MS VC++ Convert a byte array to a BSTR?

Question

I have a string that starts out in a .Net application, is encrypted and stored in AD. It's then picked up by a native C++ app and decrypted to produce an array of bytes eg "ABCDEF" becomes 00,41,00,42,00,43,00,44,00,45 once it has been decrypted at the C++ end.

I need to take this byte array and convert it to the BSTR "ABCDEF" so that I can use it elsewhere and I can't find a way to acomplish this last step.

Can anybody help?

Answer 1

If you really have an array of arbitrary bytes, use SysAllocStringByteLen . But it looks like, despite being in a byte array, your data is really a UTF-16-encoded Unicode string, so in that case, you're probably better off using SysAllocStringLen instead. Pass the byte-array pointer to the function (type-cast to OLECHAR* ), and the characters will be copied into the new string for you, along with an additional null character at the end.

Answer 2

The "decrypted string" is just a Unicode string - latin characters contain the first byte equal to null when represented in Unicode. So you don't need any real conversion, just cook a BSTR out of that buffer.

Knowing the number of Unicode characters - it will be half the length of the buffer - call SysAllocStringLen() to allocate a long enough null-terminated uninitialized BSTR. Then copy your array onto the allocated string with memcpy() . Alternatively you can call SysAllocStringLen() and pass it the byte buffer so that it does the copy for you and skip the memcpy() . Don't forget to call SysFreeString() when you no longer need the BSTR.