Fix audio URL decoding

Author: python273

vk_api/audio_url_decoder.py

@@ -1,8 +1,24 @@
 # -*- coding: utf-8 -*-
+from .exceptions import VkAudioUrlDecodeError
 
 VK_STR = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN0PQRSTUVWXYZO123456789+/="
 
 
+def splice(l, a, b, c):
+    """ JS's Array.prototype.splice
+
+    var x = [1, 2, 3],
+        y = x.splice(0, 2, 1337);
+
+    eq
+
+    x = [1, 2, 3]
+    x, y = splice(x, 0, 2, 1337)
+    """
+
+    return l[:a] + [c] + l[a + b:], l[a:a + b]
+
+
 def decode_audio_url(string):
     vals = string.split("?extra=", 1)[1].split("#")
 
@@ -20,6 +36,12 @@ def decode_audio_url(string):
 
         elif cmd == 'x':
             tstr = vk_xor(tstr, arg[0])
+        elif cmd == 's':
+            tstr = vk_s(tstr, arg[0])
+        else:
+            raise VkAudioUrlDecodeError(
+                'Unknown decode cmd: "{}"; Please send bugreport'.format(cmd)
+            )
 
     return tstr
 
@@ -73,3 +95,35 @@ def vk_xor(string, i):
     xor_val = ord(i[0])
 
     return ''.join(chr(ord(s) ^ xor_val) for s in string)
+
+
+def vk_s_child(t, e):
+    i = len(t)
+
+    if not i:
+        return []
+
+    o = []
+    e = int(e)
+
+    for a in range(i - 1, -1, -1):
+        e = abs(e) + a + i
+        o.append(e % i | 0)
+
+    return o[::-1]
+
+
+def vk_s(t, e):
+    i = len(t)
+
+    if not i:
+        return t
+
+    o = vk_s_child(t, e)
+    t = list(t)
+
+    for a in range(1, i):
+        t, y = splice(t, o[i - 1 - a], 1, t[a])
+        t[a] = y[0]
+
+    return ''.join(t)

vk_api/exceptions.py

@@ -147,3 +147,11 @@ def try_again(self, key=None):
 
     def __str__(self):
         return 'Captcha needed'
+
+
+class VkAudioException(Exception):
+    pass
+
+
+class VkAudioUrlDecodeError(VkAudioException):
+    pass