restic/internal/ui/progress/counter.go

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package progress
import (
"os"
"sync"
"sync/atomic"
"time"
"github.com/restic/restic/internal/debug"
)
// A Func is a callback for a Counter.
//
// The final argument is true if Counter.Done has been called,
// which means that the current call will be the last.
type Func func(value uint64, runtime time.Duration, final bool)
// A Counter tracks a running count and controls a goroutine that passes its
// value periodically to a Func.
//
// The Func is also called when SIGUSR1 (or SIGINFO, on BSD) is received.
type Counter struct {
report Func
start time.Time
stopped chan struct{} // Closed by run.
stop chan struct{} // Close to stop run.
tick *time.Ticker
value uint64
}
// New starts a new Counter.
func New(interval time.Duration, report Func) *Counter {
signals.Once.Do(func() {
signals.ch = make(chan os.Signal, 1)
setupSignals()
})
c := &Counter{
report: report,
start: time.Now(),
stopped: make(chan struct{}),
stop: make(chan struct{}),
tick: time.NewTicker(interval),
}
go c.run()
return c
}
// Add v to the Counter. This method is concurrency-safe.
func (c *Counter) Add(v uint64) {
if c == nil {
return
}
atomic.AddUint64(&c.value, v)
}
// Done tells a Counter to stop and waits for it to report its final value.
func (c *Counter) Done() {
if c == nil {
return
}
c.tick.Stop()
close(c.stop)
<-c.stopped // Wait for last progress report.
*c = Counter{} // Prevent reuse.
}
func (c *Counter) get() uint64 { return atomic.LoadUint64(&c.value) }
func (c *Counter) run() {
defer close(c.stopped)
defer func() {
// Must be a func so that time.Since isn't called at defer time.
c.report(c.get(), time.Since(c.start), true)
}()
for {
var now time.Time
select {
case now = <-c.tick.C:
case sig := <-signals.ch:
debug.Log("Signal received: %v\n", sig)
now = time.Now()
case <-c.stop:
return
}
c.report(c.get(), now.Sub(c.start), false)
}
}
// XXX The fact that signals is a single global variable means that only one
// Counter receives each incoming signal.
var signals struct {
ch chan os.Signal
sync.Once
}