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[youtubedl] / youtube_dl / jsinterp.py
1 from __future__ import unicode_literals
2
3 import json
4 import operator
5 import re
6
7 from .utils import (
8 ExtractorError,
9 )
10
11 _OPERATORS = [
12 ('|', operator.or_),
13 ('^', operator.xor),
14 ('&', operator.and_),
15 ('>>', operator.rshift),
16 ('<<', operator.lshift),
17 ('-', operator.sub),
18 ('+', operator.add),
19 ('%', operator.mod),
20 ('/', operator.truediv),
21 ('*', operator.mul),
22 ]
23 _ASSIGN_OPERATORS = [(op + '=', opfunc) for op, opfunc in _OPERATORS]
24 _ASSIGN_OPERATORS.append(('=', lambda cur, right: right))
25
26 _NAME_RE = r'[a-zA-Z_$][a-zA-Z_$0-9]*'
27
28
29 class JSInterpreter(object):
30 def __init__(self, code, objects=None):
31 if objects is None:
32 objects = {}
33 self.code = code
34 self._functions = {}
35 self._objects = objects
36
37 def interpret_statement(self, stmt, local_vars, allow_recursion=100):
38 if allow_recursion < 0:
39 raise ExtractorError('Recursion limit reached')
40
41 should_abort = False
42 stmt = stmt.lstrip()
43 stmt_m = re.match(r'var\s', stmt)
44 if stmt_m:
45 expr = stmt[len(stmt_m.group(0)):]
46 else:
47 return_m = re.match(r'return(?:\s+|$)', stmt)
48 if return_m:
49 expr = stmt[len(return_m.group(0)):]
50 should_abort = True
51 else:
52 # Try interpreting it as an expression
53 expr = stmt
54
55 v = self.interpret_expression(expr, local_vars, allow_recursion)
56 return v, should_abort
57
58 def interpret_expression(self, expr, local_vars, allow_recursion):
59 expr = expr.strip()
60
61 if expr == '': # Empty expression
62 return None
63
64 if expr.startswith('('):
65 parens_count = 0
66 for m in re.finditer(r'[()]', expr):
67 if m.group(0) == '(':
68 parens_count += 1
69 else:
70 parens_count -= 1
71 if parens_count == 0:
72 sub_expr = expr[1:m.start()]
73 sub_result = self.interpret_expression(
74 sub_expr, local_vars, allow_recursion)
75 remaining_expr = expr[m.end():].strip()
76 if not remaining_expr:
77 return sub_result
78 else:
79 expr = json.dumps(sub_result) + remaining_expr
80 break
81 else:
82 raise ExtractorError('Premature end of parens in %r' % expr)
83
84 for op, opfunc in _ASSIGN_OPERATORS:
85 m = re.match(r'''(?x)
86 (?P<out>%s)(?:\[(?P<index>[^\]]+?)\])?
87 \s*%s
88 (?P<expr>.*)$''' % (_NAME_RE, re.escape(op)), expr)
89 if not m:
90 continue
91 right_val = self.interpret_expression(
92 m.group('expr'), local_vars, allow_recursion - 1)
93
94 if m.groupdict().get('index'):
95 lvar = local_vars[m.group('out')]
96 idx = self.interpret_expression(
97 m.group('index'), local_vars, allow_recursion)
98 assert isinstance(idx, int)
99 cur = lvar[idx]
100 val = opfunc(cur, right_val)
101 lvar[idx] = val
102 return val
103 else:
104 cur = local_vars.get(m.group('out'))
105 val = opfunc(cur, right_val)
106 local_vars[m.group('out')] = val
107 return val
108
109 if expr.isdigit():
110 return int(expr)
111
112 var_m = re.match(
113 r'(?!if|return|true|false)(?P<name>%s)$' % _NAME_RE,
114 expr)
115 if var_m:
116 return local_vars[var_m.group('name')]
117
118 try:
119 return json.loads(expr)
120 except ValueError:
121 pass
122
123 m = re.match(
124 r'(?P<var>%s)\.(?P<member>[^(]+)(?:\(+(?P<args>[^()]*)\))?$' % _NAME_RE,
125 expr)
126 if m:
127 variable = m.group('var')
128 member = m.group('member')
129 arg_str = m.group('args')
130
131 if variable in local_vars:
132 obj = local_vars[variable]
133 else:
134 if variable not in self._objects:
135 self._objects[variable] = self.extract_object(variable)
136 obj = self._objects[variable]
137
138 if arg_str is None:
