logoutputstream.java

pastry的java实现的2.0b版

/*************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

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- Redistributions in binary form must reproduce the above copyright
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- Neither  the name  of Rice  University (RICE) nor  the names  of its
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This software is provided by RICE and the contributors on an "as is"
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********************************************************************************/
package rice.environment.logging;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;

import rice.environment.Environment;

/**
 * This class constructs an output stream that will send its output to a logger,
 * line by line. This could for example be wrapped in a PrintStream to capture
 * stdout or stderr to the log. As so: System.setOut(new PrintStream(new
 * LogOutputStream(environment, Logger.INFO, "out"), true)); System.setErr(new
 * PrintStream(new LogOutputStream(environment, Logger.INFO, "err"), true));
 *
 * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
 * @author jstewart
 */
public class LogOutputStream extends OutputStream {

  // the underlying logger to output to
  /**
   * DESCRIBE THE FIELD
   */
  protected Logger logger;

  // buffer where we build up output
  /**
   * DESCRIBE THE FIELD
   */
  protected byte[] buffer;

  // position where the next write into the buffer would go.
  /**
   * DESCRIBE THE FIELD
   */
  protected int offset;

  // log level to output as
  /**
   * DESCRIBE THE FIELD
   */
  protected int level;

  // size of the output buffer, in bytes
  /**
   * DESCRIBE THE FIELD
   */
  public final static int BUFFER_SIZE = 1024;

  /**
   * Constructs a LogOutputStream
   *
   * @param env - the environment to log to
   * @param level - the log level of this OutputStream's messages
   */
  public LogOutputStream(Environment env, int level) {
    this(env, level, "");
  }

  /**
   * Constructs a LogOutputStream
   *
   * @param env - the environment to log to
   * @param level - the log level of this OutputStream's messages
   * @param instance - an instance name string for disambiguation
   */
  public LogOutputStream(Environment env, int level, String instance) {
    logger = env.getLogManager().getLogger(LogOutputStream.class, instance);
    buffer = new byte[BUFFER_SIZE];
    offset = 0;
    this.level = level;
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param b DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public void write(int b) throws IOException {
    if (b == '\n') {
      if ((offset > 0) && (buffer[offset - 1] == '\r')) {
        offset--;
      }
      flush();
      return;
    }
    if ((offset > 0) && buffer[offset - 1] == '\r') {
      // treat bare \r as a newline
      offset--;
      flush();
    }
    // I don't actually know why it needs to be - 1 but it works
    if (offset == buffer.length - 1) {
      flush();
    }
    // okay, so we're not unicode friendly. Cry me a river.
    buffer[offset++] = (byte) (b & 0xff);
  }

  /**
   * DESCRIBE THE METHOD
   */
  public void flush() {
    if (offset == 0) {
      return;
    }
    if (logger.level <= level) {
      logger.log(new String(buffer, 0, offset));
    }
    offset = 0;
  }

  /**
   * DESCRIBE THE METHOD
   */
  public void close() {
    flush();
  }

}