FieldAccess.java

/**
 * Copyright (c) 2008, Nathan Sweet
 *  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
 *  3. Neither the name of Esoteric Software nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

package com.esotericsoftware.reflectasm;

import static org.objectweb.asm.Opcodes.*;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;

import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Type;

public abstract class FieldAccess {
	private static final Object theUnsafe;
	
	protected String[] fieldNames;
	protected Class[] fieldTypes;

	public int getIndex (String fieldName) {
		for (int i = 0, n = fieldNames.length; i < n; i++)
			if (fieldNames[i].equals(fieldName)) return i;
		throw new IllegalArgumentException("Unable to find non-private field: " + fieldName);
	}

	public void set (Object instance, String fieldName, Object value) {
		set(instance, getIndex(fieldName), value);
	}

	public Object get (Object instance, String fieldName) {
		return get(instance, getIndex(fieldName));
	}

	public String[] getFieldNames () {
		return fieldNames;
	}

	public Class[] getFieldTypes () {
		return fieldTypes;
	}

	public int getFieldCount () {
		return fieldTypes.length;
	}

	abstract public void set (Object instance, int fieldIndex, Object value);

	abstract public void setBoolean (Object instance, int fieldIndex, boolean value);

	abstract public void setByte (Object instance, int fieldIndex, byte value);

	abstract public void setShort (Object instance, int fieldIndex, short value);

	abstract public void setInt (Object instance, int fieldIndex, int value);

	abstract public void setLong (Object instance, int fieldIndex, long value);

	abstract public void setDouble (Object instance, int fieldIndex, double value);

	abstract public void setFloat (Object instance, int fieldIndex, float value);

	abstract public void setChar (Object instance, int fieldIndex, char value);

	abstract public Object get (Object instance, int fieldIndex);

	abstract public String getString (Object instance, int fieldIndex);

	abstract public char getChar (Object instance, int fieldIndex);

	abstract public boolean getBoolean (Object instance, int fieldIndex);

	abstract public byte getByte (Object instance, int fieldIndex);

	abstract public short getShort (Object instance, int fieldIndex);

	abstract public int getInt (Object instance, int fieldIndex);

	abstract public long getLong (Object instance, int fieldIndex);

	abstract public double getDouble (Object instance, int fieldIndex);

	abstract public float getFloat (Object instance, int fieldIndex);

	static public FieldAccess get (Class type) {
		ArrayList<Field> fields = new ArrayList<Field>();
		Class nextClass = type;
		while (nextClass != Object.class) {
			Field[] declaredFields = nextClass.getDeclaredFields();
			for (int i = 0, n = declaredFields.length; i < n; i++) {
				Field field = declaredFields[i];
				int modifiers = field.getModifiers();
				if (Modifier.isStatic(modifiers)) continue;
				if (Modifier.isPrivate(modifiers)) continue;
				fields.add(field);
			}
			nextClass = nextClass.getSuperclass();
		}

		String[] fieldNames = new String[fields.size()];
		Class[] fieldTypes = new Class[fields.size()];
		for (int i = 0, n = fieldNames.length; i < n; i++) {
			fieldNames[i] = fields.get(i).getName();
			fieldTypes[i] = fields.get(i).getType();
		}

		String className = type.getName();
		String accessClassName = className + "FieldAccess";
		if (accessClassName.startsWith("java.")) accessClassName = "reflectasm." + accessClassName;
		Class accessClass = null;

		AccessClassLoader loader = AccessClassLoader.get(type);
		synchronized (loader) {
			try {
				accessClass = loader.loadClass(accessClassName);
			} catch (ClassNotFoundException ignored) {
				String accessClassNameInternal = accessClassName.replace('.', '/');
				String classNameInternal = className.replace('.', '/');

