lsfs_fuse/lsfs_disk_controller.h

#ifndef LSFS_DISK_CONTROLLER_H
#define LSFS_DISK_CONTROLLER_H

#include <errno.h>
#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <time.h>
#include <unistd.h>

#include "lsfs_string.h"

typedef struct Directory_Table Directory_Table;
typedef struct struct_table_entry struct_table_entry;
typedef struct struct_partition_control partition_control;
typedef struct struct_partition_control partition_control;
typedef struct File_System_Control_Information FSCI;
typedef struct meta_information_format mif;
typedef struct tag_record tag_record;
typedef struct lsfs_file lsfs_file;
typedef enum Table_Entry_Kind Table_Entry_Kind;

typedef uint64_t lsfs_sector_offset;
typedef lsfs_sector_offset lsfs_file_id;

//typedef uint64_t sector_index;
static FILE* disk;
static partition_control p_control;
static time_t timestamp_loading;

int create_file_system(char* disk_name, char* hdd_or_partition, uint64_t filesystem_size_in_MB);
int lsfs_disk_create_entry(const char* path, Table_Entry_Kind entry_kind);
Directory_Table* lsfs_find_directory(const char* path, bool drop_filename);
int lsfs_disk_getattr(lsfs_file* find_file, const char *path);
int lsfs_disk_delete_file(lsfs_file *file);
int get_free_sectors_table();
int get_free_sectors(int num_sectors_needed, lsfs_sector_offset* output_array);
int lsfs_disk_read_data_from_file(lsfs_file* file, int buffer_size, void* buffer_for_data);
int lsfs_disk_write_data_to_file(lsfs_file* file, int data_length, char *data, size_t offset_to_next_entry);
int lsfs_disk_rename_file(const char* old_filename_, const char* new_filename);
int lsfs_disk_load_disk();
int write_data_to_disk(lsfs_sector_offset at_sector, uint32_t file_block_size, void* data_to_write);
int read_data_from_disk(lsfs_sector_offset index, uint32_t file_block_size, void* data_buffer);
int write_data_to_disk_off(lsfs_sector_offset index, uint32_t file_block_size, void* data_to_write, int offset);
int save_modified_file_information(lsfs_file* file);

#define SPACE_MBR_RECORD 2048 // Sectors
#define SPACE_VBR_RECORD 2048 // Sectors
#define SIZE_FSCI_RECORD    1 // Sectors
#define DEFAULT_ENTRY_SIZE  1 // Sectors
#define SECTOR_SIZE 512 // BYTES
#define NUMBER_OF_MBR_PARTITIONS 4
#define DEFAULT_FILE_SIZE 4 // This is in sectors
#define DEFAULT_DATA_POINTER_SIZE 4 // This is in sectors
#define DEFAULT_TABLE_SIZE 16 
#define NUM_DATA_POINTERS 27 

typedef enum Table_Entry_Kind
{
    // These are specific values since, is has to corrospond to the implementation in assembly
    ENTRY_EMPTY = 0,
    ENTRY_FILE = 1,
    ENTRY_DIRECTORY = 2,
} Table_Entry_Kind;

typedef struct Partition_Entry
{
    uint8_t  active_falg; // This has value 0x80 if it is a bootable partition / it is an active partition. 
    uint8_t  CHS_start_addr[3]; // [0] = H, [1] = S, [2] = C 
    uint8_t  partition_type; // This has a value such that one can idenfity which file system the partition is. 
    uint8_t  CHS_last_addr[3]; // [0] = H, [1] = S, [2] = C
    uint32_t LBA_abs_first_sector;
    uint32_t number_of_sectors;

