Minecraft1_2JarBiomeScheme.java

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package org.pepsoft.worldpainter.biomeschemes;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.pepsoft.util.Checksum;
import org.pepsoft.util.FileUtils;
import org.pepsoft.worldpainter.BiomeScheme;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An abstract base class for {@link BiomeScheme}s which can invoke Minecraft
 * code from a Minecraft jar file for version 1.2 through 1.6 to calculate
 * biomes.
 *
 * @author pepijn
 */
public abstract class Minecraft1_2JarBiomeScheme extends AbstractMinecraft1_2BiomeScheme {
    public Minecraft1_2JarBiomeScheme(File minecraftJar, File libDir, Checksum md5Sum, Map<Checksum, String[]> hashesToClassNames, String version) {
        if (logger.isDebugEnabled()) {
            logger.debug("Creating biome scheme using Minecraft jar {}", minecraftJar);
        }
        if (md5Sum == null) {
            try {
                md5Sum = FileUtils.getMD5(minecraftJar);
            } catch (IOException e) {
                throw new RuntimeException("I/O error calculating hash for " + minecraftJar, e);
            }
        }
        String[] classNames = hashesToClassNames.get(md5Sum);
        String landscapeClassName = classNames[0];
        String bufferManagerClassName = classNames[1];
        String worldGeneratorClassName = classNames[2];
        try {
            List<URL> classpath = new ArrayList<>();
            classpath.add(minecraftJar.toURI().toURL());
            if ((libDir != null) && libDir.isDirectory()) {
                List<URL> jars = new ArrayList<>();
                scanDir(libDir, jars);
                classpath.addAll(jars);
            }
            ClassLoader classLoader = new URLClassLoader(classpath.toArray(new URL[classpath.size()]));
            Class<?> landscapeClass = classLoader.loadClass(landscapeClassName);
            worldGeneratorClass = classLoader.loadClass(worldGeneratorClassName);
            getLandscapesMethod = landscapeClass.getMethod("a", long.class, worldGeneratorClass);
            getBiomesMethod = landscapeClass.getMethod("a", int.class, int.class, int.class, int.class);
            Class<?> bufferManagerClass = classLoader.loadClass(bufferManagerClassName);
            clearBuffersMethod = bufferManagerClass.getMethod("a");
        } catch (MalformedURLException e) {
            throw new RuntimeException("Malformed URL exception while loading minecraft.jar", e);
        } catch (ClassNotFoundException | NoSuchMethodException e) {
            throw new RuntimeException("Not a valid " + version + " minecraft.jar", e);
        }
    }

    @Override
    public void setSeed(long seed) {
        if ((seed != this.seed) || (landscape == null)) {
            try {
                landscape = ((Object[]) getLandscapesMethod.invoke(null, seed, null))[1];
                this.seed = seed;
            } catch (IllegalAccessException e) {
                throw new RuntimeException("Access denied while trying to set the seed", e);
            } catch (InvocationTargetException e) {
                throw new RuntimeException("Exception thrown while trying to set the seed", e);
            }
        }
    }
    
    @Override
    public final synchronized void getBiomes(int x, int y, int width, int height, int[] buffer) {
        try {
            int[] biomes = (int[]) getBiomesMethod.invoke(landscape, x, y, width, height);
            clearBuffersMethod.invoke(null);
            System.arraycopy(biomes, 0, buffer, 0, Math.min(biomes.length, buffer.length));
        } catch (IllegalAccessException e) {
            throw new RuntimeException("Access denied while trying to calculate biomes", e);
        } catch (InvocationTargetException e) {
            throw new RuntimeException("Exception thrown while trying to calculate biomes", e);
        }
    }
    
    private void scanDir(File dir, List<URL> classpath) {
        File[] files = dir.listFiles(pathname -> pathname.isDirectory() || pathname.getName().toLowerCase().endsWith(".jar"));
        for (File file: files) {
            if (file.isDirectory()) {
                scanDir(file, classpath);
            } else {
                try {
                    classpath.add(file.toURI().toURL());
                } catch (MalformedURLException e) {
                    throw new RuntimeException("Malformed URL", e);
                }
            }
        }
    }
    
    final Class<?> worldGeneratorClass;
    final Method getLandscapesMethod, getBiomesMethod, clearBuffersMethod;
    Object landscape;
    long seed = Long.MIN_VALUE;

    private static final Logger logger = LoggerFactory.getLogger(Minecraft1_2JarBiomeScheme.class);
}