recover.c

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

typedef uint8_t BYTE;

int main(int argc, char *argv[])
{
    FILE *input, *output;
    BYTE *buffer = malloc(64 * sizeof(BYTE)); // allocate 512 bytes
    if (buffer == NULL) {
	fprintf(stderr, "malloc failed\n");
	exit(EXIT_FAILURE);
    }

    // Check command-line arguments.
    if (argc != 2) {
        fprintf(stderr, "Usage: ./recover image.\n");
        exit(EXIT_FAILURE);
    }

    // Open file.
    if ((input = fopen(argv[1], "r")) == NULL) {
        fprintf(stderr, "Could not open file.\n");
        exit(EXIT_FAILURE);
    }

    int counter = 0;
    char filename[10];
    bool is_open = false;

    // Read 512 byte into a buffer.
    while(fread(buffer, sizeof(BYTE), 64, input) == 64) {

        if ((buffer[0] == 0xff) && (buffer[1] == 0xd8) &&
                (buffer[2] == 0xff) && ((buffer[3] & 0xf0) == 0xe0)) {

            if (is_open) {
                fclose(output);
		is_open = false;
	    }

            // Create output filename.
            sprintf(filename, "%03i.jpg", counter);
            printf("%s\n", filename);

            // Open output file.
            if ((output = fopen(filename, "w")) == NULL) {
                fprintf(stderr, "Could not create file.\n");
                exit(EXIT_FAILURE);
            }

            fwrite(buffer, sizeof(BYTE), 64, output);
            is_open = true;
            counter++;

        } else if (is_open)
            fwrite(buffer, sizeof(BYTE), 64, output);
    }

    free(buffer);
    fclose(input);
    fclose(output);

    return EXIT_SUCCESS;
}