_ Git - youtube-dl/blob - 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