unsigned char * (BYTE*) to BSTR and back

[joleary]

*MUCH* has been written on BSTR/_bstr_t conversion, but I've been unable to get my head around how it applies here.

Perhaps I just need a nudge.

My 3rd party encryption/decryption routine APIs are

BYTE* EncryptString(const BYTE* data);

BYTE* DecryptString(const BYTE* data);

and I need to store the encrypted data in a SQL Server database.

The data is truly binary. So upon advice from elsewhere in the forum, I chose BSTR and ADO.

_bstr_t encryptedBSTR = pRst->Fields->GetItem("data")->Value;

BYTE* encryptedData <<<< encryptedBSTR;

BYTE* decryptedData = DecryptString(encryptedData);

...


BYTE* encryptedData = EncryptString(decryptedData);

encryptedBSTR <<<< encryptedData;


pRst->Fields->GetItem("data")->Value = encryptedBSTR;

But what do I use in place of <<<< ???

Thanks for any hints

jim

[alex_gusev]

i guess something like this should work:

		BYTE bt[] = { 1,2,3,4 };
		BSTR bstrBuff = SysAllocStringLen((LPOLESTR)bt,sizeof(bt));
		_bstr_t bstrt(bstrBuff);
		BSTR& btOut = bstrt.GetBSTR();
		BYTE *pOut = (BYTE*)(char*)btOut;
		SysFreeString(bstrBuff);

[joleary]

Ta, Alex, for your helpful reply.

This seems to be leading me in the right direction; however, I do have some questions/issues.

1)
Because I have to work with BYTE*, I've modified your suggestion like this

BYTE* bt = new BYTE [256];
	for (int i = 0; i < 256; i++)  //my initialization for testing
	{
		bt[i] = i + 1;
	}
BSTR bstrBuff = SysAllocStringLen((LPOLESTR)bt,256);  //sizeof(bt) in this case being only 8

Is this valid?

2)
I neglected to mention that I'm using VC++ 6.0. Perhaps that explains this error message:

_bstr_t bstrt(bstrBuff);
BSTR& btOut = bstrt.GetBSTR();
error C2039: 'GetBSTR' : is not a member of '_bstr_t'

Thanks for any additional ideas.

jim

[alex_gusev]

Yes, initialization is valid, you may check it once all stuff begins to work. As for second question, it shoud be operator (BSTR) to get the same

[joleary]

Thank you again, Alex.

But, I'm afraid I don't understand your comment:

As for second question, it shoud be operator (BSTR) to get the same

Could you please elaborate?

Thanks,

jim

[alex_gusev]

I meant that _bstr_t class has something to return BSTR, so have a look at its header to discover

[joleary]

For anyone interested, the VC++ 6.0 version of Alex's .NET suggestion:

_bstr_t bstrt(bstrBuff);
BSTR& btOut = bstrt.GetBSTR();
BYTE *pOut = (BYTE*)(char*)btOut;
SysFreeString(bstrBuff);

seems to be

_bstr_t bstrt(bstrBuff);
BSTR btOut = bstrt.copy();
BYTE *pOut = (BYTE*)(char*)btOut;
SysFreeString(bstrBuff);

If anyone disagrees, I'd love to know about it.

jim

[joleary]

For anyone who may be interested:

The original issue for me was to get an encrypted BYTE* array of binary values stored into a SQL Server database.

I chose BSTR as the vehicle but that seems to have been incorrect.

I received from invaluable help from Krzemo in the CodeGuru Database forum.

I was told that although BSTR can contain binary values, it cannot be used to store binary values into a database.

I was advised to convert my BYTE* array to SAFEARRAY and use the SAFEARRAY to write to/read from the database.

To convert to/from BYTE* and SAFEARRAY, I adapted code from the sample in

http://www.codeproject.com/database/...select=1608797


All seems to be well.

jim