				ClassWriter cw = new ClassWriter(0);
				cw.visit(V1_1, ACC_PUBLIC + ACC_SUPER, accessClassNameInternal, null, "com/esotericsoftware/reflectasm/FieldAccess",
					null);
				insertConstructor(cw);
				insertGetObject(cw, classNameInternal, fields);
				insertSetObject(cw, classNameInternal, fields);
				insertGetPrimitive(cw, classNameInternal, fields, Type.BOOLEAN_TYPE);
				insertSetPrimitive(cw, classNameInternal, fields, Type.BOOLEAN_TYPE);
				insertGetPrimitive(cw, classNameInternal, fields, Type.BYTE_TYPE);
				insertSetPrimitive(cw, classNameInternal, fields, Type.BYTE_TYPE);
				insertGetPrimitive(cw, classNameInternal, fields, Type.SHORT_TYPE);
				insertSetPrimitive(cw, classNameInternal, fields, Type.SHORT_TYPE);
				insertGetPrimitive(cw, classNameInternal, fields, Type.INT_TYPE);
				insertSetPrimitive(cw, classNameInternal, fields, Type.INT_TYPE);
				insertGetPrimitive(cw, classNameInternal, fields, Type.LONG_TYPE);
				insertSetPrimitive(cw, classNameInternal, fields, Type.LONG_TYPE);
				insertGetPrimitive(cw, classNameInternal, fields, Type.DOUBLE_TYPE);
				insertSetPrimitive(cw, classNameInternal, fields, Type.DOUBLE_TYPE);
				insertGetPrimitive(cw, classNameInternal, fields, Type.FLOAT_TYPE);
				insertSetPrimitive(cw, classNameInternal, fields, Type.FLOAT_TYPE);
				insertGetPrimitive(cw, classNameInternal, fields, Type.CHAR_TYPE);
				insertSetPrimitive(cw, classNameInternal, fields, Type.CHAR_TYPE);
				insertGetString(cw, classNameInternal, fields);
				cw.visitEnd();
				accessClass = loader.defineClass(accessClassName, cw.toByteArray());
			}
		}
		try {
			FieldAccess access = (FieldAccess)accessClass.newInstance();
			access.fieldNames = fieldNames;
			access.fieldTypes = fieldTypes;
			return access;
		} catch (Throwable t) {
			throw new RuntimeException("Error constructing field access class: " + accessClassName, t);
		}
	}

	static private void insertConstructor (ClassWriter cw) {
		MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
		mv.visitCode();
		mv.visitVarInsn(ALOAD, 0);
		mv.visitMethodInsn(INVOKESPECIAL, "com/esotericsoftware/reflectasm/FieldAccess", "<init>", "()V");
		mv.visitInsn(RETURN);
		mv.visitMaxs(1, 1);
		mv.visitEnd();
	}

	static private void insertSetObject (ClassWriter cw, String classNameInternal, ArrayList<Field> fields) {
		int maxStack = 6;
		MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "set", "(Ljava/lang/Object;ILjava/lang/Object;)V", null, null);
		mv.visitCode();
		mv.visitVarInsn(ILOAD, 2);

		if (!fields.isEmpty()) {
			maxStack--;
			Label[] labels = new Label[fields.size()];
			for (int i = 0, n = labels.length; i < n; i++)
				labels[i] = new Label();
			Label defaultLabel = new Label();
			mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

			for (int i = 0, n = labels.length; i < n; i++) {
				Field field = fields.get(i);
				Type fieldType = Type.getType(field.getType());

				mv.visitLabel(labels[i]);
				mv.visitFrame(F_SAME, 0, null, 0, null);
				mv.visitVarInsn(ALOAD, 1);
				mv.visitTypeInsn(CHECKCAST, classNameInternal);
				mv.visitVarInsn(ALOAD, 3);

				switch (fieldType.getSort()) {
				case Type.BOOLEAN:
					mv.visitTypeInsn(CHECKCAST, "java/lang/Boolean");
					mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Boolean", "booleanValue", "()Z");
					break;
				case Type.BYTE:
					mv.visitTypeInsn(CHECKCAST, "java/lang/Byte");
					mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Byte", "byteValue", "()B");
					break;
				case Type.CHAR:
					mv.visitTypeInsn(CHECKCAST, "java/lang/Character");
					mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Character", "charValue", "()C");
					break;
				case Type.SHORT:
					mv.visitTypeInsn(CHECKCAST, "java/lang/Short");
					mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Short", "shortValue", "()S");
					break;
				case Type.INT:
					mv.visitTypeInsn(CHECKCAST, "java/lang/Integer");
					mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Integer", "intValue", "()I");
					break;
				case Type.FLOAT:
					mv.visitTypeInsn(CHECKCAST, "java/lang/Float");
					mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Float", "floatValue", "()F");
					break;
				case Type.LONG:
					mv.visitTypeInsn(CHECKCAST, "java/lang/Long");
					mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Long", "longValue", "()J");
					break;
				case Type.DOUBLE:
					mv.visitTypeInsn(CHECKCAST, "java/lang/Double");
					mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Double", "doubleValue", "()D");
					break;
				case Type.ARRAY:
					mv.visitTypeInsn(CHECKCAST, fieldType.getDescriptor());
					break;
				case Type.OBJECT:
					mv.visitTypeInsn(CHECKCAST, fieldType.getInternalName());
					break;
				}

				mv.visitFieldInsn(PUTFIELD, classNameInternal, field.getName(), fieldType.getDescriptor());
				mv.visitInsn(RETURN);
			}

