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[youtubedl] / youtube_dl / jsinterp.py
1 from __future__ import unicode_literals
2
3 import re
4
5 from .utils import (
6 ExtractorError,
7 )
8
9
10 class JSInterpreter(object):
11 def __init__(self, code):
12 self.code = code
13 self._functions = {}
14
15 def interpret_statement(self, stmt, local_vars, allow_recursion=20):
16 if allow_recursion < 0:
17 raise ExtractorError('Recursion limit reached')
18
19 if stmt.startswith('var '):
20 stmt = stmt[len('var '):]
21 ass_m = re.match(r'^(?P<out>[a-z]+)(?:\[(?P<index>[^\]]+)\])?' +
22 r'=(?P<expr>.*)$', stmt)
23 if ass_m:
24 if ass_m.groupdict().get('index'):
25 def assign(val):
26 lvar = local_vars[ass_m.group('out')]
27 idx = self.interpret_expression(
28 ass_m.group('index'), local_vars, allow_recursion)
29 assert isinstance(idx, int)
30 lvar[idx] = val
31 return val
32 expr = ass_m.group('expr')
33 else:
34 def assign(val):
35 local_vars[ass_m.group('out')] = val
36 return val
37 expr = ass_m.group('expr')
38 elif stmt.startswith('return '):
39 assign = lambda v: v
40 expr = stmt[len('return '):]
41 else:
42 raise ExtractorError(
43 'Cannot determine left side of statement in %r' % stmt)
44
45 v = self.interpret_expression(expr, local_vars, allow_recursion)
46 return assign(v)
47
48 def interpret_expression(self, expr, local_vars, allow_recursion):
49 if expr.isdigit():
50 return int(expr)
51
52 if expr.isalpha():
53 return local_vars[expr]
54
55 m = re.match(r'^(?P<in>[a-z]+)\.(?P<member>.*)$', expr)
56 if m:
57 member = m.group('member')
58 val = local_vars[m.group('in')]
59 if member == 'split("")':
60 return list(val)
61 if member == 'join("")':
62 return ''.join(val)
63 if member == 'length':
64 return len(val)
65 if member == 'reverse()':
66 return val[::-1]
67 slice_m = re.match(r'slice\((?P<idx>.*)\)', member)
68 if slice_m:
69 idx = self.interpret_expression(
70 slice_m.group('idx'), local_vars, allow_recursion - 1)
71 return val[idx:]
72
73 m = re.match(
74 r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
75 if m:
76 val = local_vars[m.group('in')]
77 idx = self.interpret_expression(
78 m.group('idx'), local_vars, allow_recursion - 1)
79 return val[idx]
80
81 m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
82 if m:
83 a = self.interpret_expression(
84 m.group('a'), local_vars, allow_recursion)
85 b = self.interpret_expression(
86 m.group('b'), local_vars, allow_recursion)
87 return a % b
88
89 m = re.match(
90 r'^(?P<func>[a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr)
91 if m:
92 fname = m.group('func')
93 if fname not in self._functions:
94 self._functions[fname] = self.extract_function(fname)
95 argvals = [int(v) if v.isdigit() else local_vars[v]
96 for v in m.group('args').split(',')]
97 return self._functions[fname](argvals)
98 raise ExtractorError('Unsupported JS expression %r' % expr)
99
100 def extract_function(self, funcname):
101 func_m = re.search(
102 (r'(?:function %s|[{;]%s\s*=\s*function)' % (
103 re.escape(funcname), re.escape(funcname))) +
104 r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
105 self.code)
106 if func_m is None:
107 raise ExtractorError('Could not find JS function %r' % funcname)
108 argnames = func_m.group('args').split(',')
109
110 def resf(args):
111 local_vars = dict(zip(argnames, args))
112 for stmt in func_m.group('code').split(';'):
113 res = self.interpret_statement(stmt, local_vars)
114 return res
115 return resf
116