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

  1/* Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
  2     Written by Werner Lemberg (wl@gnu.org)
  3
  4This file is part of groff.
  5
  6groff is free software; you can redistribute it and/or modify it under
  7the terms of the GNU General Public License as published by the Free
  8Software Foundation; either version 2, or (at your option) any later
  9version.
 10
 11groff is distributed in the hope that it will be useful, but WITHOUT ANY
 12WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 14for more details.
 15
 16You should have received a copy of the GNU General Public License along
 17with groff; see the file COPYING.  If not, write to the Free Software
 18Foundation, 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
 45extern "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.  */
 65static const char letters[] =
 66"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 67
 68int 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}