converting decimal to exponent and mantissa - c

Question

I am trying to convert a decimal number (329.39062) to binary (exponent, mentissa). I keep getting segmentation fault. on running the gdb test, It shows me feof. I have changed alot but it keeps showing me the segmentation fault at the same point. Where am i going wrong? Thank you for all the help.
#include <stdio.h>
#include <stdlib.h>
char* valueToConvert(int value);
int main(int argc, char *argv[])
{
FILE* input;
FILE* output;
input = fopen(argv[1],"r");
output = fopen(argv[2],"w");
float value;
unsigned char *charValue = (unsigned char *) &value;
int exponentValue;
long mantissaValue;
while(!feof(input))
{
fread(&charValue, sizeof(float),1, input);
exponentValue = ((charValue[0] & 0x7F) << 1)|((charValue[1] & 0x80) >> 7);
mantissaValue = ((charValue[1] & 0x7F) << 8)|((charValue[2] & 0xFF) <<8) | (charValue[3] & 0xFF);
fprintf(output,"%d %s %s\n",(charValue[0] & 0x80 >> 7),valueToConvert(exponentValue - 127),valueToConvert(mantissaValue));
}
}
char* valueToConvert(int value)
{
int counter = 0;
char* conversion = calloc(32,sizeof(int));
while(value>0)
{
if((value%2 == 1) && (value%2 != 0))
{
conversion[31 - counter++] = '1';
}
if((value%2 == 0) && (value%2 != 1))
{
conversion[31 - counter++] = '0';
}
value = value/2;
}
return conversion;
}

Answer 1

The problem is here:
fread(&charValue, sizeof(float),1, input);
That should be
fread(charValue, sizeof(float),1, input);
Because charValue is a pointer.
To address your problems with the output, you're filling the buffer backwards after initializing it completely with 0 via calloc, so fprintf is hitting 0 (a char used to signify the end of a string) and stopping "prematurely".
Here's a fast binary string function:
void fast_d2b(int x, char* c) {
int i;
for (i = 31; i >= 0; --i) {
*(c++) = '0' + ((x >> i) & 0x1);
}
}
It's based on the one shown here.
Only differences are that my variation doesn't write to the buffer backwards and it writes '0' and '1' instead of integral values 0 and 1.