// @(#)root/base:$Name: $:$Id: TFileCacheWrite.cxx,v 1.8 2006/10/19 19:37:29 pcanal Exp $ // Author: Rene Brun 18/05/2006 /************************************************************************* * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. * * All rights reserved. * * * * For the licensing terms see $ROOTSYS/LICENSE. * * For the list of contributors see $ROOTSYS/README/CREDITS. * *************************************************************************/ ////////////////////////////////////////////////////////////////////////// // // // TFileCacheWrite : a cache when writing files over 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, // // TXNetFile and TWebFile (via TFile::WriteBuffers()). // // // // The write cache is automatically created when writing a remote file // // (created in TFile::Open()). // // // ////////////////////////////////////////////////////////////////////////// #include "TFile.h" #include "TFileCacheWrite.h" ClassImp(TFileCacheWrite) //______________________________________________________________________________ TFileCacheWrite::TFileCacheWrite() : TObject() { // Default Constructor. fBufferSize = 0; fNtot = 0; fSeekStart = 0; fFile = 0; fBuffer = 0; fRecursive = kFALSE; } //_____________________________________________________________________________ TFileCacheWrite::TFileCacheWrite(TFile *file, Int_t buffersize) : TObject() { // 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 if (buffersize < 10000) buffersize = 512000; fBufferSize = buffersize; fSeekStart = 0; fNtot = 0; fFile = file; fRecursive = kFALSE; fBuffer = new char[fBufferSize]; if (file) file->SetCacheWrite(this); if (gDebug > 0) Info("TFileCacheWrite","Creating a write cache with buffersize=%d bytes",buffersize); } //_____________________________________________________________________________ TFileCacheWrite::~TFileCacheWrite() { // Destructor. delete [] fBuffer; } //_____________________________________________________________________________ Bool_t TFileCacheWrite::Flush() { // Flush the current write buffer to the file. // Returns kTRUE in case of error. if (!fNtot) return kFALSE; fFile->Seek(fSeekStart); //printf("Flushing buffer at fSeekStart=%lld, fNtot=%d\n",fSeekStart,fNtot); fRecursive = kTRUE; Bool_t status = fFile->WriteBuffer(fBuffer, fNtot); fRecursive = kFALSE; fNtot = 0; return status; } //_____________________________________________________________________________ void TFileCacheWrite::Print(Option_t *option) const { // Print class internal structure. TString opt = option; printf("Write cache for file %s\n",fFile->GetName()); printf("Size of write cache: %d bytes to be written at %lld\n",fNtot,fSeekStart); opt.ToLower(); } //_____________________________________________________________________________ Int_t TFileCacheWrite::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. if (pos < fSeekStart || pos+len > fSeekStart+fNtot) return -1; memcpy(buf,fBuffer+pos-fSeekStart,len); return 0; } //_____________________________________________________________________________ Int_t TFileCacheWrite::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. if (fRecursive) return 0; //printf("TFileCacheWrite::WriteBuffer, pos=%lld, len=%d, fSeekStart=%lld, fNtot=%d\n",pos,len,fSeekStart,fNtot); if (fSeekStart + fNtot != pos) { //we must flush the current cache if (Flush()) return -1; //failure } if (fNtot + len >= fBufferSize) { if (Flush()) return -1; //failure if (len >= fBufferSize) { //buffer larger than the cache itself: direct write to file fRecursive = kTRUE; if (fFile->WriteBuffer(buf,len)) return -1; // failure fRecursive = kFALSE; return 1; } } if (!fNtot) fSeekStart = pos; memcpy(fBuffer+fNtot,buf,len); fNtot += len; return 1; } //_____________________________________________________________________________ void TFileCacheWrite::SetFile(TFile *file) { // Set the file using this cache. // Any write not yet flushed will be lost. fFile = file; }