98 lines
1.5 KiB
Go
98 lines
1.5 KiB
Go
package fmsg
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import (
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"os"
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"sync"
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"sync/atomic"
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)
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var (
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wstate atomic.Bool
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dropped atomic.Uint64
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withhold = make(chan struct{}, 1)
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msgbuf = make(chan dOp, 64) // these ops are tiny so a large buffer is allocated for withholding output
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dequeueOnce sync.Once
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queueSync sync.WaitGroup
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)
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func dequeue() {
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go func() {
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for {
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select {
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case op := <-msgbuf:
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op.Do()
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queueSync.Done()
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case <-withhold:
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<-withhold
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}
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}
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}()
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}
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// queue submits ops to msgbuf but drops messages
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// when the buffer is full and dequeue is withholding
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func queue(op dOp) {
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queueSync.Add(1)
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select {
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case msgbuf <- op:
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default:
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// send the op anyway if not withholding
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// as dequeue will get to it eventually
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if !wstate.Load() {
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msgbuf <- op
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} else {
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queueSync.Done()
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// increment dropped message count
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dropped.Add(1)
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}
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}
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}
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type dOp interface{ Do() }
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func Exit(code int) {
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queueSync.Wait()
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os.Exit(code)
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}
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func Suspend() {
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dequeueOnce.Do(dequeue)
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if wstate.CompareAndSwap(false, true) {
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queueSync.Wait()
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withhold <- struct{}{}
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}
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}
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func Resume() {
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dequeueOnce.Do(dequeue)
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if wstate.CompareAndSwap(true, false) {
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withhold <- struct{}{}
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if d := dropped.Swap(0); d != 0 {
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Printf("dropped %d messages during withhold", d)
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}
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}
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}
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type dPrint []any
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func (v dPrint) Do() {
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std.Print(v...)
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}
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type dPrintf struct {
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format string
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v []any
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}
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func (d *dPrintf) Do() {
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std.Printf(d.format, d.v...)
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}
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type dPrintln []any
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func (v dPrintln) Do() {
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std.Println(v...)
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}
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