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Java/storage/MemWritable.java

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+/*   
+MemWritable.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 Benjamin Fallenstein
+ */
+package org.gzigzag;
+import java.util.*;
+
+/** A writable that stores its contents in memory.
+ * Used to make scrolls work in applets. Not necessarily very efficient;
+ * however, I don't think that's so much of an issue in applets, where we
+ * won't save a lot of data anyway.
+ */
+
+public class MemWritable implements Writable {
+String rcsid = "$Id: MemWritable.java,v 1.1 2000/12/26 22:48:37 bfallenstein Exp $";
+
+    /** The size of the chunks in which memory is allocated. */
+    final int CHUNK = 500;
+
+    /** The data. */
+    byte[] d = new byte[CHUNK];
+
+    /** The length of the data actually used.
+     * len-1 is the highest index of any data ever written.
+     */
+    int len = 0;
+
+    public void extend() {
+	byte[] nu = new byte[d.length + CHUNK];
+	System.arraycopy(d, 0, nu, 0, len);
+	d = nu;
+    }
+
+    public void write(long offset0, byte[] data) {
+	int offset = (int)offset0;
+	int n = data.length;
+	while(offset + n >= d.length) extend();
+	System.arraycopy(data, 0, d, offset, n);
+	if(offset + n > len) len = offset + n;
+    }
+    public byte[] read(long offset0, int n) {
+	byte[] res = new byte[n];
+	read(offset0, res, 0, n);
+	return res;
+    }
+    public void read(long offset0, byte b[], int off, int n){
+	System.out.println("MemWritable.read "+d.length+" "+len+" params "+
+			   offset0+" "+b.length+" "+off+" "+n);
+	int offset = (int)offset0;
+	while(offset + n >= d.length) extend();
+	System.arraycopy(d, offset, b, off, n);
+    }
+    public long length() {
+	return len;
+    }
+    public void flush() {}
+}
+