--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/prevayler/implementation/NumberFileCreator.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,80 @@
+/*
+  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.text.*;
+
+/** Creates .log and .snapshot files using a number sequence for the file name.
+*/
+class NumberFileCreator {
+
+    public static final String SNAPSHOT_SUFFIX = "snapshot";
+    public static final String LOGFILE_SUFFIX = "commandLog";
+    public static final DecimalFormat SNAPSHOT_FORMAT = new DecimalFormat("000000000000000000000'.'" + SNAPSHOT_SUFFIX); //21 zeros (enough for a long number).
+    public static final DecimalFormat LOG_FORMAT = new DecimalFormat("000000000000000000000'.'" + LOGFILE_SUFFIX);  //21 zeros (enough for a long number).
+
+    private File directory;
+    private long nextFileNumber;
+
+    public NumberFileCreator(File directory, long firstFileNumber) {
+	this.directory = directory;
+	this.nextFileNumber = firstFileNumber;
+	}
+
+    File newLog() throws IOException {
+	File log = new File(directory, LOG_FORMAT.format(nextFileNumber));
+	if(!log.createNewFile()) throw new IOException("Attempt to create command log file that already existed: " + log);;
+
+	++nextFileNumber;
+	return log;
+    }
+
+    File newSnapshot() throws IOException {
+	File snapshot = new File(directory, SNAPSHOT_FORMAT.format(nextFileNumber - 1));
+	snapshot.delete();   //If no commands are logged, the same snapshot file will be created over and over.
+	return snapshot;
+    }
+
+    File newTempSnapshot() throws IOException {
+	return File.createTempFile("temp","generatingSnapshot",directory);
+    }
+
+    NumberFileCleaner newCleaner() {
+        return new NumberFileCleaner(directory);
+    }
+}