Converting C# code to VB.NET

Question

i tried converting this code from c#

a += (uint)(url[k + 0] + (url[k + 1] << 8) + (url[k + 2] << 16) + (url[k + 3] << 24));

to vb,net i get this

a += CUInt(url(k + 0) + (url(k + 1) << 8) + (url(k + 2) << 16) + (url(k + 3) << 24))

an i get this error

Operator '<<' is not defined for types 'Char' and 'Integer'.

Can anyone help me with a correction

EDIT

uint a, b;

a = b = 0x9E3779B9;

url = string

What type is the url array? Char? Also, what are you trying to achieve? — Msonic
– Msonic, Commented Feb 17, 2012 at 18:37
i got some info about the error that c# automatically truncates integer overflow, which vb.net does not. so it was suggested that i should turn off integer overflow check, but it still does not correct the error am getting — Oghenero E.
– Oghenero E., Commented Feb 17, 2012 at 19:09
@MyK What was that reason, again? You know the syntax for C# but not for VB.NET? I fail to see how that's a language inadequacy... — Cody Gray
– Cody Gray ♦, Commented Feb 17, 2012 at 23:40
Hello Smith. Were you able to successfully port this perfect hash function by Bob Jenkins to VB.Net? I am looking for this function in VB.Net. — Ali
– Ali, Commented Apr 20, 2012 at 6:18

Henk Holterman · Accepted Answer · 2012-02-17 18:47:55Z

3

Your main problem seems to be that C# will allow bit-shifting on a char whereas VB does not.

So you would need something like (untested)

 CUInt( ... + (CUint( url(k + 1) ) << 8) + ... )

But it does look like a rather weak HashCode.

answered Feb 17, 2012 at 18:47

Henk Holterman

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9 Comments

Oghenero E. Over a year ago

i did that, an i got

'Char' values cannot be converted to 'UInteger'. Use 'Microsoft.VisualBasic.AscW' to interpret a character as a Unicode value or 'Microsoft.VisualBasic.Val' to interpret it as a digit.

Henk Holterman Over a year ago

Like I said, I didn't try or test it. Looks like you need AscW() instead of my inner CUInt().

Oghenero E. Over a year ago

i did this (CUInt(AscW(url(k + 1))) << 8) and got this error Operator '+' is not defined for types 'Char' and 'UInteger'.

MarkJ Over a year ago

Change every url(...) into AscW(url(...))

MarkJ Over a year ago

@Smith No offence, but I would like to be absolutely sure you really have changed every one. Because this compiles for me a += CUInt(AscW(url(k + 0)) + (AscW(url(k + 1)) << 8) + (AscW(url(k + 2)) << 16) + (AscW(url(k + 3)) << 24)) but on the other hand this a += CUInt(url(k + 0) + (AscW(url(k + 1)) << 8) + (AscW(url(k + 2)) << 16) + (AscW(url(k + 3)) << 24)) , where I have not wrapped url(k+0) in AscW, gives compile error Operator '+' is not defined for types 'Char' and 'Integer'

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Tod · Accepted Answer · 2012-02-17 23:37:25Z

1

I don't know VB but I would suspect you can just cast each url(k+n) first i.e.

(CUint(url(k+2))<< 8)

I'm also assuming a CUint is 32 bits Assuming you are trying to create a 32 bit int out of 4 chars there is probably more checking you can do but at a minimum I would turn this into two methods ConvertCharArrayToUint() and another one that does each shift ShiftCharLeft(char, numBits) and hide all the casting ugliness in there. I'm surprised in C# you can shift a char like that.

EDIT: Try doing this on separate lines while you're figuring it out

int part_0 = Val(url(k));
int part_1 = Val(url(k+1));
int part_2 = Val(url(k+2));
...
int shifted_1 = part_1 << 8;
...
int result = part_0 + shifted_1...

They you can step through with the debugger, check types etc and get a full understanding of what is going on, then you can refactor for whatever readability you prefer.

edited Feb 17, 2012 at 23:37

answered Feb 17, 2012 at 18:54

Tod

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4 Comments

Oghenero E. Over a year ago

i tried it an got the same error

'Char' values cannot be converted to 'UInteger'. Use 'Microsoft.VisualBasic.AscW' to interpret a character as a Unicode value or 'Microsoft.VisualBasic.Val' to interpret it as a digit.

Tod Over a year ago

OK sounds like instead of using a CUInt cast you have to wrap it in a call to Val(url(k+2)) then shift the result.

Oghenero E. Over a year ago

thanks, how would i convert the first part url(k + 0), i did this url(k + 0) + Val(url(k)) + (Val(url(k + 2)) << 8), and i got another error Operator '+' is not defined for types 'Char' and 'Integer'. vb underlined this url(k + 0) + Val(url(k))

Tod Over a year ago

You have to wrap the first one also, see the first line of my example under EDIT int part_1 = Val(url(k));

Denis Besic · Accepted Answer · 2012-02-17 23:48:53Z

0

http://msdn.microsoft.com/en-us/library/7haw1dex%28v=vs.71%29.aspx be sure that you use supported types.

answered Feb 17, 2012 at 23:48

Denis Besic

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Oghenero E. Over a year ago

throw more light on your answer

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