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From mdue...@apache.org
Subject svn commit: r1414189 - /jackrabbit/oak/trunk/doc/jsop-diff.md
Date Tue, 27 Nov 2012 13:58:41 GMT
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



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