User:Superleaf1995/lowFS: Difference between revisions

== Bootsector ==

There are three ways to identify a lowFS disk: checking byte 0x02, checking the last 4 bytes of sector 4 or checking the last 4 bytes of the disk. It should contain the characters 'LFFL' (ASCII). Followed by a table:

struct lowFS_megatable {

uint8_t attribute; // Attribute byte

uint16_t reserved;

}__attribute__((packed));

 

Attribute:

== Entry ==

The entry header is basically like a FAT entry, however, this is a header ''for entries'' not for files.

struct lowFS_entry_header {

uint8_t reserved; // Should always be 0xCC

uint64_t size; // Size of entry (lowFS_entry struct not included). If set to 0, the host must know the size parsing entry type

};

 

* nn_entry should be set to 0 if this is the final part of the entry.

 

If entry_type is set to '''ENTRY_TYPE_FILEMETADATA''' (0xF0):

struct lowFS_entry_filemetadata {

uint64_t filename_len; // length of filename

uint8_t perm; // use for unix permissions

};

* Filename should be ended with a NULL character

 

If entry_type is set to '''ENTRY_TYPE_FILEPART''' (0xF2):

struct lowFS_entry_filepart {

uint64_t clen; // Length of the bytes of the file

uint16_t checksum; // verifies that the data in the file is correct (First byte of content ANDed by the last one)

};

 

If entry type is set to '''ENTRY_TYPE_DIRECTORYMETADATA''' (0xF4):

struct lowFS_entry_directorymetadata {

uint64_t dirname_len; // length of dirname

uint8_t perm; // use for unix permissions

};

 

== Checksum ==

A checksum cannot be after the last entry or entry header in a chain.

 

struct lowFS_checksum {

uint16_t val; // 0x53BC

uint32_t fp; // FILEPART size high bytes

};