[py]Brainf*ckでループのアンローリング

bf.py

#!/usr/bin/env python

import sys

mem = [0] * 30000
ptr = 0

def bfexec(src):
    global mem, ptr
    i = 0
    start = []
    while i < len(src):
        cmd = src[i]
        if cmd == '+':
            mem[ptr] += 1
            f.write("    (*ptr)++;\n")
        elif cmd == '-':
            mem[ptr] -= 1
            f.write("    (*ptr)--;\n")
        elif cmd == '>':
            ptr += 1
            f.write("    ptr++;\n")
        elif cmd == '<':
            ptr -= 1
            f.write("    ptr--;\n")
        elif cmd == '.':
            sys.stdout.write(chr(mem[ptr]))
            f.write("    putchar(*ptr);\n")
        elif cmd == ',':
            mem[ptr] = sys.stdin.read(1)
            f.write("    *ptr = getchar();\n")
        elif cmd == '[':
            start.append(i)
            if mem[ptr] == 0:
                ind = 0
                while i < len(src):
                    cmd = src[i]
                    if cmd == '[':
                        ind += 1
                    elif cmd == ']':
                        ind -= 1
                        if ind == 0: break
                    i += 1
                if ind > 0:
                    print "block end required."
                    exit(1)
        elif cmd == ']':
            if len(start) == 0:
                print "block start required."
                exit(1)
            i = start.pop() - 1
        i += 1

if len(sys.argv) != 2:
       print "usage: " + sys.argv[0] + " source.bf"
       exit(1)

f = open(sys.argv[1], "r")
bf_src = f.read()
f.close()

f = open("bf.c", "w")
f.write("#include <stdio.h>\n")
f.write("char mem[30000];\n")
f.write("int main(void) {\n")
f.write("    char *ptr = mem;\n")

bfexec(bf_src)

f.write("    return 0;\n")
f.write("}\n")
f.close()

test.bf

>++[<++>-]

test.c

#include <stdio.h>
char mem[30000];
int main(void) {
    char *ptr = mem;
    ptr++;
    (*ptr)++;
    (*ptr)++;
    ptr--;
    (*ptr)++;
    (*ptr)++;
    ptr++;
    (*ptr)--;
    ptr--;
    (*ptr)++;
    (*ptr)++;
    ptr++;
    (*ptr)--;
    return 0;
}