			mv.visitLabel(defaultLabel);
			mv.visitFrame(F_SAME, 0, null, 0, null);
		}
		mv = insertThrowExceptionForFieldNotFound(mv);
		mv.visitMaxs(maxStack, 4);
		mv.visitEnd();
	}

	static private void insertGetObject (ClassWriter cw, String classNameInternal, ArrayList<Field> fields) {
		int maxStack = 6;
		MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "get", "(Ljava/lang/Object;I)Ljava/lang/Object;", null, null);
		mv.visitCode();
		mv.visitVarInsn(ILOAD, 2);

		if (!fields.isEmpty()) {
			maxStack--;
			Label[] labels = new Label[fields.size()];
			for (int i = 0, n = labels.length; i < n; i++)
				labels[i] = new Label();
			Label defaultLabel = new Label();
			mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

			for (int i = 0, n = labels.length; i < n; i++) {
				Field field = fields.get(i);

				mv.visitLabel(labels[i]);
				mv.visitFrame(F_SAME, 0, null, 0, null);
				mv.visitVarInsn(ALOAD, 1);
				mv.visitTypeInsn(CHECKCAST, classNameInternal);
				mv.visitFieldInsn(GETFIELD, classNameInternal, field.getName(), Type.getDescriptor(field.getType()));

				Type fieldType = Type.getType(field.getType());
				switch (fieldType.getSort()) {
				case Type.BOOLEAN:
					mv.visitMethodInsn(INVOKESTATIC, "java/lang/Boolean", "valueOf", "(Z)Ljava/lang/Boolean;");
					break;
				case Type.BYTE:
					mv.visitMethodInsn(INVOKESTATIC, "java/lang/Byte", "valueOf", "(B)Ljava/lang/Byte;");
					break;
				case Type.CHAR:
					mv.visitMethodInsn(INVOKESTATIC, "java/lang/Character", "valueOf", "(C)Ljava/lang/Character;");
					break;
				case Type.SHORT:
					mv.visitMethodInsn(INVOKESTATIC, "java/lang/Short", "valueOf", "(S)Ljava/lang/Short;");
					break;
				case Type.INT:
					mv.visitMethodInsn(INVOKESTATIC, "java/lang/Integer", "valueOf", "(I)Ljava/lang/Integer;");
					break;
				case Type.FLOAT:
					mv.visitMethodInsn(INVOKESTATIC, "java/lang/Float", "valueOf", "(F)Ljava/lang/Float;");
					break;
				case Type.LONG:
					mv.visitMethodInsn(INVOKESTATIC, "java/lang/Long", "valueOf", "(J)Ljava/lang/Long;");
					break;
				case Type.DOUBLE:
					mv.visitMethodInsn(INVOKESTATIC, "java/lang/Double", "valueOf", "(D)Ljava/lang/Double;");
					break;
				}

				mv.visitInsn(ARETURN);
			}

			mv.visitLabel(defaultLabel);
			mv.visitFrame(F_SAME, 0, null, 0, null);
		}
		insertThrowExceptionForFieldNotFound(mv);
		mv.visitMaxs(maxStack, 3);
		mv.visitEnd();
	}

	static private void insertGetString (ClassWriter cw, String classNameInternal, ArrayList<Field> fields) {
		int maxStack = 6;
		MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "getString", "(Ljava/lang/Object;I)Ljava/lang/String;", null, null);
		mv.visitCode();
		mv.visitVarInsn(ILOAD, 2);

		if (!fields.isEmpty()) {
			maxStack--;
			Label[] labels = new Label[fields.size()];
			Label labelForInvalidTypes = new Label();
			boolean hasAnyBadTypeLabel = false;
			for (int i = 0, n = labels.length; i < n; i++) {
				if (fields.get(i).getType().equals(String.class))
					labels[i] = new Label();
				else {
					labels[i] = labelForInvalidTypes;
					hasAnyBadTypeLabel = true;
				}
			}
			Label defaultLabel = new Label();
			mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

			for (int i = 0, n = labels.length; i < n; i++) {
				if (!labels[i].equals(labelForInvalidTypes)) {
					mv.visitLabel(labels[i]);
					mv.visitFrame(F_SAME, 0, null, 0, null);
					mv.visitVarInsn(ALOAD, 1);
					mv.visitTypeInsn(CHECKCAST, classNameInternal);
					mv.visitFieldInsn(GETFIELD, classNameInternal, fields.get(i).getName(), "Ljava/lang/String;");
					mv.visitInsn(ARETURN);
				}
			}
			// Rest of fields: different type
			if (hasAnyBadTypeLabel) {
				mv.visitLabel(labelForInvalidTypes);
				mv.visitFrame(F_SAME, 0, null, 0, null);
				insertThrowExceptionForFieldType(mv, "String");
			}
			// Default: field not found
			mv.visitLabel(defaultLabel);
			mv.visitFrame(F_SAME, 0, null, 0, null);
		}
		insertThrowExceptionForFieldNotFound(mv);
		mv.visitMaxs(maxStack, 3);
		mv.visitEnd();
	}