} __attribute__((packed)) Partition_Entry;

typedef struct Master_Boot_record 
{
    uint8_t            code[446]; // The code for the bootloader 
    Partition_Entry    partitions[4];
    uint16_t           mbr_signature; // Signature
} __attribute__((packed)) Master_Boot_record;

typedef struct struct_table_entry 
{
    char            filename[256]; 
    lsfs_file_id    file_id;
    uint64_t        file_size;
    mif*            ext_file_data;
    uint32_t        file_block_size;    // This tells how many block there are allocated for the specific file. eg. we read this amount of bloks for the file.    
    uint8_t         entry_kind;
    uint8_t         extra_control_bits1;
    uint8_t         extra_control_bits2;
    uint8_t         extra_control_bits3;
    lsfs_sector_offset table_entry_sector_index;
    lsfs_sector_offset data_pointer[NUM_DATA_POINTERS]; // if it is a directory, the first pointer will be to the next table. 
} __attribute__((packed)) Table_Entry; 

typedef struct Directory_Table 
{
    struct_table_entry entries[DEFAULT_TABLE_SIZE];

} __attribute__((packed)) Directory_Table; 

typedef struct File_System_Control_Information 
{
    char                  filesystem_information[256];
    lsfs_sector_offset    master_table_index;
    lsfs_sector_offset    this_partition_offset_on_disk;
    lsfs_sector_offset    next_free_sector;
    uint64_t              next_uniqe_id; // both files and directories gets this. 
    lsfs_sector_offset    next_sector_reuse_pointer;
    lsfs_sector_offset    last_sector_index_on_partition;
    lsfs_sector_offset    maximum_sectors_on_disk;
    lsfs_sector_offset    sector_size_on_disk;
    uint64_t              not_used[24];

} __attribute__((packed)) FSCI;

typedef struct struct_partition_control
{
    FSCI                 fsci;
    Directory_Table      master_table;
} __attribute__((packed)) partition_control;



typedef struct meta_information_format {
    char             filename[246]; // remeber that the 246 bytes has to be a /0 terminator.. 
    uint32_t         owner_id;
    lsfs_file_id     tags[32];
    uint64_t         file_size;
    uint32_t         control_bits;
    /* not pressent - Permission key table 64 bytes sha-265 pr. key*/ 
    uint64_t         creation_date;
    uint64_t         last_modification_data;
    uint64_t         last_access_date;
    /*
     *  256 first pointers in direct mapping to data
     *  94 next pointers is a pointer 
     *  94 next pointers to pointers to data
     */
    lsfs_sector_offset   one_level_pointer_data[NUM_DATA_POINTERS];
    lsfs_sector_offset   two_level_pointer_data[94];
    lsfs_sector_offset   three_level_pointer_data[94]; 

} __attribute__((packed)) mif;


typedef struct tag_record {
    /* SIZE 16 bytes */
    lsfs_file_id    mif_record;
    struct {
        uint64_t is_filename : 1;    
    } control_bits;

} __attribute__((packed)) tag_record;

typedef struct lsfs_file {
    lsfs_file_id file_id;
    lsfs_sector_offset table_entry_pointer;
    Table_Entry_Kind entry_kind;
    char* filename;
    uint32_t owner_id;
    uint64_t size;
    uint64_t creation_date; 
    uint64_t access_time;
    uint64_t modification_time;
    uint32_t file_block_size;
    lsfs_sector_offset table_entry_sector_index;
    lsfs_sector_offset data_pointer[NUM_DATA_POINTERS];
} lsfs_file;


Directory_Table* lsfs_find_directory(const char *path, bool drop_filename) 
{

    Directory_Table *dir_table = calloc(1, sizeof(Directory_Table));
    read_data_from_disk(p_control.fsci.master_table_index, DEFAULT_TABLE_SIZE, dir_table);
    lsfs_string_array split_path = lsfs_string_split_c(path, '/', false);

    int number_of_traversal = split_path.length;

    if (drop_filename)
    {
        number_of_traversal -= 1;
    }

    // Start from the master table
    for (int i = 0; i < number_of_traversal; ++i)
    {
        for (int j = 0; j < DEFAULT_TABLE_SIZE; ++j)
        {
            if (strcmp(dir_table->entries[j].filename, split_path.strings[i].chars) == 0)
            {
                int index_sector = dir_table->entries[j].data_pointer[0];
                read_data_from_disk(index_sector, DEFAULT_TABLE_SIZE, dir_table);
                break;
            }
        }
    }
    return dir_table;
}

int lsfs_disk_getattr(lsfs_file* find_file, const char* path) {
    lsfs_string_array split_path = lsfs_string_split_c(path, '/', false);
    lsfs_string filename = split_path.strings[split_path.length-1]; 
    
