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package mempool
import (
"unsafe"
)
const DefaultDirtyFactor = 128
// Pool provides a type-safe form
// of UnsafePool using generics.
//
// Note it is NOT safe for concurrent
// use, you must protect it yourself!
type Pool[T any] struct {
// New is an optionally provided
// allocator used when no value
// is available for use in pool.
New func() T
// Reset is an optionally provided
// value resetting function called
// on passed value to Put().
Reset func(T)
UnsafePool
}
func (p *Pool[T]) Get() T {
if ptr := p.UnsafePool.Get(); ptr != nil {
return *(*T)(ptr)
} else if p.New != nil {
return p.New()
}
var z T
return z
}
func (p *Pool[T]) Put(t T) {
if p.Reset != nil {
p.Reset(t)
}
ptr := unsafe.Pointer(&t)
p.UnsafePool.Put(ptr)
}
// UnsafePool provides an incredibly
// simple memory pool implementation
// that stores ptrs to memory values,
// and regularly flushes internal pool
// structures according to DirtyFactor.
//
// Note it is NOT safe for concurrent
// use, you must protect it yourself!
type UnsafePool struct {
// DirtyFactor determines the max
// number of $dirty count before
// pool is garbage collected. Where:
// $dirty = len(current) - len(victim)
DirtyFactor int
current []unsafe.Pointer
victim []unsafe.Pointer
}
func (p *UnsafePool) Get() unsafe.Pointer {
// First try current list.
if len(p.current) > 0 {
ptr := p.current[len(p.current)-1]
p.current = p.current[:len(p.current)-1]
return ptr
}
// Fallback to victim.
if len(p.victim) > 0 {
ptr := p.victim[len(p.victim)-1]
p.victim = p.victim[:len(p.victim)-1]
return ptr
}
return nil
}
func (p *UnsafePool) Put(ptr unsafe.Pointer) {
p.current = append(p.current, ptr)
// Get dirty factor.
df := p.DirtyFactor
if df == 0 {
df = DefaultDirtyFactor
}
if len(p.current)-len(p.victim) > df {
// Garbage collection!
p.victim = p.current
p.current = nil
}
}
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