campo-sirio/arch/_openf.cpp

//
// _OPENF.CPP
//
//  Source file for ArchiveLib 1.0
//
//  Copyright (c) Greenleaf Software, Inc. 1994
//  All Rights Reserved
//
// CONTENTS
//
//  ALOpenInputFile::operator new()
//  ALOpenOutputFile::operator new()
//  ALOpenFiles::operator new()
//  ALOpenInputFile::ALOpenInputFile()
//  ALOpenInputFile::~ALOpenInputFile()
//  ALOpenOutputFile::ALOpenOutputFile()
//  ALOpenOutputFile::~ALOpenOutputFile()
//  ALOpenFiles::ALOpenFiles()
//  ALOpenFiles::~ALOpenFiles()
//
// DESCRIPTION
//
//  The ALOpenInputFile, ALOpenOutputFile, and ALOpenFiles objects
//  are all just simple little devices I use in functions to open files,
//  then automatically close them when the function exits.  Even better,
//  if the storage object was already open when we enter the function, 
//  when we exit, we leave it open!  
//
// REVISION HISTORY
//
//  May 22, 1994  1.0A  : First release
//
//

#include "arclib.h"
#pragma hdrstop

#include "_openf.h"

//
// void * ALOpenInputFile::operator new( size_t size )
//
// ARGUMENTS:
//
//  size  : The size of the object being created.
//
// RETURNS
//
//  A pointer to the storage allocated for the object.
//
// DESCRIPTION
//
//  When we construct an object when using the DLL, trouble can arise.
//  The main bad thing is that when we call the constructor from an
//  EXE, we allocate the storage for the new object from inside our EXE.
//  When we destroy the same object, the destructor frees up the memory
//  inside the DLL.  This is bad, because you can mangle the heap inside 
//  the DLL by trying to free an object that doesn't belong to it.
//
//  The fix to this conundrum is to allocate the object inside the DLL,
//  and we can make this happen by overloading the new operator.  We don't
//  bother unless it's a DLL deal.
//
//  This lecture will be repeated at times throughout the source in this
//  project.
//
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

#if defined( AL_BUILDING_DLL )
void AL_DLL_FAR * AL_PROTO ALOpenInputFile::operator new( size_t size )
{
    return ::new char[ size ];
}
#endif

//
// void * ALOpenOutputFile::operator new( size_t size )
//
// ARGUMENTS:
//
//  size  : The size of the object being created.
//
// RETURNS
//
//  A pointer to the storage allocated for the object.
//
// DESCRIPTION
//
//  See the function directly above.
//
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

#if defined( AL_BUILDING_DLL )
void AL_DLL_FAR * AL_PROTO ALOpenOutputFile::operator new( size_t size )
{
    return ::new char[ size ];
}
#endif

//
// void * ALOpenFiles::operator new( size_t size )
//
// ARGUMENTS:
//
//  size  : The size of the object being created.
//
// RETURNS
//
//  A pointer to the storage allocated for the object.
//
// DESCRIPTION
//
//  See the function directly above.
//
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

#if defined( AL_BUILDING_DLL )
void AL_DLL_FAR * AL_PROTO ALOpenFiles::operator new( size_t size )
{
    return ::new char[ size ];
}
#endif


//
// ALOpenInputFile::ALOpenInputFile( ALStorage &file )
//
// ARGUMENTS:
//
//  file  : The storage object that has to opened.
//
// RETURNS
//
//  Nothing, this is a constructor.
//
// DESCRIPTION
//
//  You can stick this constructor at the start of a function, and it
//  opens up an ALStorage object for you.  You can then take it for
//  granted that it is open.  You can also take it for granted that
//  the storage object will be closed by the destructor when the
//  function exits.  All of this saves a lot of repetitive code.
//
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

AL_PROTO ALOpenInputFile::ALOpenInputFile( ALStorage AL_DLL_FAR &file )
{
    mpFile = &file;
    miFileWasOpen = file.IsOpen();
    if ( !miFileWasOpen )
        file.Open();
}

//
// ALOpenInputFile::~ALOpenInputFile()
//
// ARGUMENTS:
//
//  None.
//
// RETURNS
//
//  None, it is a destructor.
//
// DESCRIPTION
//
//  At the end of the function, it is time to close the storage object.
//  But only if it wasn't open when the constructor was called.
//
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

AL_PROTO ALOpenInputFile::~ALOpenInputFile()
{
    if ( !miFileWasOpen )
        mpFile->Close();
}

//
// ALOpenOutputFile::ALOpenOutputFile( ALStorage &file )
//
// ARGUMENTS:
//
//  file :  The ALStorage object that needs to be created.
//
// RETURNS
//
//  Nothing, it is a constructor.
//
// DESCRIPTION
//
//  This is just like ALOpenInputFile, except instead of calling 
//  ALStorage::Open(), it calls ALStorage::Create().  Note that if
//  the file is already open, we keep track of the fact and leave it
//  alone.
//
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

AL_PROTO ALOpenOutputFile::ALOpenOutputFile( ALStorage AL_DLL_FAR &file )
{
    mpFile = &file;
    miFileWasOpen = file.IsOpen();
    if ( !miFileWasOpen )
        file.Create();
}

//
// ALOpenOutputFile::~ALOpenOutputFile()
//
// ARGUMENTS:
//
//  None.
//
// RETURNS
//
//  Nothing.
//
// DESCRIPTION
//
//  If the file was closed when the constructor was called, we close
//  it in the constructor.  
//
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

AL_PROTO ALOpenOutputFile::~ALOpenOutputFile()
{
    if ( !miFileWasOpen )
        mpFile->Close();
}

//
// ALOpenFiles::ALOpenFiles( ALStorage &input,
//                           ALStorage &output )
//
// ARGUMENTS:
//
//  input  :  The storage object that needs to be opened, maybe.
//
//  output :  The storage object that needs to be created, maybe.
//
// RETURNS
//
//  Nothing.
//
// DESCRIPTION
//
//  This is just a combination of the ALOpenOutputFile() and 
//  ALOpenInputFile() guys rolled into one.  To combine them, we
//  just create this object that contains one of both objects.
//
//  So this guy takes care of opening an input file and an output
//  file right there at the same time.  The most exciting part of it
//  is that they both get closed up in the destructor.
//
//  So all the constructor has to do here is call the other two
//  constructors in an initializer list.
// 
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

AL_PROTO ALOpenFiles::ALOpenFiles( ALStorage AL_DLL_FAR &input,
                                   ALStorage AL_DLL_FAR &output )
    : mInputFile( input ), mOutputFile( output )
{
}

//
// ALOpenFiles::~ALOpenFiles()
//
// ARGUMENTS:
//
//  None.
//
// RETURNS
//
//  Nothing.
//
// DESCRIPTION
//
//  This guy closes the two files, if they were closed when the constructor
//  was called.  We don't have to do anything explicitly, because the
//  two data members of this object do so in their destructors.
//
// REVISION HISTORY
//
//   May 22, 1994  1.0A  : First release
//

AL_PROTO ALOpenFiles::~ALOpenFiles()
{
}