How can I convert a string from wchar_t to LPSTR.
A wchar_t string is made of 16-bit units, a LPSTR is a pointer to a string of octets, defined like this:
typedef char* PSTR, *LPSTR;
What's important is that the LPSTR may be null-terminated.
When translating from wchar_t to LPSTR, you have to decide on an encoding to use. Once you did that, you can use the WideCharToMultiByte function to perform the conversion.
For instance, here's how to translate a wide-character string into UTF8, using STL strings to simplify memory management:
#include <windows.h>
#include <string>
#include <vector>
static string utf16ToUTF8( const wstring &s )
{
const int size = ::WideCharToMultiByte( CP_UTF8, 0, s.c_str(), -1, NULL, 0, 0, NULL );
vector<char> buf( size );
::WideCharToMultiByte( CP_UTF8, 0, s.c_str(), -1, &buf[0], size, 0, NULL );
return string( &buf[0] );
}
You could use this function to translate a wchar_t* to LPSTR like this:
const wchar_t *str = L"Hello, World!";
std::string utf8String = utf16ToUTF8( str );
LPSTR lpStr = utf8String.c_str();
I use this
wstring mywstr( somewstring );
string mycstr( mywstr.begin(), mywstr.end() );
then use it as mycstr.c_str()
(edit, since i cannot comment) this is how i used this, and it works fine:
#include <string>
std::wstring mywstr(ffd.cFileName);
std::string mycstr(mywstr.begin(), mywstr.end());
pRequest->Write(mycstr.c_str());
Related
I'm trying to use MultiByteToWideChar api. for lpWideCharStr, when I use a pointer with dynamic memory allocation, it works properly. but now I should use a pointer with static memory allocation as you see in the code. and it doesn't work properly, return 0.
what's wrong with it?
how should I use a static memory allocated pointer for lpWideCharStr in MultiByteToWideChar?
thank's for your solutions.
#include <windows.h>
#include <iostream>
#include "Shlwapi.h"
#pragma comment(lib,"shlwapi.lib")
void main(int argc, char *argv[]){
int iToSizeB = 0;
iToSizeB = MultiByteToWideChar(CP_UTF8, 0, argv[1], -1 , NULL, 0);
LPWSTR lpFileAddress[260] = {0};
int nResult = 0;
//MultiByteToWideChar function reurns 0 !!!
nResult = MultiByteToWideChar(CP_UTF8, 0, argv[1], -1, lpFileAddress[0], iToSizeB);
}
Probably you mean this:
WCHAR lpFileAddress[260] = {0};
nResult = MultiByteToWideChar(CP_UTF8, 0, argv[1], -1, lpFileAddress, iToSizeB);
In your code, you define array of WCHAR pointers: LPWSTR lpFileAddress[260] instead of WCHAR array, as required: WCHAR lpFileAddress[260] = {0};
I am developing for Windows, I have not found adequate information on how to correctly declare and later on set a unicode string. So far,
wchar_t myString[1024] = L"My Test Unicode String!";
What I assume the above does is [1024] is the allocated string length of how many characters I need to have max in that string. L"" makes sure the string in quotes is unicode (An alt I found is _T()). Now later on in my program when I am trying to set that string to another value by,
myString = L"Another text";
I get compiler errors, what am I doing wrong?
Also if anyone has an easy and in-depth unicode app resource I'd like to have some links, used to have bookmarked a website which was dedicated to that but seems that now is gone.
EDIT
I provide the entire code, I intend to use this as a DLL function but nothing so far is returned.
#include "dll.h"
#include <windows.h>
#include <string>
#include <cwchar>
export LPCSTR ex_test()
{
wchar_t myUString[1024];
std::wcsncpy(myUString, L"Another text", 1024);
int myUStringLength = lstrlenW(myUString);
MessageBoxW(NULL, (LPCWSTR)myUString, L"Test", MB_OK);
int bufferLength = WideCharToMultiByte(CP_UTF8, 0, myUString, myUStringLength, NULL, 0, NULL, NULL);
if (bufferLength <= 0) { return NULL; } //ERROR in WideCharToMultiByte
return NULL;
char *buffer = new char[bufferLength+1];
bufferLength = WideCharToMultiByte(CP_UTF8, 0, myUString, myUStringLength, buffer, bufferLength, NULL, NULL);
if (bufferLength <= 0) { delete[] buffer; return NULL; } //ERROR in WideCharToMultiByte
buffer[bufferLength] = 0;
return buffer;
}
The easiest approach is to declare the string differently in the first place:
std::wstring myString;
myString = L"Another text";
If you insist in using arrays of wchar_t directly, you'd use wcscpy() or better wcsncpy() from <cwchar>:
wchar_t myString[1024];
std::wcsncpy(myString, L"Another text", 1024);
wchar_t myString[1024] = L"My Test Unicode String!";
is initializing the array like this
wchar_t myString[1024] = { 'M', 'y', ' ', ..., 'n', 'g', '!', '\0' };
but
myString = L"Another text";
is an assignment which u cannot do to arrays. u have to copy the contents of the new string into your old array:
const auto& newstring = L"Another text";
std::copy(std::begin(newstring), std::end(newstring), myString);
or if its a pointer
wchar_t* newstring = L"Another text";
std::copy(newstring, newstring + wsclen(newstring) + 1, myString);
or as nawaz suggested with copy_n
std::copy_n(newstring, wsclen(newstring) + 1, myString);
This question already has answers here:
How to convert std::wstring to a TCHAR*?
