在VC2005环境下， 以下代码无法实现使用CStdioFile向文本文件中写入中文（用notepad.exe查看不到写入的中文）
CStdioFile file;
file.Open(…);
file.WriteString(_T("abc你好"));//只能写入abc
在VC2005中的解决办法：
使用setlocale语句设定区域
#include <locale>//头文件
CStdioFile file;
file.Open(…);
char* old_locale = _strdup( setlocale(LC_CTYPE,NULL) );
setlocale( LC_CTYPE, "chs" );//设定
file.WriteString(_T("abc你好"));//正常写入
setlocale( LC_CTYPE, old_locale );
free( old_locale );//还原区域设定
简化处理可以仅使用语句setlocale( LC_CTYPE, "chs" )。
setlocale:
函数原形为：char *setlocale( int category, const char *locale );
头文件：<locale.h>
所支持的操作系统为:ANSI, Win 95, Win NT
对于简体中文可以使用如下设置：setlocale( LC_ALL, "chs" );
为什么一定要调用setlocale呢？
因为在C/C++语言标准中定义了其运行时的字符集环境为"C"，也就是ASCII字符集的一个子集，那么mbstowcs在工作时会将cstr中所包含的字符串看作是ASCII编码的字符，而不认为是一个包含有chs编码的字符串，所以他会将每一个中文拆成2个ASCII编码进行转换，这样得到的结果就是会形成4个wchar_t的字符组成的串，那么如何才能够让mbstowcs正常工作呢？在调用mbstowcs进行转换之间必须明确的告诉mbstowcs目前cstr串中包含的是chs编码的字符串，通过setlocale( LC_ALL, "chs" )函数调用来完成，需要注意的是这个函数会改变整个应用程序的字符集编码方式，必须要通过重新调用setlocale( LC_ALL, "C" )函数来还原，这样就可以保证mbstowcs在转换时将cstr中的串看作是中文串，并且转换成为2个wchar_t字符，而不是4个。
本地化设置需要具备三个条件：
a. 语言代码 (Language Code)
b. 国家代码 (Country Code)
c. 编码(Encoding)
本地名字可以用下面这些部分来构造：
语言代码_国家代码.编码 比如（zh_CN.UTF-8, en_US等）
locale的别名表见 /usr/lib/X11/locale/locale.alias(以Debian GNU/Linux为例)
setlocale语言字符串参考
另外还有一种方法就是重新写CStdioFile的派生类CStdioFileEx（网上有）。
//好像C++中没有类能够读些Unicode格式的文本文件，所以我写了下面这个类。用法很简单，大家尝试几下就明白了。
#pragma once
class CStdioFileEx: public CStdioFile
{
public:
CStdioFileEx();
CStdioFileEx( LPCTSTR lpszFileName, UINT nOpenFlags );
virtual BOOL Open( LPCTSTR lpszFileName, UINT nOpenFlags, CFileException* pError = NULL );
virtual BOOL ReadString(CString& rString);
BOOL ReadWideString(CStringW& rString);
BOOL ReadAnsiString(CStringA& rString);
virtual void WriteString(LPCTSTR lpsz);
void WriteWideString(LPCWSTR lpsz);
void WriteAnsiString(LPCSTR lpsz);
bool IsUnicodeFormat() {return m_bIsUnicodeText;}
unsigned long GetCharCount();
// Additional flag to allow Unicode text format writing
enum {modeWriteUnicode = 0x100000};
static bool IsFileUnicode(const CString& sFilePath);
protected:
UINT PreprocessFlags(const CString& sFilePath, UINT& nOpenFlags);
bool m_bIsUnicodeText;
};
//。cpp文件
#include "stdafx.h"
#include "StdioFileEx.h"
//在UCS 编码中有一个叫做"ZERO WIDTH NO-BREAK SPACE"的字符，它的编码是FEFF。而FFFE在UCS中是不存在的字符，
//所以不应该出现在实际传输中。UCS规范建议我们在传输字节流前，先传输字符"ZERO WIDTH NO-BREAK SPACE"。这样
//如果接收者收到FEFF，就表明这个字节流是Big-Endian的；如果收到FFFE，就表明这个字节流是Little-Endian的。
//因此字符"ZERO WIDTH NO-BREAK SPACE"又被称作BOM。
//UTF-8不需要BOM来表明字节顺序，但可以用BOM来表明编码方式。字符"ZERO WIDTH NO-BREAK SPACE"的UTF-8编码是
//EF BB BF。所以如果接收者收到以EF BB BF开头的字节流，就知道这是UTF-8编码了。
//Windows就是使用BOM来标记文本文件的编码方式的。
