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[youtubedl] / youtube_dl / jsinterp.py
1 from __future__ import unicode_literals
2
3 import json
4 import re
5
6 from .utils import (
7 ExtractorError,
8 )
9
10
11 class JSInterpreter(object):
12 def __init__(self, code):
13 self.code = code
14 self._functions = {}
15 self._objects = {}
16
17 def interpret_statement(self, stmt, local_vars, allow_recursion=20):
18 if allow_recursion < 0:
19 raise ExtractorError('Recursion limit reached')
20
21 if stmt.startswith('var '):
22 stmt = stmt[len('var '):]
23 ass_m = re.match(r'^(?P<out>[a-z]+)(?:\[(?P<index>[^\]]+)\])?' +
24 r'=(?P<expr>.*)$', stmt)
25 if ass_m:
26 if ass_m.groupdict().get('index'):
27 def assign(val):
28 lvar = local_vars[ass_m.group('out')]
29 idx = self.interpret_expression(
30 ass_m.group('index'), local_vars, allow_recursion)
31 assert isinstance(idx, int)
32 lvar[idx] = val
33 return val
34 expr = ass_m.group('expr')
35 else:
36 def assign(val):
37 local_vars[ass_m.group('out')] = val
38 return val
39 expr = ass_m.group('expr')
40 elif stmt.startswith('return '):
41 assign = lambda v: v
42 expr = stmt[len('return '):]
43 else:
44 # Try interpreting it as an expression
45 expr = stmt
46 assign = lambda v: v
47
48 v = self.interpret_expression(expr, local_vars, allow_recursion)
49 return assign(v)
50
51 def interpret_expression(self, expr, local_vars, allow_recursion):
52 if expr.isdigit():
53 return int(expr)
54
55 if expr.isalpha():
56 return local_vars[expr]
57
58 try:
59 return json.loads(expr)
60 except ValueError:
61 pass
62
63 m = re.match(
64 r'^(?P<var>[a-zA-Z0-9_]+)\.(?P<member>[^(]+)(?:\(+(?P<args>[^()]*)\))?$',
65 expr)
66 if m:
67 variable = m.group('var')
68 member = m.group('member')
69 arg_str = m.group('args')
70
71 if variable in local_vars:
72 obj = local_vars[variable]
73 else:
74 if variable not in self._objects:
75 self._objects[variable] = self.extract_object(variable)
76 obj = self._objects[variable]
77
78 if arg_str is None:
79 # Member access
80 if member == 'length':
81 return len(obj)
82 return obj[member]
83
84 assert expr.endswith(')')
85 # Function call
86 if arg_str == '':
87 argvals = tuple()
88 else:
89 argvals = tuple([
90 self.interpret_expression(v, local_vars, allow_recursion)
91 for v in arg_str.split(',')])
92
93 if member == 'split':
94 assert argvals == ('',)
95 return list(obj)
96 if member == 'join':
97 assert len(argvals) == 1
98 return argvals[0].join(obj)
99 if member == 'reverse':
100 assert len(argvals) == 0
101 obj.reverse()
102 return obj
103 if member == 'slice':
104 assert len(argvals) == 1
105 return obj[argvals[0]:]
106 if member == 'splice':
107 assert isinstance(obj, list)
108 index, howMany = argvals
109 res = []
110 for i in range(index, min(index + howMany, len(obj))):
111 res.append(obj.pop(index))
112 return res
113
114 return obj[member](argvals)
115
116 m = re.match(
117 r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
118 if m:
119 val = local_vars[m.group('in')]
120 idx = self.interpret_expression(
121 m.group('idx'), local_vars, allow_recursion - 1)
122 return val[idx]
123
124 m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
125 if m:
126 a = self.interpret_expression(
127 m.group('a'), local_vars, allow_recursion)
128 b = self.interpret_expression(
129 m.group('b'), local_vars, allow_recursion)
130 return a % b
131
132 m = re.match(
133 r'^(?P<func>[a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr)
134 if m:
135 fname = m.group('func')
136 argvals = tuple([
137 int(v) if v.isdigit() else local_vars[v]
138 for v in m.group('args').split(',')])
139 if fname not in self._functions:
140 self._functions[fname] = self.extract_function(fname)
141 return self._functions[fname](argvals)
142 raise ExtractorError('Unsupported JS expression %r' % expr)
143
144 def extract_object(self, objname):
145 obj = {}
146 obj_m = re.search(
147 (r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) +
148 r'\s*(?P<fields>([a-zA-Z$0-9]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' +
149 r'\}\s*;',
150 self.code)
151 fields = obj_m.group('fields')
152 # Currently, it only supports function definitions
153 fields_m = re.finditer(
154 r'(?P<key>[a-zA-Z$0-9]+)\s*:\s*function'
155 r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
156 fields)
157 for f in fields_m:
158 argnames = f.group('args').split(',')
159 obj[f.group('key')] = self.build_function(argnames, f.group('code'))
160
161 return obj
162
163 def extract_function(self, funcname):
164 func_m = re.search(
165 (r'(?:function %s|[{;]%s\s*=\s*function)' % (
166 re.escape(funcname), re.escape(funcname))) +
167 r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
168 self.code)
169 if func_m is None:
170 raise ExtractorError('Could not find JS function %r' % funcname)
171 argnames = func_m.group('args').split(',')
172
173 return self.build_function(argnames, func_m.group('code'))
174
175 def build_function(self, argnames, code):
176 def resf(args):
177 local_vars = dict(zip(argnames, args))
178 for stmt in code.split(';'):
179 res = self.interpret_statement(stmt, local_vars)
180 return res
181 return resf