# Miscellaneous utilities, meant to be included from build.py

import os


# Do a fork/execl because that way all children get the same stdout,
# i.e. if it's a tty the executed program should behave appropriately.
# Python probably has an idiomatic way to do this, but frankly idc.
def run_sync(program: str, *args):
    path = os.popen("which " + program).read().strip()
    child = os.fork()
    if child == 0:
        os.execl(path, program, *args)
        print("execl() failed")
        exit(1)
    elif child == -1:
        print("fork() failed")
        exit(1)
    status = os.waitpid(child, 0)
    if status[1] != 0:
        print(program + " exited with status code " + str(status[1]))
        exit(1)


def generate_crc_tab(poly_reverse: int):
    tab = []
    for crc in range(256):
        for _ in range(8):
            lsb = crc % 2
            crc >>= 1
            if lsb == 1:
                crc ^= poly_reverse
        tab.append(crc)
    return tab


def do_crc(data, table):
    crc = 0xffffffff
    for byte in data:
        crc = (crc >> 8) ^ table[(crc ^ byte) & 0xff]
    return ~crc & 0xffffffff


CCITT32_TAB = generate_crc_tab(0xedb88320)


def crc32(data: bytes):
    global CCITT32_TAB
    return do_crc(data, CCITT32_TAB)