Data Structures | Defines | Functions

FAT file functions
[FAT support]

Functions for managing files. More...

Data Structures

struct  fat_dir_entry_struct
 Describes a directory entry. More...

Defines

#define FAT_ATTRIB_READONLY
 The file is read-only.
#define FAT_ATTRIB_HIDDEN
 The file is hidden.
#define FAT_ATTRIB_SYSTEM
 The file is a system file.
#define FAT_ATTRIB_VOLUME
 The file is empty and has the volume label as its name.
#define FAT_ATTRIB_DIR
 The file is a directory.
#define FAT_ATTRIB_ARCHIVE
 The file has to be archived.
#define FAT_SEEK_SET
 The given offset is relative to the beginning of the file.
#define FAT_SEEK_CUR
 The given offset is relative to the current read/write position.
#define FAT_SEEK_END
 The given offset is relative to the end of the file.

Functions

uint8_t fat_get_dir_entry_of_path (struct fat_fs_struct *fs, const char *path, struct fat_dir_entry_struct *dir_entry)
 Retrieves the directory entry of a path.
struct fat_file_struct * fat_open_file (struct fat_fs_struct *fs, const struct fat_dir_entry_struct *dir_entry)
 Opens a file on a FAT filesystem.
void fat_close_file (struct fat_file_struct *fd)
 Closes a file.
intptr_t fat_read_file (struct fat_file_struct *fd, uint8_t *buffer, uintptr_t buffer_len)
 Reads data from a file.
intptr_t fat_write_file (struct fat_file_struct *fd, const uint8_t *buffer, uintptr_t buffer_len)
 Writes data to a file.
uint8_t fat_seek_file (struct fat_file_struct *fd, int32_t *offset, uint8_t whence)
 Repositions the read/write file offset.
uint8_t fat_resize_file (struct fat_file_struct *fd, uint32_t size)
 Resizes a file to have a specific size.
uint8_t fat_create_file (struct fat_dir_struct *parent, const char *file, struct fat_dir_entry_struct *dir_entry)
 Creates a file.
uint8_t fat_delete_file (struct fat_fs_struct *fs, struct fat_dir_entry_struct *dir_entry)
 Deletes a file or directory.
uint8_t fat_move_file (struct fat_fs_struct *fs, struct fat_dir_entry_struct *dir_entry, struct fat_dir_struct *parent_new, const char *file_new)
 Moves or renames a file.
void fat_get_file_modification_date (const struct fat_dir_entry_struct *dir_entry, uint16_t *year, uint8_t *month, uint8_t *day)
 Returns the modification date of a file.
void fat_get_file_modification_time (const struct fat_dir_entry_struct *dir_entry, uint8_t *hour, uint8_t *min, uint8_t *sec)
 Returns the modification time of a file.
void fat_set_file_modification_date (struct fat_dir_entry_struct *dir_entry, uint16_t year, uint8_t month, uint8_t day)
 Sets the modification time of a date.
void fat_set_file_modification_time (struct fat_dir_entry_struct *dir_entry, uint8_t hour, uint8_t min, uint8_t sec)
 Sets the modification time of a file.

Detailed Description

Functions for managing files.


Define Documentation

#define FAT_ATTRIB_ARCHIVE

The file has to be archived.

#define FAT_ATTRIB_DIR

The file is a directory.

#define FAT_ATTRIB_HIDDEN

The file is hidden.

#define FAT_ATTRIB_READONLY

The file is read-only.

#define FAT_ATTRIB_SYSTEM

The file is a system file.

#define FAT_ATTRIB_VOLUME

The file is empty and has the volume label as its name.

#define FAT_SEEK_CUR

The given offset is relative to the current read/write position.

#define FAT_SEEK_END

The given offset is relative to the end of the file.

#define FAT_SEEK_SET

The given offset is relative to the beginning of the file.


Function Documentation

void fat_close_file ( struct fat_file_struct *  fd  ) 

Closes a file.

Parameters:
[in] fd The file handle of the file to close.
See also:
fat_open_file
uint8_t fat_create_file ( struct fat_dir_struct *  parent,
const char *  file,
struct fat_dir_entry_struct dir_entry 
)

Creates a file.

Creates a file and obtains the directory entry of the new file. If the file to create already exists, the directory entry of the existing file will be returned within the dir_entry parameter.

Note:
The file name is not checked for invalid characters.
The generation of the short 8.3 file name is quite simple. The first eight characters are used for the filename. The extension, if any, is made up of the first three characters following the last dot within the long filename. If the filename (without the extension) is longer than eight characters, the lower byte of the cluster number replaces the last two characters to avoid name clashes. In any other case, it is your responsibility to avoid name clashes.
Parameters:
[in] parent The handle of the directory in which to create the file.
[in] file The name of the file to create.
[out] dir_entry The directory entry to fill for the new (or existing) file.
Returns:
0 on failure, 1 on success, 2 if the file already existed.
See also:
fat_delete_file
uint8_t fat_delete_file ( struct fat_fs_struct *  fs,
struct fat_dir_entry_struct dir_entry 
)

Deletes a file or directory.

If a directory is deleted without first deleting its subdirectories and files, disk space occupied by these files will get wasted as there is no chance to release it and mark it as free.

Parameters:
[in] fs The filesystem on which to operate.
[in] dir_entry The directory entry of the file to delete.
Returns:
0 on failure, 1 on success.
See also:
fat_create_file
uint8_t fat_get_dir_entry_of_path ( struct fat_fs_struct *  fs,
const char *  path,
struct fat_dir_entry_struct dir_entry 
)

Retrieves the directory entry of a path.

The given path may both describe a file or a directory.

