Class SequenceComparator<S extends Sequence>

  extended by org.eclipse.jgit.diff.SequenceComparator<S>
Type Parameters:
S - type of sequence the comparator supports.
Direct Known Subclasses:
HashedSequenceComparator, RawTextComparator, SubsequenceComparator

public abstract class SequenceComparator<S extends Sequence>
extends Object

Equivalence function for a Sequence compared by difference algorithm. Difference algorithms can use a comparator to compare portions of two sequences and discover the minimal edits required to transform from one sequence to the other sequence. Indexes within a sequence are zero-based.

Constructor Summary
Method Summary
abstract  boolean equals(S a, int ai, S b, int bi)
          Compare two items to determine if they are equivalent.
abstract  int hash(S seq, int ptr)
          Get a hash value for an item in a sequence.
 Edit reduceCommonStartEnd(S a, S b, Edit e)
          Modify the edit to remove common leading and trailing items.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail


public SequenceComparator()
Method Detail


public abstract boolean equals(S a,
                               int ai,
                               S b,
                               int bi)
Compare two items to determine if they are equivalent. It is permissible to compare sequence a with itself (by passing a again in position b).

a - the first sequence.
ai - item of ai to compare.
b - the second sequence.
bi - item of bi to compare.
true if the two items are identical according to this function's equivalence rule.


public abstract int hash(S seq,
                         int ptr)
Get a hash value for an item in a sequence. If two items are equal according to this comparator's equals(Sequence, int, Sequence, int) method, then this hash method must produce the same integer result for both items. It is not required for two items to have different hash values if they are are unequal according to the equals() method.

seq - the sequence.
ptr - the item to obtain the hash for.
hash the hash value.


public Edit reduceCommonStartEnd(S a,
                                 S b,
                                 Edit e)
Modify the edit to remove common leading and trailing items. The supplied edit e is reduced in size by moving the beginning A and B points so the edit does not cover any items that are in common between the two sequences. The ending A and B points are also shifted to remove common items from the end of the region.

a - the first sequence.
b - the second sequence.
e - the edit to start with and update.
e if it was updated in-place, otherwise a new edit containing the reduced region.

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