Author: mduerig
Date: Tue Nov 27 13:58:40 2012
New Revision: 1414189
URL: http://svn.apache.org/viewvc?rev=1414189&view=rev
Log:
OAK-464: RootImpl.rebase() doesn't handle move operations correctly
pseudo code form jsop diff algorithm
Added:
jackrabbit/oak/trunk/doc/jsop-diff.md
Added: jackrabbit/oak/trunk/doc/jsop-diff.md
URL: http://svn.apache.org/viewvc/jackrabbit/oak/trunk/doc/jsop-diff.md?rev=1414189&view=auto
==============================================================================
--- jackrabbit/oak/trunk/doc/jsop-diff.md (added)
+++ jackrabbit/oak/trunk/doc/jsop-diff.md Tue Nov 27 13:58:40 2012
@@ -0,0 +1,69 @@
+ // Global variable holding the JSOP journal after the diffTree below returns.
+ jsop = ""
+
+ /*
+ Create a JSOP journal, which when applied to tree S will transform
+ it to tree T.
+ */
+ diffTrees(S, T) {
+ // Create a location (trash) which will temporarily hold removed nodes.
+ // This is necessary since these (or child nodes thereof) might still be
+ // needed in move operations occurring only later in the differencing process.
+ X = S.addNode(createUniqueName)
+
+ // The main differencing process starts at the roots of the trees and
+ // progresses recursively level by level.
+ diffNodes(X, S, T)
+
+ // Remove the trash location and all its content
+ jsop += "-" + X.path
+ }
+
+ /*
+ Create JSOP operations for the differences of the immediate children
+ of trees S and T. Tree X serves as trash.
+ */
+ diffNode(X, S, T) {
+ deleted = S.childNames \ T.childNames // set difference
+ added = T.childNames \ S.childNames
+
+ // Need to take care of deleted nodes first in order to avoid
+ // name clashes when adding new nodes later.
+ for (d : deleted) {
+ t = S.child(d)
+ n = createUniqueName
+
+ // Deleted nodes are moved to trash.
+ t.moveTo(X, n) // Move node t to parent X with name n
+ op = ">" + t.sourceNode.path + ":" + t.path
+ jsop += op
+ S.apply(op) // Transform S according to the single op
+ }
+
+ for (a : added) {
+ t = T.child(a)
+
+ // assume we can detect a copied node and know its source node
+ if (isCopied(t)) {
+ op = "*" + t.sourceNode.path + ":" + t.path
+ }
+
+ // assume we can detect a moved node and know its source node
+ else if (isMoved(t)) {
+ op = ">" + t.sourceNode.path + ":" + t.path
+ }
+
+ // this is an added node
+ else {
+ op = "+" + t.path
+ }
+
+ jsop += op
+ S.apply(op) // Transform S according to the single op
+ }
+
+ // assert S.childNames == T.childNames
+ for (c : T.childNames) {
+ diffNode(S.child(c), T.child(c))
+ }
+ }
\ No newline at end of file
|