fat16.h

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#pragma once
 
#include <stdint.h>
#include "fs/file.h"
#include "drivers/disk/disk.h"
#include "drivers/disk/disk_streamer.h"
 
#define DEBUG_FAT16 0
 
#define FAT16_SIGNATURE 0x29
#define FAT16_FAT_ENTRY_SIZE 0x02
#define FAT16_BAD_SECTOR 0xFF7
#define FAT16_UNUSED 0x00
 
typedef unsigned int FAT_ITEM_TYPE;
#define FAT_ITEM_TYPE_DIRECTORY 0
#define FAT_ITEM_TYPE_FILE      1
 
// FAT Directory Entry attributes bitmask
#define FAT_FILE_READONLY     0x01
#define FAT_FILE_HIDDEN       0x02
#define FAT_FILE_SYSTEM       0x04
#define FAT_FILE_VOLUME_LABEL 0x08
#define FAT_FILE_SUBDIRECTORY 0x10
#define FAT_FILE_ARCHVED      0x20
#define FAT_FILE_DEVICE       0x40
#define FAT_FILE_RESERVED     0x80
#define FAT_FILE_LONGNAME     (FAT_FILE_READONLY | FAT_FILE_HIDDEN | FAT_FILE_SYSTEM | FAT_FILE_VOLUME_LABEL) 
 
struct fat16_header_primary
{
    uint8_t jmp_short[3];
    uint8_t oem_identifier[8];
    uint16_t bytes_per_sector;
    uint8_t sectors_per_cluster;
    uint16_t reserved_sectors;
    uint8_t fat_copies;
    uint16_t root_dir_entries;
    uint16_t numeber_of_sectors;
    uint8_t media_type;
    uint16_t sectors_per_fat;
    uint16_t sectors_per_track;
    uint16_t number_of_heads;
    uint32_t hidden_sectors;
    uint32_t sectors_big;
} __attribute__((packed));
 
struct fat16_header_extended
{
    uint8_t drive_number;
    uint8_t win_nt_bit;
    uint8_t signature;
    uint32_t volume_id;
    uint8_t volume_id_string[11];
    uint8_t system_id_string[8];
} __attribute__((packed));
 
struct fat_header
{
    struct fat16_header_primary primary;
    union fat_header_extended
    {
        struct fat16_header_extended extended;
    } shared;
} __attribute__((packed));
 
struct fat_file
{
    uint8_t filename[8];
    uint8_t ext[3];
    uint8_t attribute;
    uint8_t reserved;
    uint8_t creation_time_tenths_of_a_sec;
    uint16_t creation_time;
    uint16_t creation_date;
    uint16_t last_access;
    uint16_t high_16bits_first_cluster;
    uint16_t last_mod_time;
    uint16_t last_mod_date;
    uint16_t low_16bits_first_cluster;
    uint32_t filesize;
} __attribute__((packed));
 
struct fat_directory
{
    struct fat_file* item;
    int total;
    int sector_pos;
    int ending_sector_pos;
};
 
struct fat_item
{
    union 
    {
        struct fat_file* file;
        struct fat_directory* directory;
    };
    
    FAT_ITEM_TYPE type;
};
 
struct fat_file_descriptor
{
    struct fat_item* file;
    uint32_t pos;
    int cached_cluster;       // Cached cluster number
    int cached_offset_bytes;  // Byte offset of cached cluster
};
 
struct fat_private
{
    struct fat_header header;
    struct fat_directory root_directory;
 
    //Used to stream data clusters
    struct disk_stream* cluster_read_stream;
    //Used to stream the file allocation table
    struct disk_stream* fat_read_stream;
 
    // Used to situations where we stream the directory
    struct disk_stream* directory_stream;
 
    struct disk* disk;
    uint32_t partition_offset;
};
 
struct filesystem* fat16_init_filesystem();
int fat16_resolve(struct disk* disk);
void* fat16_open(void* private_fs, struct path_part* path, FILE_MODE mode);
int fat16_read(void* private_fs, void* desc, uint32_t size, uint32_t nmemb, char* out);
int fat16_write(void* private_fs, void* desc, uint32_t size, uint32_t nmemb, char* in);
int fat16_seek(void* desc, uint32_t offset, FILE_SEEK_MODE seek_mode);
int fat16_stat(void* desc, struct file_stat* stat);
int fat16_close(void* desc);