(6 answers)
Closed 10 years ago.
I'm fairly new to programming, and I'm trying to write a program where a user inputs a date, then that date is added to the file directory name, then that file directory is searched.
Here is what I'm working with below. I have a number of functions to do this.. I've searched online and tried doing the conversion a few different ways and I'm just not understanding it.... so I left off with (what I know is incorrected) a static_cast.
Maybe I'm just not doing the conversion right... basically this will throw it back to a function that uses the WINAPI handler. Whether I can get that to work is a completely different story... Thanks in advance for any help!
wstring fDate;
wstring fileDin;
const TCHAR* s = _T (fileDin);
std::wstring(fDate);
std::wstring(fileDin) =L"Z:\\software\\A\\AC\\" + fDate;
wcout<< fileDin;
cout <<endl;
//wstring fileDin(&arc[1]);
fileDin = static_cast<TCHAR>(arc[1]);
dir(2, arc);
TCHAR can be either wchar_t (when you use Unicode) or char (when you use Multi-byte).
On the other hand std::wstring always contains characters of type wchar_t, so it's better if you use wchar_t* directly instead of TCHAR* (if possible).
Then wchar_t* to std::wstring conversion can be done by using constructor of std::wstring:
wchar_t* wcstr = L"my string";
std::wstring wstr(wcstr);
and std::wstring to wchar_t* by simple calling c_str() method:
wchar_t* wcstr = wstr.c_str();
Then sometimes you might need to convert between "wide" strings (std::wstrings holding wchar_t characaters) and multi-byte strings (std::strings holding chars). I usually use following helpers:
// multi byte to wide char:
std::wstring s2ws(const std::string& str)
{
int size_needed = MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), NULL, 0);
std::wstring wstrTo(size_needed, 0);
MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), &wstrTo[0], size_needed);
return wstrTo;
}
// wide char to multi byte:
std::string ws2s(const std::wstring& wstr)
{
int size_needed = WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), int(wstr.length() + 1), 0, 0, 0, 0);
std::string strTo(size_needed, 0);
WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), int(wstr.length() + 1), &strTo[0], size_needed, 0, 0);
return strTo;
}
I want to convert a normal string to a wstring. For this, I am trying to use the Windows API function MultiByteToWideChar.
But it does not work for me.
Here is what I have done:
string x = "This is c++ not java";
wstring Wstring;
MultiByteToWideChar( CP_UTF8 , 0 , x.c_str() , x.size() , &Wstring , 0 );
The last line produces the compiler error:
'MultiByteToWideChar' : cannot convert parameter 5 from 'std::wstring *' to 'LPWSTR'
How do I fix this error?
Also, what should be the value of the argument cchWideChar? Is 0 okay?
You must call MultiByteToWideChar twice:
The first call to MultiByteToWideChar is used to find the buffer size you need for the wide string. Look at Microsoft's documentation; it states:
If the function succeeds and cchWideChar is 0, the return value is the required size, in characters, for the buffer indicated by lpWideCharStr.
Thus, to make MultiByteToWideChar give you the required size, pass 0 as the value of the last parameter, cchWideChar. You should also pass NULL as the one before it, lpWideCharStr.
Obtain a non-const buffer large enough to accommodate the wide string, using the buffer size from the previous step. Pass this buffer to another call to MultiByteToWideChar. And this time, the last argument should be the actual size of the buffer, not 0.
A sketchy example:
int wchars_num = MultiByteToWideChar( CP_UTF8 , 0 , x.c_str() , -1, NULL , 0 );
wchar_t* wstr = new wchar_t[wchars_num];
MultiByteToWideChar( CP_UTF8 , 0 , x.c_str() , -1, wstr , wchars_num );
// do whatever with wstr
delete[] wstr;
Also, note the use of -1 as the cbMultiByte argument. This will make the resulting string null-terminated, saving you from dealing with them.
