org.eclipse.compare.structuremergeviewer
Class Differencer
java.lang.Object
org.eclipse.compare.structuremergeviewer.Differencer
-
public class Differencer
- extends
Object
A generic two-way or three-way differencing engine.
The engine is used by calling one of the findDifferences
methods and passing
in the objects to compare.
The engine calls the following methods on the input objects to perform the compare:
-
getChildren
: for enumerating the children of an object (if any),
-
contentsEqual
: for comparing the content of leaf objects, that is, objects without children,
-
visit
: for every pair of compared object the compare result is passed in.
Clients may use as is, or subclass to provide a custom implementation for the three hooks.
However the default implementation already deals with the typical case:
-
getChildren
: tries to apply the IStructureComparator
interface to enumerate the children,
-
contentsEqual
: tries to apply the IStreamContentAccessor
interface
to perform a byte-wise content comparison,
-
visit
: creates a DiffNode
for any detected difference between the compared objects and
links it under a parent node effectively creating a tree of differences.
The different kind of changes detected by the engine are decoded as follows:
In the two-way case only NO_CHANGE, ADDITION, DELETION, and CHANGE are used.
In the three-way case these constants are bitwise ORed with one of directional constants
LEFT, RIGHT, and CONFLICTING.
Field Summary
|
static int
|
ADDITION
Difference constant (value 1) indicating one side was added. |
static int
|
CHANGE
Difference constant (value 3) indicating side changed. |
static int
|
CHANGE_TYPE_MASK
Bit mask (value 3) for extracting the kind of difference. |
static int
|
CONFLICTING
Three-way change constant (value 12) indicating a change on left and
right sides. |
static int
|
DELETION
Difference constant (value 2) indicating one side was removed. |
static int
|
DIRECTION_MASK
Bit mask (value 12) for extracting the direction of a three-way change. |
static int
|
LEFT
Three-way change constant (value 4) indicating a change on left side. |
static int
|
NO_CHANGE
Difference constant (value 0) indicating no difference. |
static int
|
PSEUDO_CONFLICT
Constant (value 16) indicating a change on left and
right side (with respect to ancestor) but left and right are identical. |
static int
|
RIGHT
Three-way change constant (value 8) indicating a change on right side. |
Constructor Summary
|
Differencer
()
Creates a new differencing engine. |
Method Summary
|
protected boolean
|
contentsEqual
(
Object input1,
Object input2)
Performs a content compare on the two given inputs. |
Object
|
findDifferences
(boolean threeWay,
IProgressMonitor pm,
Object data,
Object ancestor,
Object left,
Object right)
Starts the differencing engine on the three input objects. |
protected
Object[]
|
getChildren
(
Object input)
Returns the children of the given input or null if there are no children. |
protected void
|
updateProgress
(
IProgressMonitor progressMonitor,
Object node)
Called for every leaf or node compare to update progress information. |
protected
Object
|
visit
(
Object data,
int result,
Object ancestor,
Object left,
Object right)
Called for every node or leaf comparison. |
Methods inherited from class java.lang.
Object
|
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait
|
NO_CHANGE
public static final int NO_CHANGE
- Difference constant (value 0) indicating no difference.
-
See Also:
-
Constant Field Values
ADDITION
public static final int ADDITION
- Difference constant (value 1) indicating one side was added.
-
See Also:
-
Constant Field Values
DELETION
public static final int DELETION
- Difference constant (value 2) indicating one side was removed.
-
See Also:
-
Constant Field Values
CHANGE
public static final int CHANGE
- Difference constant (value 3) indicating side changed.
-
See Also:
-
Constant Field Values
CHANGE_TYPE_MASK
public static final int CHANGE_TYPE_MASK
- Bit mask (value 3) for extracting the kind of difference.
-
See Also:
-
Constant Field Values
LEFT
public static final int LEFT
- Three-way change constant (value 4) indicating a change on left side.
-
See Also:
-
Constant Field Values
RIGHT
public static final int RIGHT
- Three-way change constant (value 8) indicating a change on right side.
-
See Also:
-
Constant Field Values
CONFLICTING
public static final int CONFLICTING
- Three-way change constant (value 12) indicating a change on left and
right sides.
-
See Also:
-
Constant Field Values
DIRECTION_MASK
public static final int DIRECTION_MASK
- Bit mask (value 12) for extracting the direction of a three-way change.
-
See Also:
-
Constant Field Values
PSEUDO_CONFLICT
public static final int PSEUDO_CONFLICT
- Constant (value 16) indicating a change on left and
right side (with respect to ancestor) but left and right are identical.
-
See Also:
-
Constant Field Values
Differencer
public Differencer()
- Creates a new differencing engine.
findDifferences
public
Object findDifferences(boolean threeWay,
IProgressMonitor pm,
Object data,
Object ancestor,
Object left,
Object right)
- Starts the differencing engine on the three input objects. If threeWay is
true
a
three-way comparison is performed, otherwise a two-way compare (in the latter case the ancestor argument is ignored).
The progress monitor is passed to the method updateProgress
which is called for every node or
leaf compare. The method returns the object that was returned from the top-most call to method visit
.
At most two of the ancestor, left, and right parameters are allowed to be null
.
-
-
Parameters:
-
threeWay
- if true
a three-way comparison is performed, otherwise a two-way compare -
pm
- a progress monitor which is passed to method updateProgress
-
data
- a client data that is passed to the top-level call to visit
-
ancestor
- the ancestor object of the compare (may be null
) -
left
- the left object of the compare -
right
- the right object of the compare
-
Returns:
- the object returned from the top most call to method
visit
,
possibly null
visit
protected
Object visit(
Object data,
int result,
Object ancestor,
Object left,
Object right)
- Called for every node or leaf comparison.
The differencing engine passes in the input objects of the compare and the result of the compare.
The data object is the value returned from a call to the
visit
method on the parent input.
It can be considered the "parent" reference and is useful when building a tree.
The Differencer
implementation returns a new
DiffNode
which is initialized with the corresponding values.
Subclasses may override.
-
-
Parameters:
-
data
- object returned from parent call to visit
,
possibly null
-
result
- the result of the compare operation performed on the three inputs -
ancestor
- the compare ancestor of the left and right inputs -
left
- the left input to the compare -
right
- the right input to the compare
-
Returns:
- the result, possibly
null
contentsEqual
protected boolean contentsEqual(
Object input1,
Object input2)
- Performs a content compare on the two given inputs.
The Differencer
implementation
returns true
if both inputs implement IStreamContentAccessor
and their byte contents is identical. Subclasses may override to implement
a different content compare on the given inputs.
-
-
Parameters:
-
input1
- first input to contents compare -
input2
- second input to contents compare
-
Returns:
-
true
if content is equal
getChildren
protected
Object[] getChildren(
Object input)
- Returns the children of the given input or
null
if there are no children.
The Differencer
implementation checks whether the input
implements the IStructureComparator
interface. If yes it is used
to return an array containing all children. Otherwise null
is returned.
Subclasses may override to implement a different strategy to enumerate children.
-
-
Parameters:
-
input
- the object for which to return children
-
Returns:
- the children of the given input or
null
if there are no children.
updateProgress
protected void updateProgress(
IProgressMonitor progressMonitor,
Object node)
- Called for every leaf or node compare to update progress information.
The Differencer
implementation shows the name of the input object
as a subtask. Subclasses may override.
-
-
Parameters:
-
progressMonitor
- the progress monitor for reporting progress -
node
- the currently processed non-null
node
Guidelines for using Eclipse APIs.
Copyright (c) Eclipse contributors and others 2000, 2008. All rights reserved.