This is a File Allocation Table - FAT implementation in Python. The code implements a simple file system simulation using a FAT (File Allocation Table) data structure. The file system is stored in a virtual hard disk drive (HDD) represented by a 2D matrix. The code provides various functions to interact with the file system, such as creating files, deleting files, reading files, renaming files, and displaying file system information.
Constants: UA_Size: Size of each allocation unit (UA) in bytes. NR_UA: Total number of allocation units in the virtual HDD. NR_UA_FAT: Number of allocation units used for the FAT. NR_UA_ROOT: Number of allocation units used for the root directory. NAME: Length of the file name in the root directory. EXT: Length of the file extension in the root directory. DIM: Length of the file size and starting UA in the root directory. START_UA: Starting allocation unit index in the root directory. FLAG: Flag value in the root directory.
Data Structures: HDD: Represents the virtual hard disk drive. It is a 2D matrix with NR_UA rows and UA_Size columns. FAT: The File Allocation Table. It is a 1D list with NR_UA elements, representing the allocation status of each allocation unit. The values can be 0 (free), 1 (FAT), 2 (root directory), 3 (data) ROOT: The root directory. It is a 2D matrix with NR_UA_ROOT rows and UA_Size columns. Each row represents a file entry, storing the file name, extension, size, starting UA, and flag.
Functions: FAT Operations: freeUA(): Returns the index of the first free allocation unit in the FAT or -1 if none is available. initFat(matrix): Initializes the FAT with appropriate values for the FAT and root directory allocation units. printFat(matrix): Prints the contents of the FAT. updateFat(change_ua, value): Updates the allocation status of an allocation unit in the FAT. fatOnHDD(): Updates the HDD with the contents of the FAT. countFreeMemory(): Returns the number of free allocation units in the FAT. Root Directory Operations: printRoot(): Prints the contents of the root directory. freeOnRoot(): Returns the index of the first free entry in the root directory or -1 if none is available. insertInRoot(name, ext, size, startUA, flag): Inserts a new file entry into the root directory. rootOnHDD(): Updates the HDD with the contents of the root directory.
HDD Operations: printHDD(): Prints the contents of the HDD. uploadOnHDD(data): Uploads data to the HDD by storing it in consecutive free allocation units.
Data Manipulation: Various utility functions for converting data between different formats (bytes, integers, strings) and slicing lists into byte-sized elements.
User Functions: processUserInput(): Takes user commands as input and performs the corresponding file system operations. Supported commands include create, read, rename, delete, ls, exit, mem stat, help, and commands. It also provides a help message for each command.