package org.bouncycastle.crypto.modes.gcm;

import org.bouncycastle.crypto.util.Pack;
import org.bouncycastle.util.Arrays;

abstract class GCMUtil
{
    private static final int E1 = 0xe1000000;
    private static final byte E1B = (byte)0xe1;
    private static final long E1L = (E1 & 0xFFFFFFFFL) << 24;

    private static int[] generateLookup()
    {
        int[] lookup = new int[256];

        for (int c = 0; c < 256; ++c)
        {
            int v = 0;
            for (int i = 7; i >= 0; --i)
            {
                if ((c & (1 << i)) != 0)
                {
                    v ^= (E1 >>> (7 - i));
                }
            }
            lookup[c] = v;
        }

        return lookup;
    }

    private static final int[] LOOKUP = generateLookup();

    static byte[] oneAsBytes()
    {
        byte[] tmp = new byte[16];
        tmp[0] = (byte)0x80;
        return tmp;
    }

    static int[] oneAsInts()
    {
        int[] tmp = new int[4];
        tmp[0] = 1 << 31;
        return tmp;
    }

    static long[] oneAsLongs()
    {
        long[] tmp = new long[2];
        tmp[0] = 1L << 63;
        return tmp;
    }

    static byte[] asBytes(int[] x)
    {
        byte[] z = new byte[16];
        Pack.intToBigEndian(x, z, 0);
        return z;
    }

    static void asBytes(int[] x, byte[] z)
    {
        Pack.intToBigEndian(x, z, 0);
    }

    static byte[] asBytes(long[] x)
    {
        byte[] z = new byte[16];
        Pack.longToBigEndian(x, z, 0);
        return z;
    }

    static void asBytes(long[] x, byte[] z)
    {
        Pack.longToBigEndian(x, z, 0);
    }

    static int[] asInts(byte[] x)
    {
        int[] z = new int[4];
        Pack.bigEndianToInt(x, 0, z);
        return z;
    }

    static void asInts(byte[] x, int[] z)
    {
        Pack.bigEndianToInt(x, 0, z);
    }

    static long[] asLongs(byte[] x)
    {
        long[] z = new long[2];
        Pack.bigEndianToLong(x, 0, z);
        return z;
    }

    static void asLongs(byte[] x, long[] z)
    {
        Pack.bigEndianToLong(x, 0, z);
    }

    static void multiply(byte[] x, byte[] y)
    {
        byte[] r0 = Arrays.clone(x);
        byte[] r1 = new byte[16];

        for (int i = 0; i < 16; ++i)
        {
            byte bits = y[i];
            for (int j = 7; j >= 0; --j)
            {
                if ((bits & (1 << j)) != 0)
                {
                    xor(r1, r0);
                }

                if (shiftRight(r0) != 0)
                {
                    r0[0] ^= E1B;
                }
            }
        }

        System.arraycopy(r1, 0, x, 0, 16);
    }

    static void multiply(int[] x, int[] y)
    {
        int[] r0 = Arrays.clone(x);
        int[] r1 = new int[4];

        for (int i = 0; i < 4; ++i)
        {
            int bits = y[i];
            for (int j = 31; j >= 0; --j)
            {
                if ((bits & (1 << j)) != 0)
                {
                    xor(r1, r0);
                }

                if (shiftRight(r0) != 0)
                {
                    r0[0] ^= E1;
                }
            }
        }

        System.arraycopy(r1, 0, x, 0, 4);
    }

    static void multiply(long[] x, long[] y)
    {
        long[] r0 = new long[]{ x[0], x[1] };
        long[] r1 = new long[2];

        for (int i = 0; i < 2; ++i)
        {
            long bits = y[i];
            for (int j = 63; j >= 0; --j)
            {
                if ((bits & (1L << j)) != 0)
                {
                    xor(r1, r0);
                }

                if (shiftRight(r0) != 0)
                {
                    r0[0] ^= E1L;
                }
            }
        }

        x[0] = r1[0];
        x[1] = r1[1];
    }

    // P is the value with only bit i=1 set
    static void multiplyP(int[] x)
    {
        if (shiftRight(x) != 0)
        {
            x[0] ^= E1;
        }
    }

    static void multiplyP(int[] x, int[] y)
    {
        if (shiftRight(x, y) != 0)
        {
            y[0] ^= E1;
        }
    }

    // P is the value with only bit i=1 set
    static void multiplyP8(int[] x)
    {
//        for (int i = 8; i != 0; --i)
//        {
//            multiplyP(x);
//        }

        int c = shiftRightN(x, 8);
        x[0] ^= LOOKUP[c >>> 24];
    }

    static void multiplyP8(int[] x, int[] y)
    {
        int c = shiftRightN(x, 8, y);
        y[0] ^= LOOKUP[c >>> 24];
    }

    static byte shiftRight(byte[] x)
    {
//        int c = 0;
//        for (int i = 0; i < 16; ++i)
//        {
//            int b = x[i] & 0xff;
//            x[i] = (byte)((b >>> 1) | c);
//            c = (b & 1) << 7;
//        }
//        return (byte)c;

        int i = 0, c = 0;
        do
        {
            int b = x[i] & 0xff;
            x[i++] = (byte)((b >>> 1) | c);
            c = (b & 1) << 7;
            b = x[i] & 0xff;
            x[i++] = (byte)((b >>> 1) | c);
            c = (b & 1) << 7;
            b = x[i] & 0xff;
            x[i++] = (byte)((b >>> 1) | c);
            c = (b & 1) << 7;
            b = x[i] & 0xff;
            x[i++] = (byte)((b >>> 1) | c);
            c = (b & 1) << 7;
        }
        while (i < 16);
        return (byte)c;
    }

