Int to binary converstin issues

[qkslvrwolf]

I'm trying to convert an int into a binary string of a given length. here is my function...
// converts an integer to a binary. Destination string *must be empty*.
void int2binary(char binary [100], int convertee)
{
int foo;
char ret;
int i = 0;

printf("%i\n", convertee);
if (convertee != 0)
{
foo = convertee%2;
int2binary(binary, convertee/2);
ret = '0' + foo;
strcat(binary, &ret);
}
else if (convertee == 0)
{
while ((binary == '1') || (binary == '0'))
{
i++;
}
binary = '\0';
}
}
However, this returns, for say 127, a binary string that looks correct when printed (1111111), but when I run strlen on it later in order to turn it into 001111111, it says that it is taking up 14 characters. I understand that if a string is 7 characters, strlen returns 8, but nevertheless, I can't figure out why its returning 14..
thanks!

 

[Skatanic]

OK.. I had to do this as well, so I have code for it already.

void intToBits(int number, int numOfBits, char *binary) {
// numOfBits is how long you want the string to be
// ie intToBits(3, 8, binary) would make binary "00000011"

int test;

test = 1 << (numOfBits - 1);

for (int j=0; j < numOfBits; j++) {
if (number & testAgainst) {
binary[j] = '1';
} else {
binary[j] = '0';
}
number <<= 1;
}
}

 

[Skatanic]

Ooops.. Once again I forgot somehting. Make sure to malloc numOfBits worth of chars into binary before you think about accessing it...

-Skatanic

 

[qkslvrwolf]

Which is all well and good, but why isn't My code working? I mean, I do appreciate the code, but what I'd really like to know is what I'm missing from my code. Thanks alot!
sean

 

[qkslvrwolf]

I guess what I really want to know is, even if binary is changed so that the array is only of size 10, why does strlen still return 14 for the size of binary?

 

[Zyrenthian]

try memset(binary,0,100) on the binary string array before you do anything. If it is not null terminated, it could be your problem.

matt

 

[qkslvrwolf]

Thanks to everyone for suggested solutions...I sort of combined some of them/sort of just worked something out. Here is the code that works...//converts an integer to a binary. Destination string *must be empty*.
void int2binary(char *binary, int convertee, int count)
{
int foo;
char ret;
int i = 0;
char tempbinary[100];

//tempbinary = malloc(10);
printf(&quot;%i\n&quot;, convertee);
if (convertee != 0)
{

foo = convertee%2;
int2binary(binary, convertee/2, count+1);
ret = '0' + foo;
binary[count] = ret;
}
else if (convertee == 0)
{
binary[count] = '\0';
}
}

For whatever reason, using strcat to do it was putting in a
eextra 'bel' ascii character, which is apparently a non-printing character between each of the characters I was assigning. Either that, or the fact that I was passing in a char array instead of a char * was. Never did figure out which was the case. Anyway, thanks again!
sean

 

[abbeman]

I think I know what was the problem in the first program, you do this:
ret = '0' + foo;
strcat(binary, &ret);

note that in order to make this work you should have done:
ret = '0' + foo;
strncat(binary, &ret, 1);

Since strcat concatenates a string onto another string. You simply took a character ('0') and took it's adress...that means strcat will walk on after the ret-character in memory until it finds a 0-character.

 

[qkslvrwolf]

Thanks! HTats really pretty cool.

I&quot;m (obviously, I think) new to C and still working out the way it handles pointers, arrays, (and therefore strings).

Thanks again, I'll probably be able to use that later.

sean