a simple tool to generate and validate chargen stream

chargen.py

#!/usr/bin/env python3

import sys
import time
from enum import Enum

asciistr = r"""!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}"""


class State(Enum):
    LF = 1
    STR = 2


if not sys.stdin.isatty():
    state = State.LF
    offset = None

    while True:
        if state == State.LF:
            s = sys.stdin.read(1)

            if s == "\n":
                state == State.STR

        if state == State.STR:
            s = sys.stdin.read(74)

            if not offset:
                offset = asciistr.index(s[0])

            if s[:72] != asciistr[offset : offset + 72] or s[-2:] != "\r\n":
                sys.exit(1)

            offset = asciistr.index(s[1])
else:
    time.sleep(0.1)  # a short delay for counterpart to get ready to receive data
    offset = 0
    while True:
        print(f"{ asciistr[offset : offset + 72] }\r\n", end="")
        offset = offset + 1 if offset < 92 else 0