	static private void insertSetPrimitive (ClassWriter cw, String classNameInternal, ArrayList<Field> fields, Type primitiveType) {
		int maxStack = 6;
		int maxLocals = 4; // See correction below for LLOAD and DLOAD
		final String setterMethodName;
		final String typeNameInternal = primitiveType.getDescriptor();
		final int loadValueInstruction;
		switch (primitiveType.getSort()) {
		case Type.BOOLEAN:
			setterMethodName = "setBoolean";
			loadValueInstruction = ILOAD;
			break;
		case Type.BYTE:
			setterMethodName = "setByte";
			loadValueInstruction = ILOAD;
			break;
		case Type.CHAR:
			setterMethodName = "setChar";
			loadValueInstruction = ILOAD;
			break;
		case Type.SHORT:
			setterMethodName = "setShort";
			loadValueInstruction = ILOAD;
			break;
		case Type.INT:
			setterMethodName = "setInt";
			loadValueInstruction = ILOAD;
			break;
		case Type.FLOAT:
			setterMethodName = "setFloat";
			loadValueInstruction = FLOAD;
			break;
		case Type.LONG:
			setterMethodName = "setLong";
			loadValueInstruction = LLOAD;
			maxLocals++; // (LLOAD and DLOAD actually load two slots)
			break;
		case Type.DOUBLE:
			setterMethodName = "setDouble";
			loadValueInstruction = DLOAD; // (LLOAD and DLOAD actually load two slots)
			maxLocals++;
			break;
		default:
			setterMethodName = "set";
			loadValueInstruction = ALOAD;
			break;
		}
		MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, setterMethodName, "(Ljava/lang/Object;I" + typeNameInternal + ")V", null,
			null);
		mv.visitCode();
		mv.visitVarInsn(ILOAD, 2);

		if (!fields.isEmpty()) {
			maxStack--;
			Label[] labels = new Label[fields.size()];
			Label labelForInvalidTypes = new Label();
			boolean hasAnyBadTypeLabel = false;
			for (int i = 0, n = labels.length; i < n; i++) {
				if (Type.getType(fields.get(i).getType()).equals(primitiveType))
					labels[i] = new Label();
				else {
					labels[i] = labelForInvalidTypes;
					hasAnyBadTypeLabel = true;
				}
			}
			Label defaultLabel = new Label();
			mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

			for (int i = 0, n = labels.length; i < n; i++) {
				if (!labels[i].equals(labelForInvalidTypes)) {
					mv.visitLabel(labels[i]);
					mv.visitFrame(F_SAME, 0, null, 0, null);
					mv.visitVarInsn(ALOAD, 1);
					mv.visitTypeInsn(CHECKCAST, classNameInternal);
					mv.visitVarInsn(loadValueInstruction, 3);
					mv.visitFieldInsn(PUTFIELD, classNameInternal, fields.get(i).getName(), typeNameInternal);
					mv.visitInsn(RETURN);
				}
			}
			// Rest of fields: different type
			if (hasAnyBadTypeLabel) {
				mv.visitLabel(labelForInvalidTypes);
				mv.visitFrame(F_SAME, 0, null, 0, null);
				insertThrowExceptionForFieldType(mv, primitiveType.getClassName());
			}
			// Default: field not found
			mv.visitLabel(defaultLabel);
			mv.visitFrame(F_SAME, 0, null, 0, null);
		}
		mv = insertThrowExceptionForFieldNotFound(mv);
		mv.visitMaxs(maxStack, maxLocals);
		mv.visitEnd();
	}

