added Persistent

darcs-hash:20050325062957-5007d-099427c0dfd5bfe36fd39be02ccceeea2c840b62.gz

diff --git a/src/org/ibex/io/Persistent.java b/src/org/ibex/io/Persistent.java
new file mode 100644 (file)
index 0000000..f65d809
--- /dev/null
+++ b/src/org/ibex/io/Persistent.java
@@ -0,0 +1,58 @@
+// Copyright 2000-2005 the Contributors, as shown in the revision logs.
+// Licensed under the Apache Public Source License 2.0 ("the License").
+// You may not use this file except in compliance with the License.
+
+package org.ibex.io;
+import java.util.*;
+import java.io.*;
+import java.nio.*;
+import java.nio.channels.*;
+import org.ibex.util.*;
+import org.ibex.io.*;
+import com.thoughtworks.xstream.*;
+
+public class Persistent {
+
+    private static WeakHashMap cache = new WeakHashMap();
+    private static final XStream xstream = new XStream();
+
+    public transient File file;
+    public transient String path;
+    public transient FileLock lock;
+
+    public Persistent(File file) { this.file = file; this.path = file.getAbsolutePath(); }
+    public Persistent(String path) { this(new File(path)); }
+
+    public static Persistent read(File file) throws Exception {
+
+        // check the cache
+        Persistent ret = (Persistent)cache.get(file.getAbsolutePath());
+        if (ret != null) return ret;
+
+        // open a new file
+        ret = (Persistent)xstream.fromXML(new BufferedReader(new InputStreamReader(new FileInputStream(file))));
+        ret.file = file;
+        ret.path = file.getAbsolutePath();
+
+        // lock it
+        ret.lock = new RandomAccessFile(file, "rw").getChannel().tryLock();
+        if (ret.lock == null) throw new RuntimeException("could not acquire lock on " + ret.path);
+
+        // and save it for later
+        cache.put(ret.path, ret);
+        return ret;
+
+    }
+
+    public synchronized void write() throws Exception {
+        FileOutputStream fos = new FileOutputStream(path + "-");
+        FileDescriptor fd = fos.getFD();
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fos));
+        xstream.toXML(this, bw);
+        bw.flush();
+        fd.sync();
+        bw.close();
+        new File(path + "-").renameTo(file);
+    }
+
+}