66 /* These are the characters used in temporary filenames.  */
  67 static const char letters[] =
  68 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  69
  70 int gen_tempname(char *tmpl, int dir)
  71 {
  72   static uint64_t value;
  73
  74   size_t len = strlen(tmpl);
  75   if (len < 6 || strcmp(&tmpl[len - 6], "XXXXXX"))
  76     return -1; /* EINVAL */
  77
  78   /* This is where the Xs start.  */
  79   char *XXXXXX = &tmpl[len - 6];
  80
  81   /* Get some more or less random data.  */
  82 #if HAVE_GETTIMEOFDAY
  83   timeval tv;
  84   gettimeofday(&tv, NULL);
  85   uint64_t random_time_bits = ((uint64_t)tv.tv_usec << 16) ^ tv.tv_sec;
  86 #else
  87   uint64_t random_time_bits = time(NULL);
  88 #endif
  89   value += random_time_bits ^ getpid();
  90
  91   for (int count = 0; count < TMP_MAX; value += 7777, ++count) {
  92     uint64_t v = value;
  93
  94     /* Fill in the random bits.  */
  95     XXXXXX[0] = letters[v % 62];
  96     v /= 62;
  97     XXXXXX[1] = letters[v % 62];
  98     v /= 62;
  99     XXXXXX[2] = letters[v % 62];
 100     v /= 62;
 101     XXXXXX[3] = letters[v % 62];
 102     v /= 62;
 103     XXXXXX[4] = letters[v % 62];
 104     v /= 62;
 105     XXXXXX[5] = letters[v % 62];
 106
 107     int fd = dir ? mkdir(tmpl, S_IRUSR | S_IWUSR | S_IXUSR)
 108                  : open(tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 109
 110     if (fd >= 0)
 111       return fd;
 112     else if (errno != EEXIST)
 113       return -1;
 114   }
 115
 116   /* We got out of the loop because we ran out of combinations to try.  */
 117   return -1; /* EEXIST */
 118 }