recover.c

/**
 * recover.c
 *
 * Computer Science 50
 * Problem Set 4
 *
 * Recovers JPEGs from a forensic image.
 */

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

typedef uint8_t BYTE;

int main(int argc, char* argv[])
{
    // open card.raw
    FILE* card = fopen("card.raw", "r");

    // check if card.raw was opened correctly
    if (card == NULL)
    {
        printf("Could not oped card.raw");
        return 1;
    }

    // declares img file
    FILE* img;

    // int to store number of recovered images
    unsigned int rec = 0;

    // string to hold the name of the jpeg
    char* title = malloc((7 * sizeof(char)) + 1);

    // space to store image pixels
    BYTE buffer[512];

    while (fread(buffer, sizeof(buffer), 1, card) == 1)
    {
        //goes back to where it was before fread call
        fseek(card, -512, SEEK_CUR);

        // reads sequence of bytes until it spots start of jpg
        fread(buffer, sizeof(BYTE), 512, card);

        // if start of jpg
        if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff && buffer[3] >= 0xe0 && buffer[3] <= 0xef)
        {
            // closes previous img file
            if (rec != 0)
            {
                fclose(img);
            }

            // creates filename
            sprintf(title, "%03d.jpg", rec);

            // creates new image
            img = fopen(title, "a");

            // outputs error if img could not be opened
            if (img == NULL)
            {
                printf("Could not create %s.", title);
                return 2;
            }

            // updates number of recevered files
            rec++;

            // writes sequence of bytes into img file
            fwrite(buffer, sizeof(BYTE), 512, img);
        }
        else
        {
            // if jpg already found but not at the start of it just write bytes into img
            if (rec != 0)
            {
                fwrite(buffer, sizeof(BYTE), 512, img);
            }
        }
    }

    // closes last img file
    fclose(img);

    // frees title string
    free(title);

    // closes card file
    fclose(card);

    // that's all folks
    return 0;
}