Comment : effectuer une conversion entre différents types de chaînes
Cette rubrique explique comment convertir divers types de chaînes Visual C++ en d'autres chaînes.Les types de chaînes traités sont : char *, wchar_t*, _bstr_t, CComBSTR, CString, basic_string et System.String.Dans tous les cas, une copie de la chaîne est effectuée lors de la conversion vers le nouveau type.Toute modification apportée à la nouvelle chaîne n'affecte pas la chaîne d'origine, et inversement.
Exemple
Description
Cet exemple montre comment convertir un type char * en un autre type de chaîne parmi ceux répertoriés ci-dessus.Une chaîne char * (également appelée chaîne de style C) utilise un caractère null pour indiquer la fin de la chaîne.Les chaînes de style C requièrent habituellement un octet par caractère, mais peuvent également utiliser deux octets.Dans les exemples ci-dessous, les chaînes char * sont aussi appelées chaînes de caractères à plusieurs octets à cause des données de chaînes qui résultent de leur conversion depuis des chaînes Unicode.Les fonctions de caractère d'octet unique et multioctets (MBCS) peuvent fonctionner dans les chaînes char *.
Code
// convert_from_char.cpp
// compile with: /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
// Create and display a C style string, and then use it
// to create different kinds of strings.
char *orig = "Hello, World!";
cout << orig << " (char *)" << endl;
// newsize describes the length of the
// wchar_t string called wcstring in terms of the number
// of wide characters, not the number of bytes.
size_t newsize = strlen(orig) + 1;
// The following creates a buffer large enough to contain
// the exact number of characters in the original string
// in the new format. If you want to add more characters
// to the end of the string, increase the value of newsize
// to increase the size of the buffer.
wchar_t * wcstring = new wchar_t[newsize];
// Convert char* string to a wchar_t* string.
size_t convertedChars = 0;
mbstowcs_s(&convertedChars, wcstring, newsize, orig, _TRUNCATE);
// Display the result and indicate the type of string that it is.
wcout << wcstring << _T(" (wchar_t *)") << endl;
// Convert the C style string to a _bstr_t string.
_bstr_t bstrt(orig);
// Append the type of string to the new string
// and then display the result.
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert the C style string to a CComBSTR string.
CComBSTR ccombstr(orig);
if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert the C style string to a CstringA and display it.
CStringA cstringa(orig);
cstringa += " (CStringA)";
cout << cstringa << endl;
// Convert the C style string to a CStringW and display it.
CStringW cstring(orig);
cstring += " (CStringW)";
// To display a CStringW correctly, use wcout and cast cstring
// to (LPCTSTR).
wcout << (LPCTSTR)cstring << endl;
// Convert the C style string to a basic_string and display it.
string basicstring(orig);
basicstring += " (basic_string)";
cout << basicstring << endl;
// Convert the C style string to a System::String and display it.
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
Sortie
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Hello, World! (System::String)
Exemple
Description
Cet exemple montre comment convertir un type wchar_t * en un autre type de chaîne parmi ceux répertoriés ci-dessus.Plusieurs types de chaînes, notamment wchar_t *, implémentent des formats de caractères larges.Pour convertir une chaîne multioctets en une chaîne à caractères larges, vous pouvez utiliser un appel de fonction unique comme mbstowcs_s ou un appel de constructeur pour une classe comme CStringA.
Code
// convert_from_wchar_t.cpp
// compile with: /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
// Create a string of wide characters, display it, and then
// use this string to create other types of strings.
wchar_t *orig = _T("Hello, World!");
wcout << orig << _T(" (wchar_t *)") << endl;
// Convert the wchar_t string to a char* string. Record
//.the length of the original string and add 1 to it to
//.account for the terminating null character.
size_t origsize = wcslen(orig) + 1;
size_t convertedChars = 0;
// Use a multibyte string to append the type of string
// to the new string before displaying the result.
char strConcat[] = " (char *)";
size_t strConcatsize = (strlen( strConcat ) + 1)*2;
// Allocate two bytes in the multibyte output string for every wide
// character in the input string (including a wide character
// null). Because a multibyte character can be one or two bytes,
// you should allot two bytes for each character. Having extra
// space for the new string is not an error, but having
// insufficient space is a potential security problem.
const size_t newsize = origsize*2;
// The new string will contain a converted copy of the original
// string plus the type of string appended to it.
char *nstring = new char[newsize+strConcatsize];
// Put a copy of the converted string into nstring
wcstombs_s(&convertedChars, nstring, newsize, orig, _TRUNCATE);
// append the type of string to the new string.
