A JIT optimized Brain Fuck interpreter writtein in RPython

bf.py

#!/usr/bin/env python


"""BF Interpreter"""


import os
import sys


try:
    from rpython.rlib.jit import purefunction, JitDriver
except ImportError:
    def purefunction(fn):
        return fn

    class JitDriver(object):
        """Dummy JitDriver for when we're running under CPython"""

        def __init__(self, *args, **kwargs):
            pass

        def jit_merge_point(self, *args, **kwargs):
            pass

        def can_enter_jit(self, *args, **kwargs):
            pass


STDIN = sys.stdin.fileno()
STDOUT = sys.stdout.fileno()


def get_printable_location(pc, program, bmap):
        return "%s_%s_%s" % (program[:pc], program[pc], program[pc+1:])


jitdriver = JitDriver(
    greens=["pc", "program", "bmap"],
    reds=["tape"],
    get_printable_location=get_printable_location
)


class Tape(object):

    def __init__(self):
        self.thetape = [0]
        self.position = 0

    def get(self):
        return self.thetape[self.position]

    def set(self, val):
        self.thetape[self.position] = val

    def inc(self):
        self.thetape[self.position] += 1

    def dec(self):
        self.thetape[self.position] -= 1

    def advance(self):
        self.position += 1
        if len(self.thetape) <= self.position:
            self.thetape.append(0)

    def devance(self):
        self.position -= 1


@purefunction
def get_matching_bracket(bmap, pc):
    return bmap[pc]


def run(program, bmap):
    pc = 0
    tape = Tape()

    while pc < len(program):
        jitdriver.jit_merge_point(
            pc=pc, tape=tape, program=program, bmap=bmap
        )

        code = program[pc]

        if code == ">":
            tape.advance()

        elif code == "<":
            tape.devance()

        elif code == "+":
            tape.inc()

        elif code == "-":
            tape.dec()

        elif code == ".":
            # print
            os.write(STDOUT, chr(tape.get()))

        elif code == ",":
            # read from stdin
            tape.set(ord(os.read(STDIN, 1)[0]))

        elif code == "[" and tape.get() == 0:
            # Skip forward to the matching ]
            pc = get_matching_bracket(bmap, pc)

        elif code == "]" and tape.get() != 0:
            # Skip back to the matching [
            pc = get_matching_bracket(bmap, pc)

        pc += 1

    return 0


def parse(program):
    parsed = []
    bmap = {}
    leftstack = []

    pc = 0
    for char in program:
        if char in ('[', ']', '<', '>', '+', '-', ',', '.'):
            parsed.append(char)

            if char == '[':
                leftstack.append(pc)
            elif char == ']':
                left = leftstack.pop()
                right = pc
                bmap[left] = right
                bmap[right] = left
            pc += 1

    return "".join(parsed), bmap


def main(argv):
    source = open(argv[1], "rb")
    program, bmap = parse(source.read())
    return run(program, bmap)


def target(*args):
    return main, None


def jitpolicy(driver):
    from rpython.jit.codewriter.policy import JitPolicy

    return JitPolicy()


if __name__ == "__main__":
    raise SystemExit(main(sys.argv))

Getting Started

mkvirtualenv bf
pip install rpython
rpython --opt=jit --output=bf bf.py
./bf <(echo "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.")