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authorJohn Mark Bell <jmb@netsurf-browser.org>2007-07-28 23:31:11 +0000
committerJohn Mark Bell <jmb@netsurf-browser.org>2007-07-28 23:31:11 +0000
commite770e9f319a513d5fa2838629fe26c077df45df8 (patch)
tree382a6bb94403a43b735840a41a3d7273b3ab3315
parentbe76092abf32f4c586717452fe0d2357220ea29d (diff)
downloadlibdom-e770e9f319a513d5fa2838629fe26c077df45df8.tar.gz
libdom-e770e9f319a513d5fa2838629fe26c077df45df8.tar.bz2
Improve description of the list of nodes pending deletion and how it is related to the process of deleting a Document.
svn path=/trunk/dom/; revision=3469
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@@ -100,3 +100,43 @@ Example
list of nodes pending deletion).
2) The NodeList is destroyed.
+Destruction of Documents
+------------------------
+
+ Assumptions:
+
+ 1) Nodes within a document do not hold explicit references upon it.
+ 2) Container data structures which address nodes in a document hold
+ an explicit reference upon the document.
+ [FIXME: and upon the root node of the subtree they address -- this
+ implies that the explicit reference is unnecessary, as the
+ addressed node will be added to the list of nodes pending
+ deletion]
+ 3) A document has no parent (i.e. the parent pointer is always NULL).
+ 4) A given node may be located in either the document tree or the
+ list of nodes pending deletion. It may not be located in both
+ data structures simultaneously.
+ 5) Nodes in the list of nodes pending deletion are in use by the
+ client.
+
+ The above assumptions imply the following:
+
+ + If a document has a non-zero reference count, it is in use by
+ the client. (1,2)
+ + If the document's reference count reaches zero, it is no longer
+ in use and is eligible for deletion. (1,2,3)
+ + The document destructor must attempt to forcibly delete the
+ contents of the document tree as the nodes do not hold a reference
+ upon the document. (1)
+ + On destruction of a node, it must be removed from the list of nodes
+ pending deletion. (4)
+ + The document may not be destroyed if the list of nodes pending
+ deletion is non-empty after the destructor has attempted to
+ destroy the document tree. (4,5)
+
+ Therefore, document destruction proceeds as follows:
+
+ 1) Forcibly destroy the document tree.
+ 2) If the list of nodes pending deletion is non-empty, stop.
+ 3) The list of nodes pending deletion is empty, so destroy the
+ document.