What are TCHAR, WCHAR, LPSTR, LPWSTR, LPCTSTR (etc.)? Many C++ Windows programmers get confused over what bizarre identifiers like TCHAR,LPCTSTR are. Here, in brief, I would try to clear out the fog.
In general, a character can be 1 byte or 2 bytes. Let's say 1-byte character is ANSI, using which English characters are represented. And let's say 2-byte character is Unicode, which can represent ALL languages in the world.
VC++ support char and wchar_t as native datatypes for ANSI and Unicode characters respectively.
What if you want your C/C++ program to be Character-mode independent? Use generic characters. That means, instead of replacing: Collapse | Copy Code char cResponse; // 'Y' or 'N'char sUsername[64];// str* functions with Collapse | Copy Code wchar_t cResponse; // 'Y' or 'N'wchar_t sUsername[64];// wcs* functions
You can simply code it: Collapse | Copy Code #include<TCHAR.H> // Implicit or explicit includeTCHAR cResponse; // 'Y' or 'N'TCHAR sUsername[64];// _tcs* functions Thus, when your project is being compiled as Unicode, the TCHAR would translate to wchar_t. If it is being compiled as ANSI/MBCS, it would be translated to char. Likewise, instead of using strcpy, strlen, strcat(including the secure versions suffixed with _s); or wcscpy, wcslen, wcscat (including secure), you can simply use _tcscpy, _tcslen, _tcscat functions.
When you need to express hard-coded string, you can use: Collapse | Copy Code "ANSI String"; // ANSIL"Unicode String"; // Unicode_T("Either string, depending on compilation"); // ANSI or Unicode// or use TEXT macro, if you need more readability.
The non-prefixed string is ANSI string, the L prefixed string is Unicode, and string specified in _T or TEXTwould be either, depending on compilation.
String classes, like MFC/ATL's CString implement two versions using macro. There are two classes namedCStringA for ANSI, CStringW for Unicode. When you use CString (which is a macro/typedef), it translates to either of two classes. Okay. The TCHAR type-definition was for a single character. You can definitely declare an array of TCHAR. What if you want to express a character-pointer, or a const-character-pointer - Which one of the following? Collapse | Copy Code // ANSI charactersfoo_ansi(char*);foo_ansi(const char*);/*const*/ char* pString; // Unicode/wide-stringfoo_uni(WCHAR*); // or wchar_t*foo_uni(const WCHAR*);/*const*/ WCHAR* pString; // Independent foo_char(TCHAR*);foo_char(const TCHAR*);/*const*/ TCHAR* pString; After reading about TCHAR stuff, you'd definitely select the last one as your choice. But here is a better alternative. Before that, note that TCHAR.H header file declares only TCHAR datatype and for the following stuff, you need to include Windows.h (defined in WinNT.h).
NOTE: If your project implicitly or explicitly includes Windows.h, you need not include TCHAR.H
char* replacement: LPSTR const char* replacement: LPCSTR WCHAR* replacement: LPWSTR const WCHAR* replacement: LPCWSTR (C before W, since const is before WCHAR) TCHAR* replacement: LPTSTR const TCHAR* replacement: LPCTSTR Now, I hope you understand the following signatures : Collapse | Copy Code BOOL SetCurrentDirectory( LPCTSTR lpPathName );DWORD GetCurrentDirectory(DWORD nBufferLength,LPTSTR lpBuffer); Continuing. You must have seen some functions/methods asking you to pass number of characters, or returning the number of characters. Well, like GetCurrentDirectory, you need to pass number of characters, and not number of bytes. For example:: Collapse | Copy Code TCHAR sCurrentDir[255]; // Pass 255 and not 255*2 GetCurrentDirectory(sCurrentDir, 255); On the other side, if you need to allocate number or characters, you must allocate proper number of bytes. In C++, you can simply use new: Collapse | Copy Code LPTSTR pBuffer; // TCHAR* pBuffer = new TCHAR[128]; // Allocates 128 or 256 BYTES, depending on compilation. But if you use memory allocation functions like malloc, LocalAlloc, GlobalAlloc, etc; you must specify the number of bytes! Collapse | Copy Code pBuffer = (TCHAR*) malloc (128 * sizeof(TCHAR) ); Typecasting the return value is required, as you know. The expression in malloc's argument ensures that it allocates desired number of bytes - and makes up room for desired number of characters. 引用自： MFC技术资料大全与汇总
msdn ：Pointer to a null-terminated string of 8-bit Windows (ANSI) characters.
typedef __nullterminated CHAR *LPSTR;
typedef CONST CHAR *LPCCH, *PCCH;typedef __nullterminated CHAR *NPSTR, *LPSTR, *PSTR;
typedef __nullterminated PSTR *PZPSTR;
typedef __nullterminated CONST PSTR *PCZPSTR;
typedef __nullterminated CONST CHAR *LPCSTR, *PCSTR;
typedef __nullterminated PCSTR *PZPCSTR;
Many C++ Windows programmers get confused over what bizarre identifiers like TCHAR,LPCTSTR are. Here, in brief, I would try to clear out the fog.
