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| Provides support for finding and displaying the differences |
| between hierarchically structured data. |
| <h2> |
| Package Specification</h2> |
| |
| The class <b>Differencer</b> is a differencing engine for hierarchically |
| structured data. It takes two or three inputs and performs a two-way or |
| three-way compare on them. |
| <p> |
| |
| If the input elements to the differencing engine implement the <b>IStructureComparator</b> |
| interface the engine recursively applies itself to the children of |
| the input element. Leaf elements must implement the <b>org.eclipse.compare.IStreamContentAccessor</b> |
| interface so that the differencer can perform a bytewise comparison on their contents. |
| <p> |
| |
| One good example for this is <b>org.eclipse.compare.ResourceNode</b> which implements both interfaces |
| (and more) for Eclipse workspace resources (org.eclipse.core.resources.IResource). |
| <p> |
| |
| Another example is the <b>DocumentRangeNode</b> which can be used to compare hierarchical structures |
| that are superimposed on a document, that is where nodes and leafs correspond to ranges in a document |
| (<b>org.eclipse.compare.contentmergeviewer.IDocumentRange</b>). |
| <br> |
| Typically <b>DocumentRangeNode</b>s are created while parsing a document and they represent |
| the semantic entities of the document (e.g. a Java class, method or field). |
| The two subclasses <b>JavaNode</b> (in org.eclipse.jdt.internal.ui.compare) |
| and <b>PropertyNode</b> (in org.eclipse.jdt.internal.ui.compare) are good examples for this. |
| <p> |
| |
| By default the differencing engine returns the result of the compare operation |
| as a tree of <b>DiffNode</b> objects. However, this can be changed by overriding |
| a single method of the engine. |
| <p> |
| |
| Every <b>DiffNode</b> describes the changes among the two or three inputs. |
| <p> |
| |
| A tree of <b>DiffNodes</b> can be displayed in a <b>DiffTreeViewer</b>. |
| The <b>DiffTreeViewer</b> requires that inner nodes of the tree implement |
| the <b>IDiffContainer</b> interface and leafs the <b>IDiffElement</b> interface. |
| <p> |
| |
| The typical steps to compare hierarchically structured data and to display |
| the differences would be to: |
| <ul> |
| <li> |
| map the input data into a tree of <b>IStructureComparator</b> and <b>IStreamContentAccessor</b>s,</li> |
| |
| <li> |
| perform the compare operation by means of the <b>Differencer</b>, and</li> |
| |
| <li> |
| feed the differencing result into the <b>DiffTreeViewer</b>.</li> |
| |
| </ul> |
| |
| The <b>StructureDiffViewer</b> is a specialized <b>DiffTreeViewer</b> |
| that automates the three steps from above. It takes a single input object |
| of type <b>ICompareInput</b> from which it retrieves the two or three |
| input elements to compare. Then it uses a <b>IStructureCreator</b> to |
| extract a tree of <b>IStructureComparator</b> and <b>IStreamContentAccessor</b> |
| from them. These trees are then compared with the differencing engine and |
| the result is displayed in the tree viewer. |
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