BSTR to std string std wstring and vice versa

Question

While working with COM in C   the strings are usually of BSTR data type  Someone can use BSTR wrapper like CComBSTR or MS s CString  But because I can t use ATL or MFC in MinGW compiler  is there standard code snippet to convert BSTR to std  string  or std  wstring  and vice versa    Are there also some non-MS wrappers for BSTR similar to CComBSTR   Update  Thanks to everyone who helped me out in any way  Just because no one has addressed the issue on conversion between BSTR and std  string  I would like to provide here some clues on how to do it   Below are the functions I use to convert BSTR to std  string and std  string to BSTR respectively   std  string ConvertBSTRToMBS BSTR bstr        int wslen     SysStringLen bstr       return ConvertWCSToMBS  wchar t  bstr  wslen      std  string ConvertWCSToMBS const wchar t  pstr  long wslen        int len     WideCharToMultiByte CP ACP  0  pstr  wslen  NULL  0  NULL  NULL        std  string dblstr len    0        len     WideCharToMultiByte CP ACP  0    no flags                                     pstr  wslen    not necessary NULL-terminated                                      amp dblstr 0   len                                  NULL  NULL    no default char           return dblstr     BSTR ConvertMBSToBSTR const std  string amp  str        int wslen     MultiByteToWideChar CP ACP  0    no flags                                           str data    str length                                          NULL  0        BSTR wsdata     SysAllocStringLen NULL  wslen         MultiByteToWideChar CP ACP  0    no flags                               str data    str length                              wsdata  wslen       return wsdata

User · Answer

There is a c   class called  bstr t   It has useful methods and a collection of overloaded operators   For example  you can easily assign from a const wchar t   or a const char   just doing  bstr t bstr   L My string    Then you can convert it back doing const wchar t   s   bstr operator const wchar t        You can even convert it back to a regular char const char   c   bstr operator char       You can then just use the const wchar t   or the const char   to initialize a new std  wstring oe std  string

User · Answer

BSTR to std  wstring      given BSTR bs assert bs    nullptr   std  wstring ws bs  SysStringLen bs       nbsp  std  wstring to BSTR      given std  wstring ws assert  ws empty     BSTR bs   SysAllocStringLen ws data    ws size         Doc refs    std  basic string lt typename CharT gt   basic string const CharT   size type  std  basic string lt  gt   empty   const std  basic string lt  gt   data   const std  basic string lt  gt   size   const SysStringLen   SysAllocStringLen

User · Answer

You could also do this  include  lt comdef h gt   BSTR bs   SysAllocString  quot Hello quot    std  wstring myString    bstr t bs  false      will take over ownership  so no need to free  or std  string if you prefer EDIT  if your original string contains multiple embedded  0 this approach will not work

User · Answer

Simply pass the BSTR directly to the wstring constructor  it is compatible with a wchar t    BSTR btest   SysAllocString L Test    assert btest    NULL   std  wstring wtest btest   assert 0    wcscmp wtest c str    btest      Converting BSTR to std  string requires a conversion to char  first   That s lossy since BSTR stores a utf-16 encoded Unicode string   Unless you want to encode in utf-8   You ll find helper methods to do this  as well as manipulate the resulting string  in the ICU library

[c++] BSTR to std::string (std::wstring) and vice versa

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