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# SPDX-License-Identifier: AGPL-3.0-or-later
"""Calculate mathematical expressions using ack#eval
"""
import ast
import operator
from multiprocessing import Process, Queue
from flask_babel import gettext
from searx import settings
from searx.plugins import logger
name = "Basic Calculator"
description = gettext("Calculate mathematical expressions via the search bar")
default_on = False
preference_section = 'general'
plugin_id = 'calculator'
logger = logger.getChild(plugin_id)
operators = {
ast.Add: operator.add,
ast.Sub: operator.sub,
ast.Mult: operator.mul,
ast.Div: operator.truediv,
ast.Pow: operator.pow,
ast.BitXor: operator.xor,
ast.USub: operator.neg,
}
def _eval_expr(expr):
"""
>>> _eval_expr('2^6')
4
>>> _eval_expr('2**6')
64
>>> _eval_expr('1 + 2*3**(4^5) / (6 + -7)')
-5.0
"""
return _eval(ast.parse(expr, mode='eval').body)
def _eval(node):
if isinstance(node, ast.Constant) and isinstance(node.value, int):
return node.value
if isinstance(node, ast.BinOp):
return operators[type(node.op)](_eval(node.left), _eval(node.right))
if isinstance(node, ast.UnaryOp):
return operators[type(node.op)](_eval(node.operand))
raise TypeError(node)
def timeout_func(timeout, func, *args, **kwargs):
def handler(q: Queue, func, args, **kwargs): # pylint:disable=invalid-name
try:
q.put(func(*args, **kwargs))
except:
q.put(None)
raise
que = Queue()
p = Process(target=handler, args=(que, func, args), kwargs=kwargs)
p.start()
p.join(timeout=timeout)
ret_val = None
if not p.is_alive():
ret_val = que.get()
else:
logger.debug("terminate function after timeout is exceeded")
p.terminate()
p.join()
p.close()
return ret_val
def post_search(_request, search):
# don't run on public instances due to possible attack surfaces
if settings['server']['public_instance']:
return True
# only show the result of the expression on the first page
if search.search_query.pageno > 1:
return True
query = search.search_query.query
# in order to avoid DoS attacks with long expressions, ignore long expressions
if len(query) > 100:
return True
# replace commonly used math operators with their proper Python operator
query = query.replace("x", "*").replace(":", "/")
# only numbers and math operators are accepted
if any(str.isalpha(c) for c in query):
return True
# in python, powers are calculated via **
query_py_formatted = query.replace("^", "**")
# Prevent the runtime from being longer than 50 ms
result = timeout_func(0.05, _eval_expr, query_py_formatted)
if result is None:
return True
result = str(result)
if result != query:
search.result_container.answers['calculate'] = {'answer': f"{query} = {result}"}
return True
def is_allowed():
return not settings['server']['public_instance']
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