persist.h

GNU Common C++ is a very portable and highly optimized class framework for writing C++ applications

// Copyright (C) 1999-2005 Open Source Telecom Corporation.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
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// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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/**
 * @file persist.h
 * @short Persistence library classes.
 **/

#ifndef	CCXX_PERSIST_H_
#define	CCXX_PERSIST_H_

#ifndef CCXX_CONFIG_H_
#include <cc++/config.h>
#endif

#ifndef CCXX_EXCEPTIONS_H_
#include <cc++/exception.h>
#endif

#ifndef CCXX_MISSING_H_
#include <cc++/missing.h>
#endif

#ifndef	CCXX_STRING_H_
#include <cc++/string.h>
#endif

#ifdef HAVE_ZLIB_H
#ifndef NO_COMPRESSION
#include <zlib.h>
#endif
#else
#define	NO_COMPRESSION
#endif

#include <iostream>
#include <string>
#include <vector>
#include <deque>
#include <map>

#ifdef CCXX_NAMESPACES
namespace ost {
#define NS_PREFIX ost::
#else
#define	NS_PREFIX
#endif

#ifdef	CCXX_EXCEPTIONS
#ifdef	COMMON_STD_EXCEPTION

class __EXPORT PersistException : public Exception
{
public:
	PersistException(const String &what) : Exception(what) {};
};

#else

class __EXPORT PersistException
{
public:
	PersistException(const String& reason);
	inline const String& getString() const
		{return Exception::getString();};

	virtual ~PersistException() {} throw();
protected:
	String _what;
};

#endif
#endif

// This typedef allows us to declare NewBaseObjectFunction now
typedef class BaseObject* (*NewBaseObjectFunction) (void);

/**
 * This class manages the types for generation of the persistent objects.
 * Its data structures are managed automatically by the system. They are
 * implicitly filled by the constructors who declare classes to the system.
 *
 * @author Daniel Silverstone
 * @short Type manager for persistence engine.
 */
class __EXPORT TypeManager
{
public:
	
	/**
	 * This manages a registration to the typemanager - attempting to
	 * remove problems with the optimisers
	 */
	class Registration
	{
	public:
		Registration(const char* name, NewBaseObjectFunction func);
		virtual ~Registration();
	private:
		String myName;
	};
	
	/**
	 * This adds a new construction function to the type manager
	 */
	static void add(const char* name, NewBaseObjectFunction construction);
	
	/**
	 * And this one removes a type from the managers lists
	 */
	static void remove(const char* name);
	
	/**
	 * This function creates a new object of the required type and
	 * returns a pointer to it. NULL is returned if we couldn't find 
	 * the type
	 */
	static BaseObject* createInstanceOf(const char* name);
	
	typedef std::map<String,NewBaseObjectFunction> StringFunctionMap;
};


/*
 * The following defines are used to declare and define the relevant code
 * to allow a class to use the Persistence::Engine code.
 */

#define DECLARE_PERSISTENCE(ClassType)					\
  public:								\
    friend NS_PREFIX Engine& operator>>( NS_PREFIX Engine& ar, ClassType *&ob);		\
    friend NS_PREFIX Engine& operator<<( NS_PREFIX Engine& ar, ClassType const &ob);	\
    friend NS_PREFIX BaseObject *createNew##ClassType();				\
    virtual const char* getPersistenceID() const;			\
    static NS_PREFIX TypeManager::Registration registrationFor##ClassType;

