Does the pinning pointer safe?since the Read function will change the
ppBuffer points to unmanaged C++ heap,how does the dot net runtime knows
they will not move the allocated memory (pointed by ppBuffer)during the
garbage collection?
class NonGCClass
{
private:
int GetBufferLength ()
{
return rand();
}
public:
int Read(unsigned char **ppBuffer)
{
const int bufferLength=Ge tBufferLength() ;
*ppBuffer=new unsigned char[bufferLength];
memset(*ppBuffe r,0x64,bufferLe ngth);
return bufferLength;
}
};
__gc class GCClass
{
private:
NonGCClass *m_pNonGC;
public:
GCClass()
:m_pNonGC(new NonGCClass())
{
unsigned char *pBuffer=NULL;
unsigned char __pin *pPinBuffer=pBu ffer;
const int bufferLength=m_ pNonGC->Read(&pBuffer) ;
Byte byteArray[] = new Byte[bufferLength];
Marshal::Copy(( IntPtr)pBuffer, byteArray,0,buf ferLength);
delete []pBuffer;
pBuffer=NULL;
pPinBuffer=NULL ;
}
}; 1 1657
demofo wrote: Does the pinning pointer safe?since the Read function will change the ppBuffer points to unmanaged C++ heap,how does the dot net runtime knows they will not move the allocated memory (pointed by ppBuffer)during the garbage collection?
class NonGCClass { private: int GetBufferLength () { return rand(); } public: int Read(unsigned char **ppBuffer) { const int bufferLength=Ge tBufferLength() ; *ppBuffer=new unsigned char[bufferLength]; memset(*ppBuffe r,0x64,bufferLe ngth); return bufferLength; } }; __gc class GCClass { private: NonGCClass *m_pNonGC; public: GCClass() :m_pNonGC(new NonGCClass()) { unsigned char *pBuffer=NULL; unsigned char __pin *pPinBuffer=pBu ffer;
const int bufferLength=m_ pNonGC->Read(&pBuffer) ;
Byte byteArray[] = new Byte[bufferLength]; Marshal::Copy(( IntPtr)pBuffer, byteArray,0,buf ferLength);
delete []pBuffer;
pBuffer=NULL; pPinBuffer=NULL ; } };
I'm not quite sure what you're asking, but a pinning pointer pins the thing
pointed to, not the pointer used to initialize it. Above, pinning pBuffer
accomplishes nothing, as it is an unmanaged pointer. There is no problem
with your use of your Read function. It simply stores an unsigned char* in
another unsigned char*. If you were dealing with __gc pointers all around,
it would be no problem to overwrite one with the other; the pinning pointer
would be unaffected by this.
--
Doug Harrison
Microsoft MVP - Visual C++ This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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by: Bjoern Jonsson via .NET 247 |
last post by:
Hi all,
i've just encountered a problem with pinning. it seems as if a managed object is moved altough a pinning pointer to this object is still alive
code snippet:
ManagedObject __pin* pManagedObject = &this->managedObject;
/*lots of unmanaged memory allocation*/
| |
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Thanks!
--
Brian
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