FileWatcher to mirror /proc files

bindings/java/src/org/hyperic/sigar/ProcFileMirror.java

@@ -0,0 +1,173 @@
+/*
+ * Copyright (C) [2004, 2005, 2006], Hyperic, Inc.
+ * This file is part of SIGAR.
+ * 
+ * SIGAR is free software; you can redistribute it and/or modify
+ * it under the terms version 2 of the GNU General Public License as
+ * published by the Free Software Foundation. This program 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 GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA.
+ */
+
+package org.hyperic.sigar;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+import org.apache.log4j.Logger;
+
+//intended for use on systems with very large connection tables
+//where processing /proc/net/tcp may block or otherwise take much longer
+//than reading a plain 'ol text file
+public class ProcFileMirror extends FileWatcher {
+
+    private String proc;
+    private long timestamp;
+    private long expire;
+
+    private static final Logger log = 
+        SigarLog.getLogger(ProcFileMirror.class.getName());
+
+    private static final boolean isDebug = log.isDebugEnabled();
+
+    public ProcFileMirror(Sigar sigar, String proc) {
+        super(sigar);
+        this.timestamp = System.currentTimeMillis();
+        this.proc = proc;
+        this.expire = FileWatcherThread.DEFAULT_INTERVAL;
+    }
+
+    public long getExpireMillis() {
+        return this.expire;
+    }
+
+    public void setExpire(long seconds) {
+        setExpireMillis(seconds * 1000);
+    }
+
+    public void setExpireMillis(long millis) {
+        this.expire = millis;
+    }
+
+    public String getProcFile(File file) {
+        return getProcFile(file.getPath());
+    }
+
+    public String getProcFile(String file) {
+        final String PROC = "/proc/";
+        if (file.startsWith(PROC)) {
+            file = file.substring(PROC.length());
+        }
+        return this.proc + File.separator + file;
+    }
+
+    private void mirror(String source) throws IOException {
+        mirror(source, getProcFile(source));
+    }
+
+    private String mirrorToString(File source, File dest) {
+        return "mirror(" + source + ", " + dest + ")";
+    }
+
+    private void mirror(String source, String dest) throws IOException {
+        mirror(new File(source), new File(dest));
+    }
+
+    private void mirror(File source, File dest) throws IOException {
+        FileInputStream is = null;
+        FileOutputStream os = null;
+
+        try {
+            is = new FileInputStream(source);
+            os = new FileOutputStream(dest);
+            byte[] buffer = new byte[2048];
+            int nread;
+            while (true) {
+                nread = is.read(buffer);
+                if (nread == -1) {
+                    break;
+                }
+                os.write(buffer, 0, nread);
+            }
+        } catch (IOException e) {
+            String msg =
+                mirrorToString(source, dest) + " failed: " +
+                e.getMessage();
+            throw new IOException(msg);
+        } finally {
+            if (is != null) {
+                try { is.close(); } catch (IOException e) {}
+            }
+            if (os != null) {
+                os.close();
+            }
+        }
+
+        if (isDebug) {
+            log.debug(mirrorToString(source, dest));
+        }
+    }
+
+    public FileInfo add(String name)
+        throws SigarException {
+
+        File source = new File(name);
+        File dest = new File(getProcFile(source));
+        File dir = dest.getParentFile();
+
+        if (!dir.exists()) {
+            if (!dir.mkdirs()) {
+                String msg = "mkdir(" + dir + ") failed";
+                throw new SigarException(msg);
+            }
+        }
+        if (!source.canRead()) {
+            throw new SigarException("Cannot read: " + source);
+        }
+        if ((dest.isFile() && !dest.canWrite()) ||
+            !dir.isDirectory() ||
+            !dir.canWrite())
+        {
+            throw new SigarException("Cannot write: " + dest);
+        }
+
+        try {
+            mirror(source.getPath(), dest.getPath());
+        } catch (IOException e) {
+            throw new SigarException(e.getMessage());
+        }
+
+        return super.add(source.getPath());
+    }
+
+    public void onChange(FileInfo info) {
+        try {
+            mirror(info.getName());
+        } catch (IOException e) {
+            System.err.println(e.getMessage());
+        }
+    }
+
+    protected boolean changed(FileInfo info)
+        throws SigarException,
+               SigarFileNotFoundException {
+
+        long now = System.currentTimeMillis();
+        if ((now - this.timestamp) > this.expire) {
+            this.timestamp = now;
+            return true;
+        }
+        else {
+            return false;
+        }
+    }
+}