Re: Copy CLongBinary
On Thu, 4 Jun 2009 19:54:01 -0700, jc <jc@discussions.microsoft.com> wrote:
"Doug Harrison [MVP]" wrote:
On Thu, 4 Jun 2009 15:09:01 -0700, jc <jc@discussions.microsoft.com> wrote:
Hello,
I'm trying to copy from one CLongBinary to another CLongBinary,
but it's is not working.
What am I doing wrong?
LPVOID pVoid = NULL;
DWORD dwSize=460;
CLongBinary m_Data;
//Write pRecord->m_Data.m_hData - OK
m_Data.m_hData = ::GlobalAlloc(GMEM_MOVEALBE,dwSize);
pVoid = ::GlobalLock(m_Data.m_hData);
::memcpy(pVoid, pRecord->m_Data.m_hData, dwSize);
::GlobalUnlock(m_Data.m_hData);
m_Data.m_dwLength = (int)::GlobalSize(m_Data.m_hData);
//Write m_data.m_hData - bad
Look at your second argument to memcpy. You need to GlobalLock it and get a
pointer just like you did for the first argument.
Thank you for taking the time to respond to my posting.
However, I am uncertain as to what the changes
you suggested would look like. Could you please
provide a small snippet of code that demonstates
your response.
I'm assuming that pRecord's CLongBinary is also GMEM_MOVABLE and thus must
be locked before you can use it. Locking retrieves a pointer to the memory
referred to by the HGLOBAL. So, basically I'm saying to do for pRecord what
you did for m_Data:
void* p2 = GlobalLock(pRecord->m_Data.m_hData);
memcpy(pVoid, p2, dwSize);
GlobalUnlock(pRecord->m_Data.m_hData);
It's also unclear why you are using dwSize == 460 instead of getting it
from pRecord->m_Data.
If that doesn't help, you'll need to clarify what you meant by:
//Write m_data.m_hData - bad
If you try to "write" it without GlobalLocking and obtaining a pointer,
it's not going to work.
--
Doug Harrison
Visual C++ MVP
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