In general, a character can be 1 byte or 2 bytes. Let's say 1-byte character is ANSI, using which English characters are represented. And let's say 2-byte character is Unicode, which can represent ALL languages in the world.
VC++ support char and wchar_t as native datatypes for ANSI and Unicode characters respectively.
What if you want your C/C++ program to be Character-mode independent?
Use generic characters. That means, instead of replacing:
Collapse | Copy Code
char cResponse; // 'Y' or 'N'char sUsername[64];// str* functions
with
Collapse | Copy Code
wchar_t cResponse; // 'Y' or 'N'wchar_t sUsername[64];// wcs* functions
You can simply code it:
Collapse | Copy Code
#include<TCHAR.H> // Implicit or explicit includeTCHAR cResponse; // 'Y' or 'N'TCHAR sUsername[64];// _tcs* functions
Thus, when your project is being compiled as Unicode, the TCHAR would translate to wchar_t. If it is being compiled as ANSI/MBCS, it would be translated to char. Likewise, instead of using strcpy, strlen, strcat(including the secure versions suffixed with _s); or wcscpy, wcslen, wcscat (including secure), you can simply use _tcscpy, _tcslen, _tcscat functions.
When you need to express hard-coded string, you can use:
Collapse | Copy Code
"ANSI String"; // ANSIL"Unicode String"; // Unicode_T("Either string, depending on compilation"); // ANSI or Unicode// or use TEXT macro, if you need more readability.
The non-prefixed string is ANSI string, the L prefixed string is Unicode, and string specified in _T or TEXTwould be either, depending on compilation.
String classes, like MFC/ATL's CString implement two versions using macro. There are two classes namedCStringA for ANSI, CStringW for Unicode. When you use CString (which is a macro/typedef), it translates to either of two classes.
Okay. The TCHAR type-definition was for a single character. You can definitely declare an array of TCHAR.
What if you want to express a character-pointer, or a const-character-pointer - Which one of the following?
Collapse | Copy Code
// ANSI charactersfoo_ansi(char*);foo_ansi(const char*);/*const*/ char* pString; // Unicode/wide-stringfoo_uni(WCHAR*); // or wchar_t*foo_uni(const WCHAR*);/*const*/ WCHAR* pString; // Independent foo_char(TCHAR*);foo_char(const TCHAR*);/*const*/ TCHAR* pString;
After reading about TCHAR stuff, you'd definitely select the last one as your choice. But here is a better alternative. Before that, note that TCHAR.H header file declares only TCHAR datatype and for the following stuff, you need to include Windows.h (defined in WinNT.h).
NOTE: If your project implicitly or explicitly includes Windows.h, you need not include TCHAR.H
char* replacement: LPSTR
const char* replacement: LPCSTR
WCHAR* replacement: LPWSTR
const WCHAR* replacement: LPCWSTR (C before W, since const is before WCHAR)
TCHAR* replacement: LPTSTR
const TCHAR* replacement: LPCTSTR
Now, I hope you understand the following signatures :
Collapse | Copy Code
BOOL SetCurrentDirectory( LPCTSTR lpPathName );DWORD GetCurrentDirectory(DWORD nBufferLength,LPTSTR lpBuffer);
Continuing. You must have seen some functions/methods asking you to pass number of characters, or returning the number of characters. Well, like GetCurrentDirectory, you need to pass number of characters, and not number of bytes. For example::
Collapse | Copy Code
TCHAR sCurrentDir[255]; // Pass 255 and not 255*2 GetCurrentDirectory(sCurrentDir, 255);
On the other side, if you need to allocate number or characters, you must allocate proper number of bytes. In C++, you can simply use new:
Collapse | Copy Code
LPTSTR pBuffer; // TCHAR* pBuffer = new TCHAR[128]; // Allocates 128 or 256 BYTES, depending on compilation.
But if you use memory allocation functions like malloc, LocalAlloc, GlobalAlloc, etc; you must specify the number of bytes!
Collapse | Copy Code
pBuffer = (TCHAR*) malloc (128 * sizeof(TCHAR) );
Typecasting the return value is required, as you know. The expression in malloc's argument ensures that it allocates desired number of bytes - and makes up room for desired number of characters.
引用自： MFC技术资料大全与汇总