Re: How to copy string with NULL - C / C++ / MFC Discussion Boards

Re: How to copy string with NULL

Cedric Moonen1-Jun-06 1:15

Cedric Moonen

1-Jun-06 1:15

strncpy will not work:

The strncpy function copies the initial count characters of strSource to strDest and returns strDest. If count is less than or equal to the length of strSource, a null character is not appended automatically to the copied string. If count is greater than the length of strSource, the destination string is padded with null characters up to length count.

Cédric Moonen
Software developer

Charting control

Re: How to copy string with NULL

Nibu babu thomas1-Jun-06 1:17

Nibu babu thomas

1-Jun-06 1:17

Cedric Moonen wrote:
strncpy will not work:

Yeah it won't. Was just a blind hit. Was not sure about it. Read the docs now. Sorry for that. Smile | :)

Nibu thomas
A Developer

Programming tips[^] My site[^]

Re: How to copy string with NULL

<color>Aljechin 1-Jun-06 1:43

<color>Aljechin

1-Jun-06 1:43

<br />
char szSource[23] = {"Before\0After"};<br />
char szDest[23];<br />
<br />
ptr = memcpy(szDest,szSource,22);<br />
printf("%s %d",szDest,strlen(szDest));<br />

Hi, may i please request you to just try this code and comment on why memcpy is failing? Is it the way it goes or am I wrong somewhere? Can you suggest some workaround? Thanks for your time.

Rose | [Rose]

Re: How to copy string with NULL

Nibu babu thomas1-Jun-06 1:52

Nibu babu thomas

1-Jun-06 1:52

Aljechin wrote:
Hi, may i please request you to just try this code and comment on why memcpy is failing? Is it the way it goes or am I wrong somewhere? Can you suggest some workaround? Thanks for your time.

Sure! Please look up memcpy in MSDN. There is a working demo there.

See you were saying that szSource contains NULL characters right? So strlen won't work because it will return when it finds the first null character. Same with printf and other functions. They all return when the first NULL character is found. So if your string is...

"Nibu\0is a\0\0\0good\0boy\0".

strlen will return 4. printf will print only Nibu

Nibu thomas
A Developer

Programming tips[^] My site[^]

Re: How to copy string with NULL

<color>Aljechin 1-Jun-06 1:59

<color>Aljechin

1-Jun-06 1:59

Thank you so much. I will surely check that example and get back to you with the problem status.

peace homie Rose | [Rose]

Re: How to copy string with NULL

David Crow1-Jun-06 3:30

David Crow

1-Jun-06 3:30

Aljechin wrote:
ptr = memcpy(szDest,szSource,22);

Use 12 instead.

Aljechin wrote:
printf("%s %d",szDest,strlen(szDest));

This is highly dependent on szDest being nul-terminated. Using memcpy() implies that you are not treating it as a nul-terminated string.

"The largest fire starts but with the smallest spark." - David Crow

Re: How to copy string with NULL

<color>Aljechin 1-Jun-06 20:38

<color>Aljechin

1-Jun-06 20:38

Thank you so much.

Rose | [Rose]

Re: How to copy string with NULL

Nemanja Trifunovic1-Jun-06 1:35

Nemanja Trifunovic

1-Jun-06 1:35

Aljechin wrote:
I need to copy a string which may contain NULL characters in between

How about std::copy[^]?

My programming blahblahblah blog. If you ever find anything useful here, please let me know to remove it.

Re: How to copy string with NULL

<color>Aljechin 1-Jun-06 1:47

<color>Aljechin

1-Jun-06 1:47

char szSource[23] = {"Before\0After"};<br />
char szDest[23];<br />
<br />
ptr = memcpy(szDest,szSource,22);<br />
printf("%s %d",szDest,strlen(szDest));

I went through that page, but not getting it. Can you show me a small code snippet of how do i copy that szSource into szDest? Sorry if a very elementary question.

Rose | [Rose]

Re: How to copy string with NULL

Cedric Moonen1-Jun-06 1:58

Cedric Moonen

1-Jun-06 1:58

What are you trying to do exactly ?
Is not because memcpy sucessfully copied the source into the destination that the '\0' character will be removed. It will still be present in the new string so as soon as you try to get its length or print the string, you will only have the begining of the string. This is totally logical.

