go-sandbox/pkg/cgroup/subcgroup.go
2020-12-17 22:55:48 -08:00

76 lines
1.9 KiB
Go

package cgroup
import (
"errors"
"io/ioutil"
"path"
"strconv"
"strings"
"syscall"
)
// SubCgroup is the accessor for single cgroup resource with given path
type SubCgroup struct {
path string
}
// ErrNotInitialized returned when trying to read from not initialized cgroup
var ErrNotInitialized = errors.New("cgroup was not initialized")
// NewSubCgroup creates a cgroup accessor with given path (path needs to be created in advance)
func NewSubCgroup(p string) *SubCgroup {
return &SubCgroup{path: p}
}
// WriteUint writes uint64 into given file
func (c *SubCgroup) WriteUint(filename string, i uint64) error {
if c == nil || c.path == "" {
return nil
}
return c.WriteFile(filename, []byte(strconv.FormatUint(i, 10)))
}
// ReadUint read uint64 from given file
func (c *SubCgroup) ReadUint(filename string) (uint64, error) {
if c == nil || c.path == "" {
return 0, ErrNotInitialized
}
b, err := c.ReadFile(filename)
if err != nil {
return 0, err
}
s, err := strconv.ParseUint(strings.TrimSpace(string(b)), 10, 64)
if err != nil {
return 0, err
}
return s, nil
}
// WriteFile writes cgroup file and handles potential EINTR error while writes to
// the slow device (cgroup)
func (c *SubCgroup) WriteFile(name string, content []byte) error {
if c == nil || c.path == "" {
return ErrNotInitialized
}
p := path.Join(c.path, name)
err := ioutil.WriteFile(p, content, filePerm)
for err != nil && errors.Is(err, syscall.EINTR) {
err = ioutil.WriteFile(p, content, filePerm)
}
return err
}
// ReadFile reads cgroup file and handles potential EINTR error while read to
// the slow device (cgroup)
func (c *SubCgroup) ReadFile(name string) ([]byte, error) {
if c == nil || c.path == "" {
return nil, nil
}
p := path.Join(c.path, name)
data, err := ioutil.ReadFile(p)
for err != nil && errors.Is(err, syscall.EINTR) {
data, err = ioutil.ReadFile(p)
}
return data, err
}