org.python.core

Class JyAttribute

java.lang.Object

org.python.core.JyAttribute

All Implemented Interfaces:

java.io.Serializable

public abstract class JyAttribute
extends java.lang.Object
implements java.io.Serializable

Manages a linked list of general purpose Object-attributes that can be attached to arbitrary PyObjects. This method replaces the formerly used method of maintaining weak hash-maps (WeakHashMap) for such cases. These weak hash-maps were used to map PyObjects to such attributes, for instance to attach GlobalRef-objects in the WeakrefModule.

Attributes attached via the weak hash-map-method break, if the PyObject is resurrected in its finalizer. The JyAttribute-method is resurrection-safe.

To reduce memory footprint of PyObjects, the fields for FinalizeTriggers and javaProxy are included in the list; javaProxy always on top so there is no speed-regression, FinalizeTrigger on bottom, as it is usually never accessed.

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Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static byte	FINALIZE_TRIGGER_ATTR
static byte	GC_CYCLE_MARK_ATTR Used by gc-module to mark cyclic trash.
static byte	GC_DELAYED_FINALIZE_CRITICAL_MARK_ATTR Used by gc-module to mark finalizable objects that might have been resurrected during a delayed finalization process.
static byte	JAVA_PROXY_ATTR
static byte	JYNI_HANDLE_ATTR Reserved for use by JyNI.
static byte	PY_ID_ATTR Allows the id of a PyObject to persist resurrection of that object.
static byte	PYCLASS_PY2JY_CACHE_ATTR Only used internally by Py.javaPyClass(PyObject, Class)
static byte	WEAK_REF_ATTR Stores list of weak references linking to this PyObject.
static byte	WEAKREF_PENDING_GET_ATTR Holds the current thread for an AbstractReference while referent-retrieval is pending due to a potentially restored-by-resurrection weak reference.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	JyAttribute(byte attr_type)

Method Summary

Modifier and Type	Method and Description
static void	debugPrintAttributes(PyObject o, java.io.PrintStream out) Prints the current state of the attribute-list of the given object to the given stream.
static void	delAttr(PyObject ob, byte attr_type) Removes the attribute of given type from the given object's attribute-list (if it existed at all).
static java.lang.Object	getAttr(PyObject ob, byte attr_type) Retrieves the attribute of the given type from the given PyObject.
protected abstract JyAttribute	getNext()
protected abstract java.lang.Object	getValue()
static boolean	hasAttr(PyObject ob, byte attr_type) Checks whether the given PyObject has an attribute of the given type attached.
static byte	reserveCustomAttrType() Reserves and returns a new non-transient attr type for custom use.
static byte	reserveTransientCustomAttrType() Reserves and returns a new transient attr type for custom use.
static void	setAttr(PyObject ob, byte attr_type, java.lang.Object value) Sets the attribute of type attr_type in ob to value.
protected abstract void	setNext(JyAttribute next)
protected abstract void	setValue(java.lang.Object value)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

JAVA_PROXY_ATTR

public static final byte JAVA_PROXY_ATTR

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Constant Field Values

WEAK_REF_ATTR

public static final byte WEAK_REF_ATTR

Stores list of weak references linking to this PyObject. This list is weakref-based, so it does not keep the weakrefs alive. This is the only way to find out which weakrefs (i.e. AbstractReference) linked to the object after a resurrection. A weak hash-map-based approach for this purpose would break on resurrection.

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Constant Field Values

JYNI_HANDLE_ATTR

public static final byte JYNI_HANDLE_ATTR

Reserved for use by JyNI.

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Constant Field Values

PY_ID_ATTR

public static final byte PY_ID_ATTR

Allows the id of a PyObject to persist resurrection of that object.

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Constant Field Values

WEAKREF_PENDING_GET_ATTR

public static final byte WEAKREF_PENDING_GET_ATTR

Holds the current thread for an AbstractReference while referent-retrieval is pending due to a potentially restored-by-resurrection weak reference. After the restore has happened or the clear was confirmed, the thread is interrupted and the attribute is cleared.

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Constant Field Values

PYCLASS_PY2JY_CACHE_ATTR

public static final byte PYCLASS_PY2JY_CACHE_ATTR

Only used internally by Py.javaPyClass(PyObject, Class)

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Constant Field Values

GC_CYCLE_MARK_ATTR

public static final byte GC_CYCLE_MARK_ATTR

Used by gc-module to mark cyclic trash. Searching for cyclic trash is usually not required by Jython. It is only done if gc-features are enabled that mimic CPython behavior.

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Constant Field Values

GC_DELAYED_FINALIZE_CRITICAL_MARK_ATTR

public static final byte GC_DELAYED_FINALIZE_CRITICAL_MARK_ATTR

Used by gc-module to mark finalizable objects that might have been resurrected during a delayed finalization process.

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Constant Field Values

FINALIZE_TRIGGER_ATTR

public static final byte FINALIZE_TRIGGER_ATTR

See Also:

Constant Field Values

Constructor Detail

JyAttribute

protected JyAttribute(byte attr_type)

Method Detail

reserveCustomAttrType

public static byte reserveCustomAttrType()

Reserves and returns a new non-transient attr type for custom use.

Returns:

a non-transient attr type for custom use

reserveTransientCustomAttrType

public static byte reserveTransientCustomAttrType()

Reserves and returns a new transient attr type for custom use.

Returns:

a transient attr type for custom use

getNext

protected abstract JyAttribute getNext()

setNext

protected abstract void setNext(JyAttribute next)

getValue

protected abstract java.lang.Object getValue()

setValue

protected abstract void setValue(java.lang.Object value)

hasAttr

public static boolean hasAttr(PyObject ob,
                              byte attr_type)

Checks whether the given PyObject has an attribute of the given type attached.

getAttr

public static java.lang.Object getAttr(PyObject ob,
                                       byte attr_type)

Retrieves the attribute of the given type from the given PyObject. If no attribute of the given type is attached, null is returned.

debugPrintAttributes

public static void debugPrintAttributes(PyObject o,
                                        java.io.PrintStream out)

Prints the current state of the attribute-list of the given object to the given stream. (Intended for debugging)

setAttr

public static void setAttr(PyObject ob,
                           byte attr_type,
                           java.lang.Object value)

Sets the attribute of type attr_type in ob to value. If no corresponding attribute exists yet, one is created. If value == null, the attribute is removed (if it existed at all).

delAttr

public static void delAttr(PyObject ob,
                           byte attr_type)

Removes the attribute of given type from the given object's attribute-list (if it existed at all). This is equivalent to calling setAttr(ob, attr_type, null).