text: // +build linux darwin
  
  /*
     Copyright The containerd Authors.
  
     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
     You may obtain a copy of the License at
  
         http://www.apache.org/licenses/LICENSE-2.0
  
     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
  */
  
  package sysx
  
  import (
  	"bytes"
  
  	"golang.org/x/sys/unix"
  )
  
  // Listxattr calls syscall listxattr and reads all content
  // and returns a string array
  func Listxattr(path string) ([]string, error) {
  	return listxattrAll(path, unix.Listxattr)
  }
  
  // Removexattr calls syscall removexattr
  func Removexattr(path string, attr string) (err error) {
  	return unix.Removexattr(path, attr)
  }
  
  // Setxattr calls syscall setxattr
  func Setxattr(path string, attr string, data []byte, flags int) (err error) {
  	return unix.Setxattr(path, attr, data, flags)
  }
  
  // Getxattr calls syscall getxattr
  func Getxattr(path, attr string) ([]byte, error) {
  	return getxattrAll(path, attr, unix.Getxattr)
  }
  
  // LListxattr lists xattrs, not following symlinks
  func LListxattr(path string) ([]string, error) {
  	return listxattrAll(path, unix.Llistxattr)
  }
  
  // LRemovexattr removes an xattr, not following symlinks
  func LRemovexattr(path string, attr string) (err error) {
  	return unix.Lremovexattr(path, attr)
  }
  
  // LSetxattr sets an xattr, not following symlinks
  func LSetxattr(path string, attr string, data []byte, flags int) (err error) {
  	return unix.Lsetxattr(path, attr, data, flags)
  }
  
  // LGetxattr gets an xattr, not following symlinks
  func LGetxattr(path, attr string) ([]byte, error) {
  	return getxattrAll(path, attr, unix.Lgetxattr)
  }
  
  const defaultXattrBufferSize = 128
  
  type listxattrFunc func(path string, dest []byte) (int, error)
  
  func listxattrAll(path string, listFunc listxattrFunc) ([]string, error) {
  	buf := make([]byte, defaultXattrBufferSize)
  	n, err := listFunc(path, buf)
  	for err == unix.ERANGE {
  		// Buffer too small, use zero-sized buffer to get the actual size
  		n, err = listFunc(path, []byte{})
  		if err != nil {
  			return nil, err
  		}
  		buf = make([]byte, n)
  		n, err = listFunc(path, buf)
  	}
  	if err != nil {
  		return nil, err
  	}
  
  	ps := bytes.Split(bytes.TrimSuffix(buf[:n], []byte{0}), []byte{0})
  	var entries []string
  	for _, p := range ps {
  		if len(p) > 0 {
  			entries = append(entries, string(p))
  		}
  	}
  
  	return entries, nil
  }
  
  type getxattrFunc func(string, string, []byte) (int, error)
  
  func getxattrAll(path, attr string, getFunc getxattrFunc) ([]byte, error) {
  	buf := make([]byte, defaultXattrBufferSize)
  	n, err := getFunc(path, attr, buf)
  	for err == unix.ERANGE {
  		// Buffer too small, use zero-sized buffer to get the actual size
  		n, err = getFunc(path, attr, []byte{})
  		if err != nil {
  			return nil, err
  		}
  		buf = make([]byte, n)
  		n, err = getFunc(path, attr, buf)
  	}
  	if err != nil {
  		return nil, err
  	}
  	return buf[:n], nil
  }
  