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simple c program issue

mike33

Hope im in the correct room.

Hi All

Ive been wrecking my brain all day to try and check this array and where there exists only one char =>add second char 0 to it. whilst leaving the others alone.

char usable_MAC[19] = "FF:35:0:E1:80:FF";

Ive shown below my last attempt but no success.

result => i want to see is where there is "0" should now see "00" whilst leaving the rest along.

Note-> this single char could be anywhere in this array

BELOW IS WHAT I WANT as RESULT

char usable_MAC[19] = "FF:35:00:E1:80:FF";

int desiredSize = 17;

// Padding character

char paddingChar = '0';

// Create a new array with padding

char padded_MAC[desiredSize];

// Initialize the padded array with null characters

memset(padded_MAC, '\0', desiredSize);

// Copy characters from the original MAC address to the padded array

int i, j;

for (i = 0, j = 0; i < strlen(usable_MAC) && j < desiredSize - 1; ++i, ++j) {

padded_MAC[j] = usable_MAC[i];

// Check for a single character and pad with '0'

if (usable_MAC[i] == ':' && usable_MAC[i + 2] == ':' && usable_MAC[i + 1] != '0') {

padded_MAC[++j] = paddingChar;

}

// Null-terminate the padded array

padded_MAC[desiredSize - 1] = '\0';

// Display the padded MAC address

printf("Padded MAC: %s\n", padded_MAC);

Thanks in advance

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ThreeGreens

I'm struggling to understand exactly what you're trying to do.

But I suspect your problem is that putting a zero into the char array creates a null terminator.

So if your array is FF:35:00:E1:80:FF but the first "0" isn't the number 0 but rather the value 0, then your printf statement sees it as a null terminator and even though digits are in the subsequent locations, they aren't printed.

The way to check this would be to put a break point where your printf statement is and examine the contends of padded_mac one by one to see what it contains in the subsequent memory locations.

monkeybutter

you need to iterate J manually for a start if you find a :Char: situation

mike33

Hi guys thanks for getting back.

Bacically Im reciving  the following into my code =>FF:35:0:E1:80:FF

But if u look across the array one of the values is 0 but i needs it to be 00.

SO before i continue i need to format this arry from FF:35:0:E1:80:FF to FF:35:00:E1:80:FF
However this could happen anywhere in the array (Call it an error if u will)

So i need to be able to check this array each time and make sure it contains to digits in each loacation.
Where there may be one then I pad with "0".

Hope im making sense.

Donald Trump

strtok on the colon. Simples. Figure the rest out yourself. Either pointer arithmetic or scan from the string as hex and print back out at hex with a formatted print that will pad.

Or just work backwards through the string. Easy peasy

timmyntc

if (usable_MAC[i] == ':' && usable_MAC[i + 2] == ':' && usable_MAC[i + 1] != '0') {

Is bolded a typo in your post?

Donald Trump

I did up a solution for the craic. Less than 40 lines for complete program. Works on strings even when there are no numbers between the colons.

E.g

char usable_MAC[MACSTRSIZE] = "::1:23::";

Will print out

00:00:01:23:00:00

Only thing it's missing is that it doesn't check for more than 2 digits. That wasn't in the requirements though.

mike33

All sorry for delay in replying ... Got caught up in Xmass stuff.

Just to say, sorted the problem => went back to drawing board and started again.

As stated above focused on the colons and worked from there.

Thanks all for your time and ideas.