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pool.go
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pool.go
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package pr2
import (
"sync"
"sync/atomic"
_ "unsafe"
)
type Pool[T any] struct {
l sync.Mutex
newFunc func() T
elems atomic.Pointer[[]_PoolElem[T]]
capacity uint32
}
type _PoolElem[T any] struct {
refs atomic.Int32
put func() bool
incRef func()
value T
}
func NewPool[T any](
capacity uint32,
newFunc func() T,
) *Pool[T] {
pool := &Pool[T]{
capacity: capacity,
newFunc: newFunc,
}
pool.allocElems(nil)
return pool
}
func (p *Pool[T]) allocElems(old *[]_PoolElem[T]) {
p.l.Lock()
defer p.l.Unlock()
if old != nil && p.elems.Load() != old {
// refreshed
return
}
elems := make([]_PoolElem[T], p.capacity)
for i := uint32(0); i < p.capacity; i++ {
i := i
ptr := p.newFunc()
elems[i] = _PoolElem[T]{
value: ptr,
put: func() bool {
if c := elems[i].refs.Add(-1); c == 0 {
return true
} else if c < 0 {
panic("bad put")
}
return false
},
incRef: func() {
elems[i].refs.Add(1)
},
}
}
p.elems.Store(&elems)
}
func (p *Pool[T]) Get(ptr *T) (put func() bool) {
put, _ = p.GetRC(ptr)
return
}
func (p *Pool[T]) GetRC(ptr *T) (
put func() bool,
incRef func(),
) {
for {
cur := p.elems.Load()
elems := *cur
for i := 0; i < 16; i++ {
idx := fastrand() % p.capacity
if elems[idx].refs.CompareAndSwap(0, 1) {
*ptr = elems[idx].value
put = elems[idx].put
incRef = elems[idx].incRef
return
}
}
p.allocElems(cur)
}
}
func (p *Pool[T]) Getter() (
get func(*T),
putAll func(),
) {
var l sync.Mutex
var curPut func()
get = func(ptr *T) {
put := p.Get(ptr)
l.Lock()
if curPut != nil {
cur := curPut
newPut := func() {
put()
cur()
}
curPut = newPut
} else {
curPut = func() {
put()
}
}
l.Unlock()
}
putAll = func() {
l.Lock()
put := curPut
curPut = nil
l.Unlock()
put()
}
return
}
//go:linkname fastrand runtime.fastrand
func fastrand() uint32