xattr: simple wrapper for syscalls

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

xattr/xattr.go

@@ -0,0 +1,35 @@
+// +build linux
+
+package xattr
+
+import (
+	"strings"
+	"syscall"
+)
+
+// Get returns the extended attributes (xattr) on file `path`, for the given `name`.
+func Get(path, name string) ([]byte, error) {
+	dest := make([]byte, 1024)
+	i, err := syscall.Getxattr(path, name, dest)
+	if err != nil {
+		return nil, err
+	}
+	return dest[:i], nil
+}
+
+// Set sets the extended attributes (xattr) on file `path`, for the given `name` and `value`
+func Set(path, name string, value []byte) error {
+	return syscall.Setxattr(path, name, value, 0)
+}
+
+// List returns a list of all the extended attributes (xattr) for file `path`
+func List(path string) ([]string, error) {
+	dest := make([]byte, 1024)
+	i, err := syscall.Listxattr(path, dest)
+	if err != nil {
+		return nil, err
+	}
+	return strings.Split(strings.TrimRight(string(dest[:i]), nilByte), nilByte), nil
+}
+
+const nilByte = "\x00"

xattr/xattr_test.go

@@ -0,0 +1,38 @@
+package xattr
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func TestXattr(t *testing.T) {
+	fh, err := ioutil.TempFile(".", "xattr.")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(fh.Name())
+	if err := fh.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	expected := []byte("1234")
+	if err := Set(fh.Name(), "user.testing", expected); err != nil {
+		t.Fatal(fh.Name(), err)
+	}
+	l, err := List(fh.Name())
+	if err != nil {
+		t.Error(fh.Name(), err)
+	}
+	if !(len(l) > 0) {
+		t.Errorf("%q: expected a list of at least 1; got %d", len(l))
+	}
+	got, err := Get(fh.Name(), "user.testing")
+	if err != nil {
+		t.Fatal(fh.Name(), err)
+	}
+	if !bytes.Equal(got, expected) {
+		t.Errorf("%q: expected %q; got %q", fh.Name(), expected, got)
+	}
+}

xattr/xattr_unsupported.go

@@ -0,0 +1,13 @@
+// +build !linux
+
+package xattr
+
+func Get(path, name string) ([]byte, error) {
+	return nil, nil
+}
+func Set(path, name string, value []byte) error {
+	return nil
+}
+func List(path string) ([]string, error) {
+	return nil, nil
+}