string.go

/*
This file was auto-generated. Do not modify it, lest your changes be overwritten.
*/

package oncecell

import (
	"errors"
	"sync/atomic"
)

// OnceString wraps a string and enforces at runtime that the value is set at most once.
type OnceString struct {
	value string
	isSet uint32
}

// SetValue sets the value of the string to the provided value.
// This function will return an error if called more than once.
// This is thread-safe as the isSet flag is atomically set, thus ensuring that no two
// callers can check the flag at the same time.
func (o *OnceString) SetValue(value string) error {
	if atomic.CompareAndSwapUint32(&o.isSet, 0, 1) {
		o.value = value
		return nil
	} else {
		return errors.New(setErrorMsg)
	}
}

// Value returns the value stored in the cell or an error if it has not yet been set
func (o *OnceString) Value() (retval string, err error) {
	if atomic.LoadUint32(&o.isSet) == 1 {
		retval = o.value
	} else {
		err = errors.New(getErrorMsg)
	}
	return
}

// MustSetValue sets the value of the string to the provided value.
// This function will panic if the value has already been set
// This is thread-safe as the isSet flag is atomically set, thus ensuring that no two
// callers can check the flag at the same time.
func (o *OnceString) MustSetValue(value string) {
	if atomic.CompareAndSwapUint32(&o.isSet, 0, 1) {
		o.value = value
	} else {
		panic(setErrorMsg)
	}
}

// MustValue returns the value stored in the cell or panics if it has not yet been set
func (o *OnceString) MustValue() string {
	if atomic.LoadUint32(&o.isSet) == 1 {
		return o.value
	} else {
		panic(getErrorMsg)
	}
}