Ahead-of-time compiled RPN for /r/DailyProgrammer

RPNJit.py

import ctypes, mmap, struct
DEBUG = True
try:
    VirtualAlloc = ctypes.windll.kernel32.VirtualAlloc
    raise Exception("Windows not supported.")
except(AttributeError):
    libc = ctypes.CDLL("libc.so.6")
    libc.valloc.restype = ctypes.c_void_p
    def valloc(size):
        addr = libc.valloc(size)
        if not addr or libc.mprotect(addr, size, 0x07):
            raise RuntimeError("Cannot allocate RWX memory")
        return addr

def pack_number(term):
    number = float(term)
    return struct.pack('f', number)

def compile(rpn_code):
    size = mmap.PAGESIZE
    page = valloc(size)
    # cdecl header, compatible with python ctype
    buffer = ''.join((
        "\x55",                      # push rbp
        "\x48\x89\xe5",              # mov rbp, rsp
    ))

    sp = 0
    for term in rpn_code.split():
        try:
            number = pack_number(term)
            buffer += "\x68" + str(number) # mov rax, number
            sp += 1
        except(ValueError):
            binary_prelude = ''.join((
                "\xD9\x44\x24\x00", # fld [rsp]
                "\x59",             # pop rsp
                "\xD9\x44\x24\x00", # fld [rsp]
                "%s",
                "\xD9\x54\x24\x00", # fst [rsp]
            ))
            dictionary = {
                "+" : binary_prelude % "\xd8\xc1",
                "-" : binary_prelude % "\xd8\xe1",
                "*" : binary_prelude % "\xd8\xc9",
                "/" : binary_prelude % "\xd8\xf1",
                "//": binary_prelude % "\xd8\xf1\xD9\xFC",
                "%" : binary_prelude % "\xd9\xf8",
                "^" : binary_prelude % "\xD9\xF1\xDB\x14\x24\xDB\x04\x24\xDE\xE9\xD9\xF0\xD9\xE8\xDE\xC1\xDB\x04\x24\xD9\xC9\xD9\xFD",
            }

            sp -= 1
            buffer += dictionary[term]
            pass

    for _ in range(sp): buffer += "\x58"  # pop rax to clear the stack
    buffer += ''.join((
        "\x48\x89\xec", # mov rsp, rbp
        "\x5d",         # pop rbp
        "\xc3",         # ret
    ))

    if not ctypes.memmove(page, buffer, min(len(buffer), size)):
        raise RuntimeError("Input cannot not fit into memory.")

    if DEBUG: print(''.join(map(lambda x: '%02x' % ord(x), buffer)))
    return ctypes.CFUNCTYPE(ctypes.c_int)(page)

def rpn(code):
    f = compile(code)
    return struct.unpack('f', struct.pack('i', f()))[0]

if __name__ == '__main__':
    import sys
    DEBUG = True if len(sys.argv) > 2 and sys.argv[2] == '--debug' else False
    print(rpn(sys.argv[1] if len(sys.argv) > 1 else "2 0.5 ^"))