lsfs_16-bit/implementation/lsfs.c

#include "lsfs.h"
#include "../main.h"

struct lsfs_file {
    long file_id[2];
    long table_entry_pointer[2];
    Table_Entry_Kind entry_kind;
    char* filename;
    long owner_id;
    long size[2];
    long creation_date[2]; 
    long access_time[2];
    long modification_time[2];
    long number_sector;
    long table_entry_sector_index[2];
    long data_pointer[NUM_DATA_POINTERS * 2];
};

int lsfs_disk_read_data_from_file(file, buffer_size, data,  offset_to_next_entry) 
lsfs_file *file;
int buffer_size; 
char *data; 
long offset_to_next_entry;
{
    int integer_file_size = file->size;
    int integer_offset = offset_to_next_entry;
    int integer_datapointer = 0;
    int data_length = integer_file_size - integer_offset;
    int amount_read = 0;
    int amount_to_read = 0;
    int remaining_offset = offset_to_next_entry;
    /* printf("READ: buffer_size: %d\n", buffer_size); */
    /* printf("READ: Data length: %d\n", data_length); */
    /* printf("READ: Offset length: %d\n", offset_to_next_entry); */


    int data_pointer_index = 0; /*  start at first data pointer.  */
    
    if (data_length > buffer_size)
    {
        data_length = buffer_size;
    }

    while(data_length > 0) /*  We have more to write   */
    {
        /* printf("READ: Remaing Data length: %d\n", data_length); */
        if (remaining_offset == 0)
        {
            char *tmp_buffer = calloc(DEFAULT_DATA_POINTER_SIZE, SECTOR_SIZE);
            /* assert(tmp_buffer); */

            if (data_length < (DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE)) 
            {
                amount_to_read = data_length;
            }
            else 
            {
                amount_to_read = (DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE);
            }
            /* disk_service_read_data_from_disk(lsfs_sector_offset index, uint32_t number_sector, void* data_buffer) */
            integer_datapointer = file->data_pointer[data_pointer_index];
            if (integer_datapointer == 0) 
            {
                break;
            }
            disk_service_read_data_from_disk(file->data_pointer[data_pointer_index], DEFAULT_DATA_POINTER_SIZE, tmp_buffer);
            memcpy((data + amount_read), tmp_buffer, amount_to_read);
            data_length -= amount_to_read;
            amount_read += amount_to_read;
            data_pointer_index++;
            /* free(tmp_buffer); */
        }
        else if (remaining_offset < (DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE)) 
        {
            char *tmp_buffer = calloc(1, (DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE));
            /* assert(tmp_buffer); */

            if (data_length < ((DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE) - remaining_offset) ) 
            {
                amount_to_read = data_length;
            }
            else 
            {
                amount_to_read = ((DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE) - remaining_offset);
            }

            disk_service_read_data_from_disk(file->data_pointer[data_pointer_index], DEFAULT_DATA_POINTER_SIZE, tmp_buffer);

            memcpy(data, (tmp_buffer + remaining_offset), amount_to_read);
            data_length -= amount_to_read;
            amount_read += amount_to_read;
            remaining_offset -= amount_to_read;

            data_pointer_index++;
            /* free(tmp_buffer); */
        }
        else 
        {
            /*  We have to skip a whole data pointer:  */
            remaining_offset -= (DEFAULT_DATA_POINTER_SIZE * SECTOR_SIZE);
            data_pointer_index++;
        }

    }
    /*
    time_t current_time;
    time ( &current_time );
    file->access_time = current_time;
    */
    return amount_read;

}