from buzzard._a_emissary import AEmissary, ABackEmissary
[docs]class APooledEmissary(AEmissary):
"""Base abstract class defining the common behavior of all sources that can deactivate and
reactivate their underlying driver at will.
This is useful to balance the number of active file descriptors.
This is useful to perform concurrent reads if the driver does no support it.
Features Defined
----------------
- An `activate` method to manually open the driver (Mostly useless feature since opening \
is automatic if necessary)
- A `deactivate` method to close the driver (Useful to flush data to disk)
- An `active_count` property
- An `active` property
"""
[docs] def activate(self):
"""Make sure that at least one driver object is active for this Raster/Vector"""
self._back.activate()
[docs] def deactivate(self):
"""Collect all active driver object for this Raster/Vector. If a driver object is currently
being used, will raise an exception."""
self._back.deactivate()
@property
def active_count(self):
"""Count how many driver objects are currently active for this Raster/Vector"""
return self._back.active_count
@property
def active(self):
"""Is there any driver object currently active for this Raster/Vector"""
return self._back.active
class ABackPooledEmissary(ABackEmissary):
"""Implementation of APooledEmissary"""
def __init__(self, uid, **kwargs):
self.uid = uid
super(ABackPooledEmissary, self).__init__(**kwargs)
def activate(self):
self.back_ds.activate(self.uid, self.allocator)
def deactivate(self):
self.back_ds.deactivate(self.uid)
@property
def active_count(self):
return self.back_ds.active_count(self.uid)
@property
def active(self):
return self.back_ds.active_count(self.uid) > 0
def close(self):
"""Virtual method:
- May be overriden
- Should always be called
"""
self.back_ds.deactivate(self.uid)
super(ABackPooledEmissary, self).close()