Few common conversions:
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <string>
std::string ConvertWideToANSI(const std::wstring& wstr)
{
int count = WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), wstr.length(), NULL, 0, NULL, NULL);
std::string str(count, 0);
WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), -1, &str[0], count, NULL, NULL);
return str;
}
std::wstring ConvertAnsiToWide(const std::string& str)
{
int count = MultiByteToWideChar(CP_ACP, 0, str.c_str(), str.length(), NULL, 0);
std::wstring wstr(count, 0);
MultiByteToWideChar(CP_ACP, 0, str.c_str(), str.length(), &wstr[0], count);
return wstr;
}
std::string ConvertWideToUtf8(const std::wstring& wstr)
{
int count = WideCharToMultiByte(CP_UTF8, 0, wstr.c_str(), wstr.length(), NULL, 0, NULL, NULL);
std::string str(count, 0);
WideCharToMultiByte(CP_UTF8, 0, wstr.c_str(), -1, &str[0], count, NULL, NULL);
return str;
}
std::wstring ConvertUtf8ToWide(const std::string& str)
{
int count = MultiByteToWideChar(CP_UTF8, 0, str.c_str(), str.length(), NULL, 0);
std::wstring wstr(count, 0);
MultiByteToWideChar(CP_UTF8, 0, str.c_str(), str.length(), &wstr[0], count);
return wstr;
}
You can try this solution below. I tested, it works, detect special characters (example: º ä ç á ) and works on Windows XP, Windows 2000 with SP4 and later, Windows 7, 8, 8.1 and 10.
Using std::wstring instead new wchar_t / delete, we reduce problems with leak resources, overflow buffer and corrupt heap.
dwFlags was set to MB_ERR_INVALID_CHARS to works on Windows 2000 with SP4 and later, Windows XP. If this flag is not set, the function silently drops illegal code points.
std::wstring ConvertStringToWstring(const std::string &str)
{
if (str.empty())
{
return std::wstring();
}
int num_chars = MultiByteToWideChar(CP_ACP, MB_ERR_INVALID_CHARS, str.c_str(), str.length(), NULL, 0);
std::wstring wstrTo;
if (num_chars)
{
wstrTo.resize(num_chars);
if (MultiByteToWideChar(CP_ACP, MB_ERR_INVALID_CHARS, str.c_str(), str.length(), &wstrTo[0], num_chars))
{
return wstrTo;
}
}
return std::wstring();
}
Second question about this, this morning!
WideCharToMultiByte() and MultiByteToWideChar() are a pain to use. Each conversion requires two calls to the routines and you have to look after allocating/freeing memory and making sure the strings are correctly terminated. You need a wrapper!
I have a convenient C++ wrapper on my blog, here, which you are welcome to use.
Here's the other question this morning
The function cannot take a pointer to a C++ string. It will expect a pointer to a buffer of wide characters of sufficient size- you must allocate this buffer yourself.
string x = "This is c++ not java";
wstring Wstring;
Wstring.resize(x.size());
int c = MultiByteToWideChar( CP_UTF8 , 0 , x.c_str() , x.size() , &Wstring[0], 0 );
I have some code in a library which has to internally work with wstring, that's all nice and fine. But it's called with a TCHAR string parameter, from both unicode and non-unicode projects, and I'm having trouble finding a neat conversion for both cases.
I see some ATL conversions and so on but can't see the right way, without defining multiple code paths using #define
Assuming TCHAR expands to wchar_t in Unicode builds:
inline std::wstring convert2widestr(const wchar_t* const psz)
{
return psz;
}
inline std::wstring convert2widestr(const char* const psz)
{
std::size_t len = std::strlen(psz);
if( psz.empty() ) return std::wstring();
std::vector<wchar_t> result;
const int len = WideCharToMultiByte( CP_ACP
, 0
, reinterpret_cast<LPCWSTR>(psz)
, static_cast<int>(len)
, NULL
, 0
, NULL
, NULL
);
result.resize( len );
if(result.empty()) return std::wstring();
const int cbytes = WideCharToMultiByte( CP_ACP
, 0
, reinterpret_cast<LPCWSTR>(psz)
, static_cast<int>(len)
, reinterpret_cast<LPSTR>(&result[0])
, static_cast<int>(result.size())
, NULL
, NULL
);
assert(cbytes);
return std::wstring( result.begin(), result.begin() + cbytes );
}
Use like this:
void f(const TCHAR* psz)
{
std::wstring str = convert(psz);
// ...
}