117 lines
4.1 KiB
Python
117 lines
4.1 KiB
Python
from __future__ import unicode_literals
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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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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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raise ExtractorError(
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'Cannot determine left side of statement in %r' % stmt)
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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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m = re.match(r'^(?P<in>[a-z]+)\.(?P<member>.*)$', expr)
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if m:
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member = m.group('member')
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val = local_vars[m.group('in')]
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if member == 'split("")':
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return list(val)
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if member == 'join("")':
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return ''.join(val)
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if member == 'length':
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return len(val)
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if member == 'reverse()':
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return val[::-1]
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slice_m = re.match(r'slice\((?P<idx>.*)\)', member)
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if slice_m:
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idx = self.interpret_expression(
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slice_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<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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if fname not in self._functions:
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self._functions[fname] = self.extract_function(fname)
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argvals = [int(v) if v.isdigit() else local_vars[v]
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for v in m.group('args').split(',')]
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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_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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def resf(args):
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local_vars = dict(zip(argnames, args))
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for stmt in func_m.group('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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