using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class Test
{
        class _BitConverter
        {
            private Byte[] tmpfor_1ByteToInt32 = new Byte[4];
            private Byte[] tmpfor_2ByteToInt32 = new Byte[4];
            private Byte[] tmpfor_3ByteToInt32 = new Byte[4];

            private static Int32 generalToInt32(Byte[] bytes, int bitsCount)
            {
                Int32 shiftCount = 32 - bitsCount;

                UInt32 ui = BitConverter.ToUInt32(bytes, 0);
                UInt32 ui2 = ui << shiftCount;
                Int32 i = (Int32)(ui2);
                Int32 i2 = i >> shiftCount;
                return i2;
            }

            public Int32 C1ByteToInt32(Byte[] bytes, int startIndex)
            {
                tmpfor_1ByteToInt32[0] = bytes[0 + startIndex];
                return generalToInt32(tmpfor_1ByteToInt32, 8);
            }

            public Int32 C2ByteToInt32(Byte[] bytes, int startIndex)
            {
                tmpfor_2ByteToInt32[0] = bytes[0 + startIndex];
                tmpfor_2ByteToInt32[1] = bytes[1 + startIndex];
                return generalToInt32(tmpfor_2ByteToInt32, 16);
            }

            public Int32 C3ByteToInt32(Byte[] bytes, int startIndex)
            {
                tmpfor_3ByteToInt32[0] = bytes[0 + startIndex];
                tmpfor_3ByteToInt32[1] = bytes[1 + startIndex];
                tmpfor_3ByteToInt32[2] = bytes[2 + startIndex];
                return generalToInt32(tmpfor_3ByteToInt32, 24);
            }
        }

        public static void Main(string[] args)
        {
            var converter = new _BitConverter();
            Console.WriteLine(converter.C1ByteToInt32(new byte[] { 0xCC, 0xCC, 0xFE, 0xFF, 0x80 }, 3));
            Console.WriteLine(converter.C2ByteToInt32(new byte[] { 0xCC, 0xCC, 0xFE, 0xFF, 0x80 }, 2));
            Console.WriteLine(converter.C3ByteToInt32(new byte[] { 0xCC, 0xCC, 0xFE, 0xFF, 0x80 }, 2));
        }
}