C / C++ / MFC Discussion Boards

Michael Dunn23-Sep-04 11:42

23-Sep-04 11:42

Just FYI, if you're on an x86 machine, then the bytes are backwards.

You don't convert from hex to decimal, you just put the number in an int variable and use it. How you output the value (hex, octal, binary, etc.) isn't related to how the value is stored.

--Mike--
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Re: How about this?

Tom Wright23-Sep-04 11:50

Tom Wright

23-Sep-04 11:50

So...and correct me if i'm wrong.....if I move Somehex to an int...like:

int intVal = SomeHex;

then the value in intVal will be 10032? I've tried this but I get a compiler error saying "cannot convert from BYTE[4] to int". And if I type cast it as an int then I get 0x0012f408 as a value, which is not right.

So can you explain more please?

Tom Wright
tawright915@yahoo.com

Re: How about this?

BlackDice23-Sep-04 11:59

BlackDice

23-Sep-04 11:59

How about

int i1 = (int)SomeHex[0];<br />
int i2 = (int)SomeHex[1];<br />
int i3 = (int)SomeHex[2];<br />
int i4 = (int)SomeHex[3];

or maybe try this:

int* intVal = (int*)SomeHex;<br />
int intVal2 = *intVal;

Haven't tested either one, so BEWARE. But hopefully one of these will work or get you on the right path.

[insert witty comment here]

bdiamond Sleepy | :zzz:

Re: How about this?

Tom Wright23-Sep-04 12:04

Tom Wright

23-Sep-04 12:04

Nope.....just returning a hex value of 0x30270000, which is not right.
Thanks

Tom Wright
tawright915@yahoo.com

Re: How about this?

Michael Dunn23-Sep-04 12:03

Michael Dunn

23-Sep-04 12:03

To store the bytes into an int, I would do:

BYTE by[4] = { 0x30, 0x27, 0, 0 };
int n;
 
  n = *(int*) &by[0];

Keep in mind that the order of the bytes is CPU-specific. On x86 it's low->high as I showed above.

Tom Wright wrote:
And if I type cast it as an int then I get 0x0012f408 as a value, which is not right.

That's because a cast isn't a magical command that makes the compiler read your mind. Wink | ;)

You need to understand exactly what a cast does, and avoid just "throwing in casts" hoping to make it work. (This isn't a flame, it's a difficult subject, I know.)
Casting by to int returns the value of &by[0], which in your case was 0x0012f408

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Re: How about this?

Tom Wright23-Sep-04 12:24

Tom Wright

23-Sep-04 12:24

Michael Dunn wrote:
Keep in mind that the order of the bytes is CPU-specific. On x86 it's low->high as I showed above.

I see what you are saying. Here is the value that I see when I view it thru quick watch: 0x30270000 Which is reversed from what is in the array.

Okay so if I reverse this then I'll get the right Hex value in my int.

Questions:
1. The value I see in quick watch...is this the hex value or the int value?
2. If it's the hex value then I still need to convert this to a usable int. What I mean is that this BYTE array is part of a data stream from a socket.

<br />
	struct ParseData{<br />
		BYTE STAP[4]; <br />
		BYTE BlockLen[4];<br />
		BYTE HDRLen[2];<br />
		BYTE FunctionCode[2];<br />
		BYTE ValField[4];<br />
		BYTE DataLen[4];<br />
		BYTE MsgStatus[2];<br />
		BYTE Dest[2];<br />
	};<br />
	ParseData myStuff;<br />
	memcpy(&myStuff, dataBuffer, sizeof(myStuff));<br />
	char* DataPacket = new char[myStuff.DataLen];<br />

It tells me the length of another array in the stream which is a datapacket. So this BYTE array is the packet lenght. I've set up the data packet as a char* Datapacket; Can I initialize it like this:

char* DataPacket = new char[n]; ??? Confused | :confused:

and will this be the size of 10032 or 2730?

Really I'm trying to understand this and I really appreciate your help

Thanks

Tom Wright
tawright915@yahoo.com

Re: How about this?

Tom Wright23-Sep-04 12:32

Tom Wright

23-Sep-04 12:32

I got it..here is my code:

<br />
	BYTE NewDataLen[4];<br />
	NewDataLen[0] = myStuff.DataLen[3];<br />
	NewDataLen[1] = myStuff.DataLen[2];<br />
	NewDataLen[2] = myStuff.DataLen[1];<br />
	NewDataLen[3] = myStuff.DataLen[0];<br />
	<br />
	int nDataLength;<br />
	nDataLength = *(int*) &NewDataLen[0];<br />
	CString someString;<br />
	someString.Format("Here is the value: %d", nDataLength);<br />
	AfxMessageBox(someString);<br />

I'm sure there is an easier way to do the reverse but my model is "simplicity is best"...ah I'll tweak this as I go.

Now that I have my DataLen I can size my char array and put in my data..... Smile | :)

Thanks for the help again.

Tom Wright
tawright915@yahoo.com

Re: How about this?

Michael Dunn23-Sep-04 15:13

Michael Dunn

23-Sep-04 15:13

Glad you got it working. Smile | :)

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Re: How about this?

markkuk23-Sep-04 23:58

markkuk

23-Sep-04 23:58

You could (and should) just use the <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/winsock/ntohl_2.asp">ntohl()</a> function to fix the byte order of 32-bit ints received through sockets.

