mosesdecoder/moses/FilePtr.h

// $Id$

/* ---------------------------------------------------------------- */
/* Copyright 2005 (c) by RWTH Aachen - Lehrstuhl fuer Informatik VI */
/* Richard Zens                                                     */
/* ---------------------------------------------------------------- */

#ifndef moses_FilePtr_h
#define moses_FilePtr_h

#include "File.h"

namespace Moses
{

/** smart pointer for on-demand loading from file
 *  requirement: T has a constructor T(FILE*)
 */
template<typename T> class FilePtr
{
public:
  typedef T* Ptr;
private:
  FILE* f;
  OFF_T pos;
  mutable Ptr t;
public:
  FilePtr(FILE* f_=0,OFF_T p=0) : f(f_),pos(p),t(0) {}
  ~FilePtr() {}

  void set(FILE* f_,OFF_T p) {
    f=f_;
    pos=p;
  }
  void free() {
    delete t;
    t=0;
  }

  T& operator* () {
    load();
    return *t;
  }
  Ptr operator->() {
    load();
    return t;
  }
  operator Ptr () {
    load();
    return t;
  }

  const T& operator* () const {
    load();
    return *t;
  }
  Ptr operator->() const {
    load();
    return t;
  }
  operator Ptr  () const {
    load();
    return t;
  }

  // direct access to pointer, use with care!
  Ptr getPtr() {
    return t;
  }
  Ptr getPtr() const {
    return t;
  }

  operator bool() const {
    return (f && pos!=InvalidOffT);
  }

  void load() const {
    if(t) return;
    if(f && pos!=InvalidOffT) {
      fSeek(f,pos);
      t=new T(f);
    }
  }
};

}

#endif