FAT16 library written for an ATmega project with SD card
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#pragma once
/** Abstract block device interface */
typedef struct
// Sequential read
void (*load)(void* dest, const uint16_t len);
// Sequential write
void (*store)(const void* src, const uint16_t len);
// Sequential byte write
void (*write)(const uint8_t b);
// Sequential 2-byte write
void (*write16)(const uint16_t b);
// Sequential byte read
uint8_t (*read)(void);
// Sequential 2-byte read
uint16_t (*read16)(void);
// Absolute seek
void (*seek)(const uint32_t);
// Relative seek
void (*rseek)(const int16_t);
// -------------------------------
/** file types (values don't matter) */
typedef enum
FT_NONE = '-',
FT_LFN = '~',
FT_SELF = '.',
} FAT16_FT;
// File Attributes (bit flags)
#define FA_READONLY 0x01 // read only file
#define FA_HIDDEN 0x02 // hidden file
#define FA_SYSTEM 0x04 // system file
#define FA_LABEL 0x08 // volume label entry, found only in root directory.
#define FA_DIR 0x10 // subdirectory
#define FA_ARCHIVE 0x20 // archive flag
/** Boot Sector structure - INTERNAL! */
typedef struct __attribute__((packed))
// Fields loaded directly from disk:
// 13 bytes skipped
uint8_t sectors_per_cluster;
uint16_t reserved_sectors;
uint8_t num_fats;
uint16_t root_entries;
// 3 bytes skipped
uint16_t fat_size_sectors;
// 8 bytes skipped
uint32_t total_sectors; // if "short size sectors" is used, it's copied here too
// 7 bytes skipped
char volume_label[11]; // space padded, no terminator
// Added fields:
uint32_t bytes_per_cluster;
/** FAT filesystem handle - private fields! */
typedef struct __attribute__((packed))
// Backing block device
const BLOCKDEV* dev;
// Root directory sector start
uint32_t rd_addr;
// Start of first cluster (number "2")
uint32_t data_addr;
// Start of fat table
uint32_t fat_addr;
// Boot sector data struct
Fat16BootSector bs;
/** File handle struct */
typedef struct __attribute__((packed))
// Fields loaded directly from disk:
uint8_t name[11]; // Starting 0x05 converted to 0xE5, other "magic chars" left intact
uint8_t attribs; // composed of FA_* constants
// 14 bytes skipped
uint16_t clu_start;
uint32_t size;
// Added fields:
FAT16_FT type;
// --- Private fields ---
// Cursor
uint32_t cur_abs; // absolute position in device
uint32_t cur_rel; // relative position in file
uint16_t cur_clu; // cluster where the cursor is
uint16_t cur_ofs; // offset within the active cluster
// File position in the directory
uint16_t clu; // first cluster of directory
uint16_t num; // fiel entry number
// pointer to FAT
const FAT16* fat;
/** Initialize a filesystem */
void fat16_init(const BLOCKDEV* dev, FAT16* fat);
* Open the first file of the root directory.
* The file may be invalid (eg. a volume label, deleted etc),
* or blank (type FT_NONE) if the filesystem is empty.
* Either way, the prev and next functions will work as expected.
void fat16_root(const FAT16* fat, FAT16_FILE* file);
* Resolve the disk label.
char* fat16_disk_label(const FAT16* fat, char* label_out);
// ----------- FILE I/O -------------
* Move file cursor to a position relative to file start
* Returns false on I/O error (bad file, out of range...)
bool fat16_fseek(FAT16_FILE* file, uint32_t addr);
* Read bytes from file into memory
* Returns false on I/O error (bad file, out of range...)
bool fat16_fread(FAT16_FILE* file, void* target, uint32_t len);
* Write into file at a "seek" position.
* "seek" cursor must be within (0..filesize)
bool fat16_fwrite(FAT16_FILE* file, void* source, uint32_t len);
* Create a new file in given folder
* file ... open directory; new file is opened into this handle.
* name ... name of the new file, including extension
bool fat16_mkfile(FAT16_FILE* file, const char* name);
* Create a sub-directory of given name.
* Directory is allocated and populated with entries "." and ".."
bool fat16_mkdir(FAT16_FILE* file, const char* name);
* Write new file size (also to the disk).
* Allocates / frees needed clusters, does not erase them.
void fat16_resize(FAT16_FILE* file, uint32_t size);
/** Delete a file entry and free clusters. Does NOT descend into subdirectories. */
void fat16_delete(FAT16_FILE* file);
// --------- NAVIGATION ------------
/** Go to previous file in the directory (false = no prev file) */
bool fat16_prev(FAT16_FILE* file);
/** Go to next file in directory (false = no next file) */
bool fat16_next(FAT16_FILE* file);
* Open a subdirectory denoted by the file.
* Provided handle changes to first entry of the directory.
bool fat16_opendir(FAT16_FILE* file);
/** Rewind to first file in directory */
void fat16_first(FAT16_FILE* file);
* Find a file with given "display name" in this directory.
* If file is found, "dir" will contain it's handle.
* Either way, "dir" gets modified and you may need to rewind it afterwards.
bool fat16_find(FAT16_FILE* dir, const char* name);
// -------- FILE INSPECTION -----------
/** Check if file is a valid entry, or long-name/label/deleted */
bool fat16_is_file_valid(const FAT16_FILE* file);
* Resolve a file name, trim spaces and add null terminator.
* Returns the passed char*, or NULL on error.
char* fat16_dispname(const FAT16_FILE* file, char* disp_out);
* Convert filename to zero-padded fixed length one
* Returns the passed char*.
char* fat16_rawname(const char* disp_in, char* raw_out);