blocks|key|4368513|text|要在UNIX上执行此操作，请查找(RequiredFileSize+-+1)，然后写入一个字节。字节的值可以是任何值，但最明显的选择是零。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4368514|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

To do this on UNIX, seek to (RequiredFileSize - 1) and then write a byte. The value of the byte can be anything, but zero is the obvious choice.

blocks|key|4368478|text|像往常一样CreateFile，SetFilePointerEx到所需的大小，然后调用SetEndOfFile。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4368479|entityMap^0|5|A|G|G|17|C|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

You <code>CreateFile</code> as usual, <code>SetFilePointerEx</code> to the desired size and then call <code>SetEndOfFile</code>.

blocks|key|4368496|text|你不需要一个文件，你可以使用页面文件作为你的内存映射文件的备份，从MSDN+CreateFileMapping函数页面：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4368497|4368498|如果hFile为INVALID_HANDLE_VALUE，则调用进程还必须在dwMaximumSizeHigh和dwMaximumSizeLow参数中指定文件映射对象的大小。在这种情况下，CreateFileMapping创建一个指定大小的文件映射对象，该对象由系统分页文件支持，而不是由文件系统中的文件支持。|blockquote|4368499|4368500|4368501|您仍然可以使用DuplicateHandle共享映射对象。|4368502|entityMap^0|12|H|0|0|0|0|0|7|F|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|S|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|T|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|U|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|V|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|N|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|O|$]]

You don't need a file, you can use the pagefile as the backing for your memory mapped file, from the MSDN <code>CreateFileMapping</code> function page:

<blockquote>
 If hFile is INVALID_HANDLE_VALUE, the calling process must also specify a size for the file mapping object in the dwMaximumSizeHigh and dwMaximumSizeLow parameters. In this scenario, CreateFileMapping creates a file mapping object of a specified size that is backed by the system paging file instead of by a file in the file system.
</blockquote>

You can still share the mapping object by use of <code>DuplicateHandle</code>.

blocks|key|1702349|text|根据您的评论，您实际上需要跨平台的解决方案，所以请检查Boost+Interprocess库。它提供了跨平台的共享内存等功能|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1702350|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/doc/libs/1_38_0/doc/html/interprocess.html^0|R|I|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

according to your comments, you actually need cross-platform solution, so check <a href="http://www.boost.org/doc/libs/1_38_0/doc/html/interprocess.html" rel="nofollow">Boost Interprocess</a> library. it provides cross-platform shared memory facilities and more

blocks|key|1698820|text|要在Linux上执行此操作，可以执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1698821|/**
+*++Clear+the+umask+permissions+so+we+
+*++have+full+control+of+the+file+creation+(see+man+umask+on+Linux)
+*/
mode_t+origMask+=+umask(0);

int+fd+=+open("/tmp/file_name",
++++++O_RDWR,+00666);

umask(origMask);
if+(fd+<+0)
{
++perror("open+fd+failed");
++return;
}


if+(ftruncate(fd,+size)+==+0)
{
+++int+result+=+lseek(data->shmmStatsDataFd,+size+-+1,+SEEK_SET);
+++if+(result+==+-1)
+++{
+++++perror("lseek+fd+failed");
+++++close(fd);
+++++return+;
+++}

+++/*+Something+needs+to+be+written+at+the+end+of+the+file+to
++++*+have+the+file+actually+have+the+new+size.
++++*+Just+writing+an+empty+string+at+the+current+file+position+will+do.
++++*newDataSize
++++*+Note:
++++*++-+The+current+position+in+the+file+is+at+the+end+of+the+stretched
++++*++++file+due+to+the+call+to+lseek().
++++*++-+An+empty+string+is+actually+a+single+'\0'+character,+so+a+zero-byte
++++*++++will+be+written+at+the+last+byte+of+the+file.
++++*/
+++result+=+data->write(fd,+"",+1);
+++if+(result+!=+1)
+++{
+++++perror("write+fd+failed");
+++++close(fd);

+++++return;
+++}
}|code-block|syntax|javascript|1698822|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

to do this on Linux, you can do the following: 

<pre><code>/**
 * Clear the umask permissions so we 
 * have full control of the file creation (see man umask on Linux)
 */
mode_t origMask = umask(0);

int fd = open("/tmp/file_name",
 O_RDWR, 00666);

umask(origMask);
if (fd &lt; 0)
{
 perror("open fd failed");
 return;
}


if (ftruncate(fd, size) == 0)
{
 int result = lseek(data-&gt;shmmStatsDataFd, size - 1, SEEK_SET);
 if (result == -1)
 {
 perror("lseek fd failed");
 close(fd);
 return ;
 }

 /* Something needs to be written at the end of the file to
 * have the file actually have the new size.
 * Just writing an empty string at the current file position will do.
 *newDataSize
 * Note:
 * - The current position in the file is at the end of the stretched
 * file due to the call to lseek().
 * - An empty string is actually a single '\0' character, so a zero-byte
 * will be written at the last byte of the file.
 */
 result = data-&gt;write(fd, "", 1);
 if (result != 1)
 {
 perror("write fd failed");
 close(fd);

 return;
 }
}
</code></pre>

I would like to create a file of arbitrary size using the Windows C/C++ API. I am using Windows XP service pack 2 with a 32 bit virtual address memory space. I am familiar with CreateFile. 

However CreateFile does not have a size arument, The reason I want to pass in a size argument is to allow me to create memory mapping files which allow the user to access data structures of predetermined size. Could you please advise of the proper Windows C/C++ API function which allow me to create a file of arbritrary predetermined size? Thank you

Creating a file of arbitrary size using Windows C++ API

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想使用Windows C/C++ API创建一个任意大小的文件。我正在使用具有32位虚拟地址内存空间的Windows XP service pack 2。我对CreateFile很熟悉。然而，CreateFile没有大小参数，我想要传递一个大小参数的原因是允许我创建允许用户访问预定大小的数据结构的内存映射文件。你能告诉我合适的Windows C/C++ API函数，它允许我创建一个任意预定大小的

问使用Windows C++ API创建任意大小的文件
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回答 5

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