using System;

namespace Org.BouncyCastle.Crypto.Utilities
{
    internal sealed class Pack
    {
        private Pack()
        {
        }

        internal static void UInt16_To_BE(ushort n, byte[] bs)
        {
            bs[0] = (byte)(n >> 8);
            bs[1] = (byte)(n);
        }

        internal static void UInt16_To_BE(ushort n, byte[] bs, int off)
        {
            bs[off] = (byte)(n >> 8);
            bs[off + 1] = (byte)(n);
        }

        internal static void UInt16_To_BE(ushort[] ns, byte[] bs, int off)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt16_To_BE(ns[i], bs, off);
                off += 2;
            }
        }

        internal static void UInt16_To_BE(ushort[] ns, int nsOff, int nsLen, byte[] bs, int bsOff)
        {
            for (int i = 0; i < nsLen; ++i)
            {
                UInt16_To_BE(ns[nsOff + i], bs, bsOff);
                bsOff += 2;
            }
        }

        internal static byte[] UInt16_To_BE(ushort n)
        {
            byte[] bs = new byte[2];
            UInt16_To_BE(n, bs, 0);
            return bs;
        }

        internal static byte[] UInt16_To_BE(ushort[] ns)
        {
            return UInt16_To_BE(ns, 0, ns.Length);
        }

        internal static byte[] UInt16_To_BE(ushort[] ns, int nsOff, int nsLen)
        {
            byte[] bs = new byte[2 * nsLen];
            UInt16_To_BE(ns, nsOff, nsLen, bs, 0);
            return bs;
        }

        internal static ushort BE_To_UInt16(byte[] bs, int off)
        {
            uint n = (uint)bs[off] << 8
                | (uint)bs[off + 1];
            return (ushort)n;
        }

        internal static void BE_To_UInt16(byte[] bs, int bsOff, ushort[] ns, int nsOff)
        {
            ns[nsOff] = BE_To_UInt16(bs, bsOff);
        }

        internal static ushort[] BE_To_UInt16(byte[] bs)
        {
            return BE_To_UInt16(bs, 0, bs.Length);
        }

        internal static ushort[] BE_To_UInt16(byte[] bs, int off, int len)
        {
            if ((len & 1) != 0)
                throw new ArgumentException("must be a multiple of 2", "len");

            ushort[] ns = new ushort[len / 2];
            for (int i = 0; i < len; i += 2)
            {
                BE_To_UInt16(bs, off + i, ns, i >> 1);
            }
            return ns;
        }

        internal static void UInt32_To_BE(uint n, byte[] bs)
        {
            bs[0] = (byte)(n >> 24);
            bs[1] = (byte)(n >> 16);
            bs[2] = (byte)(n >> 8);
            bs[3] = (byte)(n);
        }

        internal static void UInt32_To_BE(uint n, byte[] bs, int off)
        {
            bs[off] = (byte)(n >> 24);
            bs[off + 1] = (byte)(n >> 16);
            bs[off + 2] = (byte)(n >> 8);
            bs[off + 3] = (byte)(n);
        }

        internal static void UInt32_To_BE(uint[] ns, byte[] bs, int off)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt32_To_BE(ns[i], bs, off);
                off += 4;
            }
        }

        internal static void UInt32_To_BE(uint[] ns, int nsOff, int nsLen, byte[] bs, int bsOff)
        {
            for (int i = 0; i < nsLen; ++i)
            {
                UInt32_To_BE(ns[nsOff + i], bs, bsOff);
                bsOff += 4;
            }
        }

        internal static byte[] UInt32_To_BE(uint n)
        {
            byte[] bs = new byte[4];
            UInt32_To_BE(n, bs, 0);
            return bs;
        }

        internal static byte[] UInt32_To_BE(uint[] ns)
        {
            byte[] bs = new byte[4 * ns.Length];
            UInt32_To_BE(ns, bs, 0);
            return bs;
        }

        internal static uint BE_To_UInt32(byte[] bs)
        {
            return (uint)bs[0] << 24
                | (uint)bs[1] << 16
                | (uint)bs[2] << 8
                | (uint)bs[3];
        }

