Add Library class for reading and writing .jar and .pack files

asm/pom.xml

@@ -12,4 +12,24 @@
   <packaging>jar</packaging>
 
   <name>OpenRS2 ASM Utilities</name>
+
+  <dependencies>
+    <dependency>
+      <groupId>dev.openrs2</groupId>
+      <artifactId>openrs2-util</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm-tree</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm-util</artifactId>
+    </dependency>
+  </dependencies>
 </project>

asm/src/main/java/dev/openrs2/asm/Library.java

@@ -0,0 +1,98 @@
+package dev.openrs2.asm;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.SequenceInputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.jar.JarEntry;
+import java.util.jar.JarInputStream;
+import java.util.jar.JarOutputStream;
+import java.util.jar.Pack200;
+import java.util.zip.GZIPInputStream;
+import java.util.zip.GZIPOutputStream;
+
+import dev.openrs2.util.io.DeterministicJarOutputStream;
+import dev.openrs2.util.io.SkipOutputStream;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.util.CheckClassAdapter;
+
+public final class Library {
+	private static final String CLASS_SUFFIX = ".class";
+	private static final String TEMP_PREFIX = "tmp";
+	private static final String JAR_SUFFIX = ".jar";
+	private static final byte[] GZIP_HEADER = { 0x1f, (byte) 0x8b };
+
+	public static Library readJar(Path path) throws IOException {
+		var library = new Library();
+
+		try (var in = new JarInputStream(Files.newInputStream(path))) {
+			JarEntry entry;
+			while ((entry = in.getNextJarEntry()) != null) {
+				if (!entry.getName().endsWith(CLASS_SUFFIX)) {
+					continue;
+				}
+
+				var clazz = new ClassNode();
+				var reader = new ClassReader(in);
+				reader.accept(clazz, ClassReader.SKIP_DEBUG);
+
+				library.classes.put(clazz.name, clazz);
+			}
+		}
+
+		return library;
+	}
+
+	public static Library readPack(Path path) throws IOException {
+		var temp = Files.createTempFile(TEMP_PREFIX, JAR_SUFFIX);
+		try {
+			try (var header = new ByteArrayInputStream(GZIP_HEADER);
+					var data = Files.newInputStream(path);
+					var in = new GZIPInputStream(new SequenceInputStream(header, data));
+					var out = new JarOutputStream(Files.newOutputStream(temp))) {
+				Pack200.newUnpacker().unpack(in, out);
+				return readJar(temp);
+			}
+		} finally {
+			Files.deleteIfExists(temp);
+		}
+	}
+
+	private final Map<String, ClassNode> classes = new TreeMap<>();
+
+	private Library() {
+		/* empty */
+	}
+
+	public void writeJar(Path path) throws IOException {
+		try (var out = new DeterministicJarOutputStream(Files.newOutputStream(path))) {
+			for (var entry : classes.entrySet()) {
+				var clazz = entry.getValue();
+				var writer = new ClassWriter(0);
+				clazz.accept(new CheckClassAdapter(writer, true));
+
+				out.putNextEntry(new JarEntry(clazz.name + CLASS_SUFFIX));
+				out.write(writer.toByteArray());
+			}
+		}
+	}
+
+	public void writePack(Path path) throws IOException {
+		var temp = Files.createTempFile(TEMP_PREFIX, JAR_SUFFIX);
+		try {
+			writeJar(temp);
+
+			try (var in = new JarInputStream(Files.newInputStream(temp));
+					var out = new GZIPOutputStream(new SkipOutputStream(Files.newOutputStream(path), 2))) {
+				Pack200.newPacker().pack(in, out);
+			}
+		} finally {
+			Files.deleteIfExists(temp);
+		}
+	}
+}

util/src/main/java/dev/openrs2/util/io/DeterministicJarOutputStream.java

@@ -0,0 +1,28 @@
+package dev.openrs2.util.io;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.nio.file.attribute.FileTime;
+import java.util.jar.JarOutputStream;
+import java.util.jar.Manifest;
+import java.util.zip.ZipEntry;
+
+public final class DeterministicJarOutputStream extends JarOutputStream {
+	private static final FileTime UNIX_EPOCH = FileTime.fromMillis(0);
+
+	public DeterministicJarOutputStream(OutputStream out) throws IOException {
+		super(out);
+	}
+
+	public DeterministicJarOutputStream(OutputStream out, Manifest man) throws IOException {
+		super(out, man);
+	}
+
+	@Override
+	public void putNextEntry(ZipEntry ze) throws IOException {
+		ze.setCreationTime(UNIX_EPOCH);
+		ze.setLastAccessTime(UNIX_EPOCH);
+		ze.setLastModifiedTime(UNIX_EPOCH);
+		super.putNextEntry(ze);
+	}
+}

util/src/main/java/dev/openrs2/util/io/SkipOutputStream.java

@@ -0,0 +1,37 @@
+package dev.openrs2.util.io;
+
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+public final class SkipOutputStream extends FilterOutputStream {
+	private long skipBytes;
+
+	public SkipOutputStream(OutputStream out, long skipBytes) {
+		super(out);
+		this.skipBytes = skipBytes;
+	}
+
+	@Override
+	public void write(int b) throws IOException {
+		if (skipBytes == 0) {
+			super.write(b);
+		} else {
+			skipBytes--;
+		}
+	}
+
+	@Override
+	public void write(byte[] b, int off, int len) throws IOException {
+		if (len >= skipBytes) {
+			off += skipBytes;
+			len -= skipBytes;
+			skipBytes = 0;
+		} else {
+			skipBytes -= len;
+			return;
+		}
+
+		super.write(b, off, len);
+	}
+}