Re: Getting a byte array from a generic class

The problem is not bandwidth, as I would not have to serialize a ton of obj=
ects, but the actual size. These objects are wrapped in SNMP packets and se=
nt down to field devices (dynamic message signs, speed detectors, traffic c=
ontrollers, etc.). A field device will expect an integer to arrive encoded =
in 4 bytes, not 8. Binary serialization doesn't work for the exact same rea=
son - the overhead bytes will be interpreted by something else and will con=
fuse the field device.

Thanks anyway for your suggestions.

Regards,
Eddie


-----Original Message-----
From: Discussion of advanced .NET topics. [mailto:[email protected]=
E.LSOFT.COM] On Behalf Of Steve Johnson
Sent: Tuesday, May 18, 2010 12:24 PM
To: [email protected]
Subject: Re: [ADVANCED-DOTNET] Getting a byte array from a generic class

Some other ideas, but they have issues:

1 - You could use binary serialization, but that would have a bunch of
overhead.

2 - Since you will only be supporting numeric primitives, you could do the
following, but it would be slow and require boxing.

public byte[] AsByteArray()
{
    double d =3D (double)Convert.ChangeType(_value, typeof(double));
    return BitConverter.GetBytes(d);
}

public void FromByteArray(byte[] bytes)
{
    double d =3D BitConverter.ToDouble(bytes, 0);
    _value =3D (T)Convert.ChangeType(d, typeof(T));
}

This would also require 8 bytes for any value, which would be bad if
bandwidth is an issue.

--
Steve Johnson


On Tue, May 18, 2010 at 10:54 AM, Eddie Lascu <[email protected]> wrote:

> Hi there,
>
> I need to pick your brains with regard to a more elegant solution to a
> problem I'm dealing with right now. I have a generic class that wraps any
> type of numeric values (short, int, decimal, double or float). Removing t=
he
> parts that are not interesting, this class is something like this:
>
>    public abstract class NumericNtcipObject<T> where T : struct,
> IComparable<T>
>    {
>        protected NumericNtcipObject(T value)
>        {
>            double val;
>            Debugging.Assert(typeof(T).IsValueType &&
> typeof(T).IsPrimitive);
>            Debugging.Assert(double.TryParse(value.ToString(), out val));
>
> Value =3D value;
>        }
>
>        public T Value
>        {
>            set
>            {
>                _value =3D value;
>            }
>        }
>
>        public byte[] ValueAsByteStream
>        {
>            get
>            {
>                  // Need help here
>            }
>        }
>
>        protected T _value;
>    }
>
> The class will be derived from and will only be instantiated with numeric
> values. I want to create a property that can give me a byte array contain=
ing
> all the bytes of the underlying value. If this would not be a generic cla=
ss,
> I could do:
>
> return BitConverter.GetBytes(Value);
>
> Unfortunately, BitConverter.GetBytes cannot resolve the type of Value so
> this solution goes out the window. I need the exact number of bytes, so
> casting to a type with a larger range is not good.
>
> I can do something like this:
>
>
>        public byte[] ValueAsByteStream
>        {
>            get
>            {
>                if(typeof(T) =3D=3D typeof(Int16))
>                {
>                    return BitConverter.GetBytes(Value.ToInt16(new
> NumberFormatInfo()));
>                }
>
>                if (typeof(T) =3D=3D typeof(Int32))
>                {
>                    return BitConverter.GetBytes(Value.ToInt32(new
> NumberFormatInfo()));
>                }
>
>                if (typeof(T) =3D=3D typeof(Int64))
>                {
>                    return BitConverter.GetBytes(Value.ToInt64(new
> NumberFormatInfo()));
>                }
>
>                if (typeof(T) =3D=3D typeof(UInt16))
>                {
>                    return BitConverter.GetBytes(Value.ToUInt16(new
> NumberFormatInfo()));
>                }
>
>                if (typeof(T) =3D=3D typeof(UInt32))
>                {
>                    return BitConverter.GetBytes(Value.ToUInt32(new
> NumberFormatInfo()));
>                }
>
>                if (typeof(T) =3D=3D typeof(UInt64))
>                {
>                    return BitConverter.GetBytes(Value.ToUInt64(new
> NumberFormatInfo()));
>                }
>                // rest of types here
>
>                return null;
>            }
>        }
>
> but this is not very nice.
>
> Can either of you smart guys give me a brilliant idea here?
>
> Thanks in advance,
> Eddie
>
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