atomicAdjustPosixImpl.I

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/**
 * PANDA 3D SOFTWARE
 * Copyright (c) Carnegie Mellon University.  All rights reserved.
 *
 * All use of this software is subject to the terms of the revised BSD
 * license.  You should have received a copy of this license along
 * with this source code in a file named "LICENSE."
 *
 * @file atomicAdjustPosixImpl.I
 * @author drose
 * @date 2006-02-10
 */

/**
 * Atomically increments the indicated variable.
 */
INLINE void AtomicAdjustPosixImpl::
inc(TVOLATILE AtomicAdjustPosixImpl::Integer &var) {
  pthread_mutex_lock(&_mutex);
  ++var;
  pthread_mutex_unlock(&_mutex);
}

/**
 * Atomically decrements the indicated variable and returns true if the new
 * value is nonzero, false if it is zero.
 */
INLINE bool AtomicAdjustPosixImpl::
dec(TVOLATILE AtomicAdjustPosixImpl::Integer &var) {
  pthread_mutex_lock(&_mutex);
  Integer result = --var;
  pthread_mutex_unlock(&_mutex);
  return (result != 0);
}

/**
 * Atomically computes var += delta.  It is legal for delta to be negative.
 * Returns the result of the addition.
 */
INLINE AtomicAdjustPosixImpl::Integer AtomicAdjustPosixImpl::
add(TVOLATILE AtomicAdjustPosixImpl::Integer &var,
    AtomicAdjustPosixImpl::Integer delta) {
  pthread_mutex_lock(&_mutex);
  Integer new_value = var + delta;
  var = new_value;
  pthread_mutex_unlock(&_mutex);
  return new_value;
}

/**
 * Atomically changes the indicated variable and returns the original value.
 */
INLINE AtomicAdjustPosixImpl::Integer AtomicAdjustPosixImpl::
set(TVOLATILE AtomicAdjustPosixImpl::Integer &var,
    AtomicAdjustPosixImpl::Integer new_value) {
  pthread_mutex_lock(&_mutex);
  Integer orig_value = var;
  var = new_value;
  pthread_mutex_unlock(&_mutex);
  return orig_value;
}

/**
 * Atomically retrieves the snapshot value of the indicated variable.  This is
 * the only guaranteed safe way to retrieve the value that other threads might
 * be asynchronously setting, incrementing, or decrementing (via other
 * AtomicAjust methods).
 */
INLINE AtomicAdjustPosixImpl::Integer AtomicAdjustPosixImpl::
get(const TVOLATILE AtomicAdjustPosixImpl::Integer &var) {
  pthread_mutex_lock(&_mutex);
  Integer orig_value = var;
  pthread_mutex_unlock(&_mutex);
  return orig_value;
}

/**
 * Atomically changes the indicated variable and returns the original value.
 */
INLINE AtomicAdjustPosixImpl::Pointer AtomicAdjustPosixImpl::
set_ptr(TVOLATILE AtomicAdjustPosixImpl::Pointer &var,
        AtomicAdjustPosixImpl::Pointer new_value) {
  pthread_mutex_lock(&_mutex);
  Pointer orig_value = var;
  var = new_value;
  pthread_mutex_unlock(&_mutex);
  return orig_value;
}

/**
 * Atomically retrieves the snapshot value of the indicated variable.  This is
 * the only guaranteed safe way to retrieve the value that other threads might
 * be asynchronously setting, incrementing, or decrementing (via other
 * AtomicAjust methods).
 */
INLINE AtomicAdjustPosixImpl::Pointer AtomicAdjustPosixImpl::
get_ptr(const TVOLATILE AtomicAdjustPosixImpl::Pointer &var) {
  pthread_mutex_lock(&_mutex);
  Pointer orig_value = var;
  pthread_mutex_unlock(&_mutex);
  return orig_value;
}

/**
 * Atomic compare and exchange.
 *
 * If mem is equal to old_value, store new_value in mem.  In either case,
 * return the original value of mem.  The caller can test for success by
 * comparing return_value == old_value.
 *
 * The atomic function expressed in pseudo-code:
 *
 * orig_value = mem; if (mem == old_value) { mem = new_value; } return
 * orig_value;
 *
 */
INLINE AtomicAdjustPosixImpl::Integer AtomicAdjustPosixImpl::
compare_and_exchange(TVOLATILE AtomicAdjustPosixImpl::Integer &mem,
                     AtomicAdjustPosixImpl::Integer old_value,
                     AtomicAdjustPosixImpl::Integer new_value) {
  pthread_mutex_lock(&_mutex);
  Integer orig_value = mem;
  if (mem == old_value) {
    mem = new_value;
  }
  pthread_mutex_unlock(&_mutex);
  return orig_value;
}

/**
 * Atomic compare and exchange.
 *
 * As above, but works on pointers instead of integers.
 */
INLINE AtomicAdjustPosixImpl::Pointer AtomicAdjustPosixImpl::
compare_and_exchange_ptr(TVOLATILE AtomicAdjustPosixImpl::Pointer &mem,
                         AtomicAdjustPosixImpl::Pointer old_value,
                         AtomicAdjustPosixImpl::Pointer new_value) {
  pthread_mutex_lock(&_mutex);
  Pointer orig_value = mem;
  if (mem == old_value) {
    mem = new_value;
  }
  pthread_mutex_unlock(&_mutex);
  return orig_value;
}