/************************************************************************/
/*	Circular buffer type define 									*/
/*	This file implements a circulair buffer type						*/
/*	Steve Vandenbussche											*/
/************************************************************************/

#ifndef _CIRCULAR_BUFFER
#define _CIRCULAR_BUFFER

#include <p18cxxx.h>

//Define buffer width
#define BUFFER_SIZE 64

//Define buffer type
//#define BUFFER_TYPE char

//Define index type, this type must be big enough to hold BUFFER_SIZE
//#define INDEX_TYPE  unsigned char

//Define circular buffer structure
typedef struct
{
	char			buffer[BUFFER_SIZE];			//buffer
	unsigned char	indexIn;						//Write pointer witch holds the next free location
	unsigned char	indexOut;					//Read pointer wicht holds the first location to process
	unsigned char	count;						//current number of elements in the buffer 				
}circular_buffer;

//Function prototypes
int Write_one_to_buff(circular_buffer* buffPtr, char item_to_add);
int Read_one_from_buff(circular_buffer* buffPtr, char* item_read);
int Read_block_from_buff(circular_buffer* buffPtr, char* block_read, unsigned char lenght);

/****************************************************************************
  Function:
   int Write_one_to_buffer(circular_buffer* buffPtr, char item_to_add)

  Description:
    This function adds one element to the circular buffer

  Precondition:
    Member of type circular_buffer is declared

  Parameters:
    - Pointer to a circular_buffer
    - Item to add 

  Returns:
    0 on succes
    -1 when the buffer is full

  Remarks:
    None
  ***************************************************************************/
int Write_one_to_buff(circular_buffer* buffPtr, char item_to_add)
{
	//When the buffer is not full, then add the item
	if((BUFFER_SIZE - buffPtr->count) > 0)
	{
		buffPtr->buffer[buffPtr->indexIn] = item_to_add;
		buffPtr->indexIn = (buffPtr->indexOut + 1) % BUFFER_SIZE;
		buffPtr->count++;
	}
	else
		return -1;

	return 0;
}

/****************************************************************************
  Function:
   int Read_one_from_buffer(circular_buffer* buffPtr, char* item_read

  Description:
    This function reads one element from the circular buffer

  Precondition:
    Member of type circular_buffer is declared

  Parameters:
    - Pointer to a circular_buffer
    - Pointer where to hold the readed item

  Returns:
    0 on succes
    -1 when the buffer is empty

  Remarks:
    None
  ***************************************************************************/
int Read_one_from_buff(circular_buffer* buffPtr, char* item_read)
{
	//When the buffer is not empty read the item
	if(buffPtr->count > 0)
	{
		*item_read = buffPtr->buffer[buffPtr->indexOut];
		buffPtr->indexOut = (buffPtr->indexOut - 1) % BUFFER_SIZE;
		buffPtr->count--;
	}
	else
		return -1;
	
	return 0;
}

/****************************************************************************
  Function:
   int Read_block_from_buffer(circular_buffer* buffPtr, char* block_read, unsigned char lenght)

  Description:
    This function reads a block of elements from the buffer

  Precondition:
    Member of type circular_buffer is declared

  Parameters:
    - Pointer to a circular_buffer
    - Pointer where to hold the readed block
    - Lenght of the block

  Returns:
    0 on succes
    -1 when the buffer has less elements then the lenght of the block

  Remarks:
    None
  ***************************************************************************/
int Read_block_from_buffer(circular_buffer* buffPtr, char* block_read, unsigned char lenght)
{
	
	int i;	

	//When the number of elements in the buffer is equal to or greater then the block lenght then read the block
	if(buffPtr->count >= lenght)
	{
		for(i=0; i<lenght; i++)
		{
			block_read[i]= buffPtr->buffer[buffPtr->indexOut];
			buffPtr->indexOut = (buffPtr->indexOut - 1) % BUFFER_SIZE;
			buffPtr->count--;
		}
	}
	else
		return -1;
	
	return 0;
}
#endif /*_CIRCULAR_BUFFER*/