Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array? - C# Discussion Boards

How do I store two int values into one DWORD, and then convert it to a 4 byte array?

8-Aug-11 2:48

DammyMulero wrote:
How do I write a C# code

By first learning the language of choice, C# in this case. Then you may begin by making notes on pieces of paper. But eventually you will need to enter the actual code in some sort of text editor (such as Notepad), perhaps even a full-blown and very complex application called an "Integrated Development Environment", but that may be beyond your abilities at this point.

stephen.darling7-Aug-11 11:04

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

7-Aug-11 11:04

Hi.

Please consider the following fixed values...

unsigned int value1 = 396;

unsigned int value2 = 398565;

1) The above values will change, but value1 will always be 3 digits, and value2 will always be 6 digits.

How do I....

A) Place both values into one DWORD?

b) Encode it as a 4 byte array.

So, as an example (not actual values)

396 + 398565 -> (DWORD) = 396398565 -> BYTE[] = {0x00, 0x00, 0x00, 0x00 } (whatever the hex would be)

And then, I would need to reverse it, although I think I have the code working to do that, but cant test it properly until I can get the above to work.

Thank you,
Steve

PIEBALDconsult7-Aug-11 13:44

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

7-Aug-11 13:44

I still don't see why you insist on the array of bytes.

Here's a rather simple way without unsafe code:

uint a = 396 ;
uint b = 398565 ;

uint c = ( a << 20 ) | ( b & 0x0FFFFFu ) ;

byte[] d = new byte [ sizeof(uint) ] ;

for ( int i = 0 ; i < d.Length ; i++ )
{
    d [ i ] = (byte ) ( ( c >> 8 * i ) & 0x0FF ) ;
}

uint e = 0 ;

for ( int i = 0 ; i < d.Length ; i++ )
{
    e |= (uint) ( d [ i ] << 8 * i ) ;
}

uint f = e >> 20 ;
uint g = e & 0x0FFFFFu ;

Luc Pattyn7-Aug-11 15:32

Luc Pattyn

7-Aug-11 15:32

FYI: I know you're not fond of converter classes, however

BitConverter.GetBytes()

and

BitConverter.ToUInt32()

are exactly what you want here.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

PIEBALDconsult7-Aug-11 18:02

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

7-Aug-11 18:02

Luc Pattyn wrote:
what you want

What I want?

Actually, I also looked at some code I wrote a while back that does that sort of thing, and I found that the existing tools didn't work properly with some types (e.g. enumerations, DateTime), so I wrote my own.

Here's a taste of that technique:

private static unsafe byte[]
ToByteArray
(
    object Value
,
    byte[] Buffer
)
{
    System.Runtime.InteropServices.GCHandle h =
        System.Runtime.InteropServices.GCHandle.Alloc
        ( Value , System.Runtime.InteropServices.GCHandleType.Pinned ) ;
    try
    {
        byte* b = (byte*) h.AddrOfPinnedObject().ToPointer() ;

        for ( int i = 0 ; i < Buffer.Length ; i++ )
        {
            Buffer [ i ] = b [ i ] ;
        }
    }
    finally
    {
        h.Free() ;
    }
    return ( Buffer ) ;
}

I may have to try this BitConverter, but I doubt I'll like it.

What I presented, though, is obviously very simple, about the minimum required for the stated task.

stephen.darling8-Aug-11 4:48

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

8-Aug-11 4:48

Hi Luc,

This time I was going to use BitCOnverter, but because the first problem was to get 2 int values into one uint, uint32 or whatever I would need, and then convert to a byte array.

Thank you,
Stephen

PIEBALDconsult8-Aug-11 16:37

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

8-Aug-11 16:37

Ah, I see that the BitConverter only works with a few, rarely used, datatypes (and not strings! WTF | :WTF:

) -- I want (not need) a more general solution.

stephen.darling8-Aug-11 5:08

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

8-Aug-11 5:08

Hi.

This does not seem to work.

It produces the following uint:

129098304

and I need 396398565

Thank you,
Stephen

PIEBALDconsult8-Aug-11 15:31

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

8-Aug-11 15:31

Why?

BobJanova7-Aug-11 23:12

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

7-Aug-11 23:12

BitConverter.GetBytes(a + 1000000*b)

stephen.darling8-Aug-11 4:45

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

8-Aug-11 4:45

Thank you,

Steve

stephen.darling8-Aug-11 5:28

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

8-Aug-11 5:28

Hi,

Sorry, this produces a different result than required.

uint val1 = 583;
uint val2 = 728439;

I should have 583728439, which sould be (in bytes) 0x22CAFD37.

Am I doing something wrong?

Thank you,
Stephen

BobJanova8-Aug-11 7:30

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

8-Aug-11 7:30

See below.