#define IMPLEMENT_PERSISTENCE(ClassType, FullyQualifiedName)		      \
  NS_PREFIX BaseObject *createNew##ClassType() { return new ClassType; }		      \
  const char* ClassType::getPersistenceID() const {return FullyQualifiedName;} \
  NS_PREFIX Engine& operator>>(NS_PREFIX Engine& ar, ClassType &ob)			      \
    { ar >> (NS_PREFIX BaseObject &) ob; return ar; }				      \
  NS_PREFIX Engine& operator>>(NS_PREFIX Engine& ar, ClassType *&ob)			      \
    { ar >> (NS_PREFIX BaseObject *&) ob; return ar; }				      \
  NS_PREFIX Engine& operator<<(NS_PREFIX Engine& ar, ClassType const &ob)			      \
    { ar << (NS_PREFIX BaseObject const *)&ob; return ar; }			      \
  NS_PREFIX TypeManager::Registration						      \
        ClassType::registrationFor##ClassType(FullyQualifiedName,	      \
					      createNew##ClassType);

class Engine;

/**
 * BaseObject
 *
 * This object is the base for all Persistent data which is not
 * natively serialised by the Persistence::Engine
 *
 * It registers itself with the Persistence::TypeManager
 * using a global constructor function. A matching deregister call
 * is made in a global destructor, to allow DLL's to use the
 * Persistence::Engine in a main executable.
 *
 * Persistable objects must never maintain bad pointers. If a pointer
 * doesn't point to something valid, it must be NULL.  This is so
 * the persistence engine knows whether to allocate memory for an object
 * or whether the memory has been pre-allocated.
 *
 * @author Daniel Silverstone
 * @short Base class for classes that will be persistent.
 */
class __EXPORT BaseObject
{
public:
	/**
	 * This constructor is used in serialisation processes.
	 * It is called in CreateNewInstance in order to create
	 * an instance of the class to have Read() called on it.
	 */
	 BaseObject();
	
	/**
	 * Default destructor
	 */
	 virtual ~BaseObject();
	
	/**
	 * This returns the ID of the persistent object (Its type)
	 */
	 virtual const char* getPersistenceID() const;
	
	/**
	 * This method is used to write to the Persistence::Engine
	 * It is not equivalent to the << operator as it writes only the data
	 * and not the object type etc.
	 */
	 virtual bool write(Engine& archive) const;

	/**
	 * This method is used to read from a Persistence::Engine
	 * It is not equivalent to the >> operator as it does no 
	 * typesafety or anything.
	 */
	 virtual bool read(Engine& archive);
};


/**
 * Engine
 *
 * This class constructs on a standard C++ STL stream and then
 * operates in the mode specified. The stream passed into the
 * constructor must be a binary mode to function properly.
 *
 * @author Daniel Silverstone
 * @short stream serialization of persistent classes.
 */
class __EXPORT Engine
{
public:
	/**
	 * These are the modes the Persistence::Engine can work in
	 */
	enum EngineMode
	{
		modeRead,
		modeWrite
	};
	
	/**
	 * Constructs a Persistence::Engine with the specified stream in
	 * the given mode. The stream must be initialised properly prior
	 * to this call or problems will ensue.
	 */
	Engine(std::iostream& stream, EngineMode mode) THROWS (PersistException);
	
	/**
	 * This Flushes the buffers and closes the Persistence::Engine
	 * this must happen before the underlying stream is shut down
	 */
  void sync();
  
	virtual ~Engine();


	// Write operations

	/**
	 * writes a BaseObject from a reference.
	 */
	void write(const BaseObject &object) THROWS (PersistException)
	{ write(&object); };

	/**
	 * writes a BaseObject from a pointer.
	 */
	void write(const BaseObject *object) THROWS (PersistException);

	// writes supported primitive types
  // shortcut, to make the following more readable
#define CCXX_ENGINEWRITE_REF(valref) writeBinary((const uint8*)&valref,sizeof(valref))
	void write(int8 i)   THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
	void write(uint8 i)  THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
	void write(int16 i)  THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
	void write(uint16 i) THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
	void write(int32 i)  THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
	void write(uint32 i) THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
#ifdef	HAVE_64_BITS
	void write(int64 i)  THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
	void write(uint64 i) THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
#endif
	void write(float i)  THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }
	void write(double i) THROWS (PersistException) { CCXX_ENGINEWRITE_REF(i); }