        internal static uint BE_To_UInt32(byte[] bs, int off)
        {
            return (uint)bs[off] << 24
                | (uint)bs[off + 1] << 16
                | (uint)bs[off + 2] << 8
                | (uint)bs[off + 3];
        }

        internal static void BE_To_UInt32(byte[] bs, int off, uint[] ns)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = BE_To_UInt32(bs, off);
                off += 4;
            }
        }

        internal static void BE_To_UInt32(byte[] bs, int bsOff, uint[] ns, int nsOff, int nsLen)
        {
            for (int i = 0; i < nsLen; ++i)
            {
                ns[nsOff + i] = BE_To_UInt32(bs, bsOff);
                bsOff += 4;
            }
        }

        internal static byte[] UInt64_To_BE(ulong n)
        {
            byte[] bs = new byte[8];
            UInt64_To_BE(n, bs, 0);
            return bs;
        }

        internal static void UInt64_To_BE(ulong n, byte[] bs)
        {
            UInt32_To_BE((uint)(n >> 32), bs);
            UInt32_To_BE((uint)(n), bs, 4);
        }

        internal static void UInt64_To_BE(ulong n, byte[] bs, int off)
        {
            UInt32_To_BE((uint)(n >> 32), bs, off);
            UInt32_To_BE((uint)(n), bs, off + 4);
        }

        internal static byte[] UInt64_To_BE(ulong[] ns)
        {
            byte[] bs = new byte[8 * ns.Length];
            UInt64_To_BE(ns, bs, 0);
            return bs;
        }

        internal static void UInt64_To_BE(ulong[] ns, byte[] bs, int off)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt64_To_BE(ns[i], bs, off);
                off += 8;
            }
        }

        internal static void UInt64_To_BE(ulong[] ns, int nsOff, int nsLen, byte[] bs, int bsOff)
        {
            for (int i = 0; i < nsLen; ++i)
            {
                UInt64_To_BE(ns[nsOff + i], bs, bsOff);
                bsOff += 8;
            }
        }

        internal static ulong BE_To_UInt64(byte[] bs, int off)
        {
            uint hi = BE_To_UInt32(bs, off);
            uint lo = BE_To_UInt32(bs, off + 4);
            return ((ulong)hi << 32) | (ulong)lo;
        }

        internal static void BE_To_UInt64(byte[] bs, int off, ulong[] ns)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = BE_To_UInt64(bs, off);
                off += 8;
            }
        }

        internal static void BE_To_UInt64(byte[] bs, int bsOff, ulong[] ns, int nsOff, int nsLen)
        {
            for (int i = 0; i < nsLen; ++i)
            {
                ns[nsOff + i] = BE_To_UInt64(bs, bsOff);
                bsOff += 8;
            }
        }

        internal static void UInt16_To_LE(ushort n, byte[] bs)
        {
            bs[0] = (byte)(n);
            bs[1] = (byte)(n >> 8);
        }

        internal static void UInt16_To_LE(ushort n, byte[] bs, int off)
        {
            bs[off] = (byte)(n);
            bs[off + 1] = (byte)(n >> 8);
        }

        internal static byte[] UInt16_To_LE(ushort n)
        {
            byte[] bs = new byte[2];
            UInt16_To_LE(n, bs, 0);
            return bs;
        }

        internal static ushort LE_To_UInt16(byte[] bs)
        {
            uint n = (uint)bs[0]
                | (uint)bs[1] << 8;
            return (ushort)n;
        }

        internal static ushort LE_To_UInt16(byte[] bs, int off)
        {
            uint n = (uint)bs[off]
                | (uint)bs[off + 1] << 8;
            return (ushort)n;
        }

        internal static byte[] UInt32_To_LE(uint n)
        {
            byte[] bs = new byte[4];
            UInt32_To_LE(n, bs, 0);
            return bs;
        }

        internal static void UInt32_To_LE(uint n, byte[] bs)
        {
            bs[0] = (byte)(n);
            bs[1] = (byte)(n >> 8);
            bs[2] = (byte)(n >> 16);
            bs[3] = (byte)(n >> 24);
        }

