score.java

用于移动设备上的java虚拟机源代码

/*
 * @(#)Score.java	1.19 02/07/25 @(#)
 *
 * Copyright (c) 1999-2002 Sun Microsystems, Inc.  All rights reserved.
 * PROPRIETARY/CONFIDENTIAL
 * Use is subject to license terms.
 */

package example.pushpuzzle;

import javax.microedition.rms.*;

/**
 * Keep track of the last level played.
 * For each level keep track of the number of moves.
 * <p>
 * The scores are kept in a RecordStore named PushPuzzleScores.
 * There are two types of records:
 * - Last level
 * - Level history
 *   Name of level (either resource name "/..." or...)
 */
class Score {
    // Current level record = {byte LEVEL_TAG; int level;}
    private int levelId;	// The record Id of the level record
    private byte[] levelRec;	// Byte array holding the level
    private static final int LEVEL_LEN = 9;
    private static final byte LEVEL_TAG = 1;

    // Score for level = {byte SCORE_TAG; int level, int pushes; int moves;}
    private int scoreId; // The record Id of the current level
    private byte[] scoreRec; // scores for the current level.
    private static final int SCORE_LEN = 13;
    private static final byte SCORE_TAG = 2;

    private RecordStore store;		// Record store, null if not open


    /*
     * Construct a new Score handler.
     */
    Score() {
	store = null;

	levelId = 0;
	levelRec = new byte[LEVEL_LEN];
	levelRec[0] = LEVEL_TAG;
	putInt(levelRec, 1, 0);
	putInt(levelRec, 5, 0);

	scoreId = 0;
	scoreRec = new byte[SCORE_LEN];
	scoreRec[0] = SCORE_TAG;
	putInt(scoreRec, 1, 0);
    }

    /**
     * Open the record store and locate
     * the record with the level number in it.
     */
    boolean open() {

	try {
	    store = RecordStore.openRecordStore("PushPuzzleScores", true);
	} catch (RecordStoreException ex) {
	}

	if (store == null)
	    return false;

	try {
	    /*
	     * Locate the record containing the level.
	     */
	    levelId = 0;
	    RecordEnumeration enum = store.enumerateRecords(null, null, false);
	    while (enum.hasNextElement()) {
	        int ndx = enum.nextRecordId();
		if (store.getRecordSize(ndx) == LEVEL_LEN) {
		    int l = store.getRecord(ndx, levelRec, 0);
		    if (l == LEVEL_LEN &&
		        levelRec[0] == LEVEL_TAG) {
	                levelId = ndx;
	                break;
		    }
		} 
	    }
	} catch (RecordStoreException ex) {
	    ex.printStackTrace();
	    return false;
	}

	return true;
    }

    /**
     * Get the current Theme number.
     */
    int getTheme() {
	return getInt(levelRec, 5);
    }

    /**
     * Retrieve the level from the level record.  It should
     * have already been read from the store or created.
     * The first byte is a tag, the second byte the level.
     */
    int getLevel() {
	return getInt(levelRec, 1);
    }

    /**
     * Set the level and theme into the RecordStore.
     * @param level the current level
     * @param theme the current theme
     */
    boolean setLevel(int level, int theme) {
	putInt(levelRec, 1, level);
	putInt(levelRec, 5, theme);
	putInt(scoreRec, 1, level);

	if (store == null)
	    return false;
	try {
	    if (levelId == 0) {
		levelId = store.addRecord(levelRec, 0, levelRec.length);
	    } else {
		store.setRecord(levelId, levelRec, 0, levelRec.length);
	    }
	} catch (RecordStoreException ex) {
	    System.out.println("RecordStoreException");
	    ex.printStackTrace();
	    return false;
	}
	readScore(level);	// get the score for the level
	return true;
    }

    /**
     * Get the number of pushes on the current level.
     */
    int getPushes() {
	return getInt(scoreRec, 5);
    }
    
    /**
     * Get the number of moved on the current level.
     */
    int getMoves() {
	return getInt(scoreRec, 9);
    }
    
    /**
     * Read the score for the current level.
     * Read through the records looking for the one for this level.
     */
    boolean readScore(int level) {
	try {
	    scoreId = 0;

	    // Locate the matching record
	    RecordEnumeration enum = store.enumerateRecords(null, null, false);
	    while (enum.hasNextElement()) {
	        int ndx = enum.nextRecordId();
		if (store.getRecordSize(ndx) == SCORE_LEN) {
		  int l = store.getRecord(ndx, scoreRec, 0);
		  if (l == SCORE_LEN &&
		      scoreRec[0] == SCORE_TAG &&
		      getInt(scoreRec, 1) == level) {
	            scoreId = ndx;
		    return true;
		  }
		} 
	    }
	} catch (RecordStoreException ex) {
	    ex.printStackTrace();
	    return false;
	}

	// No record found, start fresh
	scoreRec[0] = SCORE_TAG;
	putInt(scoreRec, 1, level);
	putInt(scoreRec, 5, 0);
	putInt(scoreRec, 9, 0);
	return true;
    }

    /**
     * Set the updated score to the RecordStore.
     */
    boolean setLevelScore(int pushes, int moves) {
	// Update the scores in the buffer.
	putInt(scoreRec, 5, pushes);
	putInt(scoreRec, 9, moves);

	try {
	    // Write/Add the record to the  store
	    if (scoreId == 0) {
		scoreId = store.addRecord(scoreRec, 0, scoreRec.length);
	    } else {
		store.setRecord(scoreId, scoreRec, 0, scoreRec.length);
	    }

	} catch (RecordStoreException ex) {
	    ex.printStackTrace();
	    return false;
	}
	return true;
    }

    /**
     * Get an integer from an array.
     */
    private int getInt(byte[] buf, int offset) {
	return (buf[offset+0] & 0xff) << 24 |
	    (buf[offset+1] & 0xff) << 16 |
	    (buf[offset+2] & 0xff) << 8 |
	    (buf[offset+3] & 0xff);
    }

    /**
     * Put an integer to an array
     */
    private void putInt(byte[] buf, int offset, int value) {
	buf[offset+0] = (byte)((value >> 24) & 0xff);
	buf[offset+1] = (byte)((value >> 16) & 0xff);
	buf[offset+2] = (byte)((value >>  8) & 0xff);
	buf[offset+3] = (byte)((value >>  0) & 0xff);
    }

    /**
     * Close the store.
     */
    void close() {
	try {
	    if (store != null) {
		store.closeRecordStore();
	    }
	} catch (RecordStoreException ex) {
	    ex.printStackTrace();
	}
    }

}