Qt QString, wchar_t *, TCHAR, CString和其他字符或字符串类型的转化

//QString to wchar_t *:
const wchar_t * encodedName = reinterpret_cast<const wchar_t *>(fileName.utf16());

//QString to char * given a file name:
QByteArray fileName = QFile::encodeName(aFileName);
const char * encodedName = fileName.constData(); //Valid as long as fileName exists

//QString to char * (general case):
const char * tmp = str.toUtf8().constData();
[/code]
Windows 数据类型: http://msdn.microsoft.com/en-us/library/aa383751.aspx
[code lang="cpp"]
//TCHAR:
#ifdef UNICODE
typedef wchar_t TCHAR;
#else
typedef char TCHAR;
#endif

//LPCTSTR:
#ifdef UNICODE
typedef LPCWSTR LPCTSTR;
#else
typedef LPCSTR LPCTSTR;
#endif

//LPCSTR:
typedef const char * LPCSTR;

//LPCWSTR:
typedef const wchar_t * LPCWSTR;

//LPCWSTR to QString:
QString text(QString::fromUtf16(reinterpret_cast<const unsigned short *>(tmp)));
另一种解决办法是使用QString::fromWCharArray()，但这个函数可能导致一些尚未解决的wchar_t符号问题。

最佳的编程风格： 使用L来定义wchar_t宽字符串，比如 L"text" 字义了一个UNICODE字符串"text"。

今天又看到一个文章，关于字符串之间的转换，比较全面，在此将英文翻译并整理一下。
原文地址：http://hi.baidu.com/koko200147/blog/item/7e3cad828c9b9bb66d8119cb.html

QString与其他字符类型之间的转换，QString在Qt4中是UNICODE编码的，使用utf16规范。

QString::fromAscii ( const char * str, int size = -1 );
QString::fromLatin1 ( const char * str, int size = -1 );
QString::fromLocal8Bit ( const char * str, int size = -1 );
QString::fromRawData ( const QChar * unicode, int size );
QString::fromStdString ( const std::string & str );
QString::fromStdWString ( const std::wstring & str );
QString::fromUcs4 ( const uint * unicode, int size = -1 );
QString::fromUtf8 ( const char * str, int size = -1 );
QString::fromUtf16 ( const ushort * unicode, int size = -1 );
QString::fromWCharArray ( const wchar_t * string, int size = -1 );

//qstring ->std::string
QString::toStdString () ;
QString::toStdWString ();

//BSTR<->QString，不太了解BSTR是什么，还没用到过，所以不知道对不对
BSTR bstr_str;
QString q_str((QChar*)bstr_str, wcslen(bstr_str));
bstr_str = SysAllocString(q_str.utf16());//remember use SysFreeString on BSTR

//QString<->LPCSTR
QString::toLocal8Bit().constData();
QString::fromLocal8Bit ( const char * str, int size = -1 );

//QString<->LPCWSTR
QString::utf16();
QString::fromUtf16 ( const ushort * unicode, int size = -1 );

//QString<->CString
CString c_str(qstring::utf16());
QString fromUtf16 (LPCTSTR(c_str) );
CString转换为char*

//1.传给未分配内存的const char* （LPCTSTR）指针.
CString cstr(asdd);
const char* ch = (LPCTSTR)cstr;//ch指向的地址和cstr相同。但由于使用const保证ch不会修改，所以安全.

//2.传给未分配内存的指针.
CString cstr = "ASDDSD";
char *ch = cstr.GetBuffer(cstr1.GetLength() + 1);
cstr.ReleaseBuffer();
//修改ch指向的值等于修改cstr里面的值.
//PS:用完ch后,不用delete ch,因为这样会破坏cstr内部空间,容易造成程序崩溃.

//3.第二种用法。把CString 值赋给已分配内存的char *。
CString cstr1 = "ASDDSD";
int strLength = cstr1.GetLength() + 1;
char *pValue = new char[strLength];
strncpy(pValue, cstr1, strLength);

//4.第三种用法.把CString 值赋给已分配内存char[]数组.
CString cstr2 = "ASDDSD";
int strLength1 = cstr1.GetLength() + 1;
char chArray[100];
memset(chArray,0, sizeof(bool) * 100); //将数组的垃圾内容清空.
strncpy(chArray, cstr1, strLength1);

//5.如果上述都不行，使用以下方法
CString origCString("Hello, World!");
wchar_t* wCharString = origCString.GetBuffer(origCString.GetLength()+1);
size_t origsize = wcslen(wCharString) + 1;
size_t convertedChars = 0;
char *CharString;
CharString=new char(origsize);
wcstombs_s(&convertedChars, CharString, origsize, wCharString , _TRUNCATE);
cout << CharString << endl; //成功输出字符串"Hello,World"
从UTF8编码到GB编码的字符串转换方法：

QString Utf8_To_GB(QString strText)
{
    return QString::fromUtf8(strText.toLocal8Bit().data());
}
从GB编码到UTF8编码的字符串转换方法：

QString GB_To_Utf8(char *strText)
{
    return QString::fromLocal8Bit(strText);
}