User:Bellezzasolo/CFS

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Tera File System (TFS)

TFS64

Introduction

TFS64 is my file system (Bellezzasolo's). It uses 64 bit addressing, which is the 64. It currently hasn't been implemented, but a Win32 formatter is in active development.
It is currently at version 1.00 FINAL
Note: all fileds are little-endian

Features

• User security
• Flags
• Inode style tables
• Fixed size
• Tree-based

Limitations

There are few limitations. Here are the only ones:

• One is the 64 bit addressing, which will (one day) be changed in TFS128; but for now it's plenty
• There have to be 10 times the number of files possible as directories possible. This is because there isn't room in the master table for this data, but can be calculated by the space between the DTable pointer and the FTable pointer.
• File and Directory Name lengths.

If you spot any more, add them here

Structure

TFS64 is structured in the follwing way:

• MASTER Table - logical sector 0 of the partition. Bootloader and essential data
• Cluster Availability Table - a bit representing every cluster on the partition, in logical order
• Directory Table - directory name and a pointer to the directory entry
• File Table - a filename and a pointer to the file entry
• Directory Entries - an inode-style list of directory entries in no particular order. Variable size, and pointed to by the directory table
• File Entries - similar to directory entries, but for files and pointed to by the file table

For error checking multiple copies of the tables can be kept

Detail

MASTER Table

Name	Offset (from the start of the MASTER Table)	Length (in bytes)	Meaning
Jump	0	2	A jump to the bootloader if bootable, 0 otherwise. Normally disassembles to JMP SHORT 3E
Creation Date	2	8	The creation time and date, encoded in TeraTime. TeraTime is Unix time, except the epoch is 1st Jan 2011
Creator ID	10	4	The creator's ID. This is normally 0, but could be set to a range of values for future use
Disk Size (Clusters)	14	8	The number of clusters on the partition. Need I say any more?
Bytes per Cluster	22	2	The number of bytes in a cluster. Could be the same as the disk, but then again might not be :)
Number of Tables	24	1	The number of Copies of the tables. 1 if no backup, another number for backups. 0 is invalid
Major Version	25	2	The major FS version. Can be any 2 byte value
Minor Version	27	1	The minor FS version. Is the .xy after the major version. Can only be between 0 and 99 inclusive
Directory Table Pointer	28	7	A cluster of the Directory Table. 7 bytes to save space and make an 0x3E jump. Besides, I thought the FS is pretty early ;)
File Table Pointer	35	8	A cluster of the File Table. I'm not that stingy :)
FS ID	43	8	The FS string. Only "TFS64 " is acceptable
Volume Label	51	11	The volume label. 11 characters only (ASCII)
Bootloader	62 (or 0x3E)	448	The bootloader. Duh! :)
Boot Signature	510	2	The old 0xAA55

Cluster Availability Table (CAT)

This is just an array of bits. Each bit represents a cluster on the partition. If it's set to 1, the custer is used. Otherwise it's free. The bit's offset from the start of the CAT is the cluster at that offset from the start of the partition. FS data is included (even itself!).

Directory Table

The directory table has an entry for each directory. Not to be confused with directory entries. The entry takes this structure:

Name	Offset	Size	Meaning
Directory Name	0	246	A Unicode (UTF-16) directory name
Entry Cluster	246	8	A cluster pointer to the directory entry
Entry Byte	254	2	A byte offset into the cluster

File Table

The file table has an entry for each file. The entry takes this structure:

Name	Offset	Size	Meaning
Filename	0	502	A Unicode (UTF-16) filename
Entry Cluster	502	8	A cluster pointer to the file entry
Entry Byte	510	2	A byte offset into the cluster

Directory Entry

The directory entries are pointed to by the directory table. They are similar to Ext inodes. The structure is as follows:

Name	Offset	Size	Meaning
Creation Date	0	8	A TeraTime creation date
Permissions	8	4	The permissions of the directory. Bitflags
Symbol	12	2	A registry-style database of symbols. This is the index into it
Flags	14	1	The directory flags
Size	15	4	The number of entries in the next two arrays
Clusters	19	Size*8	The cluster pointers to the tables for items in the directory
Bytes	19+Size*8	Size*2	The byte index into those clusters

File Entries

The file entry is pointeed to by the file table like an Ext inode. The structure is as follows:

Name	Offset	Size	Meaning
Creation Date	0	8	A TeraTime creation date
Modification Date	8	8	A TeraTime modification date
Permissions	16	4	The permissions of the file. Bitflags
Symbol	20	2	A registry-style database of symbols. This is the index into it
Flags	22	1	The file flags
Size	23	4	The number of entries in the next array
Clusters	27	Size*8	The clusters of the file

Special Fields

Here are decriptions of the bit-flags fields:

Permissions

Other user groups (31-2)

Administrator (1)

Owner user (0)

The user groups are defined by the OS. On a portable device these will change, so most of these fields will be unusable. The owner user is inherited from the directory, and is the only non-grouped user. The origion of the owner user is if the entry is in their personal directory.

Flags

Flags are the general attributes, such as read-only, hidden and similar.

7	6	5	4	3	2	1	0
SF	AH	NW	MO	NR	CH	HI	DO

Meanings:

• DO: Delete Only (Read only field modify protect)
• HI: Hidden
• CH: Contents Hidden (dir-only)
• NR: Non-Privileged Read - read ability for people without permissions
• MO: Modify Only (Read-only deletion protect)
• NW: Non-Privileged Write - write version of NR
• NX: Non-Privileged Execute - execute version of NW
• SF: System File - ultimate protection. Cannot be changed under TeraOS (my, Bellezzasolo's OS). Drivers should be installed to a special directory.

Flags that apply to all users

• DO
• HI
• CH
• MO
• SF

Other flag's behaviour

The NR,NW and NX flags only apply to non-privileged users, i.e those who don't have their permissions bit set.

Project Status

Not implemented, however in active development. Here are the components required and their status:

• Formatter - Active Development (Win32)
• Driver - Not Started. Waiting for HDD and formatter