    // Start from the master table
    Directory_Table *dir_table = lsfs_find_directory(path, true);

    for (int i = 0; i < DEFAULT_TABLE_SIZE; ++i)
    {
        if(strcmp( filename.chars, dir_table->entries[i].filename ) == 0) {
            find_file->file_id = dir_table->entries[i].file_id;
            find_file->entry_kind = dir_table->entries[i].entry_kind;
            find_file->table_entry_pointer = i;
            find_file->filename = dir_table->entries[i].filename;
            find_file->table_entry_sector_index = dir_table->entries[i].table_entry_sector_index;
            find_file->owner_id = getuid();
            find_file->size = dir_table->entries[i].file_size; // dir_table->entries[i].data_pointer[0]; //;
            find_file->creation_date = (uint64_t) timestamp_loading;
            find_file->access_time = (uint64_t) timestamp_loading;
            find_file->modification_time = (uint64_t) timestamp_loading;
            memcpy(find_file->data_pointer, dir_table->entries[i].data_pointer, NUM_DATA_POINTERS * 8);
            find_file->file_block_size = 1; // TODO: should be loaded from disk.
            return 1;
        }
    }
    return 0;
}



int lsfs_disk_read_data_from_file(lsfs_file *file, int buffer_size, void* buffer_for_data) {
    // TODO some offset, to tell where in the file we want to write

    int return_val = 0;

    for (int i = 0; i < NUM_DATA_POINTERS; ++i) {
        if(file->data_pointer[i] == 0) {
            break;
        }
        return_val += read_data_from_disk(file->data_pointer[i], file->file_block_size, buffer_for_data + (SECTOR_SIZE * i));
    }

    //time_t current_time;
    //time ( &current_time );

    //mif_record->last_access_date = (uint64_t) current_time;
    //write_data_to_disk(file_id, mif_record);
    //free(mif_record); 
    return return_val;
}

static inline time_t lsfs_disk_update_timestamps(lsfs_file *file) {
    return file->modification_time = file->access_time = time(NULL);
}

#define lsfs_num_sectors_for_size(x) (((x)+SECTOR_SIZE-1)&~(SECTOR_SIZE-1))

int lsfs_disk_write_data_to_file(lsfs_file *file, int data_length, char *data, size_t offset_to_next_entry) {
    int new_filesize = data_length + offset_to_next_entry;
    int amount_written = data_length;
    //printf("Data length: %d\n", data_length);
    //printf("Offset length: %d\n", offset_to_next_entry);


    int data_pointer_index = 0; // start at first data pointer. 
    while(data_length > 0) // We have more to write  
    {
        if (file->data_pointer[data_pointer_index] == 0) 
        {
            // we have to assign a free sector 
            get_free_sectors(1, (lsfs_sector_offset*) file->data_pointer[data_pointer_index]);
        }

        if (offset_to_next_entry == 0)
        {
            char *tmp_buffer = calloc(DEFAULT_DATA_POINTER_SIZE, SECTOR_SIZE);
            assert(tmp_buffer);

            memcpy(tmp_buffer, data, data_length);
            data_length -= (DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE);


            write_data_to_disk(file->data_pointer[data_pointer_index], DEFAULT_DATA_POINTER_SIZE, tmp_buffer);
            data_pointer_index++;
            free(tmp_buffer);
        }
        else if (offset_to_next_entry <= (DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE)) 
        {
            char *tmp_buffer = calloc(1, ((DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE) - offset_to_next_entry));
            assert(tmp_buffer);

