Start attributes

Author: Seggan

src/main/java/io/github/seggan/javaclasslib/ClassAccessFlags.java

@@ -0,0 +1,28 @@
+package io.github.seggan.javaclasslib;
+
+import java.util.Arrays;
+
+public enum ClassAccessFlags {
+    PUBLIC(0x0001),
+    FINAL(0x0010),
+    SUPER(0x0020),
+    INTERFACE(0x0200),
+    ABSTRACT(0x0400),
+    SYNTHETIC(0x1000),
+    ANNOTATION(0x2000),
+    ENUM(0x4000);
+
+    private final int value;
+
+    ClassAccessFlags(int value) {
+        this.value = value;
+    }
+
+    public static int combine(ClassAccessFlags... flags) {
+        return Arrays.stream(flags).mapToInt(ClassAccessFlags::getValue).sum();
+    }
+
+    public int getValue() {
+        return value;
+    }
+}

src/main/java/io/github/seggan/javaclasslib/JavaClass.java

@@ -1,11 +1,72 @@
 package io.github.seggan.javaclasslib;
 
+import io.github.seggan.javaclasslib.constantpool.ClassEntry;
 import io.github.seggan.javaclasslib.constantpool.ConstantPoolEntry;
+import io.github.seggan.javaclasslib.constantpool.UTF8Entry;
 
+import javax.annotation.Nonnull;
+import java.io.IOException;
+import java.io.OutputStream;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.regex.Pattern;
 
 public final class JavaClass {
 
+    private static final Pattern PERIOD = Pattern.compile("\\.");
+    private static final byte[] START_BYTES = new byte[]{(byte) 0xCA, (byte) 0xFE, (byte) 0xBA, (byte) 0xBE, 0, 0};
+
     private final List<ConstantPoolEntry> constantPool = new LinkedList<>();
+
+    private final ClassEntry thisClass;
+    private final ClassEntry superClass;
+    private final int classVersion;
+
+    private ClassAccessFlags[] classAccessFlags = new ClassAccessFlags[0];
+
+    public JavaClass(@Nonnull String name, @Nonnull String superclass, int javaVersion) {
+        if (javaVersion < 8) throw new IllegalArgumentException();
+        classVersion = javaVersion + 44;
+
+        UTF8Entry utf8Name = new UTF8Entry(constantPool, PERIOD.matcher(name).replaceAll("/"));
+        this.thisClass = new ClassEntry(constantPool, utf8Name);
+        UTF8Entry superName = new UTF8Entry(constantPool, PERIOD.matcher(superclass).replaceAll("/"));
+        this.superClass = new ClassEntry(constantPool, superName);
+    }
+
+    public void write(@Nonnull OutputStream out) throws IOException {
+        out.write(START_BYTES);
+        out.write(ByteUtils.twoBytesFromInt(classVersion));
+        out.write(ByteUtils.twoBytesFromInt(constantPool.size() + 1));
+        for (ConstantPoolEntry entry : constantPool) {
+            out.write(entry.getBytes());
+        }
+        out.write(ByteUtils.twoBytesFromInt(ClassAccessFlags.combine(classAccessFlags)));
+        out.write(thisClass.getIndexBytes());
+        out.write(superClass.getIndexBytes());
+    }
+
+    public List<ConstantPoolEntry> getConstantPool() {
+        return constantPool;
+    }
+
+    public ClassEntry getThisClass() {
+        return thisClass;
+    }
+
+    public ClassEntry getSuperClass() {
+        return superClass;
+    }
+
+    public int getClassVersion() {
+        return classVersion;
+    }
+
+    public ClassAccessFlags[] getClassAccessFlags() {
+        return classAccessFlags;
+    }
+
+    public void setClassAccessFlags(ClassAccessFlags... classAccessFlags) {
+        this.classAccessFlags = classAccessFlags;
+    }
 }

src/main/java/io/github/seggan/javaclasslib/attributes/Attribute.java

@@ -0,0 +1,24 @@
+package io.github.seggan.javaclasslib.attributes;
+
+import io.github.seggan.javaclasslib.constantpool.UTF8Entry;
+
+public abstract class Attribute {
+
+    private final UTF8Entry nameIndex;
+    private final int length;
+
+    public Attribute(UTF8Entry nameIndex, int length) {
+        this.nameIndex = nameIndex;
+        this.length = length;
+    }
+
+    public abstract byte[] getBytes();
+
+    public UTF8Entry getNameIndex() {
+        return nameIndex;
+    }
+
+    public int getLength() {
+        return length;
+    }
+}

src/main/java/io/github/seggan/javaclasslib/attributes/CodeAttribute.java

@@ -0,0 +1,15 @@
+package io.github.seggan.javaclasslib.attributes;
+
+import io.github.seggan.javaclasslib.constantpool.UTF8Entry;
+
+public final class CodeAttribute extends Attribute {
+
+    public CodeAttribute(UTF8Entry nameIndex, int length) {
+        super(nameIndex, length);
+    }
+
+    @Override
+    public byte[] getBytes() {
+        return new byte[0];
+    }
+}

src/main/java/io/github/seggan/javaclasslib/constantpool/ConstantPoolEntry.java

@@ -24,15 +24,29 @@ public final ConstantPoolTag getTag() {
         return tag;
     }
 
+    /**
+     * Returns the index of this entry in the constant pool. Not to be confused with {@link #getIndexBytes()}
+     *
+     * @return the index of this constant pool entry
+     */
     public final int getIndex() {
         return constantPool.indexOf(this);
     }
 
+    /**
+     * Returns the bytes that make up the index of this entry in the constant pool. Not to
+     * be confused with {@link #getIndex()}
+     *
+     * @return a byte array of size 2 representing the index of this constant pool entry
+     */
     @Nonnull
     public final byte[] getIndexBytes() {
         return ByteUtils.twoBytesFromInt(getIndex());
     }
 
+    /**
+     * Converts this constant pool entry into its byte representation in a class file
+     */
     @Nonnull
     public abstract byte[] getBytes();
 

src/test/java/io/github/seggan/javaclasslib/tests/TestAccess.java

@@ -0,0 +1,20 @@
+package io.github.seggan.javaclasslib.tests;
+
+import io.github.seggan.javaclasslib.ClassAccessFlags;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class TestAccess {
+
+    @Test
+    public void testAccess() {
+        Assertions.assertEquals("401", Integer.toHexString(ClassAccessFlags.combine(ClassAccessFlags.PUBLIC, ClassAccessFlags.ABSTRACT)));
+    }
+
+    public static String byteArrayToHex(byte[] a) {
+        StringBuilder sb = new StringBuilder(a.length * 2);
+        for(byte b: a)
+            sb.append(String.format("%02x ", b));
+        return sb.toString();
+    }
+}

src/test/java/io/github/seggan/javaclasslib/tests/TestByteUtils.java

@@ -26,11 +26,6 @@ public void testIntToByte() {
             ByteUtils.intToBytes(16));
     }
 
-    @Test
-    public void testDoubleToByte() {
-        System.out.println(byteArrayToHex(ByteBuffer.allocate(8).order(ByteOrder.BIG_ENDIAN).putDouble(1.22).array()));
-    }
-
     public static String byteArrayToHex(byte[] a) {
         StringBuilder sb = new StringBuilder(a.length * 2);
         for(byte b: a)