Cédric Moonen
Software developer

Charting control

Re: How to copy string with NULL

<color>Aljechin 1-Jun-06 2:05

<color>Aljechin

1-Jun-06 2:05

What I am doing? PIP (Peripheral Interface Programming). I have generated a sequence of binary data which will be understood by a peripheral device. For example, we issue a print command from notepad. Its not the .txt file that is sent to the printer by the OS. But a series of printer-understood data is sent. My program generates such device-understandable data which could be just dumped into the port of the device and it will print some meaningful text or act accordingly. I have this binary (kinda junk) stored in unsigned char array. So, I am trying to figure out a way to do this. Smile | :)

Re: How to copy string with NULL

Cedric Moonen1-Jun-06 2:09

Cedric Moonen

1-Jun-06 2:09

So, what is the problem ? Your data is there but if you try to display it with a function that waits for a string, you won't be able to see past the zero char. Just send your buffer and it will work. You need to remember the size of your string of course because strlen won't work.

Cédric Moonen
Software developer

Charting control

Re: How to copy string with NULL

<color>Aljechin 1-Jun-06 20:47

<color>Aljechin

1-Jun-06 20:47

Thank you very much

Re: How to copy string with NULL

Nemanja Trifunovic1-Jun-06 2:26

Nemanja Trifunovic

1-Jun-06 2:26

Aljechin wrote:
char szSource[23] = {"Before\0After"};
char szDest[23];

ptr = memcpy(szDest,szSource,22);
printf("%s %d",szDest,strlen(szDest));

<br />
char szSource[23] = {"Before\0After"};<br />
char szDest[23];<br />
<br />
std::copy(szSource, szSource + 23, szDest);<br />

However, as Cedric already noted, don't expect that printf and strlen show the whole thing if you have embedded zeroes.

My programming blahblahblah blog. If you ever find anything useful here, please let me know to remove it.

Re: How to copy string with NULL

<color>Aljechin 1-Jun-06 20:41

<color>Aljechin

1-Jun-06 20:41

Thank you so much. I will try this.

Rose | [Rose]

Get file size in mega bytes

big_denny_2001-Jun-06 0:27

big_denny_200

1-Jun-06 0:27

Hi all

How can I get file size in mega bytes ?

Is there any good API, for this ?

I have a MFC prpject.

thank you.

Re: Get file size in mega bytes

ThatsAlok1-Jun-06 0:32

ThatsAlok

1-Jun-06 0:32

big_denny_200 wrote:
Hi all

How can I get file size in mega bytes ?

Is there any good API, for this ?

GetFileSizeEx() for reteriving size of File and convert that into MB by divinding it by 1024 *1024

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief and You

Re: Get file size in mega bytes

Hamid_RT1-Jun-06 1:15

Hamid_RT

1-Jun-06 1:15

Hi ThatsAlok,
How are you? Smile | :)

and StrFormatByteSizeA

whitesky

Re: Get file size in mega bytes

ThatsAlok1-Jun-06 1:54

ThatsAlok

1-Jun-06 1:54

WhiteSky wrote:
How are you?

Fine

WhiteSky wrote:
nd StrFormatByteSizeA

Will try!

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief and You

Re: Get file size in mega bytes

ThatsAlok1-Jun-06 1:55

ThatsAlok

1-Jun-06 1:55

WhiteSky wrote:
StrFormatByteSizeA

Thanks for Api!

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief and You

Re: Get file size in mega bytes

Hamid_RT1-Jun-06 2:12

Hamid_RT

1-Jun-06 2:12

yo're welcome Mr Alok Gupta Smile | :)

whitesky

Re: Get file size in mega bytes

ThatsAlok1-Jun-06 2:40

ThatsAlok

1-Jun-06 2:40

WhiteSky wrote:
welcome Mr Alok Gupta

Even Alok will do Smile | :)

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief and You

Re: Get file size in mega bytes

Sarath C1-Jun-06 1:02

Sarath C

1-Jun-06 1:02

open the file using CFile

then call "GetLength"

it will give u size in bytes divide it by (1024*1024) ( im not sure this calculation is correct) Smile | :)

Sa^Rath.

"Don't Do Different things... Do Things Differently..."

Re: Get file size in mega bytes

David Crow1-Jun-06 3:39

David Crow

1-Jun-06 3:39

SaRath C wrote:
open the file using CFile

Not a good idea as Open() is an expensive call, not to mention that it could easily fail if another process has the file open.

"The largest fire starts but with the smallest spark." - David Crow

Re: Get file size in mega bytes

Nibu babu thomas1-Jun-06 1:06

Nibu babu thomas

1-Jun-06 1:06

This[^] will help. Smile | :)

Nibu thomas
A Developer

Programming tips[^] My site[^]

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