libcontainer: prefer bytes.TrimSpace() over strings.TrimSpace()

Perform trimming before converting to a string, which should be
somewhat more performant.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libcontainer/cgroups/fs2/create.go

@@ -105,7 +105,7 @@ func CreateCgroupPath(path string, c *configs.Cgroup) (Err error) {
 			}
 			cgTypeFile := filepath.Join(current, "cgroup.type")
 			cgType, _ := ioutil.ReadFile(cgTypeFile)
-			switch strings.TrimSpace(string(cgType)) {
+			switch string(bytes.TrimSpace(cgType)) {
 			// If the cgroup is in an invalid mode (usually this means there's an internal
 			// process in the cgroup tree, because we created a cgroup under an
 			// already-populated-by-other-processes cgroup), then we have to error out if
@@ -128,7 +128,7 @@ func CreateCgroupPath(path string, c *configs.Cgroup) (Err error) {
 				fallthrough
 			case "threaded":
 				if containsDomainController(c) {
-					return fmt.Errorf("cannot enter cgroupv2 %q with domain controllers -- it is in %s mode", current, strings.TrimSpace(string(cgType)))
+					return fmt.Errorf("cannot enter cgroupv2 %q with domain controllers -- it is in %s mode", current, string(bytes.TrimSpace(cgType)))
 				}
 			}
 		}

libcontainer/cgroups/fscommon/utils.go

@@ -79,5 +79,5 @@ func GetCgroupParamString(path, file string) (string, error) {
 		return "", err
 	}
 
-	return strings.TrimSpace(string(contents)), nil
+	return strings.TrimSpace(contents), nil
 }

libcontainer/init_linux.go

@@ -3,6 +3,7 @@
 package libcontainer
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -304,7 +305,7 @@ func setupUser(config *initConfig) error {
 	// There's nothing we can do about /etc/group entries, so we silently
 	// ignore setting groups here (since the user didn't explicitly ask us to
 	// set the group).
-	allowSupGroups := !config.RootlessEUID && strings.TrimSpace(string(setgroups)) != "deny"
+	allowSupGroups := !config.RootlessEUID && string(bytes.TrimSpace(setgroups)) != "deny"
 
 	if allowSupGroups {
 		suppGroups := append(execUser.Sgids, addGroups...)

libcontainer/integration/exec_test.go

@@ -1087,7 +1087,7 @@ func TestSysctl(t *testing.T) {
 	// Wait for process
 	waitProcess(&pconfig, t)
 
-	shmmniOutput := strings.TrimSpace(string(stdout.Bytes()))
+	shmmniOutput := string(bytes.TrimSpace(stdout.Bytes()))
 	if shmmniOutput != "8192" {
 		t.Fatalf("kernel.shmmni property expected to be 8192, but is %s", shmmniOutput)
 	}
@@ -1221,7 +1221,7 @@ func TestOomScoreAdj(t *testing.T) {
 
 	// Wait for process
 	waitProcess(&pconfig, t)
-	outputOomScoreAdj := strings.TrimSpace(string(stdout.Bytes()))
+	outputOomScoreAdj := string(bytes.TrimSpace(stdout.Bytes()))
 
 	// Check that the oom_score_adj matches the value that was set as part of config.
 	if outputOomScoreAdj != strconv.Itoa(*config.OomScoreAdj) {
@@ -1624,7 +1624,7 @@ func TestRootfsPropagationSharedMount(t *testing.T) {
 
 	// Check if mount is visible on host or not.
 	out, err := exec.Command("findmnt", "-n", "-f", "-oTARGET", dir2host).CombinedOutput()
-	outtrim := strings.TrimSpace(string(out))
+	outtrim := string(bytes.TrimSpace(out))
 	if err != nil {
 		t.Logf("findmnt error %q: %q", err, outtrim)
 	}

libcontainer/network_linux.go

@@ -3,11 +3,11 @@
 package libcontainer
 
 import (
+	"bytes"
 	"fmt"
 	"io/ioutil"
 	"path/filepath"
 	"strconv"
-	"strings"
 
 	"github.com/opencontainers/runc/libcontainer/configs"
 	"github.com/opencontainers/runc/types"
@@ -79,7 +79,7 @@ func readSysfsNetworkStats(ethInterface, statsFile string) (uint64, error) {
 	if err != nil {
 		return 0, err
 	}
-	return strconv.ParseUint(strings.TrimSpace(string(data)), 10, 64)
+	return strconv.ParseUint(string(bytes.TrimSpace(data)), 10, 64)
 }
 
 // loopback is a network strategy that provides a basic loopback device