_ Git - youtube-dl/blob - 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-z]+)\.(?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                 return obj[::-1]
 102             if member == 'slice':
 103                 assert len(argvals) == 1
 104                 return obj[argvals[0]:]
 105             if member == 'splice':
 106                 assert isinstance(obj, list)
 107                 index, howMany = argvals
 108                 res = []
 109                 for i in range(index, min(index + howMany, len(obj))):
 110                     res.append(obj.pop(i))
 111                 return res
 112
 113             return obj[member](argvals)
 114
 115         m = re.match(
 116             r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
 117         if m:
 118             val = local_vars[m.group('in')]
 119             idx = self.interpret_expression(
 120                 m.group('idx'), local_vars, allow_recursion - 1)
 121             return val[idx]
 122
 123         m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
 124         if m:
 125             a = self.interpret_expression(
 126                 m.group('a'), local_vars, allow_recursion)
 127             b = self.interpret_expression(
 128                 m.group('b'), local_vars, allow_recursion)
 129             return a % b
 130
 131         m = re.match(
 132             r'^(?P<func>[.a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr)
 133         if m:
 134             fname = m.group('func')
 135             argvals = tuple([
 136                 int(v) if v.isdigit() else local_vars[v]
 137                 for v in m.group('args').split(',')])
 138             if fname not in self._functions:
 139                 self._functions[fname] = self.extract_function(fname)
 140             return self._functions[fname](argvals)
 141         raise ExtractorError('Unsupported JS expression %r' % expr)
 142
 143     def extract_object(self, objname):
 144         obj = {}
 145         obj_m = re.search(
 146             (r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) +
 147             r'\s*(?P<fields>([a-zA-Z$0-9]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' +
 148             r'\}\s*;',
 149             self.code)
 150         fields = obj_m.group('fields')
 151         # Currently, it only supports function definitions
 152         fields_m = re.finditer(
 153             r'(?P<key>[a-zA-Z$0-9]+)\s*:\s*function'
 154             r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
 155             fields)
 156         for f in fields_m:
 157             argnames = f.group('args').split(',')
 158             obj[f.group('key')] = self.build_function(argnames, f.group('code'))
 159
 160         return obj
 161
 162     def extract_function(self, funcname):
 163         func_m = re.search(
 164             (r'(?:function %s|[{;]%s\s*=\s*function)' % (
 165                 re.escape(funcname), re.escape(funcname))) +
 166             r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
 167             self.code)
 168         if func_m is None:
 169             raise ExtractorError('Could not find JS function %r' % funcname)
 170         argnames = func_m.group('args').split(',')
 171
 172         return self.build_function(argnames, func_m.group('code'))
 173
 174     def build_function(self, argnames, code):
 175         def resf(args):
 176             local_vars = dict(zip(argnames, args))
 177             for stmt in code.split(';'):
 178                 res = self.interpret_statement(stmt, local_vars)
 179             return res
 180         return resf