Python-Sockets/FileRequest.py at main · doougal/Python-Sockets · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
"""
Class to handle file request packets for socket based file downloader

3/8/21
Alex Burling
88866582
"""


import sys

MAGIC_NO = 0x497E


"""Abstracts request packet operations"""
class FileRequest:

    def __init__(self, magic_no, type, filename_len, filename):
        self.magic_no = magic_no
        self.type = type
        self.filename = filename
        self.filename_len = filename_len


    """Initialises a FileRequest object from a filename,
       used on the client side to generate the request"""
    @classmethod
    def from_filename(cls, filename):
        magic_no = MAGIC_NO
        type = 1
        filename = filename.encode('utf-8')
        filename_len = len(filename)

        if filename_len < 1 or filename_len > 1024:
            sys.exit("SPECIFIED FILENAME IS INVALID")

        return cls(magic_no, type, filename_len, filename)


    """Initialises a FileRequest object from a bytearray,
       used on the server side to reconstruct the request.
       Filename remains as a bytearray in case a complete
       request wasn't recieved in the first chunk"""
    @classmethod
    def from_bytearray(cls, array):
        magic_no = hex(int.from_bytes([array[0], array[1]], 'big'))
        type = int.from_bytes([array[2]], 'big')
        filename_len = int.from_bytes([array[3], array[4]], 'big')
        filename = bytearray(array[5:])

        return cls(magic_no, type, filename_len, filename)


    """Converts FileRequest data into a bytearray for
       transmission over socket"""
    def generate_packet(self):
        packet = bytearray()
        packet.extend(self.magic_no.to_bytes(2, 'big'))
        packet.extend(self.type.to_bytes(1, 'big'))
        packet.extend(self.filename_len.to_bytes(2, 'big'))
        packet.extend(self.filename)
        return packet


    """Validates packet structure on server side"""
    def validate(self):
        if (self.magic_no != hex(MAGIC_NO)):
            raise AssertionError()
        if (self.type != 1):
            raise AssertionError()
        if (self.filename_len < 1 or self.filename_len > 1024):
            raise AssertionError()


    """Used to append data to FileRequest in case a complete request
    wasn't recieved in the first chunk """
    def append_data(self, data):
        self.filename.extend(data)


    def check_len(self):
        return self.filename_len == len(self.filename)


    def get_filename(self):
        return self.filename.decode("utf-8")