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package meter
import (
"fmt"
"os"
"sync"
"sync/atomic"
"time"
)
// Progress is an interface for a simple progress meter. Call
// `Start()` to begin reporting. `format` should include some kind of
// '%d' field, into which will be written the current count. A spinner
// and a CR character will be added automatically.
//
// Call `Inc()` every time the quantity of interest increases. Call
// `Stop()` to stop reporting. After an instance's `Stop()` method has
// been called, it may be reused (starting at value 0) by calling
// `Start()` again.
type Progress interface {
Start(format string)
Inc()
Add(delta int64)
Done()
}
var Spinners = []string{"|", "(", "<", "-", "<", "(", "|", ")", ">", "-", ">", ")"}
// progressMeter is a `Progress` that reports the current state every
// `period`.
type progressMeter struct {
lock sync.Mutex
format string
period time.Duration
lastShownCount int64
spinnerIndex int
// When `ticker` is changed, that tells the old goroutine that
// it's time to shut down.
ticker *time.Ticker
// `count` is updated atomically:
count int64
}
func NewProgressMeter(period time.Duration) Progress {
return &progressMeter{
period: period,
}
}
func (p *progressMeter) Start(format string) {
p.lock.Lock()
defer p.lock.Unlock()
p.format = format + " %s %s"
atomic.StoreInt64(&p.count, 0)
p.lastShownCount = -1
p.spinnerIndex = 0
ticker := time.NewTicker(p.period)
p.ticker = ticker
go func() {
for {
<-ticker.C
p.lock.Lock()
if p.ticker != ticker {
// We're done.
ticker.Stop()
p.lock.Unlock()
return
}
c := atomic.LoadInt64(&p.count)
var s string
if c == 0 {
p.spinnerIndex = (p.spinnerIndex + 1) % len(Spinners)
s = Spinners[p.spinnerIndex]
} else {
s = ""
}
fmt.Fprintf(os.Stderr, p.format, c, s, "\r")
p.lock.Unlock()
}
}()
}
func (p *progressMeter) Inc() {
atomic.AddInt64(&p.count, 1)
}
func (p *progressMeter) Add(delta int64) {
atomic.AddInt64(&p.count, delta)
}
func (p *progressMeter) Done() {
p.lock.Lock()
defer p.lock.Unlock()
p.ticker = nil
c := atomic.LoadInt64(&p.count)
fmt.Fprintf(os.Stderr, p.format, c, " ", "\n")
}
// NoProgressMeter is a `Progress` that doesn't actually report
// anything.
type NoProgressMeter struct{}
func (p *NoProgressMeter) Start(string) {}
func (p *NoProgressMeter) Inc() {}
func (p *NoProgressMeter) Add(int64) {}
func (p *NoProgressMeter) Done() {}
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