Supersede InterfaceInfoList's Item method with InterfaceInfo

Rather than repetitively calling Info method to calculate InterfaceInfo
struct address and return it one by one, a more effective method called
InterfaceInfo was introduced. The later returns all interface infos as
a Go slice.

Signed-off-by: Simon Rozman <simon@rozman.si>

wlanapi_windows.go

@@ -60,6 +60,8 @@ type InterfaceInfoList struct {
 }
 
 // Item returns interface info at the given index.
+//
+// Deprecated: Use InterfaceInfo method to obtain interface info as a slice.
 func (iil *InterfaceInfoList) Item(idx uint32) *InterfaceInfo {
 	if idx > iil.NumberOfItems {
 		panic("index out of range")
@@ -70,6 +72,13 @@ func (iil *InterfaceInfoList) Item(idx uint32) *InterfaceInfo {
 	return (*InterfaceInfo)(unsafe.Pointer(addr))
 }
 
+// InterfaceInfo returns interface info.
+func (iil *InterfaceInfoList) InterfaceInfo() []InterfaceInfo {
+	addr := uintptr(unsafe.Pointer(iil))
+	addr += unsafe.Sizeof(InterfaceInfoList{})
+	return (*[(1 << 21) - 1]InterfaceInfo)(unsafe.Pointer(addr))[:iil.NumberOfItems]
+}
+
 // Close frees the memory.
 func (iil *InterfaceInfoList) Close() {
 	wlanFreeMemory(unsafe.Pointer(iil))

wlanapi_windows_test.go

@@ -53,9 +53,7 @@ func Test(t *testing.T) {
 	}
 	defer ifaces.Close()
 
-	for i := uint32(0); i < ifaces.NumberOfItems; i++ {
+	for _, ii := range ifaces.InterfaceInfo() {
-		ii := ifaces.Item(i)
-
 		t.Logf("Interface: %v, state: %v, GUID: %v",
 			ii.InterfaceDescription(),
 			ii.State,