_CrtIsValidHeapPointer ASSERTS

BlackDice23-Sep-04 10:43

BlackDice

23-Sep-04 10:43

I posted a question earlier about SafeArrayAccessData(), but I've made a few changes to my code since then. Now when I don't delete the pointer that was allocated on the heap, I have memory leaks reported. When I try to delete the pointer to free the memory my program crashes in "dbgheap.c" in the _CrtIsValidHeapPointer() function. Does anyone know what might be going on and why I can't delete the pointer? It's not null, but stepping through the code, I see it gets changed after the calls to SafeArrayUnAccessData().

[insert witty comment here]

bdiamond Sleepy | :zzz:

Re: _CrtIsValidHeapPointer ASSERTS

Michael Dunn23-Sep-04 11:45

Michael Dunn

23-Sep-04 11:45

bdiamond wrote:
I see it gets changed after the calls to SafeArrayUnAccessData()

First off, you're getting an assert, not a crash. When the assert failed message comes up, click Retry or Break (depending on your version of VC) and look at the test that failed. Most likely, the CRT caught the fact that you have a bug - the memory was written to after it was freed.

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Re: _CrtIsValidHeapPointer ASSERTS

BlackDice23-Sep-04 11:51

BlackDice

23-Sep-04 11:51

I don't know if you looked at the earlier message I posted, but I set another pointer's address (pBytes) to that of the initial array (pBuf) and then I don't touch pBuf again (or pBytes, for that matter). All I do after that is read from the array to create the file. How could the memory be getting written to?

[insert witty comment here]

bdiamond Sleepy | :zzz:

TCHAR pointer character count

Gimpy198323-Sep-04 9:53

Gimpy1983

23-Sep-04 9:53

Hi!

I'm kinda new to C++ programming and I have difficulty understand and working with pointers. I have TCHAR *someVariable; and I wanna know how many characters are in the string pointed by the pointer "*someVariable".

I tried:

<br />
int len;<br />
len = wcslen(allTexPath);<br />

but I get the following error:
(173): error C2664: 'wcslen' : cannot convert parameter 1 from 'TCHAR *' to 'const wchar_t *'

Thanks for helping
Gimpy

----------------------
Be proud. Be yourself.

Re: TCHAR pointer character count

João Paulo Figueira23-Sep-04 10:05

João Paulo Figueira

23-Sep-04 10:05

Are you compiling for UNICODE or MCBS?

Regards,
João Paulo Figueira
Embedded MVP

Re: TCHAR pointer character count

Gimpy198323-Sep-04 10:09

Gimpy1983

23-Sep-04 10:09

For the moment not of them :P it's "Not Set" I can chose any of the two... which is the most appropriate choice? MBCS should be fine, I won't use any weird characters or oriental language.

Gimpy

----------------------
Be proud. Be yourself.

Re: TCHAR pointer character count

João Paulo Figueira23-Sep-04 11:06

João Paulo Figueira

23-Sep-04 11:06

Choose one of them and be careful with the string functions you choose. The safest way is to use the tchar.h macros that will correctly map to the appropriate functions. For instance, wcscpy is a UNICODE function that you cannot mix with TCHAR when MCBS is defined.

Regards,
João Paulo Figueira
Embedded MVP

Re: TCHAR pointer character count

Peter Weyzen23-Sep-04 11:32

Peter Weyzen

23-Sep-04 11:32

If you are going to use TCHAR, you have to use the _t version of functions.

try:
len = _tcslen(allTexPath);

TCHAR, _T, and _t -- are part of MS's UNICODE/MBCS neutral stuff. Makes code that can compile as MBCS or UNICODE -- as long as you do it right.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
<A HREF="http://www.santacruznetworks.com">Santa Cruz Networks</A>

Re: TCHAR pointer character count

Michael Dunn23-Sep-04 11:49

Michael Dunn

23-Sep-04 11:49

Take a look at my string articles, they describe the various encodings, how to use TCHAR, and the diff between strlen and wcslen.
part 1[^] | part 2[^]

--Mike--
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Source code formatter?

Ravi Bhavnani23-Sep-04 9:53

Ravi Bhavnani

23-Sep-04 9:53

Any recommendations for a (preferably free, preferably open-source) C/C++ source code formatter?

/ravi

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Re: Source code formatter?

markkuk23-Sep-04 10:27

markkuk

23-Sep-04 10:27

Artistic Style

Re: Source code formatter?

Ravi Bhavnani23-Sep-04 12:31

Ravi Bhavnani

23-Sep-04 12:31

Thanks! I've actually found a bunch of tools (including Artistic Style) on the web and was looking for thumbs up/down opinions. So I'm going to assume your's is a thumbs up. Smile | :)

/ravi

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Recommend a free unit testing framework

hyling23-Sep-04 9:44

hyling

23-Sep-04 9:44

Hi,

I found several unit testing tools for c++ here <http: www.opensourcetesting.org="" unit_c.php=""> but not sure which one is good. Is there one in particular you like?

Thanks
Hua-Ying

Re: Recommend a free unit testing framework

Ravi Bhavnani23-Sep-04 9:51

Ravi Bhavnani

23-Sep-04 9:51

We use CPP Unit[^] Cool | :cool:

/ravi

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Re: Recommend a free unit testing framework

Andrew Walker23-Sep-04 17:50

Andrew Walker

23-Sep-04 17:50

We use Boost.Test which has been terrific.

Open Source Testing is a good source for testing frameworks in most languages

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Re: Recommend a free unit testing framework

Moak24-Sep-04 1:25

Moak

24-Sep-04 1:25

Thanks, also useful for me

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