/* counter.h                                             -*-C++-*-
 *   by Will Wagner <wwagner@io.com>
 *   last updated 11 Aug 1997, 22:22:25 wwagner
 *
 * This file contains a counter primitive.  All that can be done to
 * this object is incrementation and reading, nothing else.  The
 * counter is also transparently protected with a spinlock, for
 * purposes of multithreading.
 *
 * This object supports both prefix and postfix incrementation
 * operators, for no particular reason.  Some people like one, some
 * like the other, so it's best to support everything.
 *
 * USE_THREADS controls what gets compiled here; if it is defined,
 * then thread-safe counters are produced.  Otherwise, we just get an
 * unprotected counter.
 *
 * HIGH_RESOLUTION controls how many bits of counting we get.  If it
 * is defined, we get a 64-bit unsigned integer; if not, we only get
 * 32 unsigned bits.
 *
 * Changes
 *   29 Jul 1997
 *     - Created the file.
 *
 *   11 Aug 1997
 *     - Added high-resolution counting ability, with definition of
 *     HIGH_RESOLUTION; unfortunately it only works with GNU
 *     compilers.
 *
 * Things to do
 *     - Portability!  This is pretty tightly tied to Linux; consider
 *     changing the low-level spinlock to a pthread_mutex.
 *
 */

#ifndef __INC_COUNTER_H__
#define __INC_COUNTER_H__

#ifndef USE_THREADS
#include <asm/bitops.h>
#endif

#ifdef HIGH_RESOLUTION
typedef unsigned long long counter_type;
#else
typedef unsigned long counter_type;
#endif 

class Counter
{
  private:
    counter_type value;
#ifdef USE_THREADS
    int spinlock;
#endif

  public:
    Counter(counter_type v = 0L)
    {
	value = v;
#ifdef USE_THREADS
	spinlock = 0;
#endif
    };
    ~Counter();

    inline counter_type operator++(void)
    {
#ifdef USE_THREADS
	counter_type tmp;

	while (test_and_set_bit(0, &spinlock));
	tmp = ++value;
	clear_bit(0, &spinlock);
	return tmp;
#else
	return ++value;
#endif
    };

    inline counter_type operator++(int)
    {
#ifdef USE_THREADS
	counter_type tmp;

	while (test_and_set_bit(0, &spinlock));
	tmp = value++;
	clear_bit(0, &spinlock);
	return tmp;
#else
	return value++;
#endif
    };

    inline operator int(void)
    {
#ifdef USE_THREADS
	counter_type tmp;

	while (test_and_set_bit(0, &spinlock));
	tmp = value;
	clear_bit(0, &spinlock);
	return tmp;
#else
	return value;
#endif
    };
};

#endif /* __INC_COUNTER_H__ */