            memcpy(tmp_buffer, data, data_length);
            data_length -= ((DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE) - offset_to_next_entry);


            write_data_to_disk_off(file->data_pointer[data_pointer_index], DEFAULT_DATA_POINTER_SIZE, tmp_buffer, offset_to_next_entry);
            data_pointer_index++;
            free(tmp_buffer);
        }
        else 
        {
            // We have to skip a whole data pointer: 
            offset_to_next_entry -= (DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE);
            data_pointer_index++;
        }

    }

    
    time_t current_time;
    time ( &current_time );
    //lsfs_disk_update_timestamps(&mif_record);
    file->size = new_filesize; // update file size

    file->access_time = current_time;
    file->modification_time = current_time;

    save_modified_file_information(file);
    //write_data_to_disk(file->file_id, 4, &p_control.master_table[file->file_id]);
    
    // Should return the total new file size
    return amount_written;
}

time_t lsfs_disk_truncate_file(lsfs_file *file, off_t offset) {
    //mif file_mif;
    //read_data_from_disk(file_id, &file_mif);
    
    time_t result = lsfs_disk_update_timestamps(file);
    file->size = (int) offset; // p_control.master_table.entries[i].data_pointer[0]; //;

    save_modified_file_information(file);
    //write_data_to_disk(file->file_id, 4, NULL);
    return result;
}

int lsfs_disk_rename_file(const char* old_filename, const char* new_filename) {

    lsfs_file *old_file = calloc(1, sizeof(lsfs_file));
    lsfs_file *new_file = calloc(1, sizeof(lsfs_file));

    lsfs_disk_getattr(old_file, old_filename);
    lsfs_disk_create_entry(new_filename, ENTRY_FILE);
    lsfs_disk_getattr(new_file, new_filename);

    new_file->file_id = old_file->file_id;
    new_file->size = old_file->size;
    // TODO(Jørn) The data pointer assignt to the new file should be released. 
    memcpy(new_file->data_pointer, old_file->data_pointer, NUM_DATA_POINTERS * 8);
    save_modified_file_information(new_file);
    lsfs_disk_delete_file(old_file);

    return 0;
}

int lsfs_disk_delete_file(lsfs_file *file) {
    Table_Entry *zero_buffer = calloc(1, (DEFAULT_ENTRY_SIZE * SECTOR_SIZE));
    //read_data_from_disk(file_id, 1, mif_record);
    write_data_to_disk(file->table_entry_sector_index, DEFAULT_ENTRY_SIZE, zero_buffer);
    
    free(zero_buffer); 
    return 1;
}

int get_free_sectors_table() {
    // We need DEFAULT_TABLE_SIZE sectors straight contigious for a table
    // Otherwise the file system cannot make a new table. 
    // We return the offset where the table is starting. 
    // If we cannot assing DEFAULT_TABLE_SIZE sectors, we report errror. 
    
    int return_index = p_control.fsci.next_free_sector;

    if ((p_control.fsci.next_free_sector + DEFAULT_TABLE_SIZE) > p_control.fsci.last_sector_index_on_partition)
    {
        // We don't have space, report error 
        return -EINVAL;
    }
    p_control.fsci.next_free_sector += DEFAULT_TABLE_SIZE; 

    fseek ( disk , ((p_control.fsci.this_partition_offset_on_disk) * SECTOR_SIZE), SEEK_SET );
    fwrite(&p_control.fsci, 1, SECTOR_SIZE, disk);
    printf("Table has got assigned Sector: %d\n", return_index);
    return return_index;
}

int get_free_sectors(int num_sectors_needed, lsfs_sector_offset* output_array) {

    if ((p_control.fsci.next_free_sector + num_sectors_needed) > p_control.fsci.last_sector_index_on_partition ) 
    {
        // We cannot assign what we want. 
        return -EINVAL;
    }
    for (int i = 0; i < num_sectors_needed; ++i)
    {
        output_array[i] = p_control.fsci.next_free_sector;
        p_control.fsci.next_free_sector += DEFAULT_FILE_SIZE;
    }

