recover

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

// generate new jpg files from recovered data
// accept exactly one command-line argument (img filename)
// if not one arg, print error message and return 1
// if cannot open file also return 1
// files should be named ###.jpg starting with 000.jpg
// use malloc and free
// jpg file header signature: Oxff Oxd8 Oxff Oxe{0-f}
// jpg file tail signature: Oxe{0-f}
// write 512 bytes until new jpeg is found (they are stored back to back)

typedef uint8_t BYTE;
int BLOCK_SIZE = 512;
int is_jpeg_header(BYTE block[])
{
    // jpg file header signature: Oxff Oxd8 Oxff Oxe{0-f}
    return (block[0] == 0xff && block[1] == 0xd8 && block[2] == 0xff && (block[3] & 0xf0) == 0xe0);
}

int main(int argc, char *argv[])
{
    if (argc != 2)
    {
        printf("Please provide one file name\n");
        return 1;
    }

    FILE *source_file = fopen(argv[1], "rb");

    if (source_file == NULL)
    {
        printf("Can't open the file\n");
        return 1;
    }

    FILE *output_file;

    // int *block = malloc(BLOCK_SIZE);
    BYTE block[BLOCK_SIZE];

    // read file
    // data: buffer
    // size: in bytes
    // number: of el to read
    // intptr: FILE * to read from
    // fread(data, size, number, inptr)
    int bytes_read = fread(block, sizeof(BYTE), BLOCK_SIZE, source_file);

    int counter = 0;
    int currently_writting = 0;
    char image_file_name[] = "000.jpg";

    while (bytes_read == BLOCK_SIZE)
    {
        if (is_jpeg_header(block))
        {
            if (currently_writting)
            {
                fclose(output_file);
            }

            // saving to a file
            // print a 3-digit integer
            // this would result in 002.jpg
            sprintf(image_file_name, "%03i.jpg", counter);

            counter++;
            output_file = fopen(image_file_name, "wb");
            currently_writting = 1;
        }

        if (currently_writting)
        {
            fwrite(block, sizeof(BYTE), BLOCK_SIZE, output_file);
        }
        bytes_read = fread(block, sizeof(BYTE), BLOCK_SIZE, source_file);
    }

    // close file
    fclose(source_file);

    if (currently_writting)
    {
        fclose(output_file);
    }

    // free(block);
    return 0;
}

// pracicing bitwise magic 🪄
// f7 1111 0111
// f0 1111 0000
//  & 1111 0000

// e7 1110 0111
// f0 1111 0000
//  & 1110 0000 ✅

// 57 0101 0111
// f0 1111 0000
//  & 0101 0000 🔴

// e0 1110 0000