--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/internal/BatchRangeHelper.java	Fri Dec 21 21:20:26 2012 +0100
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2012 TMate Software Ltd
+ *  
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * For information on how to redistribute this software under
+ * the terms of a license other than GNU General Public License
+ * contact TMate Software at support@hg4j.com
+ */
+package org.tmatesoft.hg.internal;
+
+import java.util.Arrays;
+import java.util.NoSuchElementException;
+
+/**
+ * Helper to break given range [start..end] (inclusive bounds) to series of ranges,
+ * all but last are of batchSize length, and the last one is at most of batchSize+batchSizeTolerance length.
+ * 
+ * Range is [{@link #start()rangeStart}..{@link #end() rangeEnd}], where rangeStart is less or equal to rangeEnd.
+ * 
+ * When reverse range iteration is requested, original range is iterated from end to start, but the subranges 
+ * boundaries are in natural order. i.e. for 0..100, 10 first subrange would be [91..100], not [100..91]. This 
+ * helps clients of this class to get [start()..end()] in natural order regardless of iteration direction.
+ * 
+ * Note, this class (and its treatment of inclusive boundaries) is designed solely for use with methods that navigate
+ * revlogs and take (start,end) pair of inclusive range.
+ *  
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+public class BatchRangeHelper {
+
+	private final int rangeCount;
+	private final int rangeDelta;
+	private final int nextValueDelta;
+	private final int firstBoundary, lastBoundary;
+	private int rangeIndex, rangeValue, rangeStart, rangeEnd;
+
+	public BatchRangeHelper(int start, int end, int batchSize, boolean reverse) {
+		this(start, end, batchSize, batchSize/5, reverse); 
+	}
+
+	public BatchRangeHelper(int start, int end, int batchSize, int batchSizeTolerance, boolean reverse) {
+		assert end >= start;
+		assert start >= 0;
+		assert batchSize > 0;
+		assert batchSizeTolerance >= 0;
+		final int totalElements = end-start+1;
+		int batchRangeCount = totalElements / batchSize;
+		// batchRangeCount == 0, totalElements > 0 => need at least 1 range
+		if (batchRangeCount == 0 || batchRangeCount*batchSize+batchSizeTolerance < totalElements) {
+			batchRangeCount++;
+		}
+		rangeCount = batchRangeCount;
+		rangeDelta = batchSize-1; // ranges are inclusive, and always grow naturally.
+		nextValueDelta = reverse ? -batchSize : batchSize;
+		firstBoundary = reverse ? end-rangeDelta : start;
+		lastBoundary = reverse ? start : end;
+		reset();
+	}
+
+	public boolean hasNext() {
+		return rangeIndex < rangeCount;
+	}
+	
+	public void next() {
+		if (!hasNext()) {
+			throw new NoSuchElementException();
+		}
+		rangeStart = rangeValue;
+		rangeEnd = rangeValue + rangeDelta;
+		rangeValue += nextValueDelta;
+		if (++rangeIndex >= rangeCount) {
+			if (nextValueDelta < 0) {
+				// reverse iteration, lastBoundary represents start
+				rangeStart = lastBoundary;
+			} else {
+				// lastBoundary represents end
+				rangeEnd = lastBoundary;
+			}
+		}
+	}
+	
+	public int start() {
+		return rangeStart;
+	}
+	
+	public int end() {
+		return rangeEnd;
+	}
+	
+	public BatchRangeHelper reset() {
+		rangeValue = firstBoundary;
+		rangeIndex = 0;
+		return this;
+	}
+
+	public int[] toArray() {
+		int[] rv = new int[rangeCount*2];
+		reset();
+		int i = 0;
+		while (hasNext()) {
+			next();
+			rv[i++] = start();
+			rv[i++] = end();
+		}
+		reset();
+		return rv;
+	}
+
+	public static void main(String[] args) {
+		System.out.println("With remainder within tolerance");
+		System.out.println(Arrays.toString(new BatchRangeHelper(0, 102, 10, 4, false).toArray()));
+		System.out.println(Arrays.toString(new BatchRangeHelper(0, 102, 10, 4, true).toArray()));
+		System.out.println("With remainder out of tolerance");
+		System.out.println(Arrays.toString(new BatchRangeHelper(0, 102, 10, 2, false).toArray()));
+		System.out.println(Arrays.toString(new BatchRangeHelper(0, 102, 10, 2, true).toArray()));
+		System.out.println("Range smaller than batch");
+		System.out.println(Arrays.toString(new BatchRangeHelper(1, 9, 10, false).toArray()));
+		System.out.println(Arrays.toString(new BatchRangeHelper(1, 9, 10, true).toArray()));
+		System.out.println("Range smaller than batch and smaller than tolerance");
+		System.out.println(Arrays.toString(new BatchRangeHelper(1, 9, 10, 20, false).toArray()));
+		System.out.println(Arrays.toString(new BatchRangeHelper(1, 9, 10, 20, true).toArray()));
+		System.out.println("Zero tolerance");
+		System.out.println(Arrays.toString(new BatchRangeHelper(0, 100, 10, 0, false).toArray()));
+		System.out.println(Arrays.toString(new BatchRangeHelper(0, 100, 10, 0, true).toArray()));
+		System.out.println("Right to boundary");
+		System.out.println(Arrays.toString(new BatchRangeHelper(1, 100, 10, false).toArray()));
+		System.out.println(Arrays.toString(new BatchRangeHelper(1, 100, 10, true).toArray()));
+	}
+}