Re: Reverse Engineering Added Numbers - C# Discussion Boards

Re: Reverse Engineering Added Numbers

20-Dec-05 22:49

You can perform logical operators to the number you have. For example:

int Wav16bit = 10;
if ((Wav16bit & SF_FORMAT_WAV) != 0)
{
    // It's a WAV file
}
if ((Wav16bit & SF_FORMAT_PCM_16) != 0)
{
    // It's 16 bit
}

NOTE: There is only one ampersand.

What it does is look at the bits in the number and perform a logical and operation. So only where positions where the bits match will it be true

0001 & 0001 = 0001 // Both numbers match
0010 & 0001 = 0000 // Not matching bits
0100 & 0101 = 0100 // Only the second bit matches

There is another useful, similar, operator - the logical or operator and it is represented by a vertical bar | It says that if any bits are on on either side then that bit will be on in the result:

0001 | 0001 = 0001
0010 | 0001 = 0011
0100 | 0011 = 0111

Does this help?

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-- modified at 5:03 Wednesday 21st December, 2005

J4amieC20-Dec-05 22:59

J4amieC

20-Dec-05 22:59

In your last example you talked about | and used &

Re: Reverse Engineering Added Numbers

Colin Angus Mackay20-Dec-05 23:04

20-Dec-05 23:04

All fixed up now, thanks. Blush | :O

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"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius

Thanks

redfish3423-Dec-05 1:22

redfish34

23-Dec-05 1:22

I think i got it now. I did not put this in my post, but i learned there are "mask" constants used to filter out values.

SF_FORMAT_TYPEMASK = 0x0FFF0000,
SF_FORMAT_SUBMASK = 0x0000FFFF,

By &-ing these with the format number i can get the main format type (WAV, AIFF, AU, etc) or the format subtype (16-bit, 24-bit, etc). From my experimenting |-ing seems to do the opposite of &-ing. It is kind of like adding and subtracting. I am sure as i code more on a low level i will get a better understanding.

Struct of array

peppepinna20-Dec-05 22:32

20-Dec-05 22:32

I need this kind of classes:

struct_db mystruct = new struct_db();

public struct str1{
public string nome;
public string lunghezza;
public string tipo;
}

public class tab{
public string nometab;
public str1[] fields;
public string[] index;
public string[] procedure;
}

public class struct_db{
public int count;
public tab[] tabs;

public struct_db(){
tabs = new tab[100];
}
}

if set a value at struct_db.tabs[i].index i have an error because this array is not initialized... how i can initialize the class tab before using?

Thanx

Colin Angus Mackay20-Dec-05 22:41

20-Dec-05 22:41

peppepinna wrote:
tabs = new tab[100];

This just reseves the space for the array - but does not initialise it. You need to do something like this on each element:

tabs[i] = new tab();

Does this help?

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"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius

peppepinna20-Dec-05 22:56

20-Dec-05 22:56

Yes i have to initialize for each elements of tabs[i] the struct tab that is not initialised, ad if i give a value at the elements of tab i have an error because this value is a "null reference", with the struct_db = new ... i reserve space for struct db and reserve the space for tabs, but i cannot reserve the space for the elements of tabs. I have try to put "tabs[i] = new tab()" into initialization of struct_db but it doesen't work.

Thanx

peppepinna20-Dec-05 23:08

20-Dec-05 23:08

Many thanx you have give me an idea, i have solved my problem, i do a new tab() for each element into the struct_db(){...} and into my tab classes i initialize my arrays.

Many many thanx bye. Smile | :)

Colin Angus Mackay20-Dec-05 23:13

20-Dec-05 23:13

Excellent - glad you got it working.

My: Blog | Photos

"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius

Colin Angus Mackay20-Dec-05 23:12

20-Dec-05 23:12

Sorry, I missed what you were getting at.

tab.index = new string[length];
for(int i=0; i<length; i++)
{
    tab.index[i] = ""; // Or what ever string needs to be initialised
}

Your class does not have a constructor (so C# will create a default one for you) perhaps you should consider creating one in order to initialise the fields properly.

Also, you may want to consider making your fields private or protected and exposing them through properties. See this article[^] for some good reasons to use properties.

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"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius

-- modified at 5:12 Wednesday 21st December, 2005

peppepinna20-Dec-05 23:17