Storage.h

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#ifndef STORAGE_FACTORY_STORAGE_H
#define STORAGE_FACTORY_STORAGE_H
 
#include "Utilities/StorageFactory/interface/IOInput.h"
#include "Utilities/StorageFactory/interface/IOOutput.h"
#include "Utilities/StorageFactory/interface/IOPosBuffer.h"
 
//
// ROOT will probe for prefetching support by calling
// ReadBufferAsync(0, 0)
// Storage turns this into:
// prefetch(0, PREFETCH_PROBE_LENGTH)
//
// For example, if the Storage implementation wants to provide a prefetch
// implementation, but prefers it not to be used by default, it
// should detect the probe and return true.
//
#define PREFETCH_PROBE_LENGTH 4096
 
class Storage : public virtual IOInput, public virtual IOOutput {
public:
  enum Relative { SET, CURRENT, END };
 
  Storage(void);
  ~Storage(void) override;
 
  using IOInput::read;
  using IOInput::readv;
  using IOOutput::write;
  using IOOutput::writev;
 
  virtual bool prefetch(const IOPosBuffer *what, IOSize n);
  virtual IOSize read(void *into, IOSize n, IOOffset pos);
  IOSize read(IOBuffer into, IOOffset pos);
  virtual IOSize readv(IOPosBuffer *into, IOSize buffers);
  virtual IOSize write(const void *from, IOSize n, IOOffset pos);
  IOSize write(IOBuffer from, IOOffset pos);
  virtual IOSize writev(const IOPosBuffer *from, IOSize buffers);
 
  virtual bool eof(void) const;
  virtual IOOffset size(void) const;
  virtual IOOffset position(void) const;
  virtual IOOffset position(IOOffset offset, Relative whence = SET) = 0;
 
  virtual void rewind(void);
 
  virtual void resize(IOOffset size) = 0;
 
  virtual void flush(void);
  virtual void close(void);
 
private:
  // undefined, no semantics
  Storage(const Storage &) = delete;
  Storage &operator=(const Storage &) = delete;
};
 
#endif  // STORAGE_FACTORY_STORAGE_H