_mbscat_s((unsigned char*)nstring, newsize+strConcatsize, (unsigned char*)strConcat);
// Display the result.
cout << nstring << endl;
// Convert a wchar_t to a _bstr_t string and display it.
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert the wchar_t string to a BSTR wide character string
// by using the ATL CComBSTR wrapper class for BSTR strings.
// Then display the result.
CComBSTR ccombstr(orig);
if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
{
// CW2A converts the string in ccombstr to a multibyte
// string in printstr, used here for display output.
CW2A printstr(ccombstr);
cout << printstr << endl;
// The following line of code is an easier way to
// display wide character strings:
// wcout << (LPCTSTR) ccombstr << endl;
}
// Convert a wide wchar_t string to a multibyte CStringA,
// append the type of string to it, and display the result.
CStringA cstringa(orig);
cstringa += " (CStringA)";
cout << cstringa << endl;
// Convert a wide character wchar_t string to a wide
// character CStringW string and append the type of string to it
CStringW cstring(orig);
cstring += " (CStringW)";
// To display a CStringW correctly, use wcout and cast cstring
// to (LPCTSTR).
wcout << (LPCTSTR)cstring << endl;
// Convert the wide character wchar_t string to a
// basic_string, append the type of string to it, and
// display the result.
wstring basicstring(orig);
basicstring += _T(" (basic_string)");
wcout << basicstring << endl;
// Convert a wide character wchar_t string to a
// System::String string, append the type of string to it,
// and display the result.
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
Sortie
Hello, World! (wchar_t *)
Hello, World! (char *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Hello, World! (System::String)
Exemple
Description
Cet exemple montre comment convertir un type _bstr_t en un autre type de chaîne parmi ceux répertoriés ci-dessus.L'objet _bstr_t permet d'encapsuler des chaînes BSTR à caractères larges.Une chaîne BSTR a une valeur de longueur et n'utilise pas de caractère Null pour terminer la chaîne, mais le type de chaîne vers lequel vous effectuez la conversion peut nécessiter un caractère Null de fin.
Code
// convert_from_bstr_t.cpp
// compile with: /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
// Create a _bstr_t string, display the result, and indicate the
// type of string that it is.
_bstr_t orig("Hello, World!");
wcout << orig << " (_bstr_t)" << endl;
// Convert the wide character _bstr_t string to a C style
// string. To be safe, allocate two bytes for each character
// in the char* string, including the terminating null.
const size_t newsize = (orig.length()+1)*2;
char *nstring = new char[newsize];
// Uses the _bstr_t operator (char *) to obtain a null
// terminated string from the _bstr_t object for
// nstring.
strcpy_s(nstring, newsize, (char *)orig);
strcat_s(nstring, newsize, " (char *)");
cout << nstring << endl;
// Prepare the type of string to append to the result.
wchar_t strConcat[] = _T(" (wchar_t *)");
size_t strConcatLen = wcslen(strConcat) + 1;
// Convert a _bstr_t to a wchar_t* string.
const size_t widesize = orig.length()+ strConcatLen;
wchar_t *wcstring = new wchar_t[newsize];
wcscpy_s(wcstring, widesize, (wchar_t *)orig);
wcscat_s(wcstring, widesize, strConcat);
wcout << wcstring << endl;
// Convert a _bstr_t string to a CComBSTR string.
CComBSTR ccombstr((char *)orig);
if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert a _bstr_t to a CStringA string.
CStringA cstringa(orig.GetBSTR());
cstringa += " (CStringA)";
cout << cstringa << endl;
// Convert a _bstr_t to a CStringW string.
