Declare BCBClass to build classes composed of methods

Signed-off-by: Brad Wood <bradley.wood@ibm.com>

bcb/src/main/java/com/ibm/bcb/BCBClass.java

@@ -0,0 +1,77 @@
+package com.ibm.bcb;
+
+import com.ibm.bcb.tree.Block;
+import com.ibm.bcb.tree.MethodContext;
+import lombok.*;
+import org.objectweb.asm.*;
+
+import java.util.List;
+
+import static org.objectweb.asm.Opcodes.*;
+
+@Data
+@Builder
+@EqualsAndHashCode
+public class BCBClass {
+
+    @Builder.Default
+    private final String name = "AnonymousClass";
+    @Builder.Default
+    private final String parent = "java/lang/Object";
+    @Singular
+    private final List<BCBMethod> methods;
+
+    public byte[] toByteArray() {
+        final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
+        cw.visit(V1_8, ACC_PUBLIC + ACC_SUPER, name, null, parent, null);
+
+        // Todo; Add default constructor if required
+        // Modify existing default constructor to initial default fields
+
+        // Todo; Add class initializer if required
+        // Modify existing initializer to initial static fields
+
+        for (final BCBMethod method : methods) {
+            writeToClass(method, cw);
+        }
+
+        cw.visitEnd();
+        return cw.toByteArray();
+    }
+
+    public void writeToClass(final BCBMethod method, final ClassVisitor cv) {
+        final Label methodEnd = new Label();
+        final MethodVisitor mv = cv.visitMethod(method.getModifiers(), method.getName(), method.getMethodType().getDescriptor(), null, null);
+        final Type clazzType = Type.getType("L" + name + ";");
+        final MethodContext ctx = new MethodContext(clazzType, method.getName(), ACC_PUBLIC + ACC_STATIC, method.getMethodType(), method.getArgNames(), methodEnd);
+
+        Block.of(method.getStatements()).evaluate(ctx, mv);
+
+        mv.visitLabel(methodEnd);
+
+        for (final String argName : method.getArgNames()) {
+            mv.visitParameter(argName, 0);
+        }
+
+        mv.visitMaxs(0, 0);
+        mv.visitEnd();
+    }
+
+    @SneakyThrows
+    public Class<?> loadClass() {
+        final byte[] bytes = toByteArray();
+
+        final ClassLoader loader = new ClassLoader() {
+            @Override
+            protected Class<?> findClass(final String name) {
+                if (name.equals(name.replace("/", "."))) {
+                    return defineClass(name, bytes, 0, bytes.length);
+                }
+
+                return null;
+            }
+        };
+
+        return loader.loadClass(name.replace("/", "."));
+    }
+}

bcb/src/main/java/com/ibm/bcb/BCBMethod.java

@@ -1,12 +1,8 @@
 package com.ibm.bcb;
 
 import com.ibm.bcb.tree.Block;
-import com.ibm.bcb.tree.MethodContext;
 import com.ibm.bcb.tree.Statement;
 import lombok.*;
-import org.objectweb.asm.ClassWriter;
-import org.objectweb.asm.Label;
-import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.Type;
 
 import java.io.File;
@@ -17,7 +13,8 @@
 import java.lang.reflect.Method;
 import java.util.List;
 
-import static org.objectweb.asm.Opcodes.*;
+import static org.objectweb.asm.Opcodes.ACC_PUBLIC;
+import static org.objectweb.asm.Opcodes.ACC_STATIC;
 
 @Builder
 @AllArgsConstructor
@@ -87,46 +84,19 @@ public Type getMethodType() {
         return Type.getMethodType(returnType, argTypes.toArray(new Type[0]));
     }
 
-    public byte[] toByteArray() {
-        final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
-        cw.visit(V1_8, ACC_PUBLIC + ACC_SUPER, declaringClass, null, "java/lang/Object", null);
-
-        final Label methodEnd = new Label();
-        final MethodVisitor mv = cw.visitMethod(modifiers, name, getMethodType().getDescriptor(), null, null);
-        final Type clazzType = Type.getType("L" + declaringClass + ";");
-        final MethodContext ctx = new MethodContext(clazzType, name, ACC_PUBLIC + ACC_STATIC, getMethodType(), argNames, methodEnd);
-
-        Block.of(statements).evaluate(ctx, mv);
-
-        mv.visitLabel(methodEnd);
-
-        for (final String argName : argNames) {
-            mv.visitParameter(argName, 0);
-        }
-
-        mv.visitMaxs(0, 0);
-        mv.visitEnd();
-
-        cw.visitEnd();
-        return cw.toByteArray();
+    private byte[] toByteArray() {
+        return BCBClass.builder()
+                .name(declaringClass)
+                .method(this)
+                .build().toByteArray();
     }
 
     @SneakyThrows
     private Class<?> loadClass() {
-        final byte[] bytes = toByteArray();
-
-        final ClassLoader loader = new ClassLoader() {
-            @Override
-            protected Class<?> findClass(final String name) {
-                if (name.equals(declaringClass.replace("/", "."))) {
-                    return defineClass(name, bytes, 0, bytes.length);
-                }
-
-                return null;
-            }
-        };
-
-        return loader.loadClass(declaringClass.replace("/", "."));
+        return BCBClass.builder()
+                .name(declaringClass)
+                .method(this)
+                .build().loadClass();
     }
 
     @SneakyThrows

bcb/src/test/java/com/ibm/bcb/TestBCBClass.java

@@ -0,0 +1,35 @@
+package com.ibm.bcb;
+
+import lombok.SneakyThrows;
+import org.junit.Assert;
+import org.junit.Test;
+import org.objectweb.asm.Type;
+
+import static com.ibm.bcb.BCB.constant;
+import static com.ibm.bcb.BCB.ret;
+
+public class TestBCBClass {
+
+    @Test
+    @SneakyThrows
+    public void testInvokeMR() {
+        final Class<?> clazz = BCBClass.builder()
+                .method(BCBMethod.builder()
+                        .name("test")
+                        .returnType(Type.INT_TYPE)
+                        .body(
+                                ret(constant(100))
+                        ).build())
+                .method(BCBMethod.builder()
+                        .name("test2")
+                        .returnType(Type.INT_TYPE)
+                        .body(
+                                ret(constant(200))
+                        ).build())
+                .build()
+                .loadClass();
+
+        Assert.assertEquals(100, (int) clazz.getMethod("test").invoke(null));
+        Assert.assertEquals(200, (int) clazz.getMethod("test2").invoke(null));
+    }
+}