package psy.lob.saw;

import java.lang.reflect.Field;
import java.nio.CharBuffer;

import sun.misc.Unsafe;

public class UnsafeString {
    private static final Unsafe unsafe;
    private static final long valueOffset;
    private static final long offsetOffset;
    private static final long countOffset;

    static {
	try {
	    // This is a bit of voodoo to force the unsafe object into
	    // visibility and acquire it.
	    // This is not playing nice, but as an established back door it is
	    // not likely to be
	    // taken away.
	    Field field = Unsafe.class.getDeclaredField("theUnsafe");
	    field.setAccessible(true);
	    unsafe = (Unsafe) field.get(null);
	    valueOffset = unsafe.objectFieldOffset(String.class
		    .getDeclaredField("value"));
	    Field declaredField;
	    try {
		declaredField = String.class.getDeclaredField("count");
	    }
	    // this will happen for jdk7 as these fields have been removed
	    catch (NoSuchFieldException e) {
		declaredField = null;
	    }
	    if (declaredField != null) {
		countOffset = unsafe.objectFieldOffset(declaredField);
	    } else {
		countOffset = -1L;
	    }
	    declaredField = null;
	    try {
		declaredField = String.class.getDeclaredField("offset");
	    }
	    // this will happen for jdk7 as these fields have been removed
	    catch (NoSuchFieldException e) {
		declaredField = null;
	    }
	    if (declaredField != null) {
		offsetOffset = unsafe.objectFieldOffset(declaredField);
	    } else {
		offsetOffset = -1L;
	    }
	} catch (Exception e) {
	    throw new RuntimeException(e);
	}
    }

    public final static String buildUnsafe(char[] chars) {
	String mutable = new String();// an empty string to hack
	unsafe.putObject(mutable, valueOffset, chars);
	if (countOffset != -1L) {
	    unsafe.putInt(mutable, countOffset, chars.length);
	}
	return mutable;
    }

    public final static String buildUnsafe(char[] chars, int offset, int length) {
	String mutable = new String();// an empty string to hack
	unsafe.putObject(mutable, valueOffset, chars);
	if (countOffset != -1L) {
	    unsafe.putInt(mutable, countOffset, length);
	    unsafe.putIntVolatile(mutable, offsetOffset, offset);
	}
	return mutable;
    }

    public final static char[] getChars(String s) {
	return (char[]) unsafe.getObject(s, valueOffset);
    }

    public final static int getOffset(String s) {
	if (offsetOffset == -1L)
	    return 0;
	else
	    return unsafe.getInt(s, offsetOffset);
    }

    public final static CharBuffer getStringAsCharBuffer(String s) {
	CharBuffer buffy = CharBuffer.wrap(getChars(s));
	return buffy;
    }

    public final static void wrapStringWithCharBuffer(String s, CharBuffer buffy) {
	UnsafeCharBuffer.wrap(buffy, getChars(s), 0, s.length());
    }

    public static void main(String[] args) {
	String text = buildUnsafe(new char[] { 'W', 'O', 'W' });
	if (text.equals("WOW")) {
	    System.out.println("WOW");
	}
    }
}