]> git.bitcoin.ninja Git - youtube-dl/blob - youtube_dl/jsinterp.py
Merge branch 'lecture2go' of https://github.com/nichdu/youtube-dl into nichdu-lecture2go
[youtube-dl] / 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