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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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