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/*
 *  ringbuf.h 
 *
 *  This file provides simple ring buffer functionality.
 *
 *  $Id: ringbuf.h,v 1.2 2001-09-27 11:59:35 chris Exp $
 */
 
#ifndef __RINGBUF_H__
#define __RINGBUF_H__
 
#ifndef RINGBUF_QUEUE_LENGTH
#define RINGBUF_QUEUE_LENGTH 128
#endif
 
typedef struct {
  char buffer[RINGBUF_QUEUE_LENGTH];
  volatile int  head;
  volatile int  tail;
} Ring_buffer_t;
 
#define Ring_buffer_Initialize( _buffer ) \
  do { \
    (_buffer)->head = (_buffer)->tail = 0; \
  } while ( 0 ) 
 
#define Ring_buffer_Is_empty( _buffer ) \
   ( (_buffer)->head == (_buffer)->tail )
 
#define Ring_buffer_Is_full( _buffer ) \
   ( (_buffer)->head == ((_buffer)->tail + 1) % RINGBUF_QUEUE_LENGTH )
 
#define Ring_buffer_Add_character( _buffer, _ch ) \
  do { \
    rtems_unsigned32 isrlevel; \
    \
    rtems_interrupt_disable( isrlevel ); \
      (_buffer)->tail = ((_buffer)->tail+1) % RINGBUF_QUEUE_LENGTH; \
      (_buffer)->buffer[ (_buffer)->tail ] = (_ch); \
    rtems_interrupt_enable( isrlevel ); \
  } while ( 0 ) 
 
#define Ring_buffer_Remove_character( _buffer, _ch ) \
  do { \
    rtems_unsigned32 isrlevel; \
    \
    rtems_interrupt_disable( isrlevel ); \
      (_buffer)->head = ((_buffer)->head+1) % RINGBUF_QUEUE_LENGTH; \
      (_ch) = (_buffer)->buffer[ (_buffer)->head ]; \
    rtems_interrupt_enable( isrlevel ); \
  } while ( 0 ) 
 
#endif