forked from marekweb/opaque-id
-
Notifications
You must be signed in to change notification settings - Fork 0
/
opaque.py
49 lines (35 loc) · 1.64 KB
/
opaque.py
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
import struct
import base64
__version__ = '0.0.1'
class OpaqueEncoder:
"""
Opaque ID encoder.
Translates between 32-bit integers (such as resource IDs) and obfuscated
scrambled values, as a one-to-one mapping. Supports hex and base64 url-safe
string representations. Expects a secret integer key in the constructor.
(c) 2011 Marek Z. @marekweb
"""
def __init__(self, key):
self.key = key
self.extra_chars = '.-';
def transform(self, i):
"""Produce an integer hash of a 16-bit integer, returning a transformed 16-bit integer."""
i = (self.key ^ i) * 0x9e3b
return i >> (i & 0xf) & 0xffff
def transcode(self, i):
"""Reversibly transcode a 32-bit integer to a scrambled form, returning a new 32-bit integer."""
r = i & 0xffff
l = i >> 16 & 0xffff ^ self.transform(r)
return ((r ^ self.transform(l)) << 16) + l
def encode_hex(self, i):
"""Transcode an integer and return it as an 8-character hex string."""
return "%08x" % self.transcode(i)
def encode_base64(self, i):
"""Transcode an integer and return it as a 6-character base64 string."""
return base64.b64encode(struct.pack('!L', self.transcode(i)), self.extra_chars)[:6]
def decode_hex(self, s):
"""Decode an 8-character hex string, returning the original integer."""
return self.transcode(int(s, 16))
def decode_base64(self, s):
"""Decode a 6-character base64 string, returning the original integer."""
return self.transcode(struct.unpack('!L', base64.b64decode(s + '==', self.extra_chars))[0])