        internal static void UInt32_To_LE(uint n, byte[] bs, int off)
        {
            bs[off] = (byte)(n);
            bs[off + 1] = (byte)(n >> 8);
            bs[off + 2] = (byte)(n >> 16);
            bs[off + 3] = (byte)(n >> 24);
        }

        internal static byte[] UInt32_To_LE(uint[] ns)
        {
            byte[] bs = new byte[4 * ns.Length];
            UInt32_To_LE(ns, bs, 0);
            return bs;
        }

        internal static void UInt32_To_LE(uint[] ns, byte[] bs, int off)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt32_To_LE(ns[i], bs, off);
                off += 4;
            }
        }

        internal static void UInt32_To_LE(uint[] ns, int nsOff, int nsLen, byte[] bs, int bsOff)
        {
            for (int i = 0; i < nsLen; ++i)
            {
                UInt32_To_LE(ns[nsOff + i], bs, bsOff);
                bsOff += 4;
            }
        }

        internal static uint LE_To_UInt32(byte[] bs)
        {
            return (uint)bs[0]
                | (uint)bs[1] << 8
                | (uint)bs[2] << 16
                | (uint)bs[3] << 24;
        }

        internal static uint LE_To_UInt32(byte[] bs, int off)
        {
            return (uint)bs[off]
                | (uint)bs[off + 1] << 8
                | (uint)bs[off + 2] << 16
                | (uint)bs[off + 3] << 24;
        }

        internal static void LE_To_UInt32(byte[] bs, int off, uint[] ns)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = LE_To_UInt32(bs, off);
                off += 4;
            }
        }

        internal static void LE_To_UInt32(byte[] bs, int bOff, uint[] ns, int nOff, int count)
        {
            for (int i = 0; i < count; ++i)
            {
                ns[nOff + i] = LE_To_UInt32(bs, bOff);
                bOff += 4;
            }
        }

        internal static uint[] LE_To_UInt32(byte[] bs, int off, int count)
        {
            uint[] ns = new uint[count];
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = LE_To_UInt32(bs, off);
                off += 4;
            }
            return ns;
        }

        internal static byte[] UInt64_To_LE(ulong n)
        {
            byte[] bs = new byte[8];
            UInt64_To_LE(n, bs, 0);
            return bs;
        }

        internal static void UInt64_To_LE(ulong n, byte[] bs)
        {
            UInt32_To_LE((uint)(n), bs);
            UInt32_To_LE((uint)(n >> 32), bs, 4);
        }

        internal static void UInt64_To_LE(ulong n, byte[] bs, int off)
        {
            UInt32_To_LE((uint)(n), bs, off);
            UInt32_To_LE((uint)(n >> 32), bs, off + 4);
        }

        internal static byte[] UInt64_To_LE(ulong[] ns)
        {
            byte[] bs = new byte[8 * ns.Length];
            UInt64_To_LE(ns, bs, 0);
            return bs;
        }

        internal static void UInt64_To_LE(ulong[] ns, byte[] bs, int off)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt64_To_LE(ns[i], bs, off);
                off += 8;
            }
        }

        internal static void UInt64_To_LE(ulong[] ns, int nsOff, int nsLen, byte[] bs, int bsOff)
        {
            for (int i = 0; i < nsLen; ++i)
            {
                UInt64_To_LE(ns[nsOff + i], bs, bsOff);
                bsOff += 8;
            }
        }

        internal static ulong LE_To_UInt64(byte[] bs)
        {
            uint lo = LE_To_UInt32(bs);
            uint hi = LE_To_UInt32(bs, 4);
            return ((ulong)hi << 32) | (ulong)lo;
        }

        internal static ulong LE_To_UInt64(byte[] bs, int off)
        {
            uint lo = LE_To_UInt32(bs, off);
            uint hi = LE_To_UInt32(bs, off + 4);
            return ((ulong)hi << 32) | (ulong)lo;
        }

        internal static void LE_To_UInt64(byte[] bs, int off, ulong[] ns)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = LE_To_UInt64(bs, off);
                off += 8;
            }
        }

        internal static void LE_To_UInt64(byte[] bs, int bsOff, ulong[] ns, int nsOff, int nsLen)
        {
            for (int i = 0; i < nsLen; ++i)
            {
                ns[nsOff + i] = LE_To_UInt64(bs, bsOff);
                bsOff += 8;
            }
        }