CStringW cstring(orig.GetBSTR());
cstring += " (CStringW)";
// To display a cstring correctly, use wcout and
// "cast" the cstring to (LPCTSTR).
wcout << (LPCTSTR)cstring << endl;
// Convert the _bstr_t to a basic_string.
string basicstring((char *)orig);
basicstring += " (basic_string)";
cout << basicstring << endl;
// Convert the _bstr_t to a System::String.
String ^systemstring = gcnew String((char *)orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
Sortie
Hello, World! (_bstr_t)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Hello, World! (System::String)
Exemple
Description
Cet exemple montre comment convertir un type CComBSTR en un autre type de chaîne parmi ceux répertoriés ci-dessus.Tout comme _bstr_t, un objet CComBSTR permet d'encapsuler des chaînes BSTR à caractères larges.Une chaîne BSTR a une valeur de longueur et n'utilise pas de caractère Null pour terminer la chaîne, mais le type de chaîne vers lequel vous effectuez la conversion peut nécessiter un caractère Null de fin.
Code
// convert_from_ccombstr.cpp
// compile with: /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
#include "vcclr.h"
using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;
int main()
{
// Create and initialize a BSTR string by using a CComBSTR object.
CComBSTR orig("Hello, World!");
// Convert the BSTR into a multibyte string, display the result,
// and indicate the type of string that it is.
CW2A printstr(orig);
cout << printstr << " (CComBSTR)" << endl;
// Convert a wide character CComBSTR string to a
// regular multibyte char* string. Allocate enough space
// in the new string for the largest possible result,
// including space for a terminating null.
const size_t newsize = (orig.Length()+1)*2;
char *nstring = new char[newsize];
// Create a string conversion object, copy the result to
// the new char* string, and display the result.
CW2A tmpstr1(orig);
strcpy_s(nstring, newsize, tmpstr1);
cout << nstring << " (char *)" << endl;
// Prepare the type of string to append to the result.
wchar_t strConcat[] = _T(" (wchar_t *)");
size_t strConcatLen = wcslen(strConcat) + 1;
// Convert a wide character CComBSTR string to a wchar_t*.
// The code first determines the length of the converted string
// plus the length of the appended type of string, then
// prepares the final wchar_t string for display.
const size_t widesize = orig.Length()+ strConcatLen;
wchar_t *wcstring = new wchar_t[widesize];
wcscpy_s(wcstring, widesize, orig);
wcscat_s(wcstring, widesize, strConcat);
// Display the result. Unlike CStringW, a wchar_t does not need
// a cast to (LPCTSTR) with wcout.
wcout << wcstring << endl;
// Convert a wide character CComBSTR to a wide character _bstr_t,
// append the type of string to it, and display the result.
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert a wide character CComBSTR to a multibyte CStringA,
// append the type of string to it, and display the result.
CStringA cstringa(orig);
cstringa += " (CStringA)";
cout << cstringa << endl;
// Convert a wide character CComBSTR to a wide character CStringW.
CStringW cstring(orig);
cstring += " (CStringW)";
// To display a cstring correctly, use wcout and cast cstring
// to (LPCTSTR).
wcout << (LPCTSTR)cstring << endl;
// Convert a wide character CComBSTR to a wide character
// basic_string.
wstring basicstring(orig);
basicstring += _T(" (basic_string)");
wcout << basicstring << endl;
// Convert a wide character CComBSTR to a System::String.
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
Sortie
Hello, World! (CComBSTR)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Hello, World! (System::String)
Exemple
Description
Cet exemple montre comment convertir un type CString en un autre type de chaîne parmi ceux répertoriés ci-dessus.CString est basé sur le type de données TCHAR, qui lui dépend de la définition du symbole _UNICODE.Si _UNICODE n'est pas défini, TCHAR est défini pour être char et CString contient une chaîne à caractères multioctets ; si _UNICODE est défini, TCHAR est défini pour être wchar_t et CString contient une chaîne à caractères larges.
