Исходники и презентации

lessons/maps/map_internals/main.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"unsafe"
+)
+
+type eface struct {
+	typ  unsafe.Pointer
+	data unsafe.Pointer
+}
+
+type hmap struct {
+	count     int
+	flags     uint8
+	B         uint8
+	noverflow uint16
+	hash0     uint32
+
+	buckets    unsafe.Pointer
+	oldbuckets unsafe.Pointer
+	nevacuate  uintptr
+}
+
+func main() {
+	data := make(map[int]int)
+	iface := any(data)
+
+	ifacePtr := unsafe.Pointer(&iface)
+	emptyIfacePtr := (*eface)(ifacePtr)
+
+	hm := (*hmap)(emptyIfacePtr.data)
+	fmt.Println("count:", hm.count, "buckets:", 1<<hm.B)
+
+	for i := 0; i < 500; i++ {
+		data[i] = i * 2
+	}
+
+	fmt.Println("count:", hm.count, "buckets:", 1<<hm.B)
+
+	for key := range data {
+		delete(data, key)
+	}
+
+	fmt.Println("count:", hm.count, "buckets:", 1<<hm.B)
+}