char* wchat_t*互转 及 A2T, T2A宏及其实现原理
char :单字节变量类型,表示ASCII码。
wchar_t :宽字节变量类型,用于表示Unicode字符。在<string.h>定义为:typedef unsigned short wchar_t。
TCHAR: VS下的中间类型。在“使用Unicode字符集”下TCHAR定义为wchar_t,在字符集 “未设置” 条件下TCHAR定义为char。
A2T,及T2A是两个非常有用的宏,可以用于实现char*和wchar_t*字符串之间的转换。宏的实现也将会在测试代码中给出,不感兴趣的直接跳过。费话不多说,直接上测试代码,参考代码注释。
/ demo1.cpp : 定义控制台应用程序的入口点。 // #include "stdafx.h" #include <iostream> #include <cstring> using namespace std; #include <atlbase.h> #include <Windows.h> void test_L_macro() { char astr[] = "hello"; cout<<"sizeof(astr):"<<sizeof(astr)<<endl <<"strlen(astr):"<<strlen(astr)<<endl; //L"str"表示将ANSI字符串转换成unicode的字符串,就是每个字符占用两个字节。 wchar_t wstr[] = L"hello"; //typedef unsigned short wchar_t cout<<"sizeof(wstr)"<<sizeof(wstr)<<endl <<"wcslen(wstr):"<<wcslen(wstr)<<endl; } void test_T_macro() { /* #ifdef _UNICODE #define __T(x) L ## x #else #define __T(x) x #endif #define _T(x) __T(x) #define _TEXT(x) __T(x) #define TEXT(quote) __TEXT(quote) #ifdef _UNICODE typedef char TCHAR; #else typede wchar_t TCHAR; #endif */ //如果在程序中使用了TCHAR,那么就不应该使用ANSI的strXXX函数或者Unicode的wcsXXX函数了, //而必须使用tchar.h中定义的_tcsXXX函数。 TCHAR buf[] = _T("hello"); cout<<"sizeof(buf):"<<sizeof(buf)<<endl <<"_tcslen(lpBuf):"<<_tcslen(buf)<<endl; /* #ifdef _UNICODE typedef wchar_t WCHAR;// wc, 16-bit UNICODE character typedef __nullterminated WCHAR *LPWSTR; typedef LPWSTR PTSTR, LPTSTR; #else typedef char CHAR; typedef __nullterminated CHAR *LPSTR; typedef LPSTR LPTSTR; #endif */ LPTSTR lpBuf = TEXT("hello"); cout<<"_tcslen(lpBuf):"<<_tcslen(lpBuf)<<endl; } void test_A2T() { USES_CONVERSION; char *astr = "hello"; LPTSTR wstr = A2T(astr); #ifdef _UNICODE wcout<<"wcout\<\<wstr:"<<wstr<<endl; #else cout<<"cout\<\<wstr:"<<wstr<<endl; #endif } void test_A2T_() { int _convert = 0; (_convert); UINT _acp = ATL::_AtlGetConversionACP() ; (_acp); LPCWSTR _lpw = 0; (_lpw); LPCSTR _lpa = 0; (_lpa); char *astr = "hello"; LPTSTR wstr = ( ((_lpa = astr) == 0) ? 0 : ( _convert = (lstrlenA(_lpa)+1), (2147483647/2<_convert)? 0 : AtlA2WHelper((LPWSTR) _alloca(_convert*sizeof(WCHAR)), _lpa, _convert, _acp))); //p.s. AtlA2WHelper调用了函数MultiByteToWideChar //_alloca函数用于在栈上分配内存,参考:http://msdn.microsoft.com/en-us/library/wb1s57t5.aspx wcout<<"wcout\<\<wstr:"<<wstr<<endl; } void test_T2A() { USES_CONVERSION; LPTSTR wstr = _T("hello"); char *astr = T2A(wstr); cout<<"cout\<\<astr:"<<astr<<endl; } void test_T2A_() { int _convert = 0; (_convert); UINT _acp = ATL::_AtlGetConversionACP() ; (_acp); LPCWSTR _lpw = 0; (_lpw); LPCSTR _lpa = 0; (_lpa); LPTSTR wstr = L"hello"; char *astr = ( ((_lpw = wstr) == 0) ? 0 : ( (_convert = (lstrlenW(_lpw)+1), (_convert>2147483647/2) ? 0 : AtlW2AHelper((LPSTR) _alloca(_convert*sizeof(WCHAR)), _lpw, _convert*sizeof(WCHAR), _acp)))); //p.s. AtlW2AHelper调用了函数WideCharToMultiByte //_alloca函数用于在栈上分配内存,参考:http://msdn.microsoft.com/en-us/library/wb1s57t5.aspx cout<<"cout\<\<astr:"<<astr<<endl; } int main() { test_L_macro(); test_T_macro(); test_A2T(); test_A2T_(); test_T2A(); test_T2A_(); }
P.S.
test_A2T_ 是 test_A2T的宏替换实现;test_T2A_ 是 test_T2A的宏替换实现;