Parameters:
[in] fs The FAT filesystem on which to search.
[in] path The path of which to read the directory entry.
[out] dir_entry The directory entry to fill.
Returns:
0 on failure, 1 on success.
See also:
fat_read_dir
void fat_get_file_modification_date ( const struct fat_dir_entry_struct dir_entry,
uint16_t *  year,
uint8_t *  month,
uint8_t *  day 
)

Returns the modification date of a file.

Parameters:
[in] dir_entry The directory entry of which to return the modification date.
[out] year The year the file was last modified.
[out] month The month the file was last modified.
[out] day The day the file was last modified.
void fat_get_file_modification_time ( const struct fat_dir_entry_struct dir_entry,
uint8_t *  hour,
uint8_t *  min,
uint8_t *  sec 
)

Returns the modification time of a file.

Parameters:
[in] dir_entry The directory entry of which to return the modification time.
[out] hour The hour the file was last modified.
[out] min The min the file was last modified.
[out] sec The sec the file was last modified.
uint8_t fat_move_file ( struct fat_fs_struct *  fs,
struct fat_dir_entry_struct dir_entry,
struct fat_dir_struct *  parent_new,
const char *  file_new 
)

Moves or renames a file.

Changes a file's name, optionally moving it into another directory as well. Before calling this function, the target file name must not exist. Moving a file to a different filesystem (i.e. parent_new doesn't lie on fs) is not supported.

After successfully renaming (and moving) the file, the given directory entry is updated such that it points to the file's new location.

Note:
The notes which apply to fat_create_file() also apply to this function.
Parameters:
[in] fs The filesystem on which to operate.
[in,out] dir_entry The directory entry of the file to move.
[in] parent_new The handle of the new parent directory of the file.
[in] file_new The file's new name.
Returns:
0 on failure, 1 on success.
See also:
fat_create_file, fat_delete_file, fat_move_dir
struct fat_file_struct* fat_open_file ( struct fat_fs_struct *  fs,
const struct fat_dir_entry_struct dir_entry 
) [read]

Opens a file on a FAT filesystem.

Parameters:
[in] fs The filesystem on which the file to open lies.
[in] dir_entry The directory entry of the file to open.
Returns:
The file handle, or 0 on failure.
See also:
fat_close_file
intptr_t fat_read_file ( struct fat_file_struct *  fd,
uint8_t *  buffer,
uintptr_t  buffer_len 
)

Reads data from a file.

The data requested is read from the current file location.

Parameters:
[in] fd The file handle of the file from which to read.
[out] buffer The buffer into which to write.
[in] buffer_len The amount of data to read.
Returns:
The number of bytes read, 0 on end of file, or -1 on failure.
See also:
fat_write_file
uint8_t fat_resize_file ( struct fat_file_struct *  fd,
uint32_t  size 
)

Resizes a file to have a specific size.

Enlarges or shrinks the file pointed to by the file descriptor to have exactly the specified size.

If the file is truncated, all bytes having an equal or larger offset than the given size are lost. If the file is expanded, the additional bytes are allocated.

Note:
Please be aware that this function just allocates or deallocates disk space, it does not explicitely clear it. To avoid data leakage, this must be done manually.
Parameters:
[in] fd The file decriptor of the file which to resize.
[in] size The new size of the file.
Returns:
0 on failure, 1 on success.
uint8_t fat_seek_file ( struct fat_file_struct *  fd,
int32_t *  offset,
uint8_t  whence 
)

Repositions the read/write file offset.

Changes the file offset where the next call to fat_read_file() or fat_write_file() starts reading/writing.

If the new offset is beyond the end of the file, fat_resize_file() is implicitly called, i.e. the file is expanded.

The new offset can be given in different ways determined by the whence parameter:

  • FAT_SEEK_SET: *offset is relative to the beginning of the file.
  • FAT_SEEK_CUR: *offset is relative to the current file position.
  • FAT_SEEK_END: *offset is relative to the end of the file.

The resulting absolute offset is written to the location the offset parameter points to.

Calling this function can also be used to retrieve the current file position:

   int32_t file_pos = 0;
   if(!fat_seek_file(fd, &file_pos, FAT_SEEK_CUR))
   {
       // error
   }
   // file_pos now contains the absolute file position
Parameters:
[in] fd The file decriptor of the file on which to seek.
[in,out] offset A pointer to the new offset, as affected by the whence parameter. The function writes the new absolute offset to this location before it returns.
[in] whence Affects the way offset is interpreted, see above.
Returns:
0 on failure, 1 on success.
void fat_set_file_modification_date ( struct fat_dir_entry_struct dir_entry,
uint16_t  year,
uint8_t  month,
uint8_t  day 
)

Sets the modification time of a date.

Parameters:
[in] dir_entry The directory entry for which to set the modification date.
[in] year The year the file was last modified.
[in] month The month the file was last modified.
[in] day The day the file was last modified.
void fat_set_file_modification_time ( struct fat_dir_entry_struct dir_entry,
uint8_t  hour,
uint8_t  min,
uint8_t  sec 
)

Sets the modification time of a file.

Parameters:
[in] dir_entry The directory entry for which to set the modification time.
[in] hour The year the file was last modified.
[in] min The month the file was last modified.
[in] sec The day the file was last modified.
intptr_t fat_write_file ( struct fat_file_struct *  fd,
const uint8_t *  buffer,
uintptr_t  buffer_len 
)

Writes data to a file.

The data is written to the current file location.

Parameters:
[in] fd The file handle of the file to which to write.
[in] buffer The buffer from which to read the data to be written.
[in] buffer_len The amount of data to write.
Returns:
The number of bytes written (0 or something less than buffer_len on disk full) or -1 on failure.
See also:
fat_read_file