//有些老的浏览器和文本编辑器不支持BOM。
#define UNICODE_BOM 0xFEFF//Unicode "byte order mark" which goes at start of file
CStdioFileEx::CStdioFileEx(): CStdioFile()
{
m_bIsUnicodeText = false;
}
CStdioFileEx::CStdioFileEx(LPCTSTR lpszFileName,UINT nOpenFlags)
:CStdioFile(lpszFileName, PreprocessFlags(lpszFileName, nOpenFlags))
{
}
BOOL CStdioFileEx::Open(LPCTSTR lpszFileName,UINT nOpenFlags,CFileException* pError /*=NULL*/)
{
PreprocessFlags(lpszFileName, nOpenFlags);
return CStdioFile::Open(lpszFileName, nOpenFlags, pError);
}
BOOL CStdioFileEx::ReadString(CString& rString)
{
#ifdef _UNICODE
return ReadWideString(rString);
#else
return ReadAnsiString(rString);
#endif
}
BOOL CStdioFileEx::ReadWideString(CStringW& rString)
{
_ASSERTE(m_pStream);
rString = L""; // empty string without deallocating
if(m_bIsUnicodeText)
{
// If at position 0, discard byte-order mark before reading
if(GetPosition() == 0)
{
wchar_t bom;
Read(&bom, sizeof(wchar_t));
}
const int nMaxSize = 128;
LPWSTR lpsz = rString.GetBuffer(nMaxSize);
LPWSTR lpszResult;
int nLen = 0;
for (;;)
{
lpszResult = fgetws(lpsz, nMaxSize+1, m_pStream);
rString.ReleaseBuffer();
// handle error/eof case
if (lpszResult == NULL && !feof(m_pStream))
{
Afx_clearerr_s(m_pStream);
AfxThrowFileException(CFileException::genericException, _doserrno,
m_strFileName);
}
// if string is read completely or EOF
if (lpszResult == NULL ||
(nLen = (int)lstrlenW(lpsz)) < nMaxSize ||
lpsz[nLen-1] == '\n')
break;
nLen = rString.GetLength();
lpsz = rString.GetBuffer(nMaxSize + nLen) + nLen;
}
//remove crlf if exist.
nLen = rString.GetLength();
if (nLen > 1 && rString.Mid(nLen-2) == L"\r\n")
{
rString.GetBufferSetLength(nLen-2);
}
return rString.GetLength() > 0;
}
else
{
CStringA ansiString;
BOOL bRetval = ReadAnsiString(ansiString);
//setlocale(LC_ALL, "chs_chn.936");//no need
rString = ansiString;
return bRetval;
}
}
BOOL CStdioFileEx::ReadAnsiString(CStringA& rString)
{
_ASSERTE(m_pStream);
rString = ""; // empty string without deallocating
if(!m_bIsUnicodeText)
{
const int nMaxSize = 128;
LPSTR lpsz = rString.GetBuffer(nMaxSize);
LPSTR lpszResult;
int nLen = 0;
for (;;)
{
lpszResult = fgets(lpsz, nMaxSize+1, m_pStream);
rString.ReleaseBuffer();
// handle error/eof case
if (lpszResult == NULL && !feof(m_pStream))
{
Afx_clearerr_s(m_pStream);
AfxThrowFileException(CFileException::genericException, _doserrno,
m_strFileName);
}
// if string is read completely or EOF
if (lpszResult == NULL ||
(nLen = (int)lstrlenA(lpsz)) < nMaxSize ||
lpsz[nLen-1] == '\n')
break;
nLen = rString.GetLength();
lpsz = rString.GetBuffer(nMaxSize + nLen) + nLen;
}
//remove crlf if exist.
