abool/bool.go

// Package abool provides atomic Boolean type for cleaner code and
// better performance.
package abool

import (
	"encoding/json"
	"errors"
	"fmt"
	"sync/atomic"
)

// New creates an AtomicBool with default set to false.
func New() *AtomicBool {
	return new(AtomicBool)
}

// NewBool creates an AtomicBool with given default value.
func NewBool(ok bool) *AtomicBool {
	ab := New()
	if ok {
		ab.Set()
	}
	return ab
}

// AtomicBool is an atomic Boolean.
// Its methods are all atomic, thus safe to be called by multiple goroutines simultaneously.
// Note: When embedding into a struct one should always use *AtomicBool to avoid copy.
type AtomicBool int32

// Set sets the Boolean to true.
func (ab *AtomicBool) Set() {
	atomic.StoreInt32((*int32)(ab), 1)
}

// UnSet sets the Boolean to false.
func (ab *AtomicBool) UnSet() {
	atomic.StoreInt32((*int32)(ab), 0)
}

// IsSet returns whether the Boolean is true.
func (ab *AtomicBool) IsSet() bool {
	return atomic.LoadInt32((*int32)(ab))&1 == 1
}

// IsNotSet returns whether the Boolean is false.
func (ab *AtomicBool) IsNotSet() bool {
	return !ab.IsSet()
}

// SetTo sets the boolean with given Boolean.
func (ab *AtomicBool) SetTo(yes bool) {
	if yes {
		atomic.StoreInt32((*int32)(ab), 1)
	} else {
		atomic.StoreInt32((*int32)(ab), 0)
	}
}

// Toggle inverts the Boolean then returns the value before inverting.
func (ab *AtomicBool) Toggle() bool {
	return atomic.AddInt32((*int32)(ab), 1)&1 == 0
}

// SetToIf sets the Boolean to new only if the Boolean matches the old.
// Returns whether the set was done.
func (ab *AtomicBool) SetToIf(old, new bool) (set bool) {
	var o, n int32
	if old {
		o = 1
	}
	if new {
		n = 1
	}
	return atomic.CompareAndSwapInt32((*int32)(ab), o, n)
}

// Marshal an AtomicBool into JSON like a normal bool
func (ab *AtomicBool) MarshalJSON() ([]byte, error) {
	return json.Marshal(ab.IsSet())
}

// Unmarshall normal bool's into AtomicBool
func (ab *AtomicBool) UnmarshalJSON(b []byte) error {
	var v interface{}
	if err := json.Unmarshal(b, &v); err != nil {
		return err
	}

	switch value := v.(type) {
	case bool:
		ab.SetTo(value)
		return nil
	default:
		return errors.New(fmt.Sprintf("%s is an invalid JSON representation for an AtomicBool\n", b))
	}
}