BucketFile.h

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// # BucketFile.h: File object for BucketCache
// # Copyright (C) 1995,1996,1999,2001
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef CASA_BUCKETFILE_H
#define CASA_BUCKETFILE_H
 
// # Includes
#include <casacore/casa/aips.h>
#include <casacore/casa/IO/ByteIO.h>
#include <casacore/casa/IO/MMapfdIO.h>
#include <casacore/casa/IO/FilebufIO.h>
#include <casacore/casa/BasicSL/String.h>
#include <unistd.h>
#include <memory>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// # Forward Declarations
class MultiFileBase;
 
// <summary>
// File object for BucketCache.
// </summary>
 
// <use visibility=local>
 
// <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="">
// </reviewed>
 
// # <prerequisite>
// # Classes you should understand before using this one.
// # </prerequisite>
 
// <etymology>
// BucketFile represents a data file for the BucketCache class.
// </etymology>
 
// <synopsis>
// A BucketFile object represents a data file. Currently it is used
// by the Table system, but it can easily be turned into
// a more general storage manager file class.
// <br>
// Creation of a BucketFile object does not open the file yet.
// An explicit open call has to be given before the file can be used.
// <p>
// The file can be opened as an ordinary file (with a file descriptor)
// or as a file in a MultiFileBase object. An ordinary file can be accessed
// in 3 ways:
// <ul>
//  <li> In an unbuffered way, where the parent BucketCache class accesses
//       a bucket at a time (and possibly keeps it in a cache).
//  <li> In a memory-mapped way, where the parent BucketMapped class does
//       the access using the MMapfdIO member.
//  <li> In a buffered way, where the parent BucketBuffered class does
//       the access using the FilebufIO member.
// </ul>
// A MultiFileBase file can only be accessed in the unbuffered way.
// </synopsis>
 
// <motivation>
// Encapsulate the file creation and access into a single class
// to hide the file IO details.
// </motivation>
 
// <example>
// <srcblock>
//     // Create the file for the given storage manager.
//     BucketFile file ("file.name");
//     // Open the file and write into it.
//     file.open();
//     file.write (someBuffer, someLength);
//     // Get the length of the file.
//     uInt size = file.fileSize();
// </srcblock>
// </example>
 
// <todo asof="$DATE:$">
//  <li> Use the ByteIO classes when they are ready.
// </todo>
 
class BucketFile {
 public:
  // Create a BucketFile object for a new file.
  // The file with the given name will be created as a normal file or
  // as part of a MultiFileBase (if mfile != 0).
  // It can be indicated if a MMapfdIO and/or FilebufIO object must be
  // created for the file. If a MultiFileBase is used, memory-mapped IO
  // cannot be used and mappedFile is ignored.
  explicit BucketFile(
      const String& fileName, uInt bufSizeFile = 0, Bool mappedFile = False,
      const std::shared_ptr<MultiFileBase>& mfile = std::shared_ptr<MultiFileBase>());
 
  // Create a BucketFile object for an existing file.
  // The file should be opened by the <src>open</src>.
  // Tell if the file must be opened writable.
  // It can be indicated if a MMapfdIO and/or FilebufIO object must be
  // created for the file. If a MultiFileBase is used, memory-mapped IO
  // cannot be used and mappedFile is ignored.
  BucketFile(const String& fileName, Bool writable, uInt bufSizeFile = 0, Bool mappedFile = False,
             const std::shared_ptr<MultiFileBase>& mfile = std::shared_ptr<MultiFileBase>());
 
  // The destructor closes the file (if open).
  virtual ~BucketFile();
 
  // Forbid copy constructor.
  BucketFile(const BucketFile&) = delete;
 
  // Forbid assignment.
  BucketFile& operator=(const BucketFile&) = delete;
 
  // Make a (temporary) buffered IO object for this file.
  // That object should not close the file.
  virtual std::shared_ptr<ByteIO> makeFilebufIO(uInt bufferSize);
 
  // Get the mapped file object.
  MMapfdIO* mappedFile() { return mappedFile_p; }
 
  // Get the buffered file object.
  FilebufIO* bufferedFile() { return bufferedFile_p; }
 
  // Open the file if not open yet.
  virtual void open();
 
  // Close the file (if open).
  virtual void close();
 
  // Remove the file (and close it if needed).
  virtual void remove();
 
  // Fsync the file (i.e. force the data to be physically written).
  virtual void fsync();
 
  // Set the file to read/write access. It is reopened if not writable.
  // It does nothing if the file is already writable.
  virtual void setRW();
 
  // Get the file name.
  virtual const String& name() const;
 
  // Has the file logically been indicated as writable?
  Bool isWritable() const;
 
  // Read bytes from the file.
  virtual uInt read(void* buffer, uInt length);
 
  // Write bytes into the file.
  virtual uInt write(const void* buffer, uInt length);
 
  // Seek in the file.
  // <group>
  virtual void seek(Int64 offset);
  void seek(Int offset);
  // </group>
 
  // Get the (physical) size of the file.
  // This is doing a seek and sets the file pointer to end-of-file.
  virtual Int64 fileSize() const;
 
  // Is the file cached, mapped, or buffered?
  // <group>
  Bool isCached() const;
  Bool isMapped() const;
  Bool isBuffered() const;
  // </group>
 
 private:
  // The file name.
  String name_p;
  // The (logical) writability of the file.
  Bool isWritable_p;
  Bool isMapped_p;
  uInt bufSize_p;
  int fd_p;  //  fd (if used) of unbuffered file
  // The unbuffered file.
  std::shared_ptr<ByteIO> file_p;
  // The optional mapped file.
  MMapfdIO* mappedFile_p;
  // The optional buffered file.
  FilebufIO* bufferedFile_p;
  // The possibly used MultiFileBase.
  std::shared_ptr<MultiFileBase> mfile_p;
 
  // Create the mapped or buffered file object.
  void createMapBuf();
 
  // Delete the possible mapped or buffered file object.
  void deleteMapBuf();
};
 
inline const String& BucketFile::name() const { return name_p; }
 
inline Bool BucketFile::isWritable() const { return isWritable_p; }
 
inline void BucketFile::seek(Int offset) { seek(Int64(offset)); }
 
inline Bool BucketFile::isCached() const { return !isMapped_p && bufSize_p == 0; }
inline Bool BucketFile::isMapped() const { return isMapped_p; }
inline Bool BucketFile::isBuffered() const { return bufSize_p > 0; }
 
}  // namespace casacore
 
#endif