392 lines
8.8 KiB
C++
Executable File
392 lines
8.8 KiB
C++
Executable File
//
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// ENGN.CPP
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//
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// Source file for ArchiveLib 2.0
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//
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// Copyright (c) Greenleaf Software, Inc. 1994-1996
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// All Rights Reserved
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//
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// CONTENTS
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//
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// ALEngine::operator new()
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// ALEngine::ALEngine()
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// ALEngine::WriteEngineData()
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// ALEngine::ReadEngineData()
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// ALEngine::~ALEngine()
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//
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// DESCRIPTION
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//
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// This file contains functions from the base class of ALEngine.
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//
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// REVISION HISTORY
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//
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// February 14, 1996 2.0A : New release
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//
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#include "arclib.h"
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#if !defined( AL_IBM )
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#pragma hdrstop
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#endif
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//
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// NAME
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//
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// ALEngine::operator new()
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//
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// PLATFORMS/ENVIRONMENTS
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//
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// Console Windows PM
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// C++
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//
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// SHORT DESCRIPTION
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//
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// Memory allocator used when ArchiveLib resides in a 16 bit DLL.
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//
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// C++ SYNOPSIS
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//
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// #include "arclib.h"
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//
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// void * ALEngine::operator new( size_t size )
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//
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// C SYNOPSIS
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//
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// None.
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//
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// VB SYNOPSIS
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//
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// None.
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//
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// DELPHI SYNOPSIS
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//
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// None.
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//
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// ARGUMENTS
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//
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// size : The number of bytes that the compiler has decided will be
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// necessary to construct a new ALEngine object.
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//
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// DESCRIPTION
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//
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// When using a DLL, it is easy to get into a dangerous situation when
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// creating objects whose ctor and dtor are both in the DLL. The problem
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// arises because when you create an object using new, the memory for
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// the object will be allocated from the EXE. However, when you destroy
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// the object using delete, the memory is freed inside the DLL. Since
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// the DLL doesn't really own that memory, bad things can happen.
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//
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// But, you say, won't the space just go back to the Windows heap regardless
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// of who tries to free it? Maybe, but maybe not. If the DLL is using
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// a subsegment allocation scheme, it might do some sort of local free
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// before returning the space to the windows heap. That is the point where
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// you could conceivably cook your heap.
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//
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// By providing our own version of operator new inside this class, we
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// ensure that all memory allocation for the class will be done from
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// inside the DLL, not the EXE calling the DLL.
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//
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// Incidentally, I suspect that this function never gets called. If an
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// object of a derived archive class is being created, it should use
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// its own new operator, rendering this one useless.
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//
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// RETURNS
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//
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// A pointer to some memory that should have been pulled out of the
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// heap for the DLL.
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//
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// EXAMPLE
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//
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// SEE ALSO
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//
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// REVISION HISTORY
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//
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// February 14, 1996 2.0A : New release
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#if defined( AL_BUILDING_DLL )
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void AL_DLL_FAR * AL_PROTO
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ALEngine::operator new( size_t size ) /* Tag internal function */
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{
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return ::new char[ size ];
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}
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#endif
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//
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// NAME
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//
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// ALEngine::ALEngine()
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//
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// PLATFORMS/ENVIRONMENTS
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//
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// Console Windows PM
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// C++
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//
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// SHORT DESCRIPTION
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//
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// Constructor for the base class ALEngine
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//
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// C++ SYNOPSIS
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//
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// #include "arclib.h"
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//
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// ALEngine::ALEngine( ALCompressionType compression_type_int,
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// const char *compression_type_string );
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//
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// C SYNOPSIS
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//
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// None.
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//
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// VB SYNOPSIS
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//
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// None.
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//
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// DELPHI SYNOPSIS
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//
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// None.
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//
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// ARGUMENTS
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//
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// compression_type_int : An integer used to indicate the compression
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// type. This needs to be selected from the
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// enumerated type defined in ALDEFS.H. This
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// value is usually what gets stored in an
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// archive to indicate what compression type was
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// used.
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//
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// compression_type_string : A pointer to a C-style string describing the
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// type of compression. This isn't used in
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// any algorithms, it's on hand as a U/I aid.
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//
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// DESCRIPTION
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//
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// ALEngine is a base class that is a parent to both ALCompressor and
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// ALDecompressor. It is really not much of a class, and only exists for
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// as a placeholder for a couple of data members (initialized in the ctor),
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// and a couple of virtual functions. Since this class has a couple of
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// pure virtual functions, you can't invoke it directly. It gets called
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// as part of the construction of the derived classes.
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//
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// RETURNS
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//
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// Nothing.
