Attempt at cs50 recover solution

recover.c

#include <stdio.h>
#include <cs50.h>
#include <stdint.h>
#include <string.h>

int logerror(char *msg, int errNum)
{
    fprintf(stderr, "%s\n", msg);
    return errNum;
}


bool check_jpg(unsigned char block[512]);

int main(int argc, char *argv[])
{
    if (argc != 2)
    {
        return logerror("Usage: ./recover card.raw", 1);
    }

    // get the filename and open
    char *filename = argv[1];
    FILE *fileptr = fopen(filename, "r");
    if (fileptr == NULL)
    {
        return logerror("Usage: ./recover card.raw", 2);
    }

    // file counter needs to start at 0 (000) because it will be used to generate file name
    int fileCount = 0;

    bool end = feof(fileptr);
    bool already_found = false;
    FILE *outfile = NULL;

    // initialize a block of length 512 bytes.
    unsigned char block[512];
    // maximum it'll be 6 characters (1000.jpg)
    char outfilename[8];
    while (!end)
    {

        int bytes_read = fread(&block, 1, 512, fileptr);

        // if the header matches our jpeg header, then start parsing a jpeg

        bool byte3ok = (block[3] & 0xf0) == 0xe0;
        bool block0ok = block[0] == 0xff;
        bool block1ok = block[1] == 0xd8;
        bool block2ok = block[2] == 0xff;
        if (byte3ok && block0ok && block1ok && block2ok)
        {
            if (already_found)
            {
                // close previous file
                fclose(outfile);
                fileCount++;
            } else
            {
                already_found = true;
            }

            // new filename
            sprintf(outfilename, "%03d.jpg", fileCount);

            // new outfile
            outfile = fopen(outfilename, "w");

            fwrite(&block, 1, bytes_read, outfile);
        } else
        {
            if (already_found)
            {
                fwrite(&block, 1, bytes_read, outfile);
            }
        }
        end = feof(fileptr);

    }

    fclose(fileptr);
    return 0;
}