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dynduration.go
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dynduration.go
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// Copyright 2015 Michal Witkowski. All Rights Reserved.
// See LICENSE for licensing terms.
package flagz
import (
"fmt"
"sync/atomic"
"time"
flag "github.com/spf13/pflag"
)
// DynDuration creates a `Flag` that represents `time.Duration` which is safe to change dynamically at runtime.
func DynDuration(flagSet *flag.FlagSet, name string, value time.Duration, usage string) *DynDurationValue {
dynValue := &DynDurationValue{ptr: (*int64)(&value)}
flag := flagSet.VarPF(dynValue, name, "", usage)
MarkFlagDynamic(flag)
return dynValue
}
// DynDurationValue is a flag-related `time.Duration` value wrapper.
type DynDurationValue struct {
ptr *int64
validator func(time.Duration) error
notifier func(oldValue time.Duration, newValue time.Duration)
}
// Get retrieves the value in a thread-safe manner.
func (d *DynDurationValue) Get() time.Duration {
return (time.Duration)(atomic.LoadInt64(d.ptr))
}
// Set updates the value from a string representation in a thread-safe manner.
// This operation may return an error if the provided `input` doesn't parse, or the resulting value doesn't pass an
// optional validator.
// If a notifier is set on the value, it will be invoked in a separate go-routine.
func (d *DynDurationValue) Set(input string) error {
v, err := time.ParseDuration(input)
if err != nil {
return err
}
if d.validator != nil {
if err := d.validator(v); err != nil {
return err
}
}
oldPtr := atomic.SwapInt64(d.ptr, (int64)(v))
if d.notifier != nil {
go d.notifier((time.Duration)(oldPtr), v)
}
return nil
}
// WithValidator adds a function that checks values before they're set.
// Any error returned by the validator will lead to the value being rejected.
// Validators are executed on the same go-routine as the call to `Set`.
func (d *DynDurationValue) WithValidator(validator func(time.Duration) error) *DynDurationValue {
d.validator = validator
return d
}
// WithNotifier adds a function is called every time a new value is successfully set.
// Each notifier is executed in a new go-routine.
func (d *DynDurationValue) WithNotifier(notifier func(oldValue time.Duration, newValue time.Duration)) *DynDurationValue {
d.notifier = notifier
return d
}
// Type is an indicator of what this flag represents.
func (d *DynDurationValue) Type() string {
return "dyn_duration"
}
// String represents the canonical representation of the type.
func (d *DynDurationValue) String() string {
return fmt.Sprintf("%v", d.Get())
}