Thread: Zero out two dimensional array

Hello,

I have an array

Code:

char host_fname[80][250];

whenever i write to it, it works fine.

the problem arises when i write to it again.

if a shorter string of characters is written than the last [to the same array element], the existing characters are displayed after the null terminator of the latest string written.

I know i can combat this by memset()ing the array to zero before writing to it again.

The problem is i do not know weather i should start from host_fname or host fname[80] and how long to set memory to zero (without, obviously affecting memory not allocated to this array) - given that i would like to reset the whole array.

thankyou for any advice regarding this matter, you help is much appreciated

Write in your shorter string of char's into the array, at the end of each string, be sure you have an end of string marker char: '\0'.

Then when you look at your array, like this:

array[0] //only the first dimension given

in a watch window, or when you print out the array, you'll see only the shorter string's char's.

I use this all the time, and have no problems with it. Never had to use memset for this.

I don't really get what you are doing. Give us a sort example

thing is, im reading UTF8 characters and i made sure i copied a Null character (0x00) into the last element of the array... i will recheck and see.

... Reading the Cprogramming lanuguage (kernighan and ritchie ) it states that if you setup a mutildimensional array it sets aside row times col of your datatypes... i just dont know if they are all consecutive memory cells or not...

I had a though, the fact that i make NSString pointers from UTF8 character pointer array, may be why i am experiencing the caching effect.

please shout me down if i am not allowed to post here because i have objective-c outputting my pure C function values

thankyou for you help

but are mulitdimensional arrays consecutive as well?

you were right about not having the problem with null terminated strings.

when i call the function recursively from obj-C the malfunction happens there.

simply calling a memset(host_fname[iteration],0,250) after converting the UTF string to an NSString* solves this bi-lingual problem

Sorry for posting off topic, and thanks for your time

ahh, thankyou,
so is this correct

Code:

int arr[2][2];

//would theoretically look like this in memory:

arr[0][0],arr[0][1]arr[0][2]arr[1][0]arr[1][1],arr[1][2],arr[2][0],arr[2][1],arr[2][2]

thanks clearing that up!

the memset after calling recursively adds extra problems however : (

I think the problem stems because I read character by character from another array.

here is the code behind the function

Code:

int q;
for(q=1; q<=248; ++q){

if(resp[q+9] == 0x00)
	break;
if(q == 248){
host_fname[y][q-1] = 0x00;
}
host_fname[y][q-1] = resp[q+9];
}

this does add a null character though (i think the utf converter function in objc reads past the null byte)

I have seen the null byte printed to the screen, in your more experienced eyes, is there a null byte printed (btw i am very sure there is a null byte from the array it takes the chars from)

tjanks for your help

lol sorry! running a memset(host_fname[y],0,250); before the for loop actually fixes this problem (im assuming it is becuase i am reading byte for byte?) or am i just bad at C