unix: use ByteSliceFromString in (*Ifreq).Name

CL 340370 introduced (*Ifreq).Name method which scans the Ifrn field
for \0 twice -- first explicitly, when by calling BytePtrToString.

It seems more straightforward to use ByteSliceToString instead. The
differences are:
 - simpler code;
 - no double scanning for \0;
 - in case there is no \0 in the Ifrn (unlikely), the full string
   (rather than an empty string) is now returned.

With the last item in mind, the test case with no \0 as input that
expects empty output fails, so drop it. Alternatively, we could test
that it returns the full string, but it will be essentially testing
ByteSliceToString, which is not the point.

Cc: Matt Layher <[email protected]>
Change-Id: I31d4f6dbe98aae5120f9b2246c93ceaa6a165395
Reviewed-on: https://go-review.googlesource.com/c/sys/+/407194
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Matt Layher <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Matt Layher <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>

Author: kolyshkin

unix/ifreq_linux.go

@@ -8,7 +8,6 @@
 package unix
 
 import (
-	"bytes"
 	"unsafe"
 )
 
@@ -45,13 +44,7 @@ func NewIfreq(name string) (*Ifreq, error) {
 
 // Name returns the interface name associated with the Ifreq.
 func (ifr *Ifreq) Name() string {
-	// BytePtrToString requires a NULL terminator or the program may crash. If
-	// one is not present, just return the empty string.
-	if !bytes.Contains(ifr.raw.Ifrn[:], []byte{0x00}) {
-		return ""
-	}
-
-	return BytePtrToString(&ifr.raw.Ifrn[0])
+	return ByteSliceToString(ifr.raw.Ifrn[:])
 }
 
 // According to netdevice(7), only AF_INET addresses are returned for numerous

unix/ifreq_linux_test.go

@@ -39,17 +39,6 @@ func TestIfreqSize(t *testing.T) {
 }
 
 func TestIfreqName(t *testing.T) {
-	// Invalid ifreq (no NULL terminator), so expect empty string.
-	var name [IFNAMSIZ]byte
-	for i := range name {
-		name[i] = 0xff
-	}
-
-	bad := &Ifreq{raw: ifreq{Ifrn: name}}
-	if got := bad.Name(); got != "" {
-		t.Fatalf("expected empty ifreq name, but got: %q", got)
-	}
-
 	// Valid ifreq, expect the hard-coded testIfreq name.
 	ifr := testIfreq(t)
 	if want, got := ifreqName, ifr.Name(); want != got {