SFN (Short File Name) and File Metadata Parser

This Python script parses and decodes various metadata fields from a given hex string representing a file's short file name (SFN) entry. It supports the decoding of file attributes, creation/modification times, dates, and file size, considering little-endian format as needed.

What is SFN?

An 8.3 filename (also called a short filename or SFN) is one that obeys the filename convention used by old versions of DOS and versions of Microsoft Windows prior to Windows 95 and Windows NT 3.5. It is also used in modern Microsoft operating systems as an alternate filename to the long filename, to provide compatibility with legacy programs. The filename convention is limited by the FAT file system. Similar 8.3 file naming schemes have also existed on earlier CP/M, TRS-80, Atari, and some Data General and Digital Equipment Corporation minicomputer operating systems.

• 8.3 filename

Features

• SFN Name & Extension: Extracts the short file name and file extension.
• File Attributes: Decodes the file attributes (e.g., Archive, Read-Only, etc.).
• Creation Time/Date: Extracts and converts the creation time and date from the hex string.
• Last Accessed Date: Extracts and converts the last accessed date.
• Last Modification Time/Date: Extracts and converts the last modification time and date.
• File Size: Decodes the file size in bytes, correctly handling little-endian format.

Prerequisites

• Python 3.x

Usage

1. Clone the Repository:

   git clone https://github.com/kengentenerende/SFN_Parser.git
   cd sfn_parser

2. Run the Script:

   Execute the script with Python:

   python SFN_calculator.py

3. Input:

   When prompted, enter the hex string representing the SFN entry. For example:

   Enter the hex string: 544558542D4F7E314A5047200000436B714B714B0100EB4EFA4A58400C990200

4. Output:

   The script will output the parsed data:

   SFN Name: TEXT-O~1
   Extension: JPG
   Attributes: Archive
   Reserved: 00
   Create Time Tenths: 00
   Creation Time: 13:26:06
   Creation Date: 2017-11-17
   Last Date Accessed: 2017-11-17
   First Cluster High: 0100
   Last Modification Time: 09:55:22
   Last Modification Date: 2017-07-26
   First Cluster Low: 5840
   File Size (Bytes): 170252
   

Script Details

Functions

• hex_to_bin_str(hex_value, length): Converts a hexadecimal string to a binary string of a specified length.

• decode_time(hex_time): Decodes the creation/modification time from a hex string, adjusting for little-endian format.

• decode_date(hex_date): Decodes the creation/modification date from a hex string, adjusting for little-endian format.

• decode_attributes(hex_value): Converts a hex attribute byte into its corresponding file attribute descriptions.

• parse_hex_input(hex_input): Parses the full hex string and decodes each component (SFN Name, Extension, Attributes, Times, Dates, File Size, etc.).

Little-Endian Handling

The script accounts for little-endian format in decoding times, dates, and file size. Little-endian means the least significant byte is stored first, so the script reverses the byte order before converting to the correct values.

Example Hex String

The hex string 544558542D4F7E314A5047200000436B714B714B0100EB4EFA4A58400C990200 is parsed as:

• SFN Name: TEXT-O~1
• Extension: JPG
• Attributes: Archive
• Creation Time: 13:26:06
• Creation Date: 2017-11-17
• Last Date Accessed: 2017-11-17
• Last Modification Time: 09:55:22
• Last Modification Date: 2017-07-26
• File Size: 170252 bytes

License

This project is licensed under the MIT License - see the LICENSE file for details.

---