/**
 * recover.c
 *
 * Computer Science 50
 * Problem Set 4
 *
 * Recovers JPEGs from a forensic image.
 *
 * open memory card file
 * find beginning of jpg
 * open a new jpg
 * write 512 bytes until new jpg is found
 * detect end of file
 */
#include <stdio.h>
#include <stdint.h>

typedef uint8_t BYTE;

int main(void)
{
    // open card file
    FILE* inptr = fopen("card.raw", "r");

    // check if file can be opened, if not, show error message
    if (inptr == NULL)
    {
        printf("Could not open card.raw.\n");
        return 1;
    }

    // counter for number of jpg files recovered
    int counter = 0;

    // create a buffer of 512 bytes
    BYTE buffer[512];

    // declare jpg file name, 3 digit number, starting from 000
    char filename[8];

    // temporary file output
    FILE* outptr = NULL;

    // repeat until end of card
    while ((fread(buffer, 512, 1, inptr)) == 1)
    {
        // detect jpg file by checking first four bytes
        if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff && (buffer[3] >= 0xe0 && buffer[3] <= 0xef))
        {
            // if temp already exists, fclose temp (start of new jpg file and end of previous jpg file, hence close old file and open new file)
            if (outptr != NULL)
            {
                fclose(outptr);
            }
            // title of jpg files
            sprintf(filename, "%03d.jpg", counter);

            // open temp file
            outptr = fopen(filename, "w");

            counter++;

            // write data to temp file
            fwrite(buffer, 512, 1, outptr);
        }

        // else if buffer conditions above not met and counter > 0
        else if (counter > 0)
        {
            // continue to fwrite to temp file (start of jpg file already written, continue to write to file currently opened)
            fwrite(buffer, 512, 1, outptr);
        }

        // continue to fread (cos if buffer condition not met + counter = 0, means havent hit jpg file yet, so keep reading)
        else
            fread(buffer, 512, 1, inptr);
    }

    // close remaining files
    fclose(inptr);
    fclose(outptr);

    return 0;
}