// exception3.cpp			By: Aiman Hanna -  ©1993-2006 Aiman Hanna

// This program introduces a standard language-level facility for 
// exception handling. This facility provides a uniform syntax and style, 
// yet it allows programmers to perform fine-tuning should they wish. 
// The exception-handling facility can significantly reduce the size and 
// complexity of program code by eliminating the need for testing anomalous
// states explicitly. 

// The try block begins with the "try" keyword followed by a sequence of 
// program statements enclosed within braces. Following the "try" block 
// is a list of handlers; these are the "catch" clauses. 

// Key Points:		1) Exception-handling facility
//			2) The "try" block
//			3) The "catch" handler and the "throw" clause


#include "exception3.h"

ProducerConsumer::ProducerConsumer()
{
	for (int i = 0; i < 10; i++)
		buff[i] = -1;

}




bool ProducerConsumer::isEmpty()
{

	if (buff[0] == -1)
		return true;

return false;
}




bool ProducerConsumer::isFull()
{

	if (buff[9] != -1)
		return true;

return false;
}




void ProducerConsumer::produceItem( int item )
{
	if (isFull())
		throw ProduceOnFull();		// Not "throw ProduceOnFull;"

	int i = 0;
	while (buff[i++] != -1);
		buff[i - 1] = item;
	
}



void ProducerConsumer::consumeItem( )
{
	if (isEmpty())
		throw ConsumeOnEmpty();		

	int i = 0, item = -1;
	while ( (i < 10) && (buff[i] != -1) ) 
		i++;
	
	item = buff[i-1];
	buff[i-1] = -1;
	
}



void ProducerConsumer::setItem(int item)
{
	produceItem( item );
}




void ProducerConsumer::displayBuffContents()
{
	cout << "\nThe buffer contents at this point are: " << endl;
	for (int i= 0; i < 10; i++)
		cout << buff[i] << "  ";
	cout << endl << endl;

}




void Excp::showExcpMessage()
{

	cerr << "An exception has occurred" << endl;
	
}




void ProducerConsumerExcp::showExcpMessage()
{
	cerr << "A producer-consumer exception has occurred" << endl;

}





void ConsumeOnEmpty::showExcpMessage()
{
	cerr << "An exception has occurred: Trying to consume from an empty buffer" << endl;
}




void ProduceOnFull::showExcpMessage()
{
	cerr << "An exception has occurred: Trying to produce to a full buffer" << endl;
}





int main()
{
	
	ProducerConsumer pc1;
	

	try{
		pc1.consumeItem( );
	}
	catch (ConsumeOnEmpty coe)
	{
		coe.showExcpMessage();
	}

	// try to produce more items than the buffer can hold
	// Notice what happens when the exception is thrown
	try
	{
		for (int i = 0; i < 13; i++)
		{
			pc1.produceItem(i * 5);		// i*5 is just a value 

			if ((i == 7) || (i ==8) || (i ==9))		// just show the buffer contents at these three points
				pc1.displayBuffContents();

		}
	}
	catch (ProduceOnFull pof)
	{	
		pof.showExcpMessage();
	}
	

	pc1.displayBuffContents();

	// try to consume more items than what the buffer has
	try
	{
		for (int i = 0; i < 13; i++)
		{
			pc1.consumeItem();	

			if ((i == 7) || (i ==8) || (i==9))		// display the contents just before the 
				pc1.displayBuffContents();	// exception should occur
					
		}
	}
	catch (ConsumeOnEmpty coe)
	{	
		coe.showExcpMessage();
	}
	

	return 0;
}

// The result of running the program
/*
An exception has occurred: Trying to consume from an empty buffer

The buffer contents at this point are:
0  5  10  15  20  25  30  35  -1  -1


The buffer contents at this point are:
0  5  10  15  20  25  30  35  40  -1


The buffer contents at this point are:
0  5  10  15  20  25  30  35  40  45

An exception has occurred: Trying to produce to a full buffer

The buffer contents at this point are:
0  5  10  15  20  25  30  35  40  45


The buffer contents at this point are:
0  5  -1  -1  -1  -1  -1  -1  -1  -1


The buffer contents at this point are:
0  -1  -1  -1  -1  -1  -1  -1  -1  -1


The buffer contents at this point are:
-1  -1  -1  -1  -1  -1  -1  -1  -1  -1

An exception has occurred: Trying to consume from an empty buffer
*/