    static byte shiftRight(byte[] x, byte[] z)
    {
//        int c = 0;
//        for (int i = 0; i < 16; ++i)
//        {
//            int b = x[i] & 0xff;
//            z[i] = (byte) ((b >>> 1) | c);
//            c = (b & 1) << 7;
//        }
//        return (byte) c;

        int i = 0, c = 0;
        do
        {
            int b = x[i] & 0xff;
            z[i++] = (byte)((b >>> 1) | c);
            c = (b & 1) << 7;
            b = x[i] & 0xff;
            z[i++] = (byte)((b >>> 1) | c);
            c = (b & 1) << 7;
            b = x[i] & 0xff;
            z[i++] = (byte)((b >>> 1) | c);
            c = (b & 1) << 7;
            b = x[i] & 0xff;
            z[i++] = (byte)((b >>> 1) | c);
            c = (b & 1) << 7;
        }
        while (i < 16);
        return (byte)c;
    }

    static int shiftRight(int[] x)
    {
//        int c = 0;
//        for (int i = 0; i < 4; ++i)
//        {
//            int b = x[i];
//            x[i] = (b >>> 1) | c;
//            c = b << 31;
//        }
//        return c;

        int b = x[0];
        x[0] = b >>> 1;
        int c = b << 31;
        b = x[1];
        x[1] = (b >>> 1) | c;
        c = b << 31;
        b = x[2];
        x[2] = (b >>> 1) | c;
        c = b << 31;
        b = x[3];
        x[3] = (b >>> 1) | c;
        return b << 31;
    }

    static int shiftRight(int[] x, int[] z)
    {
//      int c = 0;
//      for (int i = 0; i < 4; ++i)
//      {
//          int b = x[i];
//          z[i] = (b >>> 1) | c;
//          c = b << 31;
//      }
//      return c;

        int b = x[0];
        z[0] = b >>> 1;
        int c = b << 31;
        b = x[1];
        z[1] = (b >>> 1) | c;
        c = b << 31;
        b = x[2];
        z[2] = (b >>> 1) | c;
        c = b << 31;
        b = x[3];
        z[3] = (b >>> 1) | c;
        return b << 31;
    }

    static long shiftRight(long[] x)
    {
        long b = x[0];
        x[0] = b >>> 1;
        long c = b << 63; 
        b = x[1];
        x[1] = (b >>> 1) | c;
        return b << 63;
    }

    static long shiftRight(long[] x, long[] z)
    {
        long b = x[0];
        z[0] = b >>> 1;
        long c = b << 63; 
        b = x[1];
        z[1] = (b >>> 1) | c;
        return b << 63;
    }

    static int shiftRightN(int[] x, int n)
    {
//        int c = 0, nInv = 32 - n;
//        for (int i = 0; i < 4; ++i)
//        {
//            int b = x[i];
//            x[i] = (b >>> n) | c;
//            c = b << nInv;
//        }
//        return c;

        int b = x[0], nInv = 32 - n;
        x[0] = b >>> n;
        int c = b << nInv;
        b = x[1];
        x[1] = (b >>> n) | c;
        c = b << nInv;
        b = x[2];
        x[2] = (b >>> n) | c;
        c = b << nInv;
        b = x[3];
        x[3] = (b >>> n) | c;
        return b << nInv;
    }

    static int shiftRightN(int[] x, int n, int[] z)
    {
//        int c = 0, nInv = 32 - n;
//        for (int i = 0; i < 4; ++i)
//        {
//            int b = x[i];
//            z[i] = (b >>> n) | c;
//            c = b << nInv;
//        }
//        return c;

        int b = x[0], nInv = 32 - n;
        z[0] = b >>> n;
        int c = b << nInv;
        b = x[1];
        z[1] = (b >>> n) | c;
        c = b << nInv;
        b = x[2];
        z[2] = (b >>> n) | c;
        c = b << nInv;
        b = x[3];
        z[3] = (b >>> n) | c;
        return b << nInv;
    }

    static void xor(byte[] x, byte[] y)
    {
        int i = 0;
        do
        {
            x[i] ^= y[i]; ++i;
            x[i] ^= y[i]; ++i;
            x[i] ^= y[i]; ++i;
            x[i] ^= y[i]; ++i;
        }
        while (i < 16);
    }

    static void xor(byte[] x, byte[] y, int yOff, int yLen)
    {
        while (yLen-- > 0)
        {
            x[yLen] ^= y[yOff + yLen];
        }
    }

    static void xor(byte[] x, byte[] y, byte[] z)
    {
        int i = 0;
        do
        {
            z[i] = (byte)(x[i] ^ y[i]); ++i;
            z[i] = (byte)(x[i] ^ y[i]); ++i;
            z[i] = (byte)(x[i] ^ y[i]); ++i;
            z[i] = (byte)(x[i] ^ y[i]); ++i;
        }
        while (i < 16);
    }

    static void xor(int[] x, int[] y)
    {
        x[0] ^= y[0];
        x[1] ^= y[1];
        x[2] ^= y[2];
        x[3] ^= y[3];
    }

    static void xor(int[] x, int[] y, int[] z)
    {
        z[0] = x[0] ^ y[0];
        z[1] = x[1] ^ y[1];
        z[2] = x[2] ^ y[2];
        z[3] = x[3] ^ y[3];
    }

    static void xor(long[] x, long[] y)
    {
        x[0] ^= y[0];
        x[1] ^= y[1];
    }

    static void xor(long[] x, long[] y, long[] z)
    {
        z[0] = x[0] ^ y[0];
        z[1] = x[1] ^ y[1];
    }
}