_ Git - youtube-dl/blob - youtube_dl/jsinterp.py

   1 from __future__ import unicode_literals
   2
   3 import re
   4
   5 from .utils import (
   6     ExtractorError,
   7 )
   8
   9
  10 class JSInterpreter(object):
  11     def __init__(self, code):
  12         self.code = code
  13         self._functions = {}
  14         self._objects = {}
  15
  16     def interpret_statement(self, stmt, local_vars, allow_recursion=20):
  17         if allow_recursion < 0:
  18             raise ExtractorError('Recursion limit reached')
  19
  20         if stmt.startswith('var '):
  21             stmt = stmt[len('var '):]
  22         ass_m = re.match(r'^(?P<out>[a-z]+)(?:\[(?P<index>[^\]]+)\])?' +
  23                          r'=(?P<expr>.*)$', stmt)
  24         if ass_m:
  25             if ass_m.groupdict().get('index'):
  26                 def assign(val):
  27                     lvar = local_vars[ass_m.group('out')]
  28                     idx = self.interpret_expression(
  29                         ass_m.group('index'), local_vars, allow_recursion)
  30                     assert isinstance(idx, int)
  31                     lvar[idx] = val
  32                     return val
  33                 expr = ass_m.group('expr')
  34             else:
  35                 def assign(val):
  36                     local_vars[ass_m.group('out')] = val
  37                     return val
  38                 expr = ass_m.group('expr')
  39         elif stmt.startswith('return '):
  40             assign = lambda v: v
  41             expr = stmt[len('return '):]
  42         else:
  43             raise ExtractorError(
  44                 'Cannot determine left side of statement in %r' % stmt)
  45
  46         v = self.interpret_expression(expr, local_vars, allow_recursion)
  47         return assign(v)
  48
  49     def interpret_expression(self, expr, local_vars, allow_recursion):
  50         if expr.isdigit():
  51             return int(expr)
  52
  53         if expr.isalpha():
  54             return local_vars[expr]
  55
  56         m = re.match(r'^(?P<in>[a-z]+)\.(?P<member>.*)$', expr)
  57         if m:
  58             member = m.group('member')
  59             variable = m.group('in')
  60
  61             if variable not in local_vars:
  62                 if variable not in self._objects:
  63                     self._objects[variable] = self.extract_object(variable)
  64                 obj = self._objects[variable]
  65                 key, args = member.split('(', 1)
  66                 args = args.strip(')')
  67                 argvals = [int(v) if v.isdigit() else local_vars[v]
  68                            for v in args.split(',')]
  69                 return obj[key](argvals)
  70
  71             val = local_vars[variable]
  72             if member == 'split("")':
  73                 return list(val)
  74             if member == 'join("")':
  75                 return ''.join(val)
  76             if member == 'length':
  77                 return len(val)
  78             if member == 'reverse()':
  79                 return val[::-1]
  80             slice_m = re.match(r'slice\((?P<idx>.*)\)', member)
  81             if slice_m:
  82                 idx = self.interpret_expression(
  83                     slice_m.group('idx'), local_vars, allow_recursion - 1)
  84                 return val[idx:]
  85
  86         m = re.match(
  87             r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
  88         if m:
  89             val = local_vars[m.group('in')]
  90             idx = self.interpret_expression(
  91                 m.group('idx'), local_vars, allow_recursion - 1)
  92             return val[idx]
  93
  94         m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
  95         if m:
  96             a = self.interpret_expression(
  97                 m.group('a'), local_vars, allow_recursion)
  98             b = self.interpret_expression(
  99                 m.group('b'), local_vars, allow_recursion)
 100             return a % b
 101
 102         m = re.match(
 103             r'^(?P<func>[a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr)
 104         if m:
 105             fname = m.group('func')
 106             if fname not in self._functions:
 107                 self._functions[fname] = self.extract_function(fname)
 108             argvals = [int(v) if v.isdigit() else local_vars[v]
 109                        for v in m.group('args').split(',')]
 110             return self._functions[fname](argvals)
 111         raise ExtractorError('Unsupported JS expression %r' % expr)
 112
 113     def extract_object(self, objname):
 114         obj = {}
 115         obj_m = re.search(
 116             (r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) +
 117             r'\s*(?P<fields>([a-zA-Z$]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' +
 118             r'\}\s*;',
 119             self.code)
 120         fields = obj_m.group('fields')
 121         # Currently, it only supports function definitions
 122         fields_m = re.finditer(
 123             r'(?P<key>[a-zA-Z$]+)\s*:\s*function'
 124             r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
 125             fields)
 126         for f in fields_m:
 127             argnames = f.group('args').split(',')
 128             obj[f.group('key')] = self.build_function(argnames, f.group('code'))
 129
 130         return obj
 131
 132     def extract_function(self, funcname):
 133         func_m = re.search(
 134             (r'(?:function %s|[{;]%s\s*=\s*function)' % (
 135                 re.escape(funcname), re.escape(funcname))) +
 136             r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
 137             self.code)
 138         if func_m is None:
 139             raise ExtractorError('Could not find JS function %r' % funcname)
 140         argnames = func_m.group('args').split(',')
 141
 142         return self.build_function(argnames, func_m.group('code'))
 143
 144     def build_function(self, argnames, code):
 145         def resf(args):
 146             local_vars = dict(zip(argnames, args))
 147             for stmt in code.split(';'):
 148                 res = self.interpret_statement(stmt, local_vars)
 149             return res
 150         return resf