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9.0

Memory and Zlib compress

Asked by Frog153 in Handheld and PDA Programming, File Compression Utilities

Tags: Memory and Zlib compress

I use zlib in my pocket pc application to compress and uncompress data that send it via socket to an desktop application server. My code for Uncopress is below :

The InByte parameter is the compressing data from server
The dwSizeInBytes is the size of InByte in bytes

When server compress the data i putting the original size bytes of data in a DWORD so the pda make the uncompress

The size of memory that i must allocate  initially is :
DWORD dwUnCmpSize = (DWORD)(dwOrgSize + (dwOrgSize * 0.01) + 12);
and i allocated in pointer zStream
After the function 'uncompress' the dwUnCmpSize is smaller than initially and the zStream pointer has some dummy elements after the size of dwUnCmpSize

My Question is:
How can I  manipulate the zStream pointer to size of the new dwUnCmpSize without allocate new memory block and copy the data? 
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DWORD UnCompressData(LPBYTE InByte, DWORD dwSizeInBytes, LPBYTE* OutByte)
{
	LPBYTE zStream = NULL;
	DWORD dwOrgSize = 0;
 
	memcpy(&dwOrgSize, InByte, sizeof(DWORD));
	DWORD dwUnCmpSize = (DWORD)(dwOrgSize + (dwOrgSize * 0.01) + 12);
 
	zStream = new BYTE[dwUnCmpSize];
	ATLASSERT(zStream != NULL);
	if (zStream == NULL)
		return 0;
	
	ZeroMemory(zStream, dwUnCmpSize);
	int nRes = uncompress(zStream, &dwUnCmpSize, InByte + sizeof(DWORD), dwSizeInBytes);
	if (nRes != Z_OK)
	{
		delete[] zStream;
		zStream = NULL;
 
		return 0;
	}
	*OutByte = new BYTE[dwUnCmpSize];
	ATLASSERT(*OutByte != NULL);
	if (*OutByte == NULL)
	{
		*OutByte = (LPBYTE)LocalAlloc(LPTR, dwUnCmpSize);
 
		delete[] zStream;
		zStream = NULL;
 
		return 0;
	}
	ZeroMemory(*OutByte, dwUnCmpSize);
	memcpy(*OutByte , zStream, dwUnCmpSize);
 
	delete[] zStream;
	zStream = NULL;
	return dwUnCmpSize;
}
[+][-]06/14/09 05:59 AM, ID: 24623286Accepted Solution

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About this solution

Zones: Handheld and PDA Programming, File Compression Utilities
Tags: Memory and Zlib compress
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Solution Provided By: pgnatyuk
Participating Experts: 1
Solution Grade: B
 
 
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