Исходники и презентации

lessons/allocator/pool_allocator/main.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"unsafe"
+)
+
+type PoolAllocator struct {
+	objectPool  []byte
+	freeObjects map[unsafe.Pointer]struct{}
+	objectSize  int
+}
+
+func NewPoolAllocator(capacity int, objectSize int) (PoolAllocator, error) {
+	if capacity <= 0 || objectSize <= 0 || capacity%objectSize != 0 {
+		return PoolAllocator{}, errors.New("incorrect argumnets")
+	}
+
+	allocator := PoolAllocator{
+		objectPool:  make([]byte, capacity),
+		freeObjects: make(map[unsafe.Pointer]struct{}, capacity/objectSize),
+		objectSize:  objectSize,
+	}
+
+	allocator.resetMemoryState()
+	return allocator, nil
+}
+
+func (a *PoolAllocator) Allocate() (unsafe.Pointer, error) {
+	if len(a.freeObjects) == 0 {
+		// can increase capacity
+		return nil, errors.New("not enough memory")
+	}
+
+	var pointer unsafe.Pointer
+	for freePointer := range a.freeObjects {
+		pointer = freePointer
+		break
+	}
+
+	delete(a.freeObjects, pointer)
+	return pointer, nil
+}
+
+func (a *PoolAllocator) Deallocate(pointer unsafe.Pointer) error {
+	if pointer == nil {
+		return errors.New("incorrect pointer")
+	}
+
+	// potentionally incorrect pointer
+	a.freeObjects[pointer] = struct{}{}
+	return nil
+}
+
+func (a *PoolAllocator) Free() {
+	a.resetMemoryState()
+}
+
+func (a *PoolAllocator) resetMemoryState() {
+	for offset := 0; offset < len(a.objectPool); offset += a.objectSize {
+		pointer := unsafe.Pointer(&a.objectPool[offset])
+		a.freeObjects[pointer] = struct{}{}
+	}
+}
+
+func store[T any](pointer unsafe.Pointer, value T) {
+	*(*T)(pointer) = value
+}
+
+func load[T any](pointer unsafe.Pointer) T {
+	return *(*T)(pointer)
+}
+
+func main() {
+	const KB = 1 << 10
+	allocator, err := NewPoolAllocator(KB, 4)
+	if err != nil {
+		// handling...
+	}
+
+	defer allocator.Free()
+
+	pointer1, _ := allocator.Allocate()
+	pointer2, _ := allocator.Allocate()
+
+	store[int32](pointer1, 100)
+	store[int32](pointer2, 200)
+
+	value1 := load[int32](pointer1)
+	value2 := load[int32](pointer2)
+	fmt.Println("value1:", value1)
+	fmt.Println("value2:", value2)
+
+	fmt.Println("address1:", pointer1)
+	fmt.Println("address2:", pointer2)
+
+	allocator.Deallocate(pointer1)
+	allocator.Deallocate(pointer2)
+}