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263 lines
9.0 KiB
Python
263 lines
9.0 KiB
Python
from __future__ import unicode_literals
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import json
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import operator
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import re
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from .utils import (
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ExtractorError,
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remove_quotes,
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)
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_OPERATORS = [
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('|', operator.or_),
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('^', operator.xor),
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('&', operator.and_),
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('>>', operator.rshift),
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('<<', operator.lshift),
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('-', operator.sub),
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('+', operator.add),
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('%', operator.mod),
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('/', operator.truediv),
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('*', operator.mul),
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]
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_ASSIGN_OPERATORS = [(op + '=', opfunc) for op, opfunc in _OPERATORS]
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_ASSIGN_OPERATORS.append(('=', lambda cur, right: right))
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_NAME_RE = r'[a-zA-Z_$][a-zA-Z_$0-9]*'
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class JSInterpreter(object):
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def __init__(self, code, objects=None):
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if objects is None:
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objects = {}
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self.code = code
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self._functions = {}
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self._objects = objects
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def interpret_statement(self, stmt, local_vars, allow_recursion=100):
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if allow_recursion < 0:
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raise ExtractorError('Recursion limit reached')
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should_abort = False
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stmt = stmt.lstrip()
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stmt_m = re.match(r'var\s', stmt)
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if stmt_m:
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expr = stmt[len(stmt_m.group(0)):]
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else:
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return_m = re.match(r'return(?:\s+|$)', stmt)
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if return_m:
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expr = stmt[len(return_m.group(0)):]
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should_abort = True
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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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v = self.interpret_expression(expr, local_vars, allow_recursion)
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return v, should_abort
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def interpret_expression(self, expr, local_vars, allow_recursion):
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expr = expr.strip()
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if expr == '': # Empty expression
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return None
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if expr.startswith('('):
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parens_count = 0
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for m in re.finditer(r'[()]', expr):
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if m.group(0) == '(':
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parens_count += 1
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else:
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parens_count -= 1
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if parens_count == 0:
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sub_expr = expr[1:m.start()]
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sub_result = self.interpret_expression(
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sub_expr, local_vars, allow_recursion)
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remaining_expr = expr[m.end():].strip()
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if not remaining_expr:
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return sub_result
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else:
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expr = json.dumps(sub_result) + remaining_expr
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break
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else:
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raise ExtractorError('Premature end of parens in %r' % expr)
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for op, opfunc in _ASSIGN_OPERATORS:
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m = re.match(r'''(?x)
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(?P<out>%s)(?:\[(?P<index>[^\]]+?)\])?
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\s*%s
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(?P<expr>.*)$''' % (_NAME_RE, re.escape(op)), expr)
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if not m:
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continue
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right_val = self.interpret_expression(
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m.group('expr'), local_vars, allow_recursion - 1)
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if m.groupdict().get('index'):
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lvar = local_vars[m.group('out')]
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idx = self.interpret_expression(
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m.group('index'), local_vars, allow_recursion)
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assert isinstance(idx, int)
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cur = lvar[idx]
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val = opfunc(cur, right_val)
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lvar[idx] = val
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return val
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else:
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cur = local_vars.get(m.group('out'))
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val = opfunc(cur, right_val)
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local_vars[m.group('out')] = val
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return val
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if expr.isdigit():
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return int(expr)
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var_m = re.match(
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r'(?!if|return|true|false)(?P<name>%s)$' % _NAME_RE,
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expr)
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if var_m:
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return local_vars[var_m.group('name')]
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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<in>%s)\[(?P<idx>.+)\]$' % _NAME_RE, 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(
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r'(?P<var>%s)(?:\.(?P<member>[^(]+)|\[(?P<member2>[^]]+)\])\s*(?:\(+(?P<args>[^()]*)\))?$' % _NAME_RE,
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expr)
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if m:
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variable = m.group('var')
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member = remove_quotes(m.group('member') or m.group('member2'))
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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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obj.reverse()
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return obj
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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(index))
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return res
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return obj[member](argvals)
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for op, opfunc in _OPERATORS:
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m = re.match(r'(?P<x>.+?)%s(?P<y>.+)' % re.escape(op), expr)
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if not m:
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continue
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x, abort = self.interpret_statement(
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m.group('x'), local_vars, allow_recursion - 1)
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if abort:
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raise ExtractorError(
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'Premature left-side return of %s in %r' % (op, expr))
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y, abort = self.interpret_statement(
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m.group('y'), local_vars, allow_recursion - 1)
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if abort:
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raise ExtractorError(
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'Premature right-side return of %s in %r' % (op, expr))
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return opfunc(x, y)
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m = re.match(
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r'^(?P<func>%s)\((?P<args>[a-zA-Z0-9_$,]*)\)$' % _NAME_RE, 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(',')]) if len(m.group('args')) > 0 else tuple()
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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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_FUNC_NAME_RE = r'''(?:[a-zA-Z$0-9]+|"[a-zA-Z$0-9]+"|'[a-zA-Z$0-9]+')'''
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obj = {}
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obj_m = re.search(
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r'''(?x)
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(?<!this\.)%s\s*=\s*{\s*
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(?P<fields>(%s\s*:\s*function\s*\(.*?\)\s*{.*?}(?:,\s*)?)*)
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}\s*;
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''' % (re.escape(objname), _FUNC_NAME_RE),
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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'''(?x)
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(?P<key>%s)\s*:\s*function\s*\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}
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''' % _FUNC_NAME_RE,
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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[remove_quotes(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'''(?x)
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(?:function\s+%s|[{;,]\s*%s\s*=\s*function|var\s+%s\s*=\s*function)\s*
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\((?P<args>[^)]*)\)\s*
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\{(?P<code>[^}]+)\}''' % (
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re.escape(funcname), re.escape(funcname), re.escape(funcname)),
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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 call_function(self, funcname, *args):
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f = self.extract_function(funcname)
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return f(args)
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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, abort = self.interpret_statement(stmt, local_vars)
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if abort:
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break
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return res
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return resf
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