//
//  QUEUE.H
//
//  Source code from:
//
//  Serial Communications: A C++ Developer's Guide, 2nd Edition
//  by Mark Nelson, IDG Books, 1999
//
//  Please see the book for information on usage.
//
//  This header file contains the definitions needed to use the
//  Queue class.  This class is used for both the input and
//  output queues used by class PC8250.  Most of the functions
//  in this class are defined as inline, as speed is essential
//  in the interrupt service routine.  Those that aren't can
//  be found in QUEUE.CPP
//

#ifndef _QUEUE_DOT_H
#define _QUEUE_DOT_H

#ifdef _MSC_VER
# pragma warning( disable : 4505 )
#endif

const unsigned int QueueSize = 1024;
const unsigned int HighWaterMark = ( QueueSize * 3 ) / 4;
const unsigned int LowWaterMark = QueueSize / 4;

class Queue
{
    private :
        volatile unsigned int head_index;
        volatile unsigned int tail_index;
        volatile unsigned char buffer[ QueueSize ];
    public :
        Queue( void );
        int Insert( unsigned char c );
        int Remove( void );
        int Peek( unsigned char *buffer, int count );
        int InUseCount( void );
        int FreeCount( void );
        int Head( void ) { return head_index; }
        int Tail( void ) { return tail_index; }
        void Clear( void );
};

inline Queue::Queue( void )
{
    head_index = 0;
    tail_index = 0;
}

inline int Queue::Insert( unsigned char c )
{
    unsigned int temp_head = head_index;

    buffer[ temp_head++ ] = c;
    if ( temp_head >= QueueSize )
        temp_head = 0;
    if ( temp_head == tail_index )
        return 0;
    head_index = temp_head;
    return 1;
}

inline int Queue::Remove( void )
{
    unsigned char c;
    if ( head_index == tail_index )
        return( -1 );
    c = buffer[ tail_index++ ];
    if ( tail_index >= QueueSize )
        tail_index = 0;
    return c;
}

inline int Queue::InUseCount( void )
{
    if ( head_index >= tail_index )
        return head_index - tail_index;
    else
        return head_index + QueueSize - tail_index;
}

inline int Queue::FreeCount( void )
{
    return QueueSize - 1 - InUseCount();
}

inline void Queue::Clear( void )
{
    tail_index = head_index;
}

#endif  // #ifndef _QUEUE_DOT_H

// ********************* END OF QUEUE.H ********************