Commit e6bea2cf authored by Kirill Smelkov's avatar Kirill Smelkov

sync: New package that mirrors Go's sync

Add sync.Once and sync.WaitGroup.
parent e9567c7b
......@@ -182,6 +182,9 @@ handle concurrency in structured ways.
- `golang.context` provides contexts to propagate cancellation and task-scoped
values among spawned goroutines.
- `golang.sync` provides low-level primitives - for example
`sync.Once` and `sync.WaitGroup` - that are sometimes useful too.
See `Go Concurrency Patterns: Context`__ for overview of contexts.
__ https://blog.golang.org/context
......
# -*- coding: utf-8 -*-
# Copyright (C) 2019 Nexedi SA and Contributors.
# Kirill Smelkov <kirr@nexedi.com>
#
# This program is free software: you can Use, Study, Modify and Redistribute
# it under the terms of the GNU General Public License version 3, or (at your
# option) any later version, as published by the Free Software Foundation.
#
# You can also Link and Combine this program with other software covered by
# the terms of any of the Free Software licenses or any of the Open Source
# Initiative approved licenses and Convey the resulting work. Corresponding
# source of such a combination shall include the source code for all other
# software used.
#
# This program is distributed WITHOUT ANY WARRANTY; without even the implied
# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
#
# See COPYING file for full licensing terms.
# See https://www.nexedi.com/licensing for rationale and options.
"""Package sync mirrors Go package sync.
See the following link about Go sync package:
https://golang.org/pkg/sync
"""
import threading
from golang import panic
# Once allows to execute an action only once.
#
# For example:
#
# once = Once()
# ...
# once.do(doSomething)
class Once(object):
def __init__(once):
once._mu = threading.Lock()
once._done = False
def do(once, f):
with once._mu:
if not once._done:
once._done = True
f()
# WaitGroup allows to wait for collection of tasks to finish.
class WaitGroup(object):
def __init__(wg):
wg._mu = threading.Lock()
wg._count = 0
wg._event = threading.Event()
def done(wg):
wg.add(-1)
def add(wg, delta):
if delta == 0:
return
with wg._mu:
wg._count += delta
if wg._count < 0:
panic("sync: negative WaitGroup counter")
if wg._count == 0:
wg._event.set()
wg._event = threading.Event()
def wait(wg):
with wg._mu:
if wg._count == 0:
return
event = wg._event
event.wait()
# -*- coding: utf-8 -*-
# Copyright (C) 2019 Nexedi SA and Contributors.
# Kirill Smelkov <kirr@nexedi.com>
#
# This program is free software: you can Use, Study, Modify and Redistribute
# it under the terms of the GNU General Public License version 3, or (at your
# option) any later version, as published by the Free Software Foundation.
#
# You can also Link and Combine this program with other software covered by
# the terms of any of the Free Software licenses or any of the Open Source
# Initiative approved licenses and Convey the resulting work. Corresponding
# source of such a combination shall include the source code for all other
# software used.
#
# This program is distributed WITHOUT ANY WARRANTY; without even the implied
# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
#
# See COPYING file for full licensing terms.
# See https://www.nexedi.com/licensing for rationale and options.
from golang import go, chan, _PanicError
from golang import sync
import time
from pytest import raises
def test_once():
once = sync.Once()
l = []
def _():
l.append(1)
once.do(_)
assert l == [1]
once.do(_)
assert l == [1]
once.do(_)
assert l == [1]
once = sync.Once()
l = []
def _():
l.append(2)
raise RuntimeError()
with raises(RuntimeError):
once.do(_)
assert l == [2]
once.do(_) # no longer raises
assert l == [2]
once.do(_) # no longer raises
assert l == [2]
def test_waitgroup():
wg = sync.WaitGroup()
wg.add(2)
ch = chan(3)
def _():
wg.wait()
ch.send('a')
for i in range(3):
go(_)
wg.done()
assert len(ch) == 0
time.sleep(0.1)
assert len(ch) == 0
wg.done()
for i in range(3):
assert ch.recv() == 'a'
wg.add(1)
go(_)
time.sleep(0.1)
assert len(ch) == 0
wg.done()
assert ch.recv() == 'a'
with raises(_PanicError):
wg.done()
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