datareader.java

JAVA网络编程技术内幕一书的源代码

/*
 * Java Network Programming, Second Edition
 * Merlin Hughes, Michael Shoffner, Derek Hamner
 * Manning Publications Company; ISBN 188477749X
 *
 * http://nitric.com/jnp/
 *
 * Copyright (c) 1997-1999 Merlin Hughes, Michael Shoffner, Derek Hamner;
 * all rights reserved; see license.txt for details.
 */

import java.io.*;

public class DataReader extends Reader {
  protected PushbackReader pushbackReader;

  public DataReader (Reader reader) {
    super (reader);
    pushbackReader = new PushbackReader (reader);
  }

  protected boolean eof = false;

  public int read () throws IOException {
    synchronized (lock) {
      if (!eof)
        return pushbackReader.read ();
      else {
        eof = false;
        return -1;
      }
    }
  }
  
  public int read (char[] data, int offset, int length) throws IOException {
    synchronized (lock) {
      if (!eof)
        return pushbackReader.read (data, offset, length);
      else {
        eof = false;
        return -1;
      }
    }
  }

  public long skip (long amount) throws IOException {
    synchronized (lock) {
      if (amount <= 0)
        return 0;
      else if (!eof)
        return pushbackReader.skip (amount);
      else {
        eof = false;
        return 0;
      }
    }
  }

  public boolean ready () throws IOException {
    synchronized (lock) {
      return pushbackReader.ready ();
    }
  }

  public void close () throws IOException {
    synchronized (lock) {
      pushbackReader.close ();
      eof = false;
    }
  }

  protected void unread (int chr) throws IOException {
    synchronized (lock) {
      if (eof)
        throw new IOException ("Pushback buffer overflow");
      if (chr == -1)
        eof = true;
      else
        pushbackReader.unread (chr);
    }
  }

  public String readWord () throws IOException {
    synchronized (lock) {
      readExp (WHITESPACE, ZERO_OR_MORE);
      String word = readExp (NON_WHITESPACE, ZERO_OR_MORE);
      if (word.equals ("") && eof)
        throw new EOFException ("EOF reading word");
      return word;
    }
  }

  public long readLong () throws IOException, NumberFormatException {
    synchronized (lock) {
      readExp (WHITESPACE, ZERO_OR_MORE);
      String value = readExp ('-', ZERO_OR_ONE) +
        readExp (DIGITS, ZERO_OR_MORE);
      if ((value.equals ("") || value.equals ("-")) && eof)
        throw new EOFException ("EOF reading long");
      return Long.parseLong (value);
    }
  }

  public double readDouble () throws IOException, NumberFormatException {
    synchronized (lock) {
      readExp (WHITESPACE, ZERO_OR_MORE);
      String value = readExp ('-', ZERO_OR_ONE) +
        readExp (DIGITS, ZERO_OR_MORE) + readExp ('.', ZERO_OR_ONE) +
        readExp (DIGITS, ZERO_OR_MORE);
      if (eof && (value.equals ("") || value.equals (".") ||
                  value.equals ("-") || value.equals ("-.")))
        throw new EOFException ("EOF reading double");
      return Double.valueOf (value).doubleValue ();
    }
  }

  protected String readExp (int type, int volume) throws IOException {
    synchronized (lock) {
      StringBuffer result = new StringBuffer ();
      boolean done = false;
      while (!done) {
        int chr = read ();
        if (isMatch (chr, type)) {
          result.append ((char) chr);
          done = (volume == ZERO_OR_ONE);
        } else {
          unread (chr);
          done = true;
        }
      }
      return result.toString ();
    }
  }

  protected static final int WHITESPACE = 0x10000,
    NON_WHITESPACE = 0x10001, DIGITS = 0x10002;
  protected static final int ZERO_OR_MORE = 0,
    ZERO_OR_ONE = 1;
  
  protected boolean isMatch (int chr, int type) {
    switch (type) {
      case WHITESPACE:
        return Character.isWhitespace ((char) chr);
      case NON_WHITESPACE:
        return !Character.isWhitespace ((char) chr);
      case DIGITS:
        return Character.isDigit ((char) chr);
      default:
        return (type == chr);
    }
  }
}