recover.c

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>


int main (int argc, char* argv[])
{
    //Check proper usage
    if (argc != 2)
    {
        fprintf(stderr, "Usage: ./recover infile\n");
        return 1;
    }

    // Remember infile name
   char *infile = argv[1];

   // create pointer in reading mode leading to infile
   FILE *inptf = fopen(infile, "r");

   //check if correct infile, not leading to NULL
    if (inptf == NULL)
    {
        fprintf(stderr, "Can't read infile\n");
        return 2;
    }
    // declare variables that will be used inside of loops
    int buffer[512];

    int x = 0;
    int jpgcnt = 0;
    char jpgname[7];
    FILE *img;
    // actual images recovering

    do
    {
         // read infile next 512 bytes to buffer
        fread(buffer, 512 * sizeof(int), 1, inptf);

        fseek(inptf, -512, SEEK_CUR);
        x = fread(buffer, 1, 512, inptf);

            if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff && (buffer[3] & 0xf0) == 0xe0)
            {

                //if first encountered photo on card
                if (jpgcnt == 0)
                {
                    //create new jpgfile name and open new file with this name
                    sprintf(jpgname, "%03i.jpg", jpgcnt);
                    img = fopen(jpgname, "w");
                    if (img == NULL)
                    {
                        return 3;
                    }
                    //write chunk of photo to new file
                    fwrite(buffer, 512, 1, img);
                    jpgcnt++;
                }
                // when there were photos encountered on card before
                if(jpgcnt > 0)
                {
                    //first close former image file, then create name for new one, open file with this name an write chunk of photo
                    fclose(img);
                    sprintf(jpgname, "%03i.jpg", jpgcnt);
                    img = fopen(jpgname, "w");
                    if (img == NULL)
                    {
                        return 3;
                    }
                    fwrite(buffer, 512, 1, img);
                    jpgcnt++;
                }
            }
            //if we dont encounter new photo, and have one img file already opened, write other chunks of photo into it
            else if (jpgcnt > 0)
            {
                fwrite(buffer, 512, 1, img);
            }
    }
            // check if this was last 'box' in file
while (x == 512);

// write last bytes to output file, then close output file
            fwrite(buffer, 512, 1, img);
            fclose(img);

// close infile at the and of the program
    fclose(inptf);
}