1 from __future__ import unicode_literals
10 class JSInterpreter(object):
11 def __init__(self, code):
15 def interpret_statement(self, stmt, local_vars, allow_recursion=20):
16 if allow_recursion < 0:
17 raise ExtractorError('Recursion limit reached')
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>.*)$', stmt)
24 if ass_m.groupdict().get('index'):
26 lvar = local_vars[ass_m.group('out')]
27 idx = self.interpret_expression(
28 ass_m.group('index'), local_vars, allow_recursion)
29 assert isinstance(idx, int)
32 expr = ass_m.group('expr')
35 local_vars[ass_m.group('out')] = val
37 expr = ass_m.group('expr')
38 elif stmt.startswith('return '):
40 expr = stmt[len('return '):]
43 'Cannot determine left side of statement in %r' % stmt)
45 v = self.interpret_expression(expr, local_vars, allow_recursion)
48 def interpret_expression(self, expr, local_vars, allow_recursion):
53 return local_vars[expr]
55 m = re.match(r'^(?P<in>[a-z]+)\.(?P<member>.*)$', expr)
57 member = m.group('member')
58 val = local_vars[m.group('in')]
59 if member == 'split("")':
61 if member == 'join("")':
63 if member == 'length':
65 if member == 'reverse()':
67 slice_m = re.match(r'slice\((?P<idx>.*)\)', member)
69 idx = self.interpret_expression(
70 slice_m.group('idx'), local_vars, allow_recursion - 1)
74 r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
76 val = local_vars[m.group('in')]
77 idx = self.interpret_expression(
78 m.group('idx'), local_vars, allow_recursion - 1)
81 m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
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)
90 r'^(?P<func>[a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr)
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)
100 def extract_function(self, funcname):
102 (r'(?:function %s|%s\s*=\s*function)' % (
103 re.escape(funcname), re.escape(funcname))) +
104 r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
107 raise ExtractorError('Could not find JS function %r' % funcname)
108 argnames = func_m.group('args').split(',')
111 local_vars = dict(zip(argnames, args))
112 for stmt in func_m.group('code').split(';'):
113 res = self.interpret_statement(stmt, local_vars)