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package mempool
import (
"unsafe"
)
// SimplePool provides a type-safe form
// of UnsafePool using generics.
//
// Note it is NOT safe for concurrent
// use, you must protect it yourself!
type SimplePool[T any] struct {
UnsafeSimplePool
// 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) bool
}
func (p *SimplePool[T]) Get() T {
if ptr := p.UnsafeSimplePool.Get(); ptr != nil {
return *(*T)(ptr)
}
var t T
if p.New != nil {
t = p.New()
}
return t
}
func (p *SimplePool[T]) Put(t T) {
if p.Reset != nil && !p.Reset(t) {
return
}
ptr := unsafe.Pointer(&t)
p.UnsafeSimplePool.Put(ptr)
}
// UnsafeSimplePool provides an incredibly
// simple memory pool implementation
// that stores ptrs to memory values,
// and regularly flushes internal pool
// structures according to CheckGC().
//
// Note it is NOT safe for concurrent
// use, you must protect it yourself!
type UnsafeSimplePool struct {
// Check determines how often to flush
// internal pools based on underlying
// current and victim pool sizes. It gets
// called on every pool Put() operation.
//
// A flush will start a new current
// pool, make victim the old current,
// and drop the existing victim pool.
Check func(current, victim int) bool
current []unsafe.Pointer
victim []unsafe.Pointer
}
func (p *UnsafeSimplePool) 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 *UnsafeSimplePool) Put(ptr unsafe.Pointer) {
p.current = append(p.current, ptr)
// Get GC check func.
if p.Check == nil {
p.Check = defaultCheck
}
if p.Check(len(p.current), len(p.victim)) {
p.GC() // garbage collection time!
}
}
func (p *UnsafeSimplePool) GC() {
p.victim = p.current
p.current = nil
}
func (p *UnsafeSimplePool) Size() int {
return len(p.current) + len(p.victim)
}
func defaultCheck(current, victim int) bool {
return current-victim > 128 || victim > 256
}
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