Porting C/C++ to Delphi 6 -- FAQ -- JUN26/05

[vhelp]

Hello all

..This will be a dumping ground for porting C/C++ code snips to Delphi..

And is a work-in-progress
From this point onward, I will put ONLY those code snips that have
been resolved with working port examples.

I'm working on a project for someone, and it requires porting C# code to
Delphi 6 and I'm having trouble with a few syntax and other coding attributes.

I'm not very knowledgeable with C (or any variation) and some things
just don't make sense to me, hence my trouble porting to Delphi.
So, I thought I'd start a C# to Delphi topic, in hopes that I find
the answers here, where we all gather and share knowledge. Anyways.

So, here goes some first time C# code nips for you to help me in
understanding and porting.

It looks to me the C# code below is setup to take what's in A, (a TWO
DIMENTIOANL ARRAY of byte) (assuming "A[x,x] of bytes" but of UNKNOWN
size) to be further processed in this function.
It also seems to me, that after processed in this myFuncTION function,
that the return values will be a 2 dimentional array, but of Double. ie,
myFuncTION[x,x].
So, the size for myFuncTION could be, for instance, (1,1, 1,2, 1,3) or even
(1,1, 1,2) .. or whatever size. I don't know, because the code below
doesnt indicate. It's an undetermined size, legal in C# code. I think
that Delphi has this also, but the syntax eludes me, and this is a two
dimenational array. The twist to this, (to me) is that the return
value is going to B, but which seems to be a 2 dimentional array of
double. And to add more confusion, how is myFuncTION getting it's values
filled (or returned) w/ data, if its going to B (or, B[x,x],[x,x]) ??
However, B is of known size. Its a 2 dimention of 2 rows, 2 columns.

Given C#

 public double[,] myFuncTION (byte[,] A)
  {
    double TIONa, TIONb;
       int i,j;
    double[,] B = new double[2,2];
    .
    .
    return B;
  }

The closest I've come to matching the above function, is:

Type
 T_myfunction = array of array of byte;

Function myFuncTION(const a : T_myfunction): array of array of double;
var
  TIONa, TIONb: double;
          i, j: integer;

  // double[,] B = new double[2,2];
  B: array[1..2, 1..2] of Double;
begin
  for i := 1 to 2 do begin
    ...
    for j:= 1 to 2 do begin
      ...
    end;
  end;

  result := B;
end;

Then, here's another one that's confusing to me. My C++
bible say's that "*=" means Multiplication Assignment

Given C#

 B(i,j) *= (i * 0.1 * TIONa * TIONb * j)

..the equivalent in Delphi is definately unknown at this time:

  //

And then here's another bummer code snip:

Given C#

  B[s,t] = (INT) math.round((num1 / num2) - (BYTE) (n[s,t]));

And last..
But I think I figured this one out.. if someone can double-verify
for me

Given C#

 t >>= 1;

..I believe the equivalent in Delphi is:

  t := t shr 1;  // shif bit right

Thank you for any assistance,
-vhelp 3151

[mats.hogberg]

Then, here's another one that's confusing to me. My C++
bible say's that "*=" means Multiplication Assignment

Given C#

 B(i,j) *= (i * 0.1 * TIONa * TIONb * j)

That's a shorthand for

B(i,j)=B(i,j) * (i * 0.1 * TIONa * TIONb * j)

/Mats

[vhelp]

TGIF everyone

Thanks Mats.

That answer definately helps me out a lot

Now, if someone could answer some of the other ones above, that'll help
me out even more so.

Thanks again,
-vhelp 3152

[sanjayk]

Its been long long time since I left C programming. But t>>l is indeed equivalent to shifting bits to the right. Which is equivalent to the number being divided by 2 or multiple of 2 depending on the bits shifted. Similarly shifting to right is equivalent to multiplying the number.

[vhelp]

Yes.

 t := t shr 1;  // shif bit right

..is the equivalent to C++ 's

T >>= 1

Delphi/Pascal:
* shr = shift right bit
* shl = Shift left bit

I came to that knowledge, when I found it in my "Standard C++ Bible"
book, and guested at it

But, not everything is covered. For instance, like what Mat brought up
with the answer to my other C to Pascal code snip:

B(i,j) *= (i * 0.1 * TIONa * TIONb * j)

..is shorthand for

B(i,j) = B(i,j) * (i * 0.1 * TIONa * TIONb * j)

However, then I came across this, though similar to above, but notice
instead of the "*=", there is a "+=" (see the PLUS sign)

B(i,j) += (i * 0.1 * TIONa * TIONb * j)

..and my assumption is that it's a shorhand 'addition', like this:

B(i,j) = B(i,j) + (i * 0.1 * TIONa * TIONb * j)

I'm wondering if I'm correct ?? ??

