lasp_atomic.py

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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Provides a simple atomic variable:
 
>>> a = Atomic(0)
 
Retrieve the value
>>> b = a()
Set a new value:
>>> a <<= b
Get conversion to boolean:
>>> if a:
       do something
 
Atomic increment:
>>> A += 1
 
@author: J.A. de Jong - ASCEE
"""
from threading import Lock
 
 
class Atomic:
    """
    Implementation of atomic operations on integers and booleans.
 
    """
    def __init__(self, val):
        self.checkType(val)
        self._val = val
        self._lock = Lock()
 
    def checkType(self, val):
        if not (type(val) == bool or type(val) == int):
            raise RuntimeError("Invalid type for Atomic")
 
    def __iadd__(self, toadd):
        self.checkType(toadd)
        with self._lock:
            self._val += toadd
        return self
 
    def __isub__(self, toadd):
        self.checkType(toadd)
        with self._lock:
            self._val -= toadd
        return self
 
    def __bool__(self):
        with self._lock:
            return self._val
 
    def __ilshift__(self, other):
        self.checkType(other)
        with self._lock:
            self._val = other
        return self
 
    def __call__(self):
        with self._lock:
            return self._val