File Allocation Simulator

A file allocation simulator.

It's the course project (Additional Option) for Computer System Architechture, Professor Mao, Tsinghua SEM.

• File Allocation Simulator
  • Background
  • Running
    • From Packaged Distribution
    • From Source Code
      • Prerequisites
      • Install dependencies
      • Run
  • Application Instruction
    • Command Data File
      • General
      • Operation codes
      • Data File Generator
    • Main Page
    • Simulation Page
      • File Information Table
        • In Contiguous Simulation
        • In Linked Simulation
        • In Indexed Simulation
  • Known Problems
  • External Resources Used in the Project

Background

"File allocation" refers to the allocation methods described in Chapter 12.4 of Operating System Concepts, Ninth Edition by Abraham Silberschatz, Peter Baer Galvin and Greg Gagne.

The three allocation methods are:

• Contiguous Allocation
• Linked Allocation
• Indexed Allocation

Some assumptions in this simulator are:

• FAT is not used for linked allocation. The pointers are assumed to be in the file blocks instead.
• Combined scheme is not used for indexed allocation, i.e there is only direct blocks.

Running

From Packaged Distribution

Download the release and unzip the zip file. Then run file-allocation-simulator.exe.

The only supported platform is Windows 10 x64.

From Source Code

Prerequisites

• Node.js
• npm

Install dependencies

$ npm install

Run

$ npm start

Application Instruction

Command Data File

General

The command data file must be a csv-like formatted text file, with four columns and any numbers of rows.

The meaning of each columns are:

Directory	File Name	Blocks or # of the blocks	Operation code

• The separator should be , and it should not present at the end of each row.
• The spaces within the cell, which makes the source data file easier to read, is allowed.
• Directory must starts with root
• Multi-level directory should be separated by /
• Operation code must be C, R, W or D, which will be explained in the following section

Here is an example of a valid instruction file:

root, file_1, 6, C
root, file_1, 2, R
root/sub, file_2, 3, C
root/sub, file_2, 1, W
root, file_1, 6, D

You can find more of them at the test folder.

Operation codes

• C stands for create.

A file, located in Directory named File Name taking up Blocks number of blocks will be created.

• R stands for read.

The No. Blocks block of file File Name which locates in Directory will be read.

• W stands for write.

The No. Blocks block of file File Name which locates in Directory will be written.

• D stands for delete.

The file File Name which locates in Directory will be deleted. Note that the Block field in this command will be ignored according to the instruction of Prof. Mao. The whole file will be deleted whatever the Block field is, instead of deleting only the No. Block block.

Data File Generator

A very simple python script was provided to generate random data file for testing.

• Environment: Python 3.7
• Dependencies: pandas, you can install by pip install pandas

Running:

$ python test/scripts/generate.py NUMBER

• Argument NUMBER is the number of instructions generated.
• It should either be an integer greater than 1, or omitted, where the script will generate 20 instructions.

The instruction file will be created at test/assets/random-tests, named with current time.

Main Page

On main page, you can click the first three buttons to open a simulation window, or click the Documentation button, which will direct you to the github page of this README.

Simulation Page

The left part in the simulation page is the file blocks. The white ones are empty and the colored ones are full, either storing a file/directory or is a index block in the indexed allocation simulation. If one file takes up several blocks, these blocks will have the same color.

When a block is being read, its number will become blinking white R!. When a block is being written, its number will become blinking W!.

There are also three buttons at the bottom-left. Step will execute one instruction. Auto will automatically execute the instructions every 2 seconds. And the auto-execution will stop after you click it again. Select Data File will ask you to choose the source command file, which was discussed above.

Note that the Auto button is the only "on-off" switch to the auto execution. That is, if you clicked Auto, finished one simulation, and uses the Select Data File to open another simulation. The second simulation will automatically start, unless you click the Auto button again.

The right part will display the necessary information.

• Instructions lists the instructions in the data file.
• File Information Table part will be discussed in the next section.
• Messages tells you the detailed process of the execution of the command.

File Information Table

The File Information Table part in the simulation page displays various information.

In Contiguous Simulation

The columns of the table will be:

File	Start	Length

Each stands for: File Name, No. of the starting Block, length of the file.

If there is multi-level directory, then certain blocks will be used to save the sub-directory.

You can click that block to see the file information table contained in that block. And you can click the title File Information Table to get back to the main directory table.

In Linked Simulation

The name will be changed to File Information Table or Block Pointer. It displays both the directory table and the file pointer.

Initially, the colums of the table will be:

File	Start	End

Each stands for the file name, the start block and the end block.

You can also click a block containing a sub-directory to see its directory table.

If you click a block containing a part of the file, the table will display its pointer information. The columns will be:

File	Next

Here Next stands for the next block of this file.

You can return to the main directory by clicking File Information Table or Block Pointer as well.

In Indexed Simulation

The name will be changed to File Information Table or Index Block. It displays both the directory table and the index block.

Initially, the colums of the table will be:

File	Index Block

Each stands for the file name, and its index block.

You can also click a block containing a sub-directory to see its directory table.

If you click an index block, the table will display the contained index information. The columns will be:

Index

Here Index stands for the block locations of this file.

You can return to the main directory by clicking File Information Table or Index Block as well.

Known Problems

1. This application does not have good resolution adaptation and monitor-size adaption. On different devices, the display may differ, and even prevent from normal using. You can try to set different resolution on your monitor but I do not guarantee the effect.
2. If you click the Step button too fast, the R! or W! words may stay on the panel rather than returning back to the block number.

External Resources Used in the Project

• The project is built with electron.
• Electron-forge initialized the boilerplate and package the distributable.
• Table Style is derived from codepen.io, and was slightly modified.
• Button Style is built with css3 button generator.