--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/internal/RevlogCompressor.java	Wed Jan 23 17:46:12 2013 +0100
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2013 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.io.IOException;
+import java.io.OutputStream;
+import java.util.zip.Deflater;
+import java.util.zip.DeflaterOutputStream;
+
+/**
+ * 
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+public class RevlogCompressor {
+	private final Deflater zip;
+	private byte[] sourceData;
+	private int compressedLenEstimate;
+	
+	public RevlogCompressor() {
+		zip = new Deflater();
+	}
+
+	public void reset(byte[] source) {
+		sourceData = source;
+		compressedLenEstimate = -1;
+	}
+	
+	public int writeCompressedData(OutputStream out) throws IOException {
+		zip.reset();
+		DeflaterOutputStream dos = new DeflaterOutputStream(out, zip, Math.min(2048, sourceData.length));
+		dos.write(sourceData);
+		dos.finish();
+		return zip.getTotalOut();
+	}
+
+	public int getCompressedLengthEstimate() {
+		if (compressedLenEstimate != -1) {
+			return compressedLenEstimate;
+		}
+		zip.reset();
+		int rv = 0;
+		// from DeflaterOutputStream:
+		byte[] buffer = new byte[Math.min(2048, sourceData.length)];
+        for (int i = 0, stride = buffer.length; i < sourceData.length; i+= stride) {
+            zip.setInput(sourceData, i, Math.min(stride, sourceData.length - i));
+            while (!zip.needsInput()) {
+            	rv += zip.deflate(buffer, 0, buffer.length);
+            }
+        }
+        zip.finish();
+        while (!zip.finished()) {
+        	rv += zip.deflate(buffer, 0, buffer.length);
+        }
+        return compressedLenEstimate = rv;
+	}
+}