CStringA est la version de chaîne multioctets de CString, et CStringW est uniquement la version de chaîne à caractères larges.Ni CStringA, ni CStringW n'utilisent _UNICODE pour déterminer la manière dont ils doivent être compilés.CStringA et CStringW sont utilisés dans cet exemple pour clarifier les différences mineures en matière d'allocation de taille de mémoire tampon et de gestion de sortie.
Code
// convert_from_cstring.cpp
// compile with: /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
// Set up a multibyte CStringA string.
CStringA origa("Hello, World!");
cout << origa << " (CStringA)" << endl;
// Set up a wide character CStringW string.
CStringW origw("Hello, World!");
wcout << (LPCTSTR)origw << _T(" (CStringW)") << endl;
// Convert to a char* string from CStringA string
// and display the result.
const size_t newsizea = (origa.GetLength() + 1);
char *nstringa = new char[newsizea];
strcpy_s(nstringa, newsizea, origa);
cout << nstringa << " (char *)" << endl;
// Convert to a char* string from a wide character
// CStringW string. To be safe, we allocate two bytes for each
// character in the original string, including the terminating
// null.
const size_t newsizew = (origw.GetLength() + 1)*2;
char *nstringw = new char[newsizew];
size_t convertedCharsw = 0;
wcstombs_s(&convertedCharsw, nstringw, newsizew, origw, _TRUNCATE );
cout << nstringw << " (char *)" << endl;
// Convert to a wchar_t* from CStringA
size_t convertedCharsa = 0;
wchar_t *wcstring = new wchar_t[newsizea];
mbstowcs_s(&convertedCharsa, wcstring, newsizea, origa, _TRUNCATE);
wcout << wcstring << _T(" (wchar_t *)") << endl;
// Convert to a wide character wchar_t* string from
// a wide character CStringW string.
wchar_t *n2stringw = new wchar_t[newsizew];
wcscpy_s( n2stringw, newsizew, origw );
wcout << n2stringw << _T(" (wchar_t *)") << endl;
// Convert to a wide character _bstr_t string from
// a multibyte CStringA string.
_bstr_t bstrt(origa);
bstrt += _T(" (_bstr_t)");
wcout << bstrt << endl;
// Convert to a wide character_bstr_t string from
// a wide character CStringW string.
bstr_t bstrtw(origw);
bstrtw += " (_bstr_t)";
wcout << bstrtw << endl;
// Convert to a wide character CComBSTR string from
// a multibyte character CStringA string.
CComBSTR ccombstr(origa);
if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
{
// Convert the wide character string to multibyte
// for printing.
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a wide character CComBSTR string from
// a wide character CStringW string.
CComBSTR ccombstrw(origw);
// Append the type of string to it, and display the result.
if (ccombstrw.Append(_T(" (CComBSTR)")) == S_OK)
{
CW2A printstrw(ccombstrw);
wcout << printstrw << endl;
}
// Convert a multibyte character CStringA to a
// multibyte version of a basic_string string.
string basicstring(origa);
basicstring += " (basic_string)";
cout << basicstring << endl;
// Convert a wide character CStringW to a
// wide character version of a basic_string
// string.
wstring basicstringw(origw);
basicstringw += _T(" (basic_string)");
wcout << basicstringw << endl;
// Convert a multibyte character CStringA to a
// System::String.
String ^systemstring = gcnew String(origa);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
// Convert a wide character CStringW to a
// System::String.
String ^systemstringw = gcnew String(origw);
systemstringw += " (System::String)";
Console::WriteLine("{0}", systemstringw);
delete systemstringw;
}
Sortie
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (char *)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CComBSTR)
Hello, World! (basic_string)
Hello, World! (System::String)
Exemple
Description
Cet exemple montre comment convertir un type basic_string en un autre type de chaîne parmi ceux répertoriés ci-dessus.
