recover.c

/*
Recovers lost jpegs from memory card
*/

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

typedef uint8_t  BYTE;

int main (int argc, char *argv[])
{
    //check for correct no. of CLA
    if (argc != 2)
    {
        fprintf(stderr, "correct usage: one CLA with name of file to recover\n");
        return 1;
    }

    //open file for reading
    FILE *infile = fopen(argv[1], "r");
    //check that file to recover is not null
    if (infile == NULL)
        {
        fprintf(stderr, "Could not open %s.\n", argv[1]);
        return 2;
        }

    //open array for storing title
     char *title = malloc(8 * sizeof(char));

    //open buffer
    BYTE buffer[512];
    int number = 0;

   do
    {
        //start of jpeg found
        if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff && (buffer[3] & 0xf0) == 0xe0)
        {
            //name new jpeg file
            sprintf(title, "%03i.jpg", number);
            //open outfile for writing
            FILE *outfile = fopen(title, "w");
            //check that outfile opens successfully
            if (outfile == NULL)
            {
                fprintf(stderr, "could not open %s.\n", title);
                return 3;
            }
            //write 512 bytes to outfile
           fwrite(&buffer, 1, 512, outfile);
            //increase number
            number++;
        }
        else //not start of jpeg
        {
            //if jpeg already found
        if (number > 0)
        {//not start of jpeg
        //append to already open jpg
        FILE *outfile = fopen(title, "a");
        fwrite(&buffer, 1, 512, outfile);
        }
        }
    }
    while (fread(&buffer, 1, 512, infile) == 512);
     // close infile
    fclose(infile);

    //free title
    free(title);

    // success
    return 0;
}