How does visual c ++ convert string types?

This topic demonstrates how to convert various C ++ string types to other strings. The string types that can be converted include char *, wchar_t *, _ bstr_t, ccombstr, cstring, basic_string, and system. String. In all cases, a copy of the string is created when a string is converted to a new type. Any changes made to the new string will not affect the original string, and vice versa.

Convert from char *

 

// 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 () {char * orig =" Hello, world! "; Cout <orig <" (char *) "<Endl; // convert to a wchar_t * size_t origsize = strlen (orig) + 1; const size_t newsize = 100; size_t convertedchars = 0; wchar_t wcstring [newsize]; convert (& convertedchars, wcstring, origsize, orig, _ truncate); wcscat_s (wcstring, L "(wchar_t *)"); wcout <wcstring <Endl; // convert to a _ bstr_t_bstr_t bstrt (orig); bstrt + = "(_ bstr_t )"; cout <bstrt <Endl; // convert to a ccombstrccombstr ccombstr (orig); If (ccombstr. append (L "(ccombstr)") = s_ OK) {cw2a printstr (ccombstr); cout <printstr <Endl ;}// convert to a cstringcstring cstring (orig ); cstring + = "(cstring)"; cout <cstring <Endl; // convert to a basic_stringstring basicstring (orig); basicstring + = "(basic_string )"; cout <basicstring <Endl; // convert to a system: stringstring ^ systemstring = gcnew string (orig); systemstring + = "(System: string)"; console:: writeline ("{0}", systemstring); Delete systemstring ;}

 

 

Convert from wchar_t *

// 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 () {wchar_t * orig = l" Hello, world! "; Wcout <orig <L" (wchar_t *) "<Endl; // convert to a char * size_t origsize = wcslen (orig) + 1; const size_t newsize = 100; size_t convertedchars = 0; char nstring [newsize]; wcstombs_s (& convertedchars, nstring, origsize, orig, _ truncate); strcat_s (nstring, "(char *)"); cout <nstring <Endl; // convert to a _ bstr_t_bstr_t bstrt (orig); bstrt + = "(_ bstr_t )"; cout <bstrt <Endl; // convert to a ccombstrccombstr ccombstr (orig); If (ccombstr. append (L "(ccombstr)") = s_ OK) {cw2a printstr (ccombstr); cout <printstr <Endl ;}// convert to a cstringcstring cstring (orig ); cstring + = "(cstring)"; cout <cstring <Endl; // convert to a basic_stringwstring basicstring (orig); basicstring + = l "(basic_string )"; wcout <basicstring <Endl; // convert to a system: stringstring ^ systemstring = gcnew string (orig); systemstring + = "(System: string)"; console:: writeline ("{0}", systemstring); Delete systemstring ;}

 

Convert from _ bstr_t

 

// 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 () {_ bstr_t orig (" Hello, world! "); Wcout <orig <" (_ bstr_t) "<Endl; // convert to a char * const size_t newsize = 100; char nstring [newsize]; strcpy_s (nstring, (char *) orig); strcat_s (nstring, "(char *)"); cout <nstring <Endl; // convert to a wchar_t * wchar_t wcstring [newsize]; wcscpy_s (wcstring, (wchar_t *) orig); wcscat_s (wcstring, l "(wchar_t *)"); wcout <wcstring <Endl; // convert to a ccombstrccombstr ccombstr (char *) orig); If (ccombstr. append (L "(ccombstr)") = s_ OK) {cw2a printstr (ccombstr); cout <printstr <Endl ;} // convert to a cstringcstring cstring (char *) orig); cstring + = "(cstring)"; cout <cstring <Endl; // convert to a basic_stringstring basicstring (char *) orig); basicstring + = "(basic_string)"; cout <basicstring <Endl; // convert to a system :: stringstring ^ systemstring = gcnew string (char *) orig); systemstring + = "(System: string)"; Console: writeline ("{0}", systemstring ); delete systemstring ;}

 

 

Convert from cstring

// 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 () {cstring orig (" Hello, world! "); Wcout <orig <" (cstring) "<Endl; // convert to a char * const size_t newsize = 100; char nstring [newsize]; strcpy_s (nstring, orig); strcat_s (nstring, "(char *)"); cout <nstring <Endl; // convert to a wchar_t * // you must first convert to a char * for this to work. size_t origsize = strlen (orig) + 1; size_t convertedchars = 0; wchar_t wcstring [newsize]; convert (& convertedchars, wcstring, origsize, orig, _ truncate, L "(wchar_t *)"); wcout <wcstring <Endl; // convert to a _ bstr_t_bstr_t bstrt (orig); bstrt + = "(_ bstr_t )"; cout <bstrt <Endl; // convert to a ccombstrccombstr ccombstr (orig); If (ccombstr. append (L "(ccombstr)") = s_ OK) {cw2a printstr (ccombstr); cout <printstr <Endl ;}// convert to a basic_stringstring basicstring (orig ); basicstring + = "(basic_string)"; cout <basicstring <Endl; // convert to a system: stringstring ^ systemstring = gcnew string (orig ); systemstring + = "(System: string)"; Console: writeline ("{0}", systemstring); Delete systemstring ;}

 

Function: wcstombs_s, _ wcstombs_s_l

Function Description: converts a sequence of wide characters to a corresponding sequence of multibyte characters.

 
Struct (size_t * preturnvalue, char * mbstr, size_t percent, const wchar_t * wcstr, size_t count); struct _ struct (size_t * preturnvalue, char * mbstr, size_t percent, const wchar_t * wcstr, size_t count, _ locale_t locale );
 

Parameters

 [out] preturnvaluethe number of characters converted. [out] mbstrthe address of a buffer for the resulting converted multibyte character string. [in] sizeinbytesthe size in bytes of the mbstr buffer. [in] wcstrpoints to the wide character string to be converted. [in] countthe maximum number of bytes to be stored in the mbstr buffer, or _ truncate. [in] localethe locale to use.