pset4 recover handles lack of forensic image

Question

Help to recover images on this program. Thank you.

/***************************************
 * recover.c
 * problem pset4
 * computer science 50
 * Reccvers JPEGs from a foreinsic image
 * **************************************/
 #include <stdio.h>
 #include <stdint.h>

 // unsigned integers type
 #define BLOCKSIZE  512
 typedef uint8_t BYTE;

 int main(int argc, char* argv[])
 {
     // open memory card
     FILE *file = fopen("card.raw", "r");
     if (file == NULL)
     {
         printf("Cannot open file\n");
         return 1;
     }

     // open output file
     FILE *outfile = NULL;
     // create new image file
     int jpgCount = 0;

     // forever loop that that will end when the file has been reached
     while(1)
     {
         // array of type BYTE
         BYTE image[BLOCKSIZE] = {};

         // iterate over byte in each block untill the end of file
         for(int i = 0; i < BLOCKSIZE; i++)
         {
             // close the file when the file is ended
             if(feof(file))
             {
                 fclose(file);
                 if(outfile != NULL)
                 {
                     fclose(outfile);
                 }
                 return 0;
             }

             // read one byte at a time
             fread(&image[i], sizeof(BYTE), 1, file);
         }

         // first four bytes match those of jpg
         if(image[0] == 0xff &&
            image[1] == 0xd8 &&
            image[2] == 0xff &&
            image[3] == 0xe0 &&
            image[3] == 0xe1)
         {
             // close outfile if it is exit
             fclose(outfile);
             // an array of filename
             char filename[4];
             // name file using ###.jpg format
             sprintf(filename, "%3d.jpg", jpgCount);
             jpgCount++;

             // open outfile
             outfile = fopen(filename, "w");
             if(outfile == NULL)
             {
                 printf("Could not write images\n");
                 return 1;
             }

             // photo written to the outfile
             fwrite(&image, sizeof(BYTE) * BLOCKSIZE, 1, outfile);
        }    
     }
     // close file
     fclose(file);
 }

Answer 1

The error message you describe is due to your code not testing argc. You are meant to complain if no file name is passed, and use argv[1] as the file name if it is provided. card.raw is just the sample card image, the actual file name might differ.

And look up how bitmasks work, they are great in testing whether a number's first hexadecimal digit is e.