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/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.common.util;

/** Utility methods to do byte-level encoding. These methods are biased towards little-endian byte order because it is the most
 *  common byte order and reading several bytes at once may be optimizable in the future with the help of sun.mist.Unsafe. */
public enum ByteUtils {
    ;

    public static final int MAX_BYTES_VLONG = 9;

    /** Zig-zag decode. */
    public static long zigZagDecode(long n) {
        return ((n >>> 1) ^ -(n & 1));
    }

    /** Zig-zag encode: this helps transforming small signed numbers into small positive numbers. */
    public static long zigZagEncode(long n) {
        return (n >> 63) ^ (n << 1);
    }

    /** Write a long in little-endian format. */
    public static void writeLongLE(long l, byte[] arr, int offset) {
        for (int i = 0; i < 8; ++i) {
            arr[offset++] = (byte) l;
            l >>>= 8;
        }
        assert l == 0;
    }

    /** Write a long in little-endian format. */
    public static long readLongLE(byte[] arr, int offset) {
        long l = arr[offset++] & 0xFFL;
        for (int i = 1; i < 8; ++i) {
            l |= (arr[offset++] & 0xFFL) << (8 * i);
        }
        return l;
    }

    /** Write an int in little-endian format. */
    public static void writeIntLE(int l, byte[] arr, int offset) {
        for (int i = 0; i < 4; ++i) {
            arr[offset++] = (byte) l;
            l >>>= 8;
        }
        assert l == 0;
    }

    /** Read an int in little-endian format. */
    public static int readIntLE(byte[] arr, int offset) {
        int l = arr[offset++] & 0xFF;
        for (int i = 1; i < 4; ++i) {
            l |= (arr[offset++] & 0xFF) << (8 * i);
        }
        return l;
    }

    /** Write a double in little-endian format. */
    public static void writeDoubleLE(double d, byte[] arr, int offset) {
        writeLongLE(Double.doubleToRawLongBits(d), arr, offset);
    }

    /** Read a double in little-endian format. */
    public static double readDoubleLE(byte[] arr, int offset) {
        return Double.longBitsToDouble(readLongLE(arr, offset));
    }

    /** Write a float in little-endian format. */
    public static void writeFloatLE(float d, byte[] arr, int offset) {
        writeIntLE(Float.floatToRawIntBits(d), arr, offset);
    }

    /** Read a float in little-endian format. */
    public static float readFloatLE(byte[] arr, int offset) {
        return Float.intBitsToFloat(readIntLE(arr, offset));
    }

}