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//
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// EXAMPLE
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//
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// SEE ALSO
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//
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// REVISION HISTORY
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//
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// February 14, 1996 2.0A : New release
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//
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AL_PROTO
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ALEngine::ALEngine( ALCompressionType compression_type_int, /* Tag public function */
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const char AL_DLL_FAR *compression_type_string )
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: miCompressionType( compression_type_int ),
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mszCompressionType( compression_type_string )
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{
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}
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//
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// NAME
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//
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// ALEngine::WriteEngineData()
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//
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// PLATFORMS/ENVIRONMENTS
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//
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// Console Windows PM
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// C++
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//
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// SHORT DESCRIPTION
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//
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// Writes out private engine data.
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//
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// C++ SYNOPSIS
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//
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// #include "arclib.h"
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//
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// int ALEngine::WriteEngineData( ALStorage * archive );
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//
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// C SYNOPSIS
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//
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// None.
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//
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// VB SYNOPSIS
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//
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// None.
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//
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// DELPHI SYNOPSIS
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//
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// None.
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//
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// ARGUMENTS
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//
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// archive : A pointer to the storage object that is usually the target of
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// the compression. This doesn't have to be an archive,
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// so maybe the parameter has a bad name. You could just
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// as easily be writing this out to an ALCompressedObject,
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// or even a raw binary compressed file.
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//
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// DESCRIPTION
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//
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// Compression engines can write private data out to the archive
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// directory to provide customization information. For example, the
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// Greenleaf compression engine writes its compression level
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// using this function. By default, there is no data, which is what
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// this function writes out, a 0 length string.
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//
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// Any engine that doesn't have any customized data that needs to be
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// stored can just use the default version of this function right here.
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//
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// RETURNS
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//
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// AL_SUCCESS, or < AL_SUCCESS if something bad happens.
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//
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// EXAMPLE
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//
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// SEE ALSO
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//
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// REVISION HISTORY
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//
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// February 14, 1996 2.0A : New release
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//
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int AL_PROTO
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ALEngine::WriteEngineData( ALStorage AL_DLL_FAR * archive ) /* Tag protected function */
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{
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return archive->WriteGlShort( 0 );
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}
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//
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// NAME
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//
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// ALEngine::ReadEngineData()
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//
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// PLATFORMS/ENVIRONMENTS
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//
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// Console Windows PM
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// C++
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//
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// SHORT DESCRIPTION
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//
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// Read the customized engine data from a storage object.
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//
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// C++ SYNOPSIS
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//
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// #include "arclib.h"
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//
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// int ALEngine::ReadEngineData( ALStorage * archive )
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//
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// C SYNOPSIS
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//
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// None.
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//
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// VB SYNOPSIS
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//
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// None.
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//
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// DELPHI SYNOPSIS
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//
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// None.
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//
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// ARGUMENTS
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//
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// archive : A pointer to the storage object that is usually the source of
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// the decompression. This doesn't have to be an archive,
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// so maybe the parameter has a bad name. You could just
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// as easily be reading this in from an ALCompressedObject,
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// or even a raw binary compressed file.
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//
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// DESCRIPTION
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//
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// Compression engines can write private data out to the archive
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// directory to provide customization information. For example, the
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// Greenleaf compression engine reads its compression level
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// using this function. By default, no data is read in. This
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// function expects to find a zero length string, and complains
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// with a fatal error if it doesn't.
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//
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// Any engine that doesn't have any customized data that needs to be
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// stored can just use the default version of this function right here.
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//
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// RETURNS
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//
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// AL_SUCCESS, or < AL_SUCCESS if something bad happened.
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//
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// EXAMPLE
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//
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// SEE ALSO
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//
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// REVISION HISTORY
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//
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// February 14, 1996 2.0A : New release
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//
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int AL_PROTO
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ALEngine::ReadEngineData( ALStorage AL_DLL_FAR * archive ) /* Tag protected function */
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{
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short temp;
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int status = archive->ReadGlShort( temp );
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AL_ASSERT( temp == 0, "ReadEngineData: engine data not 0 length" );
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return status;
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}
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//
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// NAME
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//
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// ALEngine::~ALEngine()
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//
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// PLATFORMS/ENVIRONMENTS
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//
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// Console Windows PM
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// C++
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//
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// SHORT DESCRIPTION
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//
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// The destructor for ALEngine.
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//
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// C++ SYNOPSIS
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//
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// #include "arclib.h"
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//
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// ALEngine::~ALEngine()
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//
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// C SYNOPSIS
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//
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// None.
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//
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// VB SYNOPSIS
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//
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// None.
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//
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// DELPHI SYNOPSIS
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//
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// None.
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//
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// ARGUMENTS
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//
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// None.
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//
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// DESCRIPTION
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//
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// This virtual destructor has virtually nothing to do. At least in
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// the debug version of the library it checks the type of this.
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//
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// RETURNS
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//
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// Nothing.
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//
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// EXAMPLE
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//
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// SEE ALSO
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//
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// REVISION HISTORY
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//
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// February 14, 1996 2.0A : New release
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//
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AL_PROTO
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ALEngine::~ALEngine() /* Tag public function */
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{
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AL_ASSERT( GoodTag(), "~ALEngine: attempt to delete invalid object" );
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}
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