icodein / rbf

A simple optimizing Brainfuck interpreter written in Rust

rbf

A simple optimizing Brainfuck interpreter written in Rust

rbf (short for either "Run BrainFuck" or "Rust BrainFuck") is a simple program you can use to run brainfuck code straight from your command line. Code can be read from a file, stdin or directly from a command-line argument. The input for the brainfuck program is stdin by default but can be specified using command-line arguments.

Setup

This program requires rust to be installed. You can find a guide on how to install rust on the official website. After that, everything else should happen automatically:

git clone https://github.com/slerpyyy/rbf.git
cd rbf
cargo install --path .

Usage

You can get a quick guide on how to run rbf by running it with the --help flag or without any command-line arguments:

Usage: rbf FILE [options]

A simple optimizing Brainfuck interpreter written in Rust.

Options:
    -h, --help          print this help message
    -c, --cmd CODE      run code from command
    -i, --input TEXT    use string as input
    -f, --force         allow invalid code to run
    -s, --static        only print the generated code

Internal Representation

To speed up evaluation, rbf uses an internal representation which is generated from the brainfuck code. The IR mainly consists of the following instructions:

Instruction	Example	Description
Touch(high, low)		Makes sure cells in range ]low+index, high+index] are allocated.
Set(off, val)	[-]+++	Set cell at index+off to val.
Add(off, val)	+++++	Add val to the cell at index+off.
Mul(off, val)	[>++<-]	Multiply val with the register and add the result to the cell at index+off.
Move(off)	>>>>	Add off to the current index.
Store(off)		Write the value of the cell at index+off to the register.
Loop(sub)	[>>+++]	Run the sub program while the cell at index is not 0.
Scan(val, step)	[->>+]	Begin at index and move by step until a cell with a value of val is found.
Fill(off, val, step)	[[-]++>]	Begin at index and move by step while setting cells with offset off to val until a cell with value 0 is found.
Input(off)	,	Receive one byte and write it to the cell at index+off.
Output(off)	.	Send the value of the cell at index+off.

You can take a look at the generated IR using the --static flag.

Benchmarks

Here are some execution times of rbf compared with the two fastest brainfuck interpreters I know. The times shown in the table below are averages of multiple runs.

	hanoi.b	bench.b	sort.b*	mandelbrot.b	long.b	99bottles.b
copy.sh	10.872s	0.176s		29.035s	0.746s	5.303s
bfc	0.586s	0.592s	12.129s	7.428s	3.851s	0.002s
rbf (this one)	0.412s	0.516s	13.295s	9.090s	2.805s	0.006s

* the program was run with the man-page of man as input. Interpreters, which refused to work with such manly inputs, have no time in this column.

Extra Credits

Some basic ideas of this project go back to this post by Mats Linander titled "brainfuck optimization strategies".