Region.java

/*
 * Copyright (C) 2011, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
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 *   notice, this list of conditions and the following disclaimer.
 *
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package org.eclipse.jgit.blame;

/**
 * Region of the result that still needs to be computed.
 * <p>
 * Regions are held in a singly-linked-list by {@link Candidate} using the
 * {@link Candidate#regionList} field. The list is kept in sorted order by
 * {@link #resultStart}.
 */
class Region {
    /** Next entry in the region linked list. */
    Region next;

    /** First position of this region in the result file blame is computing. */
    int resultStart;

    /** First position in the {@link Candidate} that owns this Region. */
    int sourceStart;

    /** Length of the region, always >= 1. */
    int length;

    Region(int rs, int ss, int len) {
        resultStart = rs;
        sourceStart = ss;
        length = len;
    }

    /**
     * Copy the entire result region, but at a new source position.
     *
     * @param newSource
     *            the new source position.
     * @return the same result region, but offset for a new source.
     */
    Region copy(int newSource) {
        return new Region(resultStart, newSource, length);
    }

    /**
     * Split the region, assigning a new source position to the first half.
     *
     * @param newSource
     *            the new source position.
     * @param newLen
     *            length of the new region.
     * @return the first half of the region, at the new source.
     */
    Region splitFirst(int newSource, int newLen) {
        return new Region(resultStart, newSource, newLen);
    }

    /**
     * Edit this region to remove the first {@code d} elements.
     *
     * @param d
     *            number of elements to remove from the start of this region.
     */
    void slideAndShrink(int d) {
        resultStart += d;
        sourceStart += d;
        length -= d;
    }

    Region deepCopy() {
        Region head = new Region(resultStart, sourceStart, length);
        Region tail = head;
        for (Region n = next; n != null; n = n.next) {
            Region q = new Region(n.resultStart, n.sourceStart, n.length);
            tail.next = q;
            tail = q;
        }
        return head;
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        StringBuilder buf = new StringBuilder();
        Region r = this;
        do {
            if (r != this)
                buf.append(',');
            buf.append(r.resultStart);
            buf.append('-');
            buf.append(r.resultStart + r.length);
            r = r.next;
        } while (r != null);
        return buf.toString();
    }
}