reading a big bin-file(~2mb) in c - c

Question

I want to read a bin-file with a size under 2mb.
At the moment my code for reading the bin file looks like this:
edit:
#define MAX_BYTES_IN_FILE 500000 // ~ 2mb
#define ERROR_FILE 1
int get_byte_from_file(FILE *stream, unsigned char *dataarray) {
int counter = 0;
while ((dataarray[counter] = fgetc(stream)) != EOF) {
counter += 1;
}
return counter;
}
Main looks like this for the example use of the function.
int main(int argc, char **argv) {
FILE *datei;
unsigned int number_of_bytes;
unsigned char *dataarray;
dataarray = (unsigned char *)malloc(sizeof(unsigned char) * MAX_BYTES_IN_FILE);
datei = fopen(argv[1], "rb");
number_of_bytes = get_byte_from_file(datei, dataarray);
for (int i = 0; i < number_of_bytes; i++)
printf("%x ", dataarray[i]);
return 0;
}
Maybe I did a simple mistake but cant see it the error is still: Segmentation fault (core dumped)

Answer 1

This line is sufficient to crash your program:
while ((dataarray[counter] = fgetc(stream)) != EOF) {
Let's go through it step by step:
fgetc(stream) reads a byte and returns its value or EOF. Because a byte can have any possible value, fgetc() returns a larger int, which can hold an EOF value that is distinct from any byte value that might be found in the file.
You assign this int value to an unsigned char. An EOF value will be truncated to this datatype.
The value of the assignment is of type unsigned char, and the converted EOF value is not equal to EOF anymore. Thus, the comparison always fails, and your program keeps fetching data until the buffer overruns and nasty things begin to happen.
You need to store the result of fgetc() in an int variable until you've checked that it is indeed not the EOF value.

Answer 2

Maybe something like this.
void *readfile(FILE *fi, long *filesize)
{
void *buff;
fseek(fi, 0, SEEK_END);
*filesize = ftell(fi);
fseek(fi, 0, SEEK_SET);
buff = malloc(*filesize);
if(buff)
{
fread(buff, 1, *filesize, fi);
}
return buff;
}
You need to add error checks- I did not as it is only the idea.
And your usage:
int main(int argc, char **argv) {
FILE *datei;
long number_of_bytes;
unsigned char *dataarray;
datei=fopen(argv[1],"rb");
dataarray = readfile(datei, &number_of_bytes);
for (int i=0;dataarray && i<number_of_bytes;i++)
printf("%hhx ",dataarray[i]);
return 0;
}

Answer 3

The reason you get a segmentation fault is your allocation is incorrect: you allocate MAX_BYTES_IN_FILE bytes instead of unsigned int elements. As allocated, the array has only MAX_BYTES_IN_FILE / sizeof(unsigned int) elements, whereas the file is probably MAX_BYTES_IN_FILE * sizeof(unsigned int) bytes long.
You are reading bytes from the file (values between 0 and 255) but you use unsigned int elements. What is the logic? Does the file contain 32-bit values or individual bytes?
Once you can confirm that the file contents is exactly the same as the representation of the array in memory, you can use fread() to read the whole file in a single call.