Move cgroups package into libcontainer

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

libcontainer/cgroups/fs/utils.go

@@ -0,0 +1,40 @@
+package fs
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+var (
+	ErrNotSupportStat = errors.New("stats are not supported for subsystem")
+	ErrNotValidFormat = errors.New("line is not a valid key value format")
+)
+
+// Parses a cgroup param and returns as name, value
+//  i.e. "io_service_bytes 1234" will return as io_service_bytes, 1234
+func getCgroupParamKeyValue(t string) (string, float64, error) {
+	parts := strings.Fields(t)
+	switch len(parts) {
+	case 2:
+		value, err := strconv.ParseFloat(parts[1], 64)
+		if err != nil {
+			return "", 0.0, fmt.Errorf("Unable to convert param value to float: %s", err)
+		}
+		return parts[0], value, nil
+	default:
+		return "", 0.0, ErrNotValidFormat
+	}
+}
+
+// Gets a single float64 value from the specified cgroup file.
+func getCgroupParamFloat64(cgroupPath, cgroupFile string) (float64, error) {
+	contents, err := ioutil.ReadFile(filepath.Join(cgroupPath, cgroupFile))
+	if err != nil {
+		return -1.0, err
+	}
+	return strconv.ParseFloat(strings.TrimSpace(string(contents)), 64)
+}