--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/prevayler/implementation/NumberFileFinder.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,126 @@
+/*
+  The copyright of all source code included in this Prevayler distribution is
+  held by Klaus Wuestefeld, except the files that specifically state otherwise.
+  All rights are reserved. "PREVAYLER" is a trademark of Klaus Wuestefeld.
+
+
+  BSD License:
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+
+  - Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+  - Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+ 
+  - Neither the name of Prevayler nor the names of its contributors may be used
+  to endorse or promote products derived from this software without specific
+  prior written permission.
+
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
+  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
+  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
+  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
+  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+  POSSIBILITY OF SUCH DAMAGE.
+*/
+
+package org.prevayler.implementation;
+
+import java.io.*;
+import java.util.Arrays;
+import java.text.*;
+
+/** Finds the last .snapshot file by number and finds all the subsequent pending .log files.
+*/
+class NumberFileFinder {
+
+    private File directory;
+	private File lastSnapshot;
+    private long fileNumber;
+    private NumberFileCreator fileCreator;
+
+    /** @throws IOException if location does not exist and cannot be created as a directory.
+    * @throws IllegalArgumentException If location exists and is not a directory.
+    */
+    public NumberFileFinder(String directoryName) throws IOException {
+	this.directory = new File(directoryName);
+	if (!directory.exists() && !directory.mkdirs()) throw new IOException("Directory doesn't exist and could not be created: " + directoryName);
+	if (!directory.isDirectory()) throw new IllegalArgumentException("Path exists but is not a directory: " + directoryName);
+
+	init();
+	}
+
+    /** Returns the last snapshot file. Returns null if there are no snapshots.
+    */
+    public File lastSnapshot() {
+	return lastSnapshot;
+	}
+
+    /** @throws EOFException if there are no more pending .log files.
+    */
+    public File nextPendingLog() throws EOFException {
+	File log = new File(directory, NumberFileCreator.LOG_FORMAT.format(fileNumber + 1));
+	if (!log.exists()) {
+	    fileCreator = new NumberFileCreator(directory, fileNumber + 1);
+	    throw new EOFException();
+	}
+	++fileNumber;
+	return log;
+	}
+
+    /** Returns a NumberFileCreator that will start off with the first number after the last .log file number.
+    * @return null if there are still .log files pending.
+    */
+    public NumberFileCreator fileCreator() {
+	return fileCreator;
+    }
+
+    private void init() throws IOException {
+	findLastSnapshot();
+	fileNumber = lastSnapshot == null
+	    ? 0
+	    : number(lastSnapshot);
+	}
+
+    private long number(File snapshot) throws NumberFormatException {  //NumberFomatException is a RuntimeException.
+	String name = snapshot.getName();
+	if (!name.endsWith("." + NumberFileCreator.SNAPSHOT_SUFFIX)) throw new NumberFormatException();
+	return Long.parseLong(name.substring(0,name.indexOf('.')));    // "00000.snapshot" becomes "00000".
+	//The following doesn't work! It throws ParseException (UnparseableNumber): return (NumberFileCreator.SNAPSHOT_FORMAT.parse(snapshot.getName())).longValue();
+	}
+
+    private void findLastSnapshot() throws IOException {
+	File[] snapshots = directory.listFiles(new SnapshotFilter());
+	if (snapshots == null) throw new IOException("Error reading file list from directory " + directory);
+
+	Arrays.sort(snapshots);
+
+	lastSnapshot = snapshots.length > 0
+	    ? snapshots[snapshots.length - 1]
+	    : null;
+	}
+
+
+    private class SnapshotFilter implements FileFilter {
+
+	public boolean accept(File file) {
+	    try {
+		number(file);
+	    } catch (NumberFormatException nfx) {
+		return false;
+	    }
+	    return true;
+		}
+	}
+
+}