文件倒序示例应用程序关键代码（使用内存映射文件）——摘自Windows 核心编程

BOOL FileReverse(PCTSTR pszPathname, PBOOL pfIsTextUnicode) {

*pfIsTextUnicode = FALSE; // Assume text is Unicode

// Open the file for reading and writing.
HANDLE hFile = CreateFile(pszPathname, GENERIC_WRITE | GENERIC_READ, 0,
NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

if (hFile == INVALID_HANDLE_VALUE) {
chMB("File could not be opened.");
return(FALSE);
}

// Get the size of the file (I assume the whole file can be mapped).
DWORD dwFileSize = GetFileSize(hFile, NULL);

// Create the file-mapping object. The file-mapping object is 1 character
// bigger than the file size so that a zero character can be placed at the
// end of the file to terminate the string (file). Because I don't yet know
// if the file contains ANSI or Unicode characters, I assume worst case
// and add the size of a WCHAR instead of CHAR.
HANDLE hFileMap = CreateFileMapping(hFile, NULL, PAGE_READWRITE,
0, dwFileSize + sizeof(WCHAR), NULL);

if (hFileMap == NULL) {
chMB("File map could not be opened.");
CloseHandle(hFile);
return(FALSE);
}

// Get the address where the first byte of the file is mapped into memory.
PVOID pvFile = MapViewOfFile(hFileMap, FILE_MAP_WRITE, 0, 0, 0);

if (pvFile == NULL) {
chMB("Could not map view of file.");
CloseHandle(hFileMap);
CloseHandle(hFile);
return(FALSE);
}

// Does the buffer contain ANSI or Unicode?
int iUnicodeTestFlags = -1; // Try all tests
*pfIsTextUnicode = IsTextUnicode(pvFile, dwFileSize, &iUnicodeTestFlags);

if (!*pfIsTextUnicode) {
// For all the file manipulations below, we explicitly use ANSI
// functions because we are processing an ANSI file.

// Put a zero character at the very end of the file.
PSTR pchANSI = (PSTR) pvFile;
pchANSI[dwFileSize / sizeof(CHAR)] = 0;

// Reverse the contents of the file.
_strrev(pchANSI);

// Convert all "/n/r" combinations back to "/r/n" to
// preserve the normal end-of-line sequence.
pchANSI = strchr(pchANSI, '/n'); // Find first '/n'.

while (pchANSI != NULL) {
// We have found an occurrence....
*pchANSI++ = '/r'; // Change '/n' to '/r'.
*pchANSI++ = '/n'; // Change '/r' to '/n'.
pchANSI = strchr(pchANSI, '/n'); // Find the next occurrence.
}

} else {
// For all the file manipulations below, we explicitly use Unicode
// functions because we are processing a Unicode file.

// Put a zero character at the very end of the file.
PWSTR pchUnicode = (PWSTR) pvFile;
pchUnicode[dwFileSize / sizeof(WCHAR)] = 0;

if ((iUnicodeTestFlags & IS_TEXT_UNICODE_SIGNATURE) != 0) {
// If the first character is the Unicode BOM (byte-order-mark),
// 0xFEFF, keep this character at the beginning of the file.
pchUnicode++;
}

// Reverse the contents of the file.
_wcsrev(pchUnicode);

// Convert all "/n/r" combinations back to "/r/n" to
// preserve the normal end-of-line sequence.
pchUnicode = wcschr(pchUnicode, L'/n'); // Find first '/n'.

while (pchUnicode != NULL) {
// We have found an occurrence....
*pchUnicode++ = L'/r'; // Change '/n' to '/r'.
*pchUnicode++ = L'/n'; // Change '/r' to '/n'.
pchUnicode = wcschr(pchUnicode, L'/n'); // Find the next occurrence.
}
}

// Clean up everything before exiting.
UnmapViewOfFile(pvFile);
CloseHandle(hFileMap);

// Remove trailing zero character added earlier.
SetFilePointer(hFile, dwFileSize, NULL, FILE_BEGIN);
SetEndOfFile(hFile);
CloseHandle(hFile);

return(TRUE);
}