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Zero-allocation implementations of fast non-cryptographic hash functions for byte sequences or blocks of memory

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/*
 * Copyright 2014 Higher Frequency Trading http://www.higherfrequencytrading.com
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.openhft.hashing;

import static java.nio.ByteOrder.LITTLE_ENDIAN;
import static java.nio.ByteOrder.nativeOrder;

final class Primitives {

    private Primitives() {}

    static final boolean NATIVE_LITTLE_ENDIAN = nativeOrder() == LITTLE_ENDIAN;

    static long unsignedInt(int i) {
        return i & 0xFFFFFFFFL;
    }

    static int unsignedShort(int s) {
        return s & 0xFFFF;
    }

    static int unsignedByte(int b) {
        return b & 0xFF;
    }

    private static final ByteOrderHelper H2LE = NATIVE_LITTLE_ENDIAN ? new ByteOrderHelper() : new ByteOrderHelperReverse();
    private static final ByteOrderHelper H2BE = NATIVE_LITTLE_ENDIAN ? new ByteOrderHelperReverse() : new ByteOrderHelper();

    static long nativeToLittleEndian(final long v) { return H2LE.adjustByteOrder(v); }
    static int nativeToLittleEndian(final int v) { return H2LE.adjustByteOrder(v); }
    static short nativeToLittleEndian(final short v) { return H2LE.adjustByteOrder(v); }
    static char nativeToLittleEndian(final char v) { return H2LE.adjustByteOrder(v); }

    static long nativeToBigEndian(final long v) { return H2BE.adjustByteOrder(v); }
    static int nativeToBigEndian(final int v) { return H2BE.adjustByteOrder(v); }
    static short nativeToBigEndian(final short v) { return H2BE.adjustByteOrder(v); }
    static char nativeToBigEndian(final char v) { return H2BE.adjustByteOrder(v); }

    private static class ByteOrderHelper {
        long adjustByteOrder(final long v) { return v; }
        int adjustByteOrder(final int v) { return v; }
        short adjustByteOrder(final short v) { return v; }
        char adjustByteOrder(final char v) { return v; }
    }
    private static class ByteOrderHelperReverse extends ByteOrderHelper {
        long adjustByteOrder(final long v) { return Long.reverseBytes(v); }
        int adjustByteOrder(final int v) { return Integer.reverseBytes(v); }
        short adjustByteOrder(final short v) { return Short.reverseBytes(v); }
        char adjustByteOrder(final char v) { return Character.reverseBytes(v); }
    }
}