Copy from uchar vector to byte array [duplicate] - arrays

Question

I'm trying to send an image from C++ to C# with an interop (marshaling) of C++ managed. image->getStream() return a const char* from a string.
I'm having exception with my Marshal::Copy function.
An unhandled exception of type 'System.AccessViolationException' occurred in mscorlib.dll
Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
Am I doing the right thing for the copy from a const char* to a byte array ? My dll is compiled with ASCII char set in VS2010.
array<System::Byte>^ OsgViewer::getLastImage()
{
array< Byte >^ byteArray;
m_ImageQueue->lock();
int index = m_ImageQueue->getCurrentImageIndex();
std::shared_ptr<Image> image = m_ImageQueue->getImage(static_cast<unsigned int>(index));
if( image && image->isValid() == true)
{
int wLen = image->getStreamSize();
char* wStream = const_cast<char*>(image->getStream());
byteArray = gcnew array< Byte >(wLen);
// convert native pointer to System::IntPtr with C-Style cast
Marshal::Copy((IntPtr)wStream ,byteArray , 0, wLen);
}
m_ImageQueue->unlock();
return byteArray;
}
Image is a home made C++ class
class ADAPTER Image
{
public :
Image();
~Image();
const char* getStream() const;
int getStreamSize();
bool setStringStream(std::ostringstream* iStringStream);
void setIsValid(bool isValid){ m_isValid = isValid;}
bool isValid() const{return m_isValid;}
std::ostringstream* getOStringStream() {return m_StringStream;}
private:
std::ostringstream* m_StringStream;
bool m_isValid;
};

Answer 1

I wouldn't use Marshal::Copy. Since you have the array locally, why not just pin it and use memcpy?
pin_ptr<Byte> ptrBuffer = &byteArray[byteArray->GetLowerBound(0)];
You can now call memcpy to ptrBuffer.
When the scope ends the pinning is automatically undone.