Arrays.java

package the8472.utils;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;

public class Arrays {
	
	private static final java.lang.invoke.MethodHandle compareImpl;
	private static final java.lang.invoke.MethodHandle mismatchImpl;
	
	static {
		
		MethodHandle compU = null;
		MethodHandle mism = null;
		
		try {
			compU = MethodHandles.lookup().findStatic(java.util.Arrays.class, "compareUnsigned", MethodType.methodType(int.class, byte[].class, byte[].class));
			mism = MethodHandles.lookup().findStatic(java.util.Arrays.class, "mismatch", MethodType.methodType(int.class, byte[].class, byte[].class));
		} catch (NoSuchMethodException | IllegalAccessException e) {
			// no java9
		}
		
		if(compU == null) {
			try {
				compU = MethodHandles.lookup().findStatic(Arrays.class, "compareUnsignedFallback", MethodType.methodType(int.class, byte[].class, byte[].class));
				mism  = MethodHandles.lookup().findStatic(Arrays.class, "mismatchFallback", MethodType.methodType(int.class, byte[].class, byte[].class));
				
			}  catch (NoSuchMethodException | IllegalAccessException e) {
				throw new Error("should not happen");
			}
		}
		
		
		compareImpl = compU;
		mismatchImpl = mism;
	}
	
	public static int compareUnsigned(byte[] a, byte[] b) {
		try {
			return (int) compareImpl.invokeExact(a, b);
		} catch(RuntimeException e) {
			throw e;
		} catch(Throwable e) {
			throw new Error("should not happen", e);
		}
		
	}
	
	public static int mismatch(byte[] a, byte[] b) {
		try {
			return (int) mismatchImpl.invokeExact(a, b);
		} catch(RuntimeException e) {
			throw e;
		} catch(Throwable e) {
			throw new Error("should not happen", e);
		}
		
	}
	
	
	
	@SuppressWarnings("unused")
	private static int compareUnsignedFallback(byte[] a, byte[] b) {
		int minLength = Math.min(a.length, b.length);
		for(int i=0;i+7<minLength;i+=8)
		{
			long la = Byte.toUnsignedLong(a[i]) << 56 |
					Byte.toUnsignedLong(a[i+1]) << 48 |
					Byte.toUnsignedLong(a[i+2]) << 40 |
					Byte.toUnsignedLong(a[i+3]) << 32 |
					Byte.toUnsignedLong(a[i+4]) << 24 |
					Byte.toUnsignedLong(a[i+5]) << 16 |
					Byte.toUnsignedLong(a[i+6]) << 8 |
					Byte.toUnsignedLong(a[i+7]) << 0;
			long lb = Byte.toUnsignedLong(b[i]) << 56 |
					Byte.toUnsignedLong(b[i+1]) << 48 |
					Byte.toUnsignedLong(b[i+2]) << 40 |
					Byte.toUnsignedLong(b[i+3]) << 32 |
					Byte.toUnsignedLong(b[i+4]) << 24 |
					Byte.toUnsignedLong(b[i+5]) << 16 |
					Byte.toUnsignedLong(b[i+6]) << 8 |
					Byte.toUnsignedLong(b[i+7]) << 0;
			
			if(la != lb)
				return Long.compareUnsigned(la, lb);
			
		}
		
		int offset = minLength - minLength & 0x7;
		
		for(int i=offset;i<minLength;i++) {
			int ia = Byte.toUnsignedInt(a[i]);
			int ib = Byte.toUnsignedInt(b[i]);
			if(ia != ib)
				return Integer.compare(ia, ib);
		}
		
		return a.length - b.length;
	}
	
	@SuppressWarnings("unused")
	private static int mismatchFallback(byte[] a, byte[] b) {
		int min = Math.min(a.length, b.length);
		for(int i=0;i<min;i++) {
			if(a[i] != b[i])
				return i;
		}
		
		return a.length == b.length ? -1 : min;
	}

}