3e31ee9455
With the recent merging of embedded package imports and the entry CLI package, it is now possible for users to build in mcl code into a single binary. This additional permission makes it explicitly clear that this is permitted to make it easier for those users. The condition is phrased so that the terms can be "patched" by the original author if it's necessary for the project. For example, if the name of the language (mcl) changes, has a differently named new version, someone finds a phrasing improvement or a legal loophole, or for some other reasonable circumstance. Now go write some beautiful embedded tools!
124 lines
4.3 KiB
Go
124 lines
4.3 KiB
Go
// Mgmt
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// Copyright (C) 2013-2024+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//
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// Additional permission under GNU GPL version 3 section 7
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//
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// If you modify this program, or any covered work, by linking or combining it
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// with embedded mcl code and modules (and that the embedded mcl code and
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// modules which link with this program, contain a copy of their source code in
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// the authoritative form) containing parts covered by the terms of any other
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// license, the licensors of this program grant you additional permission to
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// convey the resulting work. Furthermore, the licensors of this program grant
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// the original author, James Shubin, additional permission to update this
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// additional permission if he deems it necessary to achieve the goals of this
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// additional permission.
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package util
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import (
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"context"
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"fmt"
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"sync"
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"time"
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)
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// BlockedTimer is a helper facility for printing log messages when you have a
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// possible deadlock. Alternatively, it can run an arbitrary function instead.
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// It does this by starting a timer, and if that timer isn't cancelled soon
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// enough, it executes the task. This is usually most useful before a select
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// statement which should ordinarily unblock rather quickly. It's helpful to
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// avoid unnecessary "waiting for select" log messages being constantly printed,
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// but should those block for longer, you'd definitely like to know where to
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// look first. This is safe for concurrent use. Multiple invocations of Printf
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// or Run are permitted. They each have their own separate countdown timers, but
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// are all cancelled when Cancel is run. It is safe to call Cancel multiple
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// times. If Cancel is called before Printf or Run, then those will never run. A
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// BlockedTimer must not be copied after first use.
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type BlockedTimer struct {
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// Duration specifies how long we should wait before we run (or print)
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// the function or message. The counter starts when that respective
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// function is run. For an easier method, specify the Seconds parameter
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// instead.
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Duration time.Duration
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// Seconds works exactly as Duration does, except it can be used as a
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// shorter method to accomplish the same thing. If this value is zero,
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// then Duration is used instead.
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Seconds int
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ctx context.Context
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cancel func()
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cancelled bool
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mutex sync.Mutex
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}
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// Printf will print as expected when the timer expires if Cancel isn't run
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// first. This can be used multiple times.
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func (obj *BlockedTimer) Printf(format string, v ...interface{}) {
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f := func() {
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// safe Logf in case f.String contains %? chars...
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s := fmt.Sprintf(format, v...)
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fmt.Printf("%s", s)
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}
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obj.Run(f)
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}
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// Run will run the passed function as expected when the timer expires if Cancel
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// isn't run first. This can be used multiple times.
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func (obj *BlockedTimer) Run(f func()) {
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obj.mutex.Lock()
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defer obj.mutex.Unlock()
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if obj.cancelled { // we already cancelled
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return
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}
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if obj.cancel == nil { // only do it once
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obj.ctx, obj.cancel = context.WithCancel(context.Background())
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}
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d := time.Duration(obj.Seconds) * time.Second
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if obj.Seconds == 0 {
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d = obj.Duration
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}
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go func() {
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select {
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case <-time.After(d):
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// print!
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case <-obj.ctx.Done():
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// cancel the print
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return
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}
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f() // run it
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}()
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}
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// Cancel cancels the execution of any Run or Printf functions. It is safe to
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// call it multiple times. It is important to call this at least once (on defer
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// for example) if you've used either Printf or Run, because otherwise you will
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// leak goroutines.
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func (obj *BlockedTimer) Cancel() {
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obj.mutex.Lock()
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defer obj.mutex.Unlock()
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obj.cancelled = true
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if obj.cancel == nil { // race! never let it run
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return
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}
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obj.cancel()
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}
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