Read 2 Byte of a Pointer

[ghostcoder]

Hi everyone

I have an operation in my programm where i have to copy parts of a pointer pointing to an array of chars into another char at another pointers address.

Declaration:

struct EXIF
{

	char DateTimeOriginal[20];		
	char Year[4];
	char Month[2];
	char Day[2];
	char Hour[2];
	char Minute[2];
	char Second[2];
	...
};

The function:

for (int a = 0; a <= 3; a++)
{		
   pEXIF->Year[a] = pEXIF->DateTimeOriginal[a];

   ...
}

However this just copies the whole string into the other array but i just want the first 4 characters of pEXIF->DateTimeOriginal stored into pEXIF->Year.
I'm not that firm in pointer stuff so I hope one of you has a tip for me

greetings

ghost

[kmdv]

Hi everyone

for (int a = 0; a <= 3; a++)
{		
   pEXIF->Year[a] = pEXIF->DateTimeOriginal[a];

   ...
}

However this just copies the whole string into the other array but i just want the first 4 characters of pEXIF->DateTimeOriginal stored into pEXIF->Year.
I'm not that firm in pointer stuff so I hope one of you has a tip for me

Why does the topic says about 2? It indeed copies the first 4 characters, but you probably tried to display this year and it displayed something else. It did, because the Year has no null-terminating character, which ends the string.

struct EXIF {
...
char Year[5];
...
};


for (int i = 0; i < 4; ++i)
{		
   pEXIF->Year[i] = pEXIF->DateTimeOriginal[i];
}
pEXIF->Year[4] = '\0';

[tabstop]

If you want to copy just four characters, you need to do this:

for (int a = 0; a <= 3; a++)
{		
   pEXIF->Year[a] = pEXIF->DateTimeOriginal[a];
}

Yes, that's what you have. Yes, that's what it does. I don't know why you think the rest of it is in there, since Year only has room for four characters in it.

Now, you do appear to have made a deliberate design choice to make all your data non-printable. That is to say, there's no built-in function, such as >>, that will print any of your data fields. So you will have to write a custom print function (overloading >> isn't possible here) if you want to actually look at the data on the screen. (OR, you could reverse the original design decision, and make each of your char arrays one byte longer to handle the \0 character at the end which would turn your char arrays into C-style strings. OR, you could just use C++ strings.)

[ghostcoder]

Thank you all for your replies.
The NUL termination mehtod be expanding the arrays worked but for structural reasons I exchanged them by C-strings.

[iMalc]

Thank you all for your replies.
The NUL termination mehtod be expanding the arrays worked but for structural reasons I exchanged them by C-strings.

Err, those are C-strings. Perhaps you mean you decided to use C++ strings?