	static private void insertGetPrimitive (ClassWriter cw, String classNameInternal, ArrayList<Field> fields, Type primitiveType) {
		int maxStack = 6;
		final String getterMethodName;
		final String typeNameInternal = primitiveType.getDescriptor();
		final int returnValueInstruction;
		switch (primitiveType.getSort()) {
		case Type.BOOLEAN:
			getterMethodName = "getBoolean";
			returnValueInstruction = IRETURN;
			break;
		case Type.BYTE:
			getterMethodName = "getByte";
			returnValueInstruction = IRETURN;
			break;
		case Type.CHAR:
			getterMethodName = "getChar";
			returnValueInstruction = IRETURN;
			break;
		case Type.SHORT:
			getterMethodName = "getShort";
			returnValueInstruction = IRETURN;
			break;
		case Type.INT:
			getterMethodName = "getInt";
			returnValueInstruction = IRETURN;
			break;
		case Type.FLOAT:
			getterMethodName = "getFloat";
			returnValueInstruction = FRETURN;
			break;
		case Type.LONG:
			getterMethodName = "getLong";
			returnValueInstruction = LRETURN;
			break;
		case Type.DOUBLE:
			getterMethodName = "getDouble";
			returnValueInstruction = DRETURN;
			break;
		default:
			getterMethodName = "get";
			returnValueInstruction = ARETURN;
			break;
		}
		MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, getterMethodName, "(Ljava/lang/Object;I)" + typeNameInternal, null, null);
		mv.visitCode();
		mv.visitVarInsn(ILOAD, 2);

		if (!fields.isEmpty()) {
			maxStack--;
			Label[] labels = new Label[fields.size()];
			Label labelForInvalidTypes = new Label();
			boolean hasAnyBadTypeLabel = false;
			for (int i = 0, n = labels.length; i < n; i++) {
				if (Type.getType(fields.get(i).getType()).equals(primitiveType))
					labels[i] = new Label();
				else {
					labels[i] = labelForInvalidTypes;
					hasAnyBadTypeLabel = true;
				}
			}
			Label defaultLabel = new Label();
			mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);

			for (int i = 0, n = labels.length; i < n; i++) {
				Field field = fields.get(i);
				if (!labels[i].equals(labelForInvalidTypes)) {
					mv.visitLabel(labels[i]);
					mv.visitFrame(F_SAME, 0, null, 0, null);
					mv.visitVarInsn(ALOAD, 1);
					mv.visitTypeInsn(CHECKCAST, classNameInternal);
					mv.visitFieldInsn(GETFIELD, classNameInternal, field.getName(), typeNameInternal);
					mv.visitInsn(returnValueInstruction);
				}
			}
			// Rest of fields: different type
			if (hasAnyBadTypeLabel) {
				mv.visitLabel(labelForInvalidTypes);
				mv.visitFrame(F_SAME, 0, null, 0, null);
				insertThrowExceptionForFieldType(mv, primitiveType.getClassName());
			}
			// Default: field not found
			mv.visitLabel(defaultLabel);
			mv.visitFrame(F_SAME, 0, null, 0, null);
		}
		mv = insertThrowExceptionForFieldNotFound(mv);
		mv.visitMaxs(maxStack, 3);
		mv.visitEnd();
	}

	static private MethodVisitor insertThrowExceptionForFieldNotFound (MethodVisitor mv) {
		mv.visitTypeInsn(NEW, "java/lang/IllegalArgumentException");
		mv.visitInsn(DUP);
		mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
		mv.visitInsn(DUP);
		mv.visitLdcInsn("Field not found: ");
		mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V");
		mv.visitVarInsn(ILOAD, 2);
		mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;");
		mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;");
		mv.visitMethodInsn(INVOKESPECIAL, "java/lang/IllegalArgumentException", "<init>", "(Ljava/lang/String;)V");
		mv.visitInsn(ATHROW);
		return mv;
	}

	static private MethodVisitor insertThrowExceptionForFieldType (MethodVisitor mv, String fieldType) {
		mv.visitTypeInsn(NEW, "java/lang/IllegalArgumentException");
		mv.visitInsn(DUP);
		mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
		mv.visitInsn(DUP);
		mv.visitLdcInsn("Field not declared as " + fieldType + ": ");
		mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V");
		mv.visitVarInsn(ILOAD, 2);
		mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;");
		mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;");
		mv.visitMethodInsn(INVOKESPECIAL, "java/lang/IllegalArgumentException", "<init>", "(Ljava/lang/String;)V");
		mv.visitInsn(ATHROW);
		return mv;
	}
	
	static public  FieldAccess getAccessUnsafe(Class<?> type)
	{
		if(theUnsafe == null)
			throw new UnsupportedOperationException();
		
		return new FieldAccessUnsafe(type, (sun.misc.Unsafe)theUnsafe);
	}
	
	static {
		Object unsafe = null;
		try {
			Class<?> clazz = Class.forName("sun.misc.Unsafe");
			Field field = clazz.getDeclaredField("theUnsafe");
			field.setAccessible(true);
			unsafe = field.get(null);
		} catch (Exception e) {
		} finally {
			theUnsafe = unsafe;
		}
	}
}