CowBF

A Brainfuck interpreter in the Cowgol programming language. Three different versions are provided, as a demonstration of different options for interpreter implementation:

• cowbf_case selects the next Brainfuck operation using the case statement in a loop.

• cowbf_subrcall selects the next operation using subroutine calls in a loop.

• cowbf_passto selects the next operation using the passto statement, a language extension that adds a form of proper tail calls to Cowgol. It is part of my own fork of Cowgol.

This interpreter is a good testbed for dispatch techniques because the operations are simple. Dispatch takes up a fairly large amount of execution time as a result.

Building

Download this repository as well as the Cowgol fork. Change the COWGOL_LOC variable in the makefile to something like /path/to/cowgol_fork/. Run make.

Usage

cowbf [program file] [input file]

The program file is the Brainfuck program. Any usage of the . instruction in that program will read from the input file, and any usage of the , instruction will output to the console.

Benchmarks

These were performed on a Debian 11 system with an Intel Core i3-3220 @ 3.30GHz. The program file was a ROT13 filter, and the input file was the text of the book Accelerando. Recorded times are the average of 100 runs.

Variant	Binary size	Execution time (s)
subrcall	19.72 kB	17.00
case	15.95 kB	13.73
passto	19.66 kB	10.98

The raw output of perf is included in the repo for further examination.