Code
// convert_from_basic_string.cpp
// compile with: /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
// Set up a basic_string string.
string orig("Hello, World!");
cout << orig << " (basic_string)" << endl;
// Convert a wide char basic_string string to a multibyte char*
// string. To be safe, we allocate two bytes for each character
// in the original string, including the terminating null.
const size_t newsize = (strlen(orig.c_str()) + 1)*2;
char *nstring = new char[newsize];
strcpy_s(nstring, newsize, orig.c_str());
cout << nstring << " (char *)" << endl;
// Convert a basic_string string to a wide character
// wchar_t* string. You must first convert to a char*
// for this to work.
const size_t newsizew = strlen(orig.c_str()) + 1;
size_t convertedChars = 0;
wchar_t *wcstring = new wchar_t[newsizew];
mbstowcs_s(&convertedChars, wcstring, newsizew, orig.c_str(), _TRUNCATE);
wcout << wcstring << _T(" (wchar_t *)") << endl;
// Convert a basic_string string to a wide character
// _bstr_t string.
_bstr_t bstrt(orig.c_str());
bstrt += _T(" (_bstr_t)");
wcout << bstrt << endl;
// Convert a basic_string string to a wide character
// CComBSTR string.
CComBSTR ccombstr(orig.c_str());
if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
{
// Make a multibyte version of the CComBSTR string
// and display the result.
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert a basic_string string into a multibyte
// CStringA string.
CStringA cstring(orig.c_str());
cstring += " (CStringA)";
cout << cstring << endl;
// Convert a basic_string string into a wide
// character CStringW string.
CStringW cstringw(orig.c_str());
cstringw += _T(" (CStringW)");
wcout << (LPCTSTR)cstringw << endl;
// Convert a basic_string string to a System::String
String ^systemstring = gcnew String(orig.c_str());
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
Sortie
Hello, World! (basic_string)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (System::String)
Exemple
Description
Cet exemple montre comment convertir une [System::String] à caractères larges (Unicode) dans l'un des types de chaînes répertoriés ci-dessus.
Code
// convert_from_system_string.cpp
// compile with: /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
#include "vcclr.h"
using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;
int main()
{
// Set up a System::String and display the result.
String ^orig = gcnew String("Hello, World!");
Console::WriteLine("{0} (System::String)", orig);
// Obtain a pointer to the System::String in order to
// first lock memory into place, so that the
// Garbage Collector (GC) cannot move that object
// while we call native functions.
pin_ptr<const wchar_t> wch = PtrToStringChars(orig);
// Make a copy of the system string as a multibyte
// char* string. Allocate two bytes in the multibyte
// output string for every wide character in the input
// string, including space for a terminating null.
size_t origsize = wcslen(wch) + 1;
const size_t newsize = origsize*2;
size_t convertedChars = 0;
char *nstring = new char[newsize];
wcstombs_s(&convertedChars, nstring, newsize, wch, _TRUNCATE);
cout << nstring << " (char *)" << endl;
// Convert a wide character system string to a
// wide character wchar_t* string.
const size_t newsizew = origsize;
wchar_t *wcstring = new wchar_t[newsizew];
wcscpy_s(wcstring, newsizew, wch);
wcout << wcstring << _T(" (wchar_t *)") << endl;
// Convert a wide character system string to a
// wide character _bstr_t string.
_bstr_t bstrt(wch);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert a wide character system string
// to a wide character CComBSTR string.
CComBSTR ccombstr(wch);
if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
{
// Make a multibyte copy of the CComBSTR string
// and display the result.
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert a wide character System::String to
// a multibyte CStringA string.
CStringA cstring(wch);
cstring += " (CStringA)";
cout << cstring << endl;
// Convert a wide character System::String to
// a wide character CStringW string.
CStringW cstringw(wch);
cstringw += " (CStringW)";
wcout << (LPCTSTR)cstringw << endl;
// Convert a wide character System::String to
// a wide character basic_string.
wstring basicstring(wch);
basicstring += _T(" (basic_string)");
wcout << basicstring << endl;
delete orig;
}
Sortie
Hello, World! (System::String)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Voir aussi
Tâches
Comment : convertir une chaîne standard en System::String
Comment : convertir System::String en chaîne standard
Comment : convertir System::String en wchar_t * ou char*
Référence
Concepts
Macros de conversion de chaînes ATL et MFC