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 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 *
 * proxy_apr.swg: This file forms part of the core module (it is %included
 *   only in one place, core.i).  It contains Python pool related code.
 */

#ifdef SWIGPYTHON
%nodefault apr_array_header_t;
%nodefault apr_file_t;
%nodefault apr_hash_t;
%nodefault apr_pool_t;

%opaque_proxy(apr_array_header_t);
%opaque_proxy(apr_file_t);
%opaque_proxy(apr_hash_t);

/*
 * SWIG/Python Automatic Memory Management in Subversion: An Overview
 * ------------------------------------------------------------------
 *
 * The python memory management code is designed to mark pools as invalid
 * when their parent pools have been garbage collected.  This is implemented
 * by registering a callback with the Python garbage collector, so that when
 * the object's parent pool is deleted, we can be notified.  For more info on
 * how these callbacks work, read the Python documentation for the
 * weakref.ref() function.
 *
 * Each object has an _is_valid member, and stores a weakref to its parent
 * pool's _is_valid, and when that weakref is broken _mark_weakpool_invalid()
 * gets called in order to mark the object as invalid.
 *
 * You can destroy a pool in three ways:
 *   pool.destroy()
 *   pool.clear()
 *   pool.__del__()
 *
 * Each of the above functions destroys the pool's _is_valid member, setting
 * off a cascade of callback functions that set all the child objects that were
 * created in the pool to invalid.
 *
 * If a SWIG object is created from a memory pool, the Python wrapper should
 * store a full reference to the memory pool and a weakreference to _is_valid.
 * When you try to access the SWIG object, the Python wrapper will check the
 * _is_valid weakref to ensure that the pool has not been destroyed (see
 * proxy.swg to read the implementation details).
 *
 * This lets us gracefully throw an exception if you try to use an object
 * that was allocated out of a pool that was cleared, rather than crashing
 * like we used to do.
 *
 */

%pythoncode %{
import threading

application_pool = None
application_pool_lock = threading.Lock()
class GenericSWIGWrapper:
  def __init__(self, this, pool):
    """Create new Generic SWIG wrapper object"""
    import weakref
    self.this = this
    self._parent_pool = pool
    self._is_valid = weakref.ref(pool._is_valid)

  def set_parent_pool(self, pool):
    """Set the parent pool of this object"""
    self._parent_pool = pool

  def valid(self):
    """Is this object valid?"""
    return self._is_valid()

  def assert_valid(self):
    """Assert that this object is still valid"""
    assert self.valid(), "This object has already been destroyed"

  def _unwrap(self):
    """Return underlying SWIG object"""
    self.assert_valid()
    return self.this

def _mark_weakpool_invalid(weakpool):
  if weakpool and weakpool() and hasattr(weakpool(), "_is_valid"):
    del weakpool()._is_valid

%}

struct apr_pool_t {
  %extend {
    %pythoncode %{
      def set_parent_pool(self, parent_pool=None):
        """Create a new memory pool"""
        global application_pool

        try:
          application_pool_lock.acquire()

          self._parent_pool = parent_pool or application_pool
          self._mark_valid()

          # Protect important functions from GC
          self._apr_pool_destroy = _core.apr_pool_destroy
          self._svn_swig_py_clear_application_pool = \
            _core.svn_swig_py_clear_application_pool

          # If we are an application-level pool,
          # then set this pool to be the application-level pool
          if not self._parent_pool:
            svn_swig_py_set_application_pool(self, self)
            application_pool = self
        finally:
          application_pool_lock.release()

      def valid(self):
        """Check whether this memory pool and its parents
        are still valid"""