    fseek ( disk , (p_control.fsci.this_partition_offset_on_disk) * SECTOR_SIZE, SEEK_SET );
    fwrite(&p_control.fsci, 1, SECTOR_SIZE, disk);
    
    return 0;
}

int create_file_system(char* disk_name, char* hdd_or_partition, uint64_t filesystem_size_in_MB) {
    //char* sector_to_write;
    // make default File System Control information (FSCI)
    // first integer says how many pointers we got
    // to master tag tables 
    // Second and forward is the pointers to the master Tag Tables
    // we need the first number to allocate memory at one go. 
    FSCI *fsci = calloc(1, sizeof(FSCI));
    // Create disk on host system: 

    disk = fopen ( disk_name , "wb" );
    ftruncate(fileno(disk), (filesystem_size_in_MB * 2048 * 512));
    
    if (hdd_or_partition[0] == '1')
    {
        // This is the create hdd case
        // This means that we setup the partition table. 
        Master_Boot_record *mbr = calloc(1, sizeof(Master_Boot_record));
        mbr->partitions[0].partition_type = 0x18;        
        mbr->partitions[0].LBA_abs_first_sector = 2048;
        mbr->partitions[0].number_of_sectors = filesystem_size_in_MB * 2048; 
        mbr->mbr_signature = 0xaa55;
        write_data_to_disk(0, 1, mbr); // Write this to the first sector of the disk. 
    }


    if ((hdd_or_partition[0] == '1') || (hdd_or_partition[0] == '2'))
    {
        printf("HEY YUP\n");
        // This is just a single partition
        // And then the file system is the only thing in the system. 
        sprintf(fsci->filesystem_information, "LSFS v1.0.0-a1\n(LessSimpelFileSystem)(Generated by the disk_manager_utility.c)\nDeveloped to SingOS\nby Jorn Guldberg\n");
        
        if (hdd_or_partition[0] == '1')
        {
            fsci->this_partition_offset_on_disk = SPACE_MBR_RECORD + SPACE_VBR_RECORD;
        }
        else 
        {
            fsci->this_partition_offset_on_disk = SPACE_VBR_RECORD;
        }
        
        fsci->master_table_index = fsci->this_partition_offset_on_disk + SIZE_FSCI_RECORD;
        fsci->next_free_sector = fsci->master_table_index + DEFAULT_TABLE_SIZE; 
        fsci->next_uniqe_id = 1;
        fsci->next_sector_reuse_pointer = 0; 
        fsci->last_sector_index_on_partition = filesystem_size_in_MB * 2048; // Todo, this is the ssectors pr MB, this should not be hardcoded.
        fsci->maximum_sectors_on_disk = filesystem_size_in_MB * 2048; //TODO(Jørn) Not in use yet
        fsci->sector_size_on_disk = SECTOR_SIZE;
    }
    else 
    {
        // This is an error case, and we should not hit this case. 
        assert(NULL);
    }

    write_data_to_disk(fsci->this_partition_offset_on_disk, 1, fsci);

    return 0;
}

int lsfs_disk_install_bootloader(char *bootloader_name)
{
    FILE *bootloader = fopen ( bootloader_name , "r+b" );
    Master_Boot_record *bootloader_mbr = calloc(1, sizeof(Master_Boot_record));
    fseek(bootloader, 0 * SECTOR_SIZE, SEEK_SET);
    fread(bootloader_mbr, 1, SECTOR_SIZE, bootloader);

