package posix;

/** Instances of Syslog maintain a connection to the system error logger.
    A work in progress.
    FIXME:  So far, this uses the C library calls.  After a little reflection,
    it seems much more flexible to make this 100% Java and simply send
    datagrams to the syslog server.  This would allow the
    syslog server to be on a remote machine.  The C library only works
    for the local machine.

@author <a href="mailto:stuart@bmsi.com">Stuart D. Gathman</a>
Copyright (C) 1998 Business Management Systems, Inc.  <br>
<p>
This code is distributed under the
<a href="http://www.gnu.org/copyleft/lgpl.html">
GNU Library General Public License </a>
<p>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
<p>
This library 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
Library General Public License for more details.
<p>
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA  02111-1307, USA.

 */
public class Syslog {
  private long syslogData = CPtr.NULL;
  /** Allocate an initialized syslog_data_struct.  */
  private native long initdata();
  /** Set options for a syslog_data_struct and optionally connect immediately
      to the syslog server.
      @return 0 or errno|0x80000000
   */
  private native int openlog(String id,int logopt,int facility,long data);
  /** All message expansion should be done on the Java end, and any '%' doubled
      to prevent expansion by the C library. NOOP if data is NULL.
      @return 0 or errno|0x80000000
   */
  private native int syslog(int prior,long data,String msg);
  /** Close the log and free the syslog_data_struct. */
  private native void closelog(long data);
  /** Change the priority mask and return the old mask. 
      NOOP if data is NULL.
   */
  private native int setlogmask(int maskprior,long data);

  // FIXME: openlog option values might need to be determined at runtime.
  /** log the pid with each message */
  public static final byte LOG_PID	= 0x01;
  /** log on the console if errors in sending */
  public static final byte LOG_CONS	= 0x02;
  /** delay open until syslog() is called */
  public static final byte LOG_ODELAY	= 0x04;
  /** don't delay open */
  public static final byte LOG_NDELAY	= 0x08;
  /** if forking to log on console, don't wait().  This is always
    needed for a JVM because it typically uses SIGCLD to implement
    java.lang.Process.  We might also want to ban LOG_CONS if an
    extra fork() might confuse the JVM. */
  private static final byte LOG_NOWAIT	= 0x10;	

  /* priority levels should be constant across posix platforms. */
  public static final byte LOG_EMERG	= 0; // system is unusable
  public static final byte LOG_ALERT	= 1; // action must be taken immediately
  public static final byte LOG_CRIT	= 2; // critical conditions
  public static final byte LOG_ERR	= 3; // error conditions
  public static final byte LOG_WARNING	= 4; // warning conditions
  public static final byte LOG_NOTICE	= 5; // normal but significant condition
  public static final byte LOG_INFO	= 6; // informational
  public static final byte LOG_DEBUG	= 7; // debug-level messages

  public Syslog(String id) throws IPCException {
    syslogData = initdata();
    int rc = openlog(id,LOG_NOWAIT,LOG_USER,syslogData);
    if (rc < 0) {
      rc &= 0x7FFFFFFF;
      throw new IPCException("openlog",rc);
    }
  }

  /** Replace all '%' with "%%" to prevent expansion by C library. */
  private static String escape(String s) {
    int pos = s.indexOf('%');
    if (pos < 0) return s;
    // leave room for expanding up to 5 '%' without reallocating
    StringBuffer buf = new StringBuffer(s.length() + 5);
    do {
      buf.append(s.substring(0,++pos));
      buf.append('%');
      if (pos >= s.length()) break;
      s = s.substring(pos);
      pos = s.indexOf('%');
    } while (pos >= 0);
    return buf.toString();
  }

  public void log(String msg) throws IPCException {
    int rc = syslog(0,syslogData,escape(s));
    if (rc < 0) {
      rc &= 0x7FFFFFFF;
      throw new IPCException("syslog",rc);
    }
  }

  public synchronized void dispose() {
    if (syslogData != CPtr.NULL) {
      closelog(syslogData);
      syslogData = CPtr.NULL;
    }
  }

  protected void finalize() {
    dispose();
  }
}