This class represents the encapsulation of a block request.
It contains the chunks to be prefetched and also serves as a
container for the information read.
These blocks are prefetch in a special reader thread by the
TFilePrefetch class.
class TFPBlock : public TObject


   char     *fBuffer;       ///< Content of the block
   Int_t     fNblock;       ///< Number of segment in the block
   Long64_t  fDataSize;     ///< Total size of useful data in the block
   Long64_t  fCapacity;     ///< Capacity of the buffer
   Int_t    *fLen;          ///< Array of lengths of each segment
   Long64_t *fPos;          ///< Array of positions of each segment
   Long64_t *fRelOffset;    ///< Relative offset of piece in the buffer

   TFPBlock(const TFPBlock&);            // Not implemented.
   TFPBlock &operator=(const TFPBlock&); // Not implemented.


   TFPBlock(Long64_t*, Int_t*, Int_t);
   virtual ~TFPBlock();

   Long64_t  GetPos(Int_t) const;
   Int_t     GetLen(Int_t) const;

   Long64_t *GetPos() const;
   Int_t    *GetLen() const;
   Long64_t  GetDataSize() const;
   Long64_t  GetCapacity() const;
   Int_t     GetNoElem() const;
   char     *GetBuffer() const;
   char     *GetPtrToPiece(Int_t index) const;

   void SetBuffer(char*);/// Set block buffer.
   void SetPos(Int_t, Long64_t);/// Set pos value for index idx.
   void ReallocBlock(Long64_t*, Int_t*, Int_t);
/// Reallocate the block's buffer based on the length
/// of the elements it will contain.