    Master_Boot_record *mbr = calloc(1, sizeof(Master_Boot_record));
    fseek( disk , 0 * SECTOR_SIZE, SEEK_SET );
    fread(mbr, 1, SECTOR_SIZE, disk);
    memcpy(mbr->code, bootloader_mbr->code, 446);        
    write_data_to_disk(0, 1, mbr); // Write this to the first sector of the disk. 
    return 0;
}


int lsfs_disk_load_disk() {
    // Find the partition talbe: 
    // This makes is BIOS dependent. 
    // UEFI is not supported. 
    time(&timestamp_loading);

    Master_Boot_record mbr;
    fseek( disk , 0 * SECTOR_SIZE, SEEK_SET );
    fread(&mbr, 1, sizeof(mbr), disk);
    if (mbr.mbr_signature != 0xaa55 )
    {
        // Means that it is a sigle partition we try to mount
        fseek(disk, (SPACE_VBR_RECORD * SECTOR_SIZE), SEEK_SET );
        fread(&p_control.fsci, 1, SECTOR_SIZE , disk);
        //printf("next free sector: %d\n", p_control.fsci.next_free_sector);
        //printf("next free ID: %d\n", p_control.fsci.next_uniqe_id);

        // next we find the Mater Table. 
        fseek (disk, (p_control.fsci.master_table_index * SECTOR_SIZE), SEEK_SET );
        fread(&p_control.master_table, 1, DEFAULT_TABLE_SIZE * SECTOR_SIZE , disk);
        return 1;
    }
    else 
    {
        for (int i = 0; i < NUMBER_OF_MBR_PARTITIONS; ++i)
        {
            // TODO (Jørn) We maybe wnat to optimize, such that we can detect if we have more than one partition opn the system. 
            if (mbr.partitions[i].partition_type == 0x18)
            {
                // First we find the File system control information. 
                fseek(disk , ((mbr.partitions[i].LBA_abs_first_sector + SPACE_VBR_RECORD) * SECTOR_SIZE), SEEK_SET );
                fread(&p_control.fsci, 1, SECTOR_SIZE , disk);

                // next we find the Mater Table. 
                fseek (disk, (p_control.fsci.master_table_index * SECTOR_SIZE), SEEK_SET );
                fread(&p_control.master_table, 1, DEFAULT_TABLE_SIZE * SECTOR_SIZE , disk);

                return 1;
            }
        }
    }
    return 0; 
}


int lsfs_disk_create_entry(const char* path, Table_Entry_Kind entry_kind) 
{

    // First check if file exist: 
    lsfs_file *file = calloc(1, sizeof(lsfs_file));
    if (lsfs_disk_getattr(file, path)) 
    {
        return -EINVAL;
    }
    free(file);

    // Start from the master table
    int free_index = -1; // -1 is no index found. 
    Directory_Table *dir_table = calloc(1, sizeof(Directory_Table));
    read_data_from_disk(p_control.fsci.master_table_index, DEFAULT_TABLE_SIZE, dir_table);
    lsfs_sector_offset table_disk_position = p_control.fsci.master_table_index;
    

    lsfs_string_array split_path = lsfs_string_split_c(path, '/', false);
    lsfs_string filename = split_path.strings[split_path.length-1];   

    //printf("spilt length: %d\n", split_path.length); 

    for (int i = 0; i < split_path.length -1; ++i)
    {
        for (int j = 0; j < DEFAULT_TABLE_SIZE; ++j)
        {
            if (strcmp(dir_table->entries[j].filename, split_path.strings[i].chars) == 0)
            {
                // We have found the next directory to traverse. 
                //printf("Get next dir at sector: ");
                table_disk_position = dir_table->entries[j].data_pointer[0];
                //printf("%d\n", table_disk_position);
                read_data_from_disk(table_disk_position, DEFAULT_TABLE_SIZE, dir_table);
                break;
            }
        }
    }


    for (int table_index = 0; table_index < DEFAULT_TABLE_SIZE; ++table_index)
    {
        // Find free index.
        if (dir_table->entries[table_index].entry_kind == ENTRY_EMPTY)
        {
            // Set the free index, continue to see if the filename exist. 
            // if not -1, we have found a better index. 
            if (free_index == -1) 
            {
                printf("Index found for file: %d\n", table_index);
                table_disk_position += table_index; // Abselout index in file system
                free_index = table_index;
            }
        }
    }

    if (free_index == -1)
    {
        // The table is full, and we cannot create an entry
        return -EINVAL;
    }