Matt Meyer8-Aug-11 6:55

Matt Meyer

8-Aug-11 6:55

You can combine them using division and modulo operations:

const uint shift = 1000000;
uint val1 = 539;
uint val2 = 666666;

// creat a combined value
uint combined = (val1 * shift) + val2;
// restore from the combined value
uint restore_val1 = combined / shift;
uint restore_val2 = combined % shift;

As for getting the byte array, you can use the BitConverter:

byte[] combined_bin = BitConverter.GetBytes(combined);

Re: How do I store two int values into one DWORD, and then convert it to a 4 byte array?

stephen.darling8-Aug-11 7:38

8-Aug-11 7:38

Thank you very much.

That works perfect.

Steve

Is this the same?

stephen.darling7-Aug-11 10:07

7-Aug-11 10:07

Hi.

The following function was taken from c++ code, and I have tried to adapt it for my c# code, however, I am not sure if it is doing the same thing?

The full c++ function is...

void ShowProdKey(unsigned char *ProdKey)
{
	unsigned int Val1, Val2;

	Val1 = *(unsigned int *)ProdKey;
	Val1 &= 0x7fffffff;
	Val1 >>= 1;

	Val2 = CheckDigit(Val1 % 1000000);
	Val1 /= 1000000;

	printf("Your product ID should be XXXXX-%.3u-%.7u-XXXXX.\n", Val1, Val2);
}

and my adapted function is the following (it works as in as far as it is producing a result which looks correct, but I am unsure if the changed part of the function is doing the same as in the above code)

void ShowProdKey(byte[] prodKey)
        {
            uint val1, val2;

            val1 = BitConverter.ToUInt32(prodKey, 0);

            val1 &= 0x7fffffff;
            val1 >>= 1;

            val2 = CheckDigit(val1 % 1000000);
            val1 /= 1000000;

            string output = ("");

            output = val1.ToString();
            output += val2.ToString();


            MessageBox.Show(output);

        }

So the part I changed was this in c++

Val1 = *(unsigned int *)ProdKey;

To this...

val1 = BitConverter.ToUInt32(prodKey, 0);

The output should be a double word formatted something like...

000 - 0000000

My version does produce a value like this, so I think it may be doing the same thing?

Also, how would I write code to reverse the function?
Or, in other words, the above function takes 4 bytes and produces a DWORD, which it formats into two unsigned ints...

How would I write a function that would take two unsigned ints, and produce a DWORD, and then encode that into 4 bytes, the reverse of the above function?

Thank you VERY much for your help...
Stephen

PIEBALDconsult7-Aug-11 10:20

7-Aug-11 10:20

stephen.darling wrote:
Val1 = *(unsigned int *)ProdKey;

Can probably be done with unsafe code.

stephen.darling wrote:
Val1 >>= 1;

Probably makes it non-reversible (except with a 50/50 probability of being correct).

stephen.darling wrote:
CheckDigit

What does that do?

What is it trying to do? It doesn't seem to use all the bits that are sent in.

stephen.darling7-Aug-11 10:33

7-Aug-11 10:33

Hi,

Well, using that function, if the 4 bytes are:

0x22CAFD37, the function should produce the following number:

583728439

Now, using the c++ version it works correct, but my c# version does not produce the correct value, it does produce a 9 digit number, but not that one.

However, if I try to use:

Val1 = *(unsigned int *)ProdKey;

in my c# version, it wont compile, so not sure if the code I changed is doing something else?

To answer what it is, let me explain...

My keygenerator generates the above 9 digit number, as a kind of product ID value, and encodes it into a 4 byte array to build part of a serial number..

When the serial number is entered into my application, the 4 bytes are decoded back into a dword, and the above function formats it into the 9 digits shown, and my app checks them,

It is working, and 9 digits are produced, but they are incorrect????

Also, how do I reverse the code to get two int values into one DWORD, and then encode it back into a 4 byte array?

Thank you,
Stephen

BobJanova7-Aug-11 23:10

7-Aug-11 23:10

The BitConverter code looks correct. (Just like a cast in C, though, it will give a different answer if the machine has the opposite endianness.) Your code is doing more than just that – what is CheckDigit doing?

stephen.darling8-Aug-11 4:44

8-Aug-11 4:44

Hi.

Thank you. So How do I check and/or fix the endian?

If it helps, the text I have says that it is stored in little endian byte order, and the following four bytes: 0x22CAFD37 should produce 583728439.

The checkdigit function then calculates and adds a checkdigit so that the above is then:

5837284392

here is the code for check digit...

XML

<pre>uint CheckDigit(uint val)
    {
        uint sum, copy;
        sum = 0;
        copy = val;
        while (copy !=0)
        {
            sum += copy % 10;
            copy /= 10;
        }
        return val * 10 + 7 - (sum % 7);
    }</pre>

thank you

BobJanova8-Aug-11 7:25

8-Aug-11 7:25

On my machine (Windows 32 bit) I'm getting the opposite order:

      $BitConverter:GetBytes(5)
(5 0 0 0)
      $BitConverter:GetBytes(583728439)
(55 253 202 34)
      {x: x:ToString "X2"}¨($BitConverter:GetBytes(583728439))
(37 FD CA 22)

This should be the same in C++, however.

(I can't so easily test the other way around, my toy language doesn't understand about bytes as a native type at the moment.)

stephen.darling8-Aug-11 7:40