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package atomics
import "sync"
// State provides user-friendly means of performing atomic-like
// operations on a uint32 state, and allowing callbacks on successful
// state change. This is a bit of a misnomer being where it is, as it
// actually uses a mutex under-the-hood.
type State struct {
mutex sync.Mutex
state uint32
}
// Store will update State value safely within mutex lock.
func (st *State) Store(val uint32) {
st.mutex.Lock()
st.state = val
st.mutex.Unlock()
}
// Load will get value of State safely within mutex lock.
func (st *State) Load() uint32 {
st.mutex.Lock()
state := st.state
st.mutex.Unlock()
return state
}
// WithLock performs fn within State mutex lock, useful if you want
// to just use State's mutex for locking instead of creating another.
func (st *State) WithLock(fn func()) {
st.mutex.Lock()
defer st.mutex.Unlock()
fn()
}
// Update performs fn within State mutex lock, with the current state
// value provided as an argument, and return value used to update state.
func (st *State) Update(fn func(state uint32) uint32) {
st.mutex.Lock()
defer st.mutex.Unlock()
st.state = fn(st.state)
}
// CAS performs a compare-and-swap on State, calling fn on success. Success value is also returned.
func (st *State) CAS(cmp, swp uint32, fn func()) (ok bool) {
// Acquire lock
st.mutex.Lock()
defer st.mutex.Unlock()
// Perform CAS operation, fn() on success
if ok = (st.state == cmp); ok {
st.state = swp
fn()
}
return
}
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