package usync

import "sync"

// Locker guards access to a value
type Locker[T any] struct {
	value T
	mutex sync.Mutex
}

// NewLocker creates a new locker with the specified value.
func NewLocker[T any] (value T) Locker[T] {
	return Locker[T] {
		value: value,
	}
}

// Set sets the value of the locker.
func (this *Locker[T]) Set (value T) {
	this.mutex.Lock()
	defer this.mutex.Unlock()
	this.value = value
}

// Borrow borrows the value from the locker, and returns a function that must
// immediately be deferred, like this:
//
//   value, done := locker.Borrow()
//   defer done()
//
// From the time Borrow is called to the time the done function is called, it is
// safe to access the locked object from within the current goroutine.
func (this *Locker[T]) Borrow () (T, func ()) {
	this.mutex.Lock()
	return this.value, this.mutex.Unlock
}