181 lines
6.1 KiB
Python
181 lines
6.1 KiB
Python
from __future__ import unicode_literals
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import json
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import re
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from .utils import (
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ExtractorError,
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)
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class JSInterpreter(object):
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def __init__(self, code):
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self.code = code
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self._functions = {}
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self._objects = {}
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def interpret_statement(self, stmt, local_vars, allow_recursion=20):
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if allow_recursion < 0:
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raise ExtractorError('Recursion limit reached')
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if stmt.startswith('var '):
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stmt = stmt[len('var '):]
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ass_m = re.match(r'^(?P<out>[a-z]+)(?:\[(?P<index>[^\]]+)\])?' +
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r'=(?P<expr>.*)$', stmt)
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if ass_m:
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if ass_m.groupdict().get('index'):
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def assign(val):
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lvar = local_vars[ass_m.group('out')]
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idx = self.interpret_expression(
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ass_m.group('index'), local_vars, allow_recursion)
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assert isinstance(idx, int)
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lvar[idx] = val
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return val
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expr = ass_m.group('expr')
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else:
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def assign(val):
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local_vars[ass_m.group('out')] = val
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return val
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expr = ass_m.group('expr')
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elif stmt.startswith('return '):
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assign = lambda v: v
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expr = stmt[len('return '):]
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else:
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# Try interpreting it as an expression
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expr = stmt
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assign = lambda v: v
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v = self.interpret_expression(expr, local_vars, allow_recursion)
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return assign(v)
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def interpret_expression(self, expr, local_vars, allow_recursion):
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if expr.isdigit():
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return int(expr)
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if expr.isalpha():
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return local_vars[expr]
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try:
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return json.loads(expr)
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except ValueError:
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pass
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m = re.match(
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r'^(?P<var>[a-z]+)\.(?P<member>[^(]+)(?:\(+(?P<args>[^()]*)\))?$',
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expr)
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if m:
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variable = m.group('var')
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member = m.group('member')
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arg_str = m.group('args')
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if variable in local_vars:
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obj = local_vars[variable]
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else:
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if variable not in self._objects:
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self._objects[variable] = self.extract_object(variable)
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obj = self._objects[variable]
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if arg_str is None:
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# Member access
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if member == 'length':
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return len(obj)
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return obj[member]
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assert expr.endswith(')')
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# Function call
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if arg_str == '':
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argvals = tuple()
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else:
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argvals = tuple([
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self.interpret_expression(v, local_vars, allow_recursion)
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for v in arg_str.split(',')])
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if member == 'split':
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assert argvals == ('',)
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return list(obj)
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if member == 'join':
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assert len(argvals) == 1
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return argvals[0].join(obj)
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if member == 'reverse':
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assert len(argvals) == 0
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return obj[::-1]
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if member == 'slice':
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assert len(argvals) == 1
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return obj[argvals[0]:]
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if member == 'splice':
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assert isinstance(obj, list)
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index, howMany = argvals
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res = []
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for i in range(index, min(index + howMany, len(obj))):
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res.append(obj.pop(i))
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return res
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return obj[member](argvals)
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m = re.match(
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r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
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if m:
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val = local_vars[m.group('in')]
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idx = self.interpret_expression(
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m.group('idx'), local_vars, allow_recursion - 1)
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return val[idx]
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m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
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if m:
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a = self.interpret_expression(
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m.group('a'), local_vars, allow_recursion)
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b = self.interpret_expression(
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m.group('b'), local_vars, allow_recursion)
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return a % b
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m = re.match(
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r'^(?P<func>[.a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr)
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if m:
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fname = m.group('func')
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argvals = tuple([
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int(v) if v.isdigit() else local_vars[v]
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for v in m.group('args').split(',')])
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if fname not in self._functions:
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self._functions[fname] = self.extract_function(fname)
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return self._functions[fname](argvals)
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raise ExtractorError('Unsupported JS expression %r' % expr)
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def extract_object(self, objname):
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obj = {}
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obj_m = re.search(
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(r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) +
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r'\s*(?P<fields>([a-zA-Z$0-9]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' +
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r'\}\s*;',
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self.code)
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fields = obj_m.group('fields')
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# Currently, it only supports function definitions
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fields_m = re.finditer(
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r'(?P<key>[a-zA-Z$0-9]+)\s*:\s*function'
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r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
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fields)
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for f in fields_m:
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argnames = f.group('args').split(',')
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obj[f.group('key')] = self.build_function(argnames, f.group('code'))
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return obj
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def extract_function(self, funcname):
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func_m = re.search(
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(r'(?:function %s|[{;]%s\s*=\s*function)' % (
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re.escape(funcname), re.escape(funcname))) +
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r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
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self.code)
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if func_m is None:
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raise ExtractorError('Could not find JS function %r' % funcname)
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argnames = func_m.group('args').split(',')
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return self.build_function(argnames, func_m.group('code'))
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def build_function(self, argnames, code):
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def resf(args):
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local_vars = dict(zip(argnames, args))
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for stmt in code.split(';'):
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res = self.interpret_statement(stmt, local_vars)
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return res
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return resf
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