Thanks.
-vhelp 3239

[vhelp]

And, here is yet another (on-going) question, if you or anyone else know
the answer to. Given the code snip below:

01: public double[,] calculateVALUES (byte[,] A)
02: {
03:   double[,] BValues = new double[8,8];
04:  
05:   for (r=0;  r<8;  r++)
06:     for (c=0;  c<8;  c++)
07:       BValues[r,c] += A[r,c] * math.pi
08: 
09:   return A
10: }

My understanding of the above code seems to belive that..

* LN 01 - the user is feeding in an array matrix of [8,8] values of Bytes.
* LN 03 - is assigning an variable [8,8] array values of Double to BValues.
* LN 05-07 is calculating the values to fill in to BValues[8,8] array.
* LN 05-07 is taking the VAR param from 'byte[,] A' and calculating those
values with the '* math.pi' C++ math function, and storing them in BValues[8,8].
* LN 09 - is returning the values calculated in BValues[8,8], into A[8,8].

And, here's what I think the Delphi/Pascal equivalent is:

01: Type
02:     byteARRAY = array[1..8, 1..8] of Byte;
03:   doubleARRAY = array[1..8, 1..8] of Double;
04: .
05: .
06: Function calculateVALUES(A: byteARRAY) : doubleARRAY;
07: var
08:       r,c: integer;
09:   BValues: doubleARRAY;
10: begin
11: 
12:   for r := 1 to 8 do
13:     for c := 1 to 8 do
14:       BValues[r,c] := BValues[r,c] + A[r,c] * math.pi
15: 
16:   result := BValues
17:
18: end;

I belive the above delphi/pascal code snip is the equivalent to the C++
( or C# ) code.

Can anyone validate the above to be correct, for me ??

Thanks.
-vhelp 3240

[sanjayk]

The assignment statement inside the for loop is wrong. It should be like

BValues[r,c] := BValues[r,c] + A[r,c] * math.pi

[mats.hogberg]

B(i,j) *= (i * 0.1 * TIONa * TIONb * j)

..and my assumption is that it's a shorhand 'addition', like this:

B(i,j) = B(i,j) + (i * 0.1 * TIONa * TIONb * j)

I'm wondering if I'm correct ?? ??

Correct!
/Mats

[vhelp]

@ sanjayk

Thanks. I can't believe I missed that.., pretty ironic though.

@ mats.

I cought an error in my code post above, and I fixed it (but you'r
quote, is showing the error) - fwiw

Thank you both for your help on everything so far.

-vhelp 3242

[mats.hogberg]

B(i,j) *= (i * 0.1 * TIONa * TIONb * j)

..and my assumption is that it's a shorhand 'addition', like this:

B(i,j) = B(i,j) + (i * 0.1 * TIONa * TIONb * j)

I'm wondering if I'm correct ?? ??

Correct!
/Mats

Um - sorry -Yes, it should be
B(i,j) = B(i,j) * (i * 0.1 * TIONa * TIONb * j)

Lesson learned:
Never debug read code when you don't have unlimited time to throw at it!

/Mats

[vhelp]

Hello again all

I have another porting job. Below is a code snip from a DCT example
written in C code, and is awaiting a port to Delphi. I'm working on
this now, but I thought I would post what I have. I think I have it,
but I need to finish to be sure. The secret (to this type of delphi
port) will be unleashed soon, I hope.

I will post on the main page ( pg. 1 ) should I have a working port.

const
N = 8;
struct zigzag {
int row;
int col;
} ZigZag[ N * N ] =
{
{0, 0},
{0, 1}, {1, 0},
{2, 0}, {1, 1}, {0, 2},
{0, 3}, {1, 2}, {2, 1}, {3, 0},
{4, 0}, {3, 1}, {2, 2}, {1, 3}, {0, 4},
{0, 5}, {1, 4}, {2, 3}, {3, 2}, {4, 1}, {5, 0},
{6, 0}, {5, 1}, {4, 2}, {3, 3}, {2, 4}, {1, 5}, {0, 6},
{0, 7}, {1, 6}, {2, 5}, {3, 4}, {4, 3}, {5, 2}, {6, 1}, {7, 0},
{7, 1}, {6, 2}, {5, 3}, {4, 4}, {3, 5}, {2, 6}, {1, 7},
{2, 7}, {3, 6}, {4, 5}, {5, 4}, {6, 3}, {7, 2},
{7, 3}, {6, 4}, {5, 5}, {4, 6}, {3, 7},
{4, 7}, {5, 6}, {6, 5}, {7, 4},
{7, 5}, {6, 6}, {5, 7},
{6, 7}, {7, 6},
{7, 7}
};

-vhelp 3409

[vhelp]

Ok. I finally got it.., after about 100 variations of trial 'n error scenarios,
I finally snagged it.

Yea.

For dificulty in char position and space reason, I am demo'ing an image
as a representation of my final port. If anyone has a better way of demo'ing
source code on this forum, please advise. Thanks.



-vhelp 3410