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package stm
// Atomically executes the atomic function fn.
func Atomically(fn func(*Tx)) {
retry:
// run the transaction
tx := &Tx{
reads: make(map[*Var]uint64),
writes: make(map[*Var]interface{}),
}
if catchRetry(fn, tx) {
// wait for one of the variables we read to change before retrying
tx.wait()
goto retry
}
// verify the read log
globalLock.Lock()
if !tx.verify() {
globalLock.Unlock()
goto retry
}
// commit the write log and broadcast that variables have changed
if len(tx.writes) > 0 {
tx.commit()
globalCond.Broadcast()
}
globalLock.Unlock()
}
// AtomicGet is a helper function that atomically reads a value.
func AtomicGet(v *Var) interface{} {
// since we're only doing one operation, we don't need a full transaction
globalLock.Lock()
v.mu.Lock()
val := v.val
v.mu.Unlock()
globalLock.Unlock()
return val
}
// AtomicSet is a helper function that atomically writes a value.
func AtomicSet(v *Var, val interface{}) {
// since we're only doing one operation, we don't need a full transaction
globalLock.Lock()
v.mu.Lock()
v.val = val
v.version++
v.mu.Unlock()
globalCond.Broadcast()
globalLock.Unlock()
}
// Compose is a helper function that composes multiple transactions into a
// single transaction.
func Compose(fns ...func(*Tx)) func(*Tx) {
return func(tx *Tx) {
for _, f := range fns {
f(tx)
}
}
}
// Select runs the supplied functions in order. Execution stops when a
// function succeeds without calling Retry. If no functions succeed, the
// entire selection will be retried.
func Select(fns ...func(*Tx)) func(*Tx) {
return func(tx *Tx) {
switch len(fns) {
case 0:
// empty Select blocks forever
tx.Retry()
case 1:
fns[0](tx)
default:
if catchRetry(fns[0], tx) {
Select(fns[1:]...)(tx)
}
}
}
}
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