recover.c

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

//taking in command line arguements
int main(int argc, char *argv[])
{
    if (argc != 2)
    {
        fprintf(stderr, "Usage : ./recover forensic file\n");
        return 1;
    }
    char *infile = argv[1];
    //opening the corrupted file
    FILE *corrupt = fopen(infile, "r");
    if (corrupt == NULL)
    {
        fprintf(stderr, "The file  cannot be opened\n");
        return 1;
    }
    //using unsigned char as it has a range of 0 to 255
    unsigned char *cont = malloc(512);
    //variables to control the naming of the recovered jpegs
    int i = 0;
    char name[8];
    if (cont == NULL)
    {
        fprintf(stderr, "The memory space cannot be allocated\n");
        return 2;
    }
    //reading until the end of file until a beginning of a jpg is encountered
    while (fread(cont, 1, 512, corrupt) == 512)
    {
        //test condition of jpg
        if (cont[0] == 0xff && cont[1] == 0xd8 && cont[2] == 0xff && (cont[3] & 0xf0) == 0xe0)
        {
            do
            {
                //opening of a new jpg
                if (cont[0] == 0xff && cont[1] == 0xd8 && cont[2] == 0xff && (cont[3] & 0xf0) == 0xe0)
                {
                    sprintf(name, "%.3d.jpg", i);
                    FILE *img = fopen(name, "w");
                    if (corrupt == NULL)
                    {
                        fprintf(stderr, "The jpg file cannot be created\n");
                        return 3;
                    }
                    fwrite(cont, 1, 512, img);
                    fclose(img);
                    i++;
                }
                //appending data blocks at the already opened jpg
                else
                {
                    FILE *img = fopen(name, "a");
                    fwrite(cont, 1, 512, img);
                    fclose(img);

                }
            }
            while (fread(cont, 1, 512, corrupt) == 512);
        }
    }
    free(cont);

}