release 2017.11.06
[ytdl] / 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     remove_quotes,
10 )
11
12 _OPERATORS = [
13     ('|', operator.or_),
14     ('^', operator.xor),
15     ('&', operator.and_),
16     ('>>', operator.rshift),
17     ('<<', operator.lshift),
18     ('-', operator.sub),
19     ('+', operator.add),
20     ('%', operator.mod),
21     ('/', operator.truediv),
22     ('*', operator.mul),
23 ]
24 _ASSIGN_OPERATORS = [(op + '=', opfunc) for op, opfunc in _OPERATORS]
25 _ASSIGN_OPERATORS.append(('=', lambda cur, right: right))
26
27 _NAME_RE = r'[a-zA-Z_$][a-zA-Z_$0-9]*'
28
29
30 class JSInterpreter(object):
31     def __init__(self, code, objects=None):
32         if objects is None:
33             objects = {}
34         self.code = code
35         self._functions = {}
36         self._objects = objects
37
38     def interpret_statement(self, stmt, local_vars, allow_recursion=100):
39         if allow_recursion < 0:
40             raise ExtractorError('Recursion limit reached')
41
42         should_abort = False
43         stmt = stmt.lstrip()
44         stmt_m = re.match(r'var\s', stmt)
45         if stmt_m:
46             expr = stmt[len(stmt_m.group(0)):]
47         else:
48             return_m = re.match(r'return(?:\s+|$)', stmt)
49             if return_m:
50                 expr = stmt[len(return_m.group(0)):]
51                 should_abort = True
52             else:
53                 # Try interpreting it as an expression
54                 expr = stmt
55
56         v = self.interpret_expression(expr, local_vars, allow_recursion)
57         return v, should_abort
58
59     def interpret_expression(self, expr, local_vars, allow_recursion):
60         expr = expr.strip()
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<in>%s)\[(?P<idx>.+)\]$' % _NAME_RE, expr)
125         if m:
126             val = local_vars[m.group('in')]
127             idx = self.interpret_expression(
128                 m.group('idx'), local_vars, allow_recursion - 1)
129             return val[idx]
130
131         m = re.match(
132             r'(?P<var>%s)(?:\.(?P<member>[^(]+)|\[(?P<member2>[^]]+)\])\s*(?:\(+(?P<args>[^()]*)\))?$' % _NAME_RE,
133             expr)
134         if m:
135             variable = m.group('var')
136             member = remove_quotes(m.group('member') or m.group('member2'))
137             arg_str = m.group('args')
138
139             if variable in local_vars:
140                 obj = local_vars[variable]
141             else:
142                 if variable not in self._objects:
143                     self._objects[variable] = self.extract_object(variable)
144                 obj = self._objects[variable]
145
146             if arg_str is None:
147                 # Member access
148                 if member == 'length':
149                     return len(obj)
150                 return obj[member]
151
152             assert expr.endswith(')')
153             # Function call
154             if arg_str == '':
155                 argvals = tuple()
156             else:
157                 argvals = tuple([
158                     self.interpret_expression(v, local_vars, allow_recursion)
159                     for v in arg_str.split(',')])
160
161             if member == 'split':
162                 assert argvals == ('',)
163                 return list(obj)
164             if member == 'join':
165                 assert len(argvals) == 1
166                 return argvals[0].join(obj)
167             if member == 'reverse':
168                 assert len(argvals) == 0
169                 obj.reverse()
170                 return obj
171             if member == 'slice':
172                 assert len(argvals) == 1
173                 return obj[argvals[0]:]
174             if member == 'splice':
175                 assert isinstance(obj, list)
176                 index, howMany = argvals
177                 res = []
178                 for i in range(index, min(index + howMany, len(obj))):
179                     res.append(obj.pop(index))
180                 return res
181
182             return obj[member](argvals)
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(',')]) if len(m.group('args')) > 0 else tuple()
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         _FUNC_NAME_RE = r'''(?:[a-zA-Z$0-9]+|"[a-zA-Z$0-9]+"|'[a-zA-Z$0-9]+')'''
215         obj = {}
216         obj_m = re.search(
217             r'''(?x)
218                 (?<!this\.)%s\s*=\s*{\s*
219                     (?P<fields>(%s\s*:\s*function\s*\(.*?\)\s*{.*?}(?:,\s*)?)*)
220                 }\s*;
221             ''' % (re.escape(objname), _FUNC_NAME_RE),
222             self.code)
223         fields = obj_m.group('fields')
224         # Currently, it only supports function definitions
225         fields_m = re.finditer(
226             r'''(?x)
227                 (?P<key>%s)\s*:\s*function\s*\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}
228             ''' % _FUNC_NAME_RE,
229             fields)
230         for f in fields_m:
231             argnames = f.group('args').split(',')
232             obj[remove_quotes(f.group('key'))] = self.build_function(argnames, f.group('code'))
233
234         return obj
235
236     def extract_function(self, funcname):
237         func_m = re.search(
238             r'''(?x)
239                 (?:function\s+%s|[{;,]\s*%s\s*=\s*function|var\s+%s\s*=\s*function)\s*
240                 \((?P<args>[^)]*)\)\s*
241                 \{(?P<code>[^}]+)\}''' % (
242                 re.escape(funcname), re.escape(funcname), re.escape(funcname)),
243             self.code)
244         if func_m is None:
245             raise ExtractorError('Could not find JS function %r' % funcname)
246         argnames = func_m.group('args').split(',')
247
248         return self.build_function(argnames, func_m.group('code'))
249
250     def call_function(self, funcname, *args):
251         f = self.extract_function(funcname)
252         return f(args)
253
254     def build_function(self, argnames, code):
255         def resf(args):
256             local_vars = dict(zip(argnames, args))
257             for stmt in code.split(';'):
258                 res, abort = self.interpret_statement(stmt, local_vars)
259                 if abort:
260                     break
261             return res
262         return resf