Microsoft.Scripting.Utils.MathUtils.Random C# (CSharp) Метод

        public static BigInt Random(this Random generator, BigInt limit) {
            ContractUtils.Requires(limit.Sign > 0, "limit");
            ContractUtils.RequiresNotNull(generator, "generator");

            BigInt res = BigInt.Zero;

            while (true) {
                // if we've run out of significant digits, we can return the total
                if (limit == BigInt.Zero) {
                    return res;
                }

                // if we're small enough to fit in an int, do so
                int iLimit;
                if (limit.AsInt32(out iLimit)) {
                    return res + generator.Next(iLimit);
                }

                // get the 3 or 4 uppermost bytes that fit into an int
                int hiData;
                byte[] data = limit.ToByteArray();
                int index = data.Length;
                while (data[--index] == 0) ;
                if (data[index] < 0x80) {
                    hiData = data[index] << 24;
                    data[index--] = (byte)0;
                } else {
                    hiData = 0;
                }
                hiData |= data[index] << 16;
                data[index--] = (byte)0;
                hiData |= data[index] << 8;
                data[index--] = (byte)0;
                hiData |= data[index];
                data[index--] = (byte)0;

                // get a uniform random number for the uppermost portion of the bigint
                byte[] randomData = new byte[index + 2];
                generator.NextBytes(randomData);
                randomData[index + 1] = (byte)0;
                res += new BigInt(randomData);
                res += (BigInt)generator.Next(hiData) << ((index + 1) * 8);

                // sum it with a uniform random number for the remainder of the bigint
                limit = new BigInt(data);
            }
        }