How to copy string with NULL

Nemanja Trifunovic

Aljechin wrote:

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

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color Aljechin

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

color Aljechin

char szSource[23] = {"Before\0After"}; char szDest[23]; ptr = memcpy(szDest,szSource,22); 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:

Nibu babu thomas

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[^]

Cedric Moonen

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
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color Aljechin

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

color Aljechin

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. :) :rose:

Cedric Moonen

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

Nemanja Trifunovic

Aljechin wrote:

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

char szSource[23] = {"Before\0After"}; char szDest[23]; std::copy(szSource, szSource + 23, szDest); However, as Cedric already noted, don't expect that printf and strlen show the whole thing if you have embedded zeroes.

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David Crow

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

color Aljechin

Thank you so much. :rose:

color Aljechin

Thank you so much. I will try this. :rose:

color Aljechin

Thank you very much