Compressing and Decompressing Memory Streams

The Zip Compression Library, EZLib provides stream compression and decompression functionality for the Symbian platforms. This tutorial summarizes the procedure involved in the compression and decompression of memory streams by EZLib.

1. 
   Define a buffer manager that implements MEZBufferManager.
2. 
   Create an instance of the classs CEZCompressor.
   1. 
      Invoke CEZCompressor::CompressL() for small buffers.
   2. 
      Invoke CEZCompressor::DeflateL() repeatedly on larger buffers until the entire buffer is compressed.

   class CBufferManager : public CBase, public MEZBufferManager
       {
   public:
     CBufferManager* CBufferManager::NewLC();
     CBufferManager* CBufferManager::NewL();
       ~CBufferManager();
       void InitializeL(CEZZStream &aZStream);
       void NeedInputL(CEZZStream &aZStream);
       void NeedOutputL(CEZZStream &aZStream);
       void FinalizeL(CEZZStream &aZStream);
       };
           
   CBufferManager* CBufferManager::NewLC()
       {
       CBufferManager* bm = new (ELeave) CBufferManager();
       CleanupStack::PushL(bm);
       return bm;
       }
   
   CBufferManager* CBufferManager::NewL()
       {
       CBufferManager* bm = new (ELeave) CBufferManager();
       CleanupStack::PushL(bm);
       CleanupStack::Pop();
       return bm;
       }
    
   static void doExampleL()
       {
       
     CBufferManager* bm = CBufferManager::NewLC();
     //TInt aLevel = EDefaultCompression, TInt aWindowBits = EMaxWBits, TInt aMemLevel = EDefMemLevel, TStrategy aStrategy = EDefaultStrategy);
     CEZCompressor* iCEZCompressor = CEZCompressor::NewLC(*bm); // all other flag values are default in its constructer
      
     while(icompressor->DeflateL())
           {       
           }     
      
   
     CleanupStack::PopAndDestroy(2);
   
       }