p1/machine/Config.java

// PART OF THE MACHINE SIMULATION. DO NOT CHANGE.

package nachos.machine;

import java.util.HashMap;
import java.io.File;
import java.io.FileReader;
import java.io.Reader;
import java.io.StreamTokenizer;

/**
 * Provides routines to access the Nachos configuration.
 */
public final class Config {
    /**
     * Load configuration information from the specified file. Must be called
     * before the Nachos security manager is installed.
     *
     * @param	fileName	the name of the file containing the
     *				configuration to use.
     */
    public static void load(String fileName) {
	System.out.print(" config");
	
	Lib.assertTrue(!loaded);
	loaded = true;
	
	configFile = fileName;
	
	try {
	    config = new HashMap<String, String>();
	
	    File file = new File(configFile);
	    Reader reader = new FileReader(file);
	    StreamTokenizer s = new StreamTokenizer(reader);

	    s.resetSyntax();
	    s.whitespaceChars(0x00, 0x20);
	    s.wordChars(0x21, 0xFF);
	    s.eolIsSignificant(true);
	    s.commentChar('#');
	    s.quoteChar('"');

	    int line = 1;

	    s.nextToken();

	    while (true) {
		if (s.ttype == StreamTokenizer.TT_EOF)
		    break;

		if (s.ttype == StreamTokenizer.TT_EOL) {
		    line++;
		    s.nextToken();
		    continue;
		}

		if (s.ttype != StreamTokenizer.TT_WORD)
		    loadError(line);

		String key = s.sval;

		if (s.nextToken() != StreamTokenizer.TT_WORD ||
		    !s.sval.equals("="))
		    loadError(line);

		if (s.nextToken() != StreamTokenizer.TT_WORD && s.ttype != '"')
		    loadError(line);

		String value = s.sval;

		// ignore everything after first string
		while (s.nextToken() != StreamTokenizer.TT_EOL &&
		       s.ttype != StreamTokenizer.TT_EOF);

		if (config.get(key) != null)
		    loadError(line);

		config.put(key, value);
		line++;
	    }
	}
	catch (Throwable e) {
	    System.err.println("Error loading " + configFile);
	    System.exit(1);
	}
    }

    private static void loadError(int line) {
	System.err.println("Error in " + configFile + " line " + line);
	System.exit(1);
    }

    private static void configError(String message) {
	System.err.println("");
	System.err.println("Error in " + configFile + ": " + message);
	System.exit(1);
    }

    /**
     * Get the value of a key in <tt>nachos.conf</tt>.
     *
     * @param	key	the key to look up.
     * @return	the value of the specified key, or <tt>null</tt> if it is not
     *		present.
     */
    public static String getString(String key) {
	return (String) config.get(key);
    }

    /**
     * Get the value of a key in <tt>nachos.conf</tt>, returning the specified
     * default if the key does not exist.
     *
     * @param	key		the key to look up.
     * @param	defaultValue	the value to return if the key does not exist.
     * @return	the value of the specified key, or <tt>defaultValue</tt> if it
     *		is not present.
     */
    public static String getString(String key, String defaultValue) {
	String result = getString(key);

	if (result == null)
	    return defaultValue;

	return result;
    }

    private static Integer requestInteger(String key) {
	try {
	    String value = getString(key);
	    if (value == null)
		return null;
	    
	    return new Integer(value);
	}
	catch (NumberFormatException e) {
	    configError(key + " should be an integer");
	    
	    Lib.assertNotReached();
	    return null;
	}
    }	

    /**
     * Get the value of an integer key in <tt>nachos.conf</tt>.
     *
     * @param	key	the key to look up.
     * @return	the value of the specified key.
     */
    public static int getInteger(String key) {
	Integer result = requestInteger(key);

	if (result == null)
	    configError("missing int " + key);

	return result.intValue();
    }

    /**
     * Get the value of an integer key in <tt>nachos.conf</tt>, returning the
     * specified default if the key does not exist.
     *
     * @param	key		the key to look up.
     * @param	defaultValue	the value to return if the key does not exist.
     * @return	the value of the specified key, or <tt>defaultValue</tt> if the
     *		key does not exist.
     */
    public static int getInteger(String key, int defaultValue) {
	Integer result = requestInteger(key);

	if (result == null)
	    return defaultValue;
	
	return result.intValue();
    }

    private static Double requestDouble(String key) {
	try {
	    String value = getString(key);
	    if (value == null)
		return null;

	    return new Double(value);
	}
	catch (NumberFormatException e) {
	    configError(key + " should be a double");

	    Lib.assertNotReached();
	    return null;
	}
    }	

    /**
     * Get the value of a double key in <tt>nachos.conf</tt>.
     *
     * @param	key	the key to look up.
     * @return	the value of the specified key.
     */
    public static double getDouble(String key) {
	Double result = requestDouble(key);

	if (result == null)
	    configError("missing double " + key);

	return result.doubleValue();
    }

    /**
     * Get the value of a double key in <tt>nachos.conf</tt>, returning the
     * specified default if the key does not exist.
     *
     * @param	key		the key to look up.
     * @param	defaultValue	the value to return if the key does not exist.
     * @return	the value of the specified key, or <tt>defaultValue</tt> if the
     *		key does not exist.
     */
    public static double getDouble(String key, double defaultValue) {
	Double result = requestDouble(key);

	if (result == null)
	    return defaultValue;
	
	return result.doubleValue();
    }

    private static Boolean requestBoolean(String key) {
	String value = getString(key);

	if (value == null)
	    return null;

	if (value.equals("1") || value.toLowerCase().equals("true")) {
	    return Boolean.TRUE;
	}
	else if (value.equals("0") || value.toLowerCase().equals("false")) {
	    return Boolean.FALSE;
	}
	else {
	    configError(key + " should be a boolean");

	    Lib.assertNotReached();
	    return null;
	}
    }	

    /**
     * Get the value of a boolean key in <tt>nachos.conf</tt>.
     *
     * @param	key	the key to look up.
     * @return	the value of the specified key.
     */
    public static boolean getBoolean(String key) {
	Boolean result = requestBoolean(key);

	if (result == null)
	    configError("missing boolean " + key);

	return result.booleanValue();
    }

    /**
     * Get the value of a boolean key in <tt>nachos.conf</tt>, returning the
     * specified default if the key does not exist.
     *
     * @param	key		the key to look up.
     * @param	defaultValue	the value to return if the key does not exist.
     * @return	the value of the specified key, or <tt>defaultValue</tt> if the
     *		key does not exist.
     */
    public static boolean getBoolean(String key, boolean defaultValue) {
	Boolean result = requestBoolean(key);

	if (result == null)
	    return defaultValue;
	
	return result.booleanValue();
    }	    

    private static boolean loaded = false;
    private static String configFile;
    private static HashMap<String, String> config;
}