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Java/storage/GZZ0.java

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+/*   
+GZZ0.java
+ *    
+ *    Copyright (c) 2000, Ted Nelson and Tuomas Lukka
+ *
+ *    You may use and distribute under the terms of either the GNU Lesser
+ *    General Public License, either version 2 of the license or,
+ *    at your choice, any later version. Alternatively, you may use and
+ *    distribute under the terms of the XPL.
+ *
+ *    See the LICENSE.lgpl and LICENSE.xpl files for the specific terms of 
+ *    the licenses.
+ *
+ *    This software 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 README
+ *    file for more details.
+ *
+ */
+/*
+ * Written by Tuomas Lukka
+ */
+
+package org.gzigzag;
+import java.io.*;
+
+/** An implementation of the GZZ0 file format.
+ */
+
+public class GZZ0 {
+String rcsid = "$Id: GZZ0.java,v 1.7 2001/03/01 13:53:53 ajk Exp $";
+    public static boolean dbg = false;
+    final static void p(String s) { if(dbg) System.out.println(s); }
+    final static void pa(String s) { System.out.println(s); }
+
+    final int magic = 0x475a5a30; // "GZZ0"
+    final int version = 0;
+    final byte rTime = 116;
+
+    public interface Runner {
+	/** Returns the GZZ0 content type of this runner.
+	 */
+	int getContentType();
+	/** Returns the GZZ0 content version of this runner.
+	 */
+	int getContentVersion();
+	/** Read a run.
+	 */
+	void readRun(InputStream is);
+	/** Start writing.
+	 */
+	void startWrite(OutputStream os);
+	/** Finish writing.
+	 */
+	void endWrite();
+
+    }
+
+    StreamSet ss;
+    String id;
+
+    public GZZ0(StreamSet ss, String id) {
+	this.ss = ss; this.id = id;
+    }
+
+    /** Read the latest dataset into the given runner.
+     * @param r The runner into which to give the runs
+     * @param maxtimestamp The maximum timestamp whose changes to include.
+     * @return The latest timestamp read.
+     */
+    public int read(Runner r, int maxtimestamp) {
+	InputStream is = ss.getInputStream(id);
+	CountingStream counts = null;
+	if(dbg) {
+	    is = counts = new CountingStream(is);
+	}
+	DataInputStream dis = new DataInputStream(is);
+
+	// Read header
+	try {
+	    int i = dis.readInt();
+	    if(i != magic) 
+		throw new ZZFatalError("Invalid file format! Doesn't begin with GZZ0 magic");
+	    i = dis.readInt();
+	    if(i != version)
+		throw new ZZFatalError("Invalid file version! Not "+version);
+	    i = dis.readInt();
+	    if(i != r.getContentType())
+		throw new ZZFatalError("Wrong content type!");
+	    i = dis.readInt();
+	    if(i != r.getContentVersion())
+		throw new ZZFatalError("Wrong content version!");
+	} catch(IOException e) {
+	    ZZLogger.exc(e);
+	    throw new ZZFatalError("Reading file");
+	}
+
+	// Read body.
+
+	int lastTime = -1;
+	boolean eofOk = true;
+	byte[] byt = new byte[4096];
+	try {
+	    while(true) {
+		eofOk = true;
+		byte rectype = dis.readByte();
+		eofOk = false;
+		if(rectype != rTime)
+		    throw new ZZFatalError("Invalid timestamp record! " + id + " " +
+			(counts != null ? counts.getCount() : -1));
+		lastTime = dis.readInt();
+		int nbytes = dis.readInt();
+
+		if(maxtimestamp > 0 && lastTime > maxtimestamp) {
+		    dis.close();
+		    return lastTime;
+		}
+
+		if(nbytes > byt.length)
+			byt = new byte[nbytes];
+
+		dis.readFully(byt, 0, nbytes);
+		ByteArrayInputStream bis = 
+			new ByteArrayInputStream(byt, 0, nbytes);
+		r.readRun(bis);
+	    }
+	} catch(EOFException e) {
+	    if(!eofOk)
+		throw new ZZFatalError("Unexpected eof in simpledimfile");
+	} catch(IOException e) {
+	    ZZLogger.exc(e);
+	    throw new ZZFatalError("Reading file");
+	}
+	return lastTime;
+    }
+
+    ByteArrayOutputStream outputStream;
+    DataOutputStream dos;
+    Runner runner;
+    int timestamp;
+
+    /** Write the changes back. 
+     * XXX Should check runner's type...
+     */
+    public void startWrite(int timestamp, Runner r) {
+
+	outputStream = new ByteArrayOutputStream();
+	this.timestamp = timestamp;
+	this.runner = r;
+
+	runner.startWrite(new DataOutputStream(outputStream));
+    }
+
+    /** Finish writing. */
+    public void endWrite(boolean forceStamp) {
+	boolean ex = ss.exists(id);
+	runner.endWrite();
+
+	try {
+	    OutputStream os = ss.getAppendStream(id);
+	    dos = new DataOutputStream(os);
+	    if(!ex) {
+		// Write header.
+		dos.writeInt(magic);
+		dos.writeInt(version);
+		dos.writeInt(runner.getContentType());
+		dos.writeInt(runner.getContentVersion());
+		dos.flush();
+	    }
+	    byte[] byt = outputStream.toByteArray();
+	    if(byt.length == 0 && !forceStamp) {
+		pa("Not writing "+id);
+		return;
+	    }
+	    pa("Writing "+id+" "+byt.length);
+
+	    dos.writeByte(rTime);
+	    dos.writeInt(timestamp);
+	    dos.writeInt(byt.length);
+	    dos.write(byt);
+	    dos.flush();
+	    dos = null;
+	    outputStream = null;
+	    runner = null;
+	} catch(IOException e) {
+	    ZZLogger.exc(e);
+	    throw new ZZFatalError("Writing file");
+	}
+    }
+
+}