win32的mkstemp()实现

Question

谁能给我指出在Win32上实现mkstemp() (C/C++)的代码，或者非常相似的代码。

必须是无种族的。

它应该看起来像是

#include <windows.h>
#include <io.h>

// port of mkstemp() to win32. race-free.
// behaviour as described in http://linux.die.net/man/3/mkstemp
// 
int mkstemp(char *template) {
     ...
}

谢谢

Answer 1

您可以使用从wcecompat库(从文件src/stdlib_extras.cpp)中提取的以下函数

/* mkstemp extracted from libc/sysdeps/posix/tempname.c.  Copyright
   (C) 1991-1999, 2000, 2001, 2006 Free Software Foundation, Inc.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.  */

static const char letters[] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

/* Generate a temporary file name based on TMPL.  TMPL must match the
   rules for mk[s]temp (i.e. end in "XXXXXX").  The name constructed
   does not exist at the time of the call to mkstemp.  TMPL is
   overwritten with the result.  */
int
mkstemp (char *tmpl)
{
  int len;
  char *XXXXXX;
  static unsigned long long value;
  unsigned long long random_time_bits;
  unsigned int count;
  int fd = -1;
  int save_errno = errno;

  /* A lower bound on the number of temporary files to attempt to
     generate.  The maximum total number of temporary file names that
     can exist for a given template is 62**6.  It should never be
     necessary to try all these combinations.  Instead if a reasonable
     number of names is tried (we define reasonable as 62**3) fail to
     give the system administrator the chance to remove the problems.  */
#define ATTEMPTS_MIN (62 * 62 * 62)

  /* The number of times to attempt to generate a temporary file.  To
     conform to POSIX, this must be no smaller than TMP_MAX.  */
#if ATTEMPTS_MIN < TMP_MAX
  unsigned int attempts = TMP_MAX;
#else
  unsigned int attempts = ATTEMPTS_MIN;
#endif

  len = strlen (tmpl);
  if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
    {
      errno = EINVAL;
      return -1;
    }

/* This is where the Xs start.  */
  XXXXXX = &tmpl[len - 6];

  /* Get some more or less random data.  */
  {
    SYSTEMTIME      stNow;
    FILETIME ftNow;

    // get system time
    GetSystemTime(&stNow);
    stNow.wMilliseconds = 500;
    if (!SystemTimeToFileTime(&stNow, &ftNow))
    {
        errno = -1;
        return -1;
    }

    random_time_bits = (((unsigned long long)ftNow.dwHighDateTime << 32)
                        | (unsigned long long)ftNow.dwLowDateTime);
  }
  value += random_time_bits ^ (unsigned long long)GetCurrentThreadId ();

  for (count = 0; count < attempts; value += 7777, ++count)
    {
      unsigned long long 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];

      fd = open (tmpl, O_RDWR | O_CREAT | O_EXCL, _S_IREAD | _S_IWRITE);
      if (fd >= 0)
    {
      errno = save_errno;
      return fd;
    }
      else if (errno != EEXIST)
    return -1;
    }

  /* We got out of the loop because we ran out of combinations to try.  */
  errno = EEXIST;
  return -1;
}

它将O_EXCL定义为；

#define _O_EXCL         0x0400
#define O_EXCL          _O_EXCL

您可以很容易地取消对mkstemp的支持。

Answer 2

实际上，使用_mktemp_s()是一个非常糟糕的想法--在任何一个上下文中只有26个可能的文件名候选者，而且，由于要攻击的范围有限，它暴露了mkstemp()旨在克服的竞争条件。然而，另一种建议的解决方案虽然好得多，但也有缺陷，因为它在选择替代文件名字符时具有62个自由度，而Windows文件系统的不区分大小写消耗了其中的26个，因此只剩下36个；这具有加权选择任何逻辑上可区分的字母字符的概率的两倍于数字的效果。

考虑到这一点，我在这里发布了一个MinGW补丁：https://sourceforge.net/p/mingw/bugs/2003/

如果采用，这将正式将mkstemp()和mkdtemp()添加到标准MinGW发行版中。

Answer 3

你可以使用_mktemp_s()函数，或者它的任何变体：

errno_t _mktemp_s(
   char *template,
   size_t sizeInChars
);

其中：

• 模板:文件名_mktemp_s中缓冲区的大小(以单字节字符为单位)；_wmktemp_s中的宽字符(包括空终止符)。

成功时返回0，失败时返回错误代码。请注意，该函数修改了template参数。