add a span-like allocator without zeroing of slices

alloc_test.go

@@ -0,0 +1,72 @@
+package smux
+
+import "testing"
+
+func TestAllocGet(t *testing.T) {
+	alloc := NewAllocator()
+	if alloc.Get(0) != nil {
+		t.Fatal(0)
+	}
+	if len(alloc.Get(1)) != 1 {
+		t.Fatal(1)
+	}
+	if len(alloc.Get(2)) != 2 {
+		t.Fatal(2)
+	}
+	if len(alloc.Get(3)) != 3 || cap(alloc.Get(3)) != 4 {
+		t.Fatal(3)
+	}
+	if len(alloc.Get(4)) != 4 {
+		t.Fatal(4)
+	}
+	if len(alloc.Get(1023)) != 1023 || cap(alloc.Get(1023)) != 1024 {
+		t.Fatal(1023)
+	}
+	if len(alloc.Get(1024)) != 1024 {
+		t.Fatal(1024)
+	}
+	if len(alloc.Get(65536)) != 65536 {
+		t.Fatal(65536)
+	}
+	if alloc.Get(65537) != nil {
+		t.Fatal(65537)
+	}
+}
+
+func TestAllocPut(t *testing.T) {
+	alloc := NewAllocator()
+	if err := alloc.Put(nil); err == nil {
+		t.Fatal("put nil misbehavior")
+	}
+	if err := alloc.Put(make([]byte, 3, 3)); err == nil {
+		t.Fatal("put elem:3 []bytes misbehavior")
+	}
+	if err := alloc.Put(make([]byte, 4, 4)); err != nil {
+		t.Fatal("put elem:4 []bytes misbehavior")
+	}
+	if err := alloc.Put(make([]byte, 1023, 1024)); err != nil {
+		t.Fatal("put elem:1024 []bytes misbehavior")
+	}
+	if err := alloc.Put(make([]byte, 65536, 65536)); err != nil {
+		t.Fatal("put elem:65536 []bytes misbehavior")
+	}
+	if err := alloc.Put(make([]byte, 65537, 65537)); err == nil {
+		t.Fatal("put elem:65537 []bytes misbehavior")
+	}
+}
+
+func TestAllocPutThenGet(t *testing.T) {
+	alloc := NewAllocator()
+	data := alloc.Get(4)
+	for k := range data {
+		data[k] = 99
+	}
+	alloc.Put(data)
+
+	newData := alloc.Get(4)
+	for k := range newData {
+		if newData[k] != 99 {
+			t.Fatal("cannot fetch written []bytes from pool")
+		}
+	}
+}