139 # Member access
140 if member == 'length':
141 return len(obj)
142 return obj[member]
143
144 assert expr.endswith(')')
145 # Function call
146 if arg_str == '':
147 argvals = tuple()
148 else:
149 argvals = tuple([
150 self.interpret_expression(v, local_vars, allow_recursion)
151 for v in arg_str.split(',')])
152
153 if member == 'split':
154 assert argvals == ('',)
155 return list(obj)
156 if member == 'join':
157 assert len(argvals) == 1
158 return argvals[0].join(obj)
159 if member == 'reverse':
160 assert len(argvals) == 0
161 obj.reverse()
162 return obj
163 if member == 'slice':
164 assert len(argvals) == 1
165 return obj[argvals[0]:]
166 if member == 'splice':
167 assert isinstance(obj, list)
168 index, howMany = argvals
169 res = []
170 for i in range(index, min(index + howMany, len(obj))):
171 res.append(obj.pop(index))
172 return res
173
174 return obj[member](argvals)
175
176 m = re.match(
177 r'(?P<in>%s)\[(?P<idx>.+)\]$' % _NAME_RE, expr)
178 if m:
179 val = local_vars[m.group('in')]
180 idx = self.interpret_expression(
181 m.group('idx'), local_vars, allow_recursion - 1)
182 return val[idx]
183
184 for op, opfunc in _OPERATORS:
185 m = re.match(r'(?P<x>.+?)%s(?P<y>.+)' % re.escape(op), expr)
186 if not m:
187 continue
188 x, abort = self.interpret_statement(
189 m.group('x'), local_vars, allow_recursion - 1)
190 if abort:
191 raise ExtractorError(
192 'Premature left-side return of %s in %r' % (op, expr))
193 y, abort = self.interpret_statement(
194 m.group('y'), local_vars, allow_recursion - 1)
195 if abort:
196 raise ExtractorError(
197 'Premature right-side return of %s in %r' % (op, expr))
198 return opfunc(x, y)
199
200 m = re.match(
201 r'^(?P<func>%s)\((?P<args>[a-zA-Z0-9_$,]+)\)$' % _NAME_RE, expr)
202 if m:
203 fname = m.group('func')
204 argvals = tuple([
205 int(v) if v.isdigit() else local_vars[v]
206 for v in m.group('args').split(',')])
207 if fname not in self._functions:
208 self._functions[fname] = self.extract_function(fname)
209 return self._functions[fname](argvals)
210
211 raise ExtractorError('Unsupported JS expression %r' % expr)
212
213 def extract_object(self, objname):
214 obj = {}
215 obj_m = re.search(
216 (r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) +
217 r'\s*(?P<fields>([a-zA-Z$0-9]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' +
218 r'\}\s*;',
219 self.code)
220 fields = obj_m.group('fields')
221 # Currently, it only supports function definitions
222 fields_m = re.finditer(
223 r'(?P<key>[a-zA-Z$0-9]+)\s*:\s*function'
224 r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
225 fields)
226 for f in fields_m:
227 argnames = f.group('args').split(',')
228 obj[f.group('key')] = self.build_function(argnames, f.group('code'))
229
230 return obj
231
232 def extract_function(self, funcname):
233 func_m = re.search(
234 r'''(?x)
235 (?:function\s+%s|[{;]%s\s*=\s*function)\s*
236 \((?P<args>[^)]*)\)\s*
237 \{(?P<code>[^}]+)\}''' % (
238 re.escape(funcname), re.escape(funcname)),
239 self.code)
240 if func_m is None:
241 raise ExtractorError('Could not find JS function %r' % funcname)
242 argnames = func_m.group('args').split(',')
243
244 return self.build_function(argnames, func_m.group('code'))
245
246 def call_function(self, funcname, *args):
247 f = self.extract_function(funcname)
248 return f(args)
249
250 def build_function(self, argnames, code):
251 def resf(args):
252 local_vars = dict(zip(argnames, args))
253 for stmt in code.split(';'):
254 res, abort = self.interpret_statement(stmt, local_vars)
255 if abort:
256 break
257 return res
258 return resf