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package com
import (
"context"
"github.com/icinga/icingadb/pkg/contracts"
"golang.org/x/sync/errgroup"
)
// WaitAsync calls Wait() on the passed Waiter in a new goroutine and
// sends the first non-nil error (if any) to the returned channel.
// The returned channel is always closed when the Waiter is done.
func WaitAsync(w contracts.Waiter) <-chan error {
errs := make(chan error, 1)
go func() {
defer close(errs)
if e := w.Wait(); e != nil {
errs <- e
}
}()
return errs
}
// ErrgroupReceive adds a goroutine to the specified group that
// returns the first non-nil error (if any) from the specified channel.
// If the channel is closed, it will return nil.
func ErrgroupReceive(g *errgroup.Group, err <-chan error) {
g.Go(func() error {
if e := <-err; e != nil {
return e
}
return nil
})
}
// CopyFirst asynchronously forwards all items from input to forward and synchronously returns the first item.
func CopyFirst(
ctx context.Context, input <-chan contracts.Entity,
) (first contracts.Entity, forward <-chan contracts.Entity, err error) {
var ok bool
select {
case <-ctx.Done():
return nil, nil, ctx.Err()
case first, ok = <-input:
}
if !ok {
return
}
// Buffer of one because we receive an entity and send it back immediately.
fwd := make(chan contracts.Entity, 1)
fwd <- first
forward = fwd
go func() {
defer close(fwd)
for {
select {
case <-ctx.Done():
return
case e, ok := <-input:
if !ok {
return
}
select {
case <-ctx.Done():
return
case fwd <- e:
}
}
}
}()
return
}
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