library: libCore
#include "TFileCacheWrite.h"

TFileCacheWrite

class description - header file - source file - inheritance tree (.pdf)

class TFileCacheWrite : public TObject

Inheritance Chart:

TObject

TFileCacheWrite


    protected:

                       TFileCacheWrite(const TFileCacheWrite&)
      TFileCacheWrite& operator=(const TFileCacheWrite&)

    public:

                      TFileCacheWrite()
                      TFileCacheWrite(TFile* file, Int_t buffersize)
              virtual ~TFileCacheWrite()
       static TClass* Class()
       virtual Bool_t Flush()
        virtual Int_t GetBytesInCache() const
      virtual TClass* IsA() const
         virtual void Print(Option_t* option = "") const
        virtual Int_t ReadBuffer(char* buf, Long64_t pos, Int_t len)
         virtual void SetFile(TFile* file)
         virtual void ShowMembers(TMemberInspector& insp, char* parent)
         virtual void Streamer(TBuffer& b)
                 void StreamerNVirtual(TBuffer& b)
        virtual Int_t WriteBuffer(const char* buf, Long64_t pos, Int_t len)

Data Members


    protected:

      Long64_t fSeekStart   Seek value of first block in cache
         Int_t fBufferSize  Allocated size of fBuffer
         Int_t fNtot        Total size of cached blocks
        TFile* fFile        Pointer to file
         char* fBuffer      [fBufferSize] buffer of contiguous prefetched blocks
        Bool_t fRecursive   flag to avoid recursive calls

Class Description

                                                                      
 TFileCacheWrite : a cache when writing files on the network          
                                                                      
 A caching system to speed up network I/O, i.e. when there is         
 no operating system caching support (like the buffer cache for       
 local disk I/O). The cache makes sure that every I/O is done with    
 a (large) fixed length buffer thereby avoiding many small I/O's.     
 Currently the write cache system is used by the classes TNetFile,    
 TRFIOFile and TWebFile.                                              
 The write cache is automativally created when writing a remote file.

TFileCacheWrite()

 Default Constructor.

TFileCacheWrite(TFile *file, Int_t buffersize)

 Creates a TFileCacheWrite data structure.
 The write cache will be connected to file.
 The size of the cache will be buffersize,
 if buffersize < 10000 a default size of 512 Kbytes is used

TFileCacheWrite(const TFileCacheWrite &pf)

 Copy Constructor.

TFileCacheWrite& operator=(const TFileCacheWrite& pf)

 Assignment.

~TFileCacheWrite()

 Destructor.

Bool_t Flush()

 Flush the current write buffer to the file.
 Returns kTRUE in case of error.

void Print(Option_t *option)

 Print class internal structure.

Int_t ReadBuffer(char *buf, Long64_t pos, Int_t len)

 Called by the read cache to check if the requested data is not
 in the write cache buffer. Returns -1 if data not in write cache,
 0 otherwise.

Int_t WriteBuffer(const char *buf, Long64_t pos, Int_t len)

 Write buffer at position pos in the write buffer.
 The function returns 1 if the buffer has been successfully entered into the write buffer.
 The function returns 0 in case WriteBuffer() was recusively called via Flush().
 The function returns -1 in case of error.

void SetFile(TFile *file)

 Set the file using this cache.

Int_t GetBytesInCache()

Author: Rene Brun 18/05/2006
Last update: root/base:$Name: $:$Id: TFileCacheWrite.cxx,v 1.6 2006/06/30 14:24:48 rdm Exp $
Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *

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