MurmurHash2のJava実装。32ビットハッシュを求めるやつと64ビットハッシュを求めるやつ

EncodeUtils.java

public class EncodeUtils {
	
	public static long toLongBE(byte[] b, int offset) {
		
		return (((long)b[offset+0] << 56) +
				((long)(b[offset+1] & 255) << 48) +
				((long)(b[offset+2] & 255) << 40) +
				((long)(b[offset+3] & 255) << 32) +
				((long)(b[offset+4] & 255) << 24) +
				((b[offset+5] & 255) << 16) +
				((b[offset+6] & 255) <<  8) +
				((b[offset+7] & 255) <<  0));
		
	}

	public static long toLongLE(byte[] b, int offset) {
		
		return (((long)b[offset+7] << 56) +
				((long)(b[offset+6] & 255) << 48) +
				((long)(b[offset+5] & 255) << 40) +
				((long)(b[offset+4] & 255) << 32) +
				((long)(b[offset+3] & 255) << 24) +
				((b[offset+2] & 255) << 16) +
				((b[offset+1] & 255) <<  8) +
				((b[offset+0] & 255) <<  0));
		
	}
	
}

MurmurHash2.java

public class MurmurHash2 {

	public static int digest32(byte[] data, int seed, boolean bigendian) {
		
		final int m = 0x5bd1e995;
		final int r = 24;
		final int len = data.length;
		
		int h = seed ^ len;
		
		int block_remain = len % 4;
		int block_size = len - block_remain;

		int i = 0;
		for (i = 0; i < block_size; i += 4) {
			int k = bigendian
					? ((data[i+0] << 24) + (data[i+1] << 16) + (data[i+2] << 8) + (data[i+3] << 0))
					: ((data[i+3] << 24) + (data[i+2] << 16) + (data[i+1] << 8) + (data[i+0] << 0));
					
			k *= m;
			k ^= k >>> r;
			k *= m;
			
			h *= m;
			h ^= k;
		}

		switch (block_remain) {
		case 3:
			h ^= data[i + 2] << 16;
		case 2:
			h ^= data[i + 1] << 8;
		case 1:
			h ^= data[i];
			h *= m;
		}

		h ^= h >>> 13;
		h *= m;
		h ^= h >>> 15;

		return h;
		
	}
	
	public static long digest64(byte[] data, long seed, boolean bigendian) {
		
		final long m = 0xc6a4a7935bd1e995L;
		final int r = 47;
		final int len = data.length;
		
		long h = seed ^ (m * len);
		
		int block_remain = len % 8;
		int block_size = len - block_remain;

		int i = 0;
		for (i = 0; i < block_size; i += 8) {
			
			long k = bigendian
					? EncodeUtils.toLongBE(data, i)
					: EncodeUtils.toLongLE(data, i);
					
			k *= m;
			k ^= k >>> r;
			k *= m;
			
			h ^= k;
			h *= m;
			
		}

		switch (block_remain) {
		case 7: h ^= (long)data[i + 6] << 48;
		case 6: h ^= (long)data[i + 5] << 40;
		case 5: h ^= (long)data[i + 4] << 32;
		case 4: h ^= (long)data[i + 3] << 24;
		case 3: h ^= data[i + 2] << 16;
		case 2: h ^= data[i + 1] << 8;
		case 1: h ^= data[i + 0];
			h *= m;
		}
		
		h ^= h >>> r;
		h *= m;
		h ^= h >>> r;
		
		return h;
	}
	
}