    // Find the entry for the file in the table structure: 
    dir_table->entries[free_index].file_id = p_control.fsci.next_uniqe_id;
    p_control.fsci.next_uniqe_id++; 

    sprintf(dir_table->entries[free_index].filename, "%s", filename.chars);  
    dir_table->entries[free_index].entry_kind = entry_kind;
    dir_table->entries[free_index].table_entry_sector_index = table_disk_position;
    if (entry_kind == ENTRY_DIRECTORY) 
    {
        dir_table->entries[free_index].data_pointer[0] = get_free_sectors_table();
        dir_table->entries[free_index].file_size = DEFAULT_TABLE_SIZE * SECTOR_SIZE;
    }
    else if (entry_kind == ENTRY_FILE)
    {
        // We assign one data pointer consiting of DEFAULT_FILE_SIZE sectors
        dir_table->entries[free_index].file_size = 0;
        get_free_sectors(1, dir_table->entries[free_index].data_pointer);
    }
    else
    {
        return -EINVAL;
    }

    /*
    find_file->creation_date = (uint64_t) current_time;
    find_file->access_time = (uint64_t) current_time;
    find_file->modification_time = (uint64_t) current_time;
    find_file->data = p_control.master_table.entries[i].data_pointer;
    find_file->owner_id = getuid();
    new_file_data.owner_id = getuid();
    time_t current_time;
    time ( &current_time );
    */
    //printf("File is written to sector: %d\n", table_disk_position);
    write_data_to_disk(table_disk_position, DEFAULT_ENTRY_SIZE, &dir_table->entries[free_index]);
    return 0;
}

int save_modified_file_information(lsfs_file* file) {
    // Write the file struct into the table_entry, such that we can save the data correct. 
    
    Table_Entry *entry = calloc(1, sizeof(Table_Entry));
    read_data_from_disk(file->table_entry_sector_index, DEFAULT_ENTRY_SIZE, entry);


    //entry.file_id = file->file_id;
    memcpy(entry->filename, file->filename, 256);
    entry->file_size = file->size; // p_control.master_table.entries[i].data_pointer[0]; //;
    memcpy(entry->data_pointer, file->data_pointer, NUM_DATA_POINTERS * 8);

    write_data_to_disk(file->table_entry_sector_index, DEFAULT_ENTRY_SIZE, entry);
    return 0;
}


int write_data_to_disk(lsfs_sector_offset index, uint32_t file_block_size, void* data_to_write) {
    fseek ( disk, (index * SECTOR_SIZE), SEEK_SET ); // SEEK_SET start offset at index 0 and move 1 * SECTOR_SIZE, and write here.
    int written = fwrite(data_to_write, 1, (file_block_size * SECTOR_SIZE), disk);
    return written;
}

int write_data_to_disk_off(lsfs_sector_offset index, uint32_t file_block_size, void* data_to_write, int offset) {
    fseek ( disk, ((index * SECTOR_SIZE) + offset), SEEK_SET ); // SEEK_SET start offset at index 0 and move 1 * SECTOR_SIZE, and write here.
    int written = fwrite(data_to_write, 1, ((file_block_size * SECTOR_SIZE) - offset), disk);
    return written;
}

int read_data_from_disk(lsfs_sector_offset index, uint32_t file_block_size, void* data_buffer) {
    fseek ( disk, (index * SECTOR_SIZE ), SEEK_SET ); // SEEK_SET start offset at index 0 and move 1 * SECTOR_SIZE, and write here.
    int read = fread(data_buffer, 1, (file_block_size * SECTOR_SIZE), disk);
    return read;
}

#endif