#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
        internal static uint BE_To_UInt32(ReadOnlySpan<byte> bs)
        {
            return (uint)bs[0] << 24
                |  (uint)bs[1] << 16
                |  (uint)bs[2] <<  8
                |        bs[3];
        }

        internal static void BE_To_UInt32(ReadOnlySpan<byte> bs, Span<uint> ns)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = BE_To_UInt32(bs);
                bs = bs[4..];
            }
        }

        internal static ulong BE_To_UInt64(ReadOnlySpan<byte> bs)
        {
            uint hi = BE_To_UInt32(bs);
            uint lo = BE_To_UInt32(bs[4..]);
            return ((ulong)hi << 32) | lo;
        }

        internal static void BE_To_UInt64(ReadOnlySpan<byte> bs, Span<ulong> ns)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = BE_To_UInt64(bs);
                bs = bs[8..];
            }
        }

        internal static uint LE_To_UInt32(ReadOnlySpan<byte> bs)
        {
            return      bs[0]
                | (uint)bs[1] <<  8
                | (uint)bs[2] << 16
                | (uint)bs[3] << 24;
        }

        internal static void LE_To_UInt32(ReadOnlySpan<byte> bs, Span<uint> ns)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = LE_To_UInt32(bs);
                bs = bs[4..];
            }
        }

        internal static ulong LE_To_UInt64(ReadOnlySpan<byte> bs)
        {
            uint lo = LE_To_UInt32(bs);
            uint hi = LE_To_UInt32(bs[4..]);
            return (ulong)hi << 32 | lo;
        }

        internal static void LE_To_UInt64(ReadOnlySpan<byte> bs, Span<ulong> ns)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                ns[i] = LE_To_UInt64(bs);
                bs = bs[8..];
            }
        }

        internal static void UInt32_To_BE(uint n, Span<byte> bs)
        {
            bs[0] = (byte)(n >> 24);
            bs[1] = (byte)(n >> 16);
            bs[2] = (byte)(n >>  8);
            bs[3] = (byte) n;
        }

        internal static void UInt32_To_BE(ReadOnlySpan<uint> ns, Span<byte> bs)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt32_To_BE(ns[i], bs);
                bs = bs[4..];
            }
        }

        internal static void UInt32_To_LE(uint n, Span<byte> bs)
        {
            bs[0] = (byte) n;
            bs[1] = (byte)(n >>  8);
            bs[2] = (byte)(n >> 16);
            bs[3] = (byte)(n >> 24);
        }

        internal static void UInt32_To_LE(ReadOnlySpan<uint> ns, Span<byte> bs)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt32_To_LE(ns[i], bs);
                bs = bs[4..];
            }
        }

        internal static void UInt64_To_BE(ulong n, Span<byte> bs)
        {
            UInt32_To_BE((uint)(n >> 32), bs);
            UInt32_To_BE((uint)n, bs[4..]);
        }

        internal static void UInt64_To_BE(ReadOnlySpan<ulong> ns, Span<byte> bs)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt64_To_BE(ns[i], bs);
                bs = bs[8..];
            }
        }

        internal static void UInt64_To_LE(ulong n, Span<byte> bs)
        {
            UInt32_To_LE((uint)n, bs);
            UInt32_To_LE((uint)(n >> 32), bs[4..]);
        }

        internal static void UInt64_To_LE(ReadOnlySpan<ulong> ns, Span<byte> bs)
        {
            for (int i = 0; i < ns.Length; ++i)
            {
                UInt64_To_LE(ns[i], bs);
                bs = bs[8..];
            }
        }
#endif
    }
}
