How to convert binary-encoded files into ASCII for files produced by Stellarium

Question

There is a piece of software known as Stellarium. It produces files like this one.

I would like to know how to convert the file from a binary encoding to ASCII. My attempts are shown below:

import binascii
import inspect

def int2bytes(i):
    hex_string = '%x' % i
    n = len(hex_string)
    return binascii.unhexlify(hex_string.zfill(n + (n & 1)))

def text_from_bits(bits, encoding='utf-8', errors='surrogatepass'):
    n = int(bits, 2)
    return int2bytes(n).decode(encoding, errors)

def attempt(code):
    frame = inspect.currentframe().f_back
    globalz = frame.f_globals
    localz = frame.f_locals
    r = ''.join([
        "\n", 40*"#",
        "\nTRYING: ", repr(code),
        "\nRESULT: "
    ])
    try:
        r += repr(eval(code, globalz, localz))
    except BaseException as exc:
        r += str(type(exc).__name__) + " " + str(exc)
    print(r, 40*"#", sep="\n")

with open("stars_4_1v0_2.cat", "rb") as text_file:
    line = next(iter(text_file))
    blah = binascii.hexlify(line)
    attempt('text_from_bits(blah)')
    attempt('blah.decode(\'utf-8\')')
    attempt('binascii.a2b_base64(blah)')
    attempt('line.decode(\'utf-8\')')

print(100* "!")

with open("stars_4_1v0_2.cat", "rb") as text_file:
    for _ in range(4):
        line = next(iter(text_file))
        attempt("line.decode('utf-8')")

The output is:

########################################
TRYING: 'text_from_bits(blah)'
RESULT: ValueError invalid literal for int() with base 2: b'0a'
########################################

########################################
TRYING: "blah.decode('utf-8')"
RESULT: '0a'
########################################

########################################
TRYING: 'binascii.a2b_base64(blah)'
RESULT: Error Incorrect padding
########################################

########################################
TRYING: "line.decode('utf-8')"
RESULT: '\n'
########################################
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

########################################
TRYING: "line.decode('utf-8')"
RESULT: '\n'
########################################

########################################
TRYING: "line.decode('utf-8')"
RESULT: UnicodeDecodeError 'utf-8' codec can't decode byte 0x83 in position 2: invalid start byte
########################################

########################################
TRYING: "line.decode('utf-8')"
RESULT: UnicodeDecodeError 'utf-8' codec can't decode byte 0xfa in position 11: invalid start byte
########################################

########################################
TRYING: "line.decode('utf-8')"
RESULT: UnicodeDecodeError 'utf-8' codec can't decode byte 0xfd in position 7: invalid start byte
########################################

Stackoverflow says, "It looks like your post is mostly code; please add some more details.," so I'm forced to write some text at the end here in order to post this.

Is this what you're looking for? https://stackoverflow.com/questions/7396849/convert-binary-to-ascii-and-vice-versa — Rithin Chalumuri, Nov 04 '19 at 13:38

score 0 · Answer 1 · answered Nov 04 '19 at 14:36

It's not clear that you can do a straight conversion from binary file type .cat to a text file.

The Stellarium Wiki outlines how the data is stored in .cat files. You could feasibly write a script to parse the .cat file and generate a text file representation, but as .cat is not a standard format you're (likely) not going to find something that will let you binary_to_text(some_file.cat) and get what you want.

How to convert binary-encoded files into ASCII for files produced by Stellarium

1 Answers1