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from __future__ import unicode_literals
import json
import re
from .utils import (
ExtractorError,
)
class JSInterpreter(object):
def __init__(self, code):
self.code = code
self._functions = {}
self._objects = {}
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:
# Try interpreting it as an expression
expr = stmt
assign = lambda v: v
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]
try:
return json.loads(expr)
except ValueError:
pass
m = re.match(
r'^(?P<var>[a-z]+)\.(?P<member>[^(]+)(?:\(+(?P<args>[^()]*)\))?$',
expr)
if m:
variable = m.group('var')
member = m.group('member')
arg_str = m.group('args')
if variable in local_vars:
obj = local_vars[variable]
else:
if variable not in self._objects:
self._objects[variable] = self.extract_object(variable)
obj = self._objects[variable]
if arg_str is None:
# Member access
if member == 'length':
return len(obj)
return obj[member]
assert expr.endswith(')')
# Function call
if arg_str == '':
argvals = tuple()
else:
argvals = tuple([
self.interpret_expression(v, local_vars, allow_recursion)
for v in arg_str.split(',')])
if member == 'split':
assert argvals == ('',)
return list(obj)
if member == 'join':
assert len(argvals) == 1
return argvals[0].join(obj)
if member == 'reverse':
assert len(argvals) == 0
obj.reverse()
return obj
if member == 'slice':
assert len(argvals) == 1
return obj[argvals[0]:]
if member == 'splice':
assert isinstance(obj, list)
index, howMany = argvals
res = []
for i in range(index, min(index + howMany, len(obj))):
res.append(obj.pop(i))
return res
return obj[member](argvals)
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')
argvals = tuple([
int(v) if v.isdigit() else local_vars[v]
for v in m.group('args').split(',')])
if fname not in self._functions:
self._functions[fname] = self.extract_function(fname)
return self._functions[fname](argvals)
raise ExtractorError('Unsupported JS expression %r' % expr)
def extract_object(self, objname):
obj = {}
obj_m = re.search(
(r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) +
r'\s*(?P<fields>([a-zA-Z$0-9]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' +
r'\}\s*;',
self.code)
fields = obj_m.group('fields')
# Currently, it only supports function definitions
fields_m = re.finditer(
r'(?P<key>[a-zA-Z$0-9]+)\s*:\s*function'
r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
fields)
for f in fields_m:
argnames = f.group('args').split(',')
obj[f.group('key')] = self.build_function(argnames, f.group('code'))
return obj
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(',')
return self.build_function(argnames, func_m.group('code'))
def build_function(self, argnames, code):
def resf(args):
local_vars = dict(zip(argnames, args))
for stmt in code.split(';'):
res = self.interpret_statement(stmt, local_vars)
return res
return resf
|