nLen = rString.GetLength();
if (nLen > 1 && rString.Mid(nLen-2) == "\r\n")
{
rString.GetBufferSetLength(nLen-2);
}
return rString.GetLength() > 0;
}
else
{
CStringW wideString;
BOOL bRetval = ReadWideString(wideString);
//setlocale(LC_ALL, "chs_chn.936");//no need
rString = wideString;
return bRetval;
}
}
// Purpose: Writes string to file either in Unicode or multibyte, depending on whether the caller specified the
// CStdioFileEx::modeWriteUnicode flag. Override of base class function.
void CStdioFileEx::WriteString(LPCTSTR lpsz)
{
#ifdef _UNICODE
WriteWideString(lpsz);
#else
WriteAnsiString(lpsz);
#endif
}
void CStdioFileEx::WriteWideString(LPCWSTR lpsz)
{
ASSERT(lpsz != NULL);
if (lpsz == NULL)
{
AfxThrowInvalidArgException();
}
if(m_bIsUnicodeText)
{
ASSERT(m_pStream != NULL);
// If writing Unicode and at the start of the file, need to write byte mark
if(GetPosition() == 0)
{
wchar_t cBOM = (wchar_t)UNICODE_BOM;
CFile::Write(&cBOM, sizeof(wchar_t));
}
if (fputws(lpsz, m_pStream) == _TEOF)
AfxThrowFileException(CFileException::diskFull, _doserrno, m_strFileName);
}
else
{
USES_CONVERSION;
WriteAnsiString(CW2A(lpsz));
}
}
void CStdioFileEx::WriteAnsiString(LPCSTR lpsz)
{
ASSERT(lpsz != NULL);
if (lpsz == NULL)
{
AfxThrowInvalidArgException();
}
if(!m_bIsUnicodeText)
{
ASSERT(m_pStream != NULL);
if (fputs(lpsz, m_pStream) == _TEOF)
AfxThrowFileException(CFileException::diskFull, _doserrno, m_strFileName);
}
else
{
USES_CONVERSION;
WriteWideString(CA2W(lpsz));
}
}
UINT CStdioFileEx::PreprocessFlags(const CString& sFilePath, UINT& nOpenFlags)
{
m_bIsUnicodeText = false;
// If we have writeUnicode we must have write or writeRead as well
if (nOpenFlags & CStdioFileEx::modeWriteUnicode)
{
ASSERT(nOpenFlags & CFile::modeWrite || nOpenFlags & CFile::modeReadWrite);
m_bIsUnicodeText = true;
}
// If reading in text mode and not creating...
else if (nOpenFlags & CFile::typeText && !(nOpenFlags & CFile::modeCreate) && !(nOpenFlags & CFile::modeWrite ))
{
m_bIsUnicodeText = IsFileUnicode(sFilePath);
}
//如果要读写Unicode格式的文本文件, 必须切换到typeBinary方式, 因为这会影响fputws/fgetws的工作方式(具体情况参考MSDN)。
if (m_bIsUnicodeText)
{
nOpenFlags &= ~(CFile::typeText);
nOpenFlags |= CFile::typeBinary;
}
return nOpenFlags;
}
// Purpose: Determines whether a file is Unicode by reading the first character and detecting
// whether it's the Unicode byte marker.
bool CStdioFileEx::IsFileUnicode(const CString& sFilePath)
{
CFile file;
wchar_t cFirstChar;
CFileException exFile;
bool bIsUnicode = false;
// Open file in binary mode and read first character
if (file.Open(sFilePath, CFile::typeBinary | CFile::modeRead, &exFile))
{
// If byte is Unicode byte-order marker, let's say it's Unicode
if (file.Read(&cFirstChar, sizeof(wchar_t)) > 0 && cFirstChar == (wchar_t)UNICODE_BOM)
{
bIsUnicode = true;
}
file.Close();
}
else
{
// Handle error here if you like
}
return bIsUnicode;
}
unsigned long CStdioFileEx::GetCharCount()
{
int nCharSize;
unsigned long nByteCount, nCharCount = 0;
if (m_pStream)
{
// Get size of chars in file
nCharSize = m_bIsUnicodeText ? sizeof(wchar_t): sizeof(char);
// If Unicode, remove byte order mark from count
nByteCount = (unsigned long)GetLength();
if (m_bIsUnicodeText)
{
nByteCount = nByteCount - sizeof(wchar_t);
}
// Calc chars
nCharCount = (nByteCount / nCharSize);
}
return nCharCount;
}