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from __future__ import unicode_literals
import re
from .utils import (
ExtractorError,
)
class JSInterpreter(object):
def __init__(self, code):
self.code = code
self._functions = {}
def interpret_statement(self, stmt, local_vars, allow_recursion=20):
if allow_recursion < 0:
raise ExtractorError('Recursion limit reached')
if stmt.startswith('var '):
stmt = stmt[len('var '):]
ass_m = re.match(r'^(?P<out>[a-z]+)(?:\[(?P<index>[^\]]+)\])?' +
r'=(?P<expr>.*)$', stmt)
if ass_m:
if ass_m.groupdict().get('index'):
def assign(val):
lvar = local_vars[ass_m.group('out')]
idx = self.interpret_expression(
ass_m.group('index'), local_vars, allow_recursion)
assert isinstance(idx, int)
lvar[idx] = val
return val
expr = ass_m.group('expr')
else:
def assign(val):
local_vars[ass_m.group('out')] = val
return val
expr = ass_m.group('expr')
elif stmt.startswith('return '):
assign = lambda v: v
expr = stmt[len('return '):]
else:
raise ExtractorError(
'Cannot determine left side of statement in %r' % stmt)
v = self.interpret_expression(expr, local_vars, allow_recursion)
return assign(v)
def interpret_expression(self, expr, local_vars, allow_recursion):
if expr.isdigit():
return int(expr)
if expr.isalpha():
return local_vars[expr]
m = re.match(r'^(?P<in>[a-z]+)\.(?P<member>.*)$', expr)
if m:
member = m.group('member')
val = local_vars[m.group('in')]
if member == 'split("")':
return list(val)
if member == 'join("")':
return ''.join(val)
if member == 'length':
return len(val)
if member == 'reverse()':
return val[::-1]
slice_m = re.match(r'slice\((?P<idx>.*)\)', member)
if slice_m:
idx = self.interpret_expression(
slice_m.group('idx'), local_vars, allow_recursion - 1)
return val[idx:]
m = re.match(
r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
if m:
val = local_vars[m.group('in')]
idx = self.interpret_expression(
m.group('idx'), local_vars, allow_recursion - 1)
return val[idx]
m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
if m:
a = self.interpret_expression(
m.group('a'), local_vars, allow_recursion)
b = self.interpret_expression(
m.group('b'), local_vars, allow_recursion)
return a % b
m = re.match(
r'^(?P<func>[a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr)
if m:
fname = m.group('func')
if fname not in self._functions:
self._functions[fname] = self.extract_function(fname)
argvals = [int(v) if v.isdigit() else local_vars[v]
for v in m.group('args').split(',')]
return self._functions[fname](argvals)
raise ExtractorError('Unsupported JS expression %r' % expr)
def extract_function(self, funcname):
func_m = re.search(
(r'(?:function %s|[{;]%s\s*=\s*function)' % (
re.escape(funcname), re.escape(funcname))) +
r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
self.code)
if func_m is None:
raise ExtractorError('Could not find JS function %r' % funcname)
argnames = func_m.group('args').split(',')
def resf(args):
local_vars = dict(zip(argnames, args))
for stmt in func_m.group('code').split(';'):
res = self.interpret_statement(stmt, local_vars)
return res
return resf
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