1// +build linux darwin
2
3/*
4   Copyright The containerd Authors.
5
6   Licensed under the Apache License, Version 2.0 (the "License");
7   you may not use this file except in compliance with the License.
8   You may obtain a copy of the License at
9
10       http://www.apache.org/licenses/LICENSE-2.0
11
12   Unless required by applicable law or agreed to in writing, software
13   distributed under the License is distributed on an "AS IS" BASIS,
14   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   See the License for the specific language governing permissions and
16   limitations under the License.
17*/
18
19package sysx
20
21import (
22	"bytes"
23
24	"golang.org/x/sys/unix"
25)
26
27// Listxattr calls syscall listxattr and reads all content
28// and returns a string array
29func Listxattr(path string) ([]string, error) {
30	return listxattrAll(path, unix.Listxattr)
31}
32
33// Removexattr calls syscall removexattr
34func Removexattr(path string, attr string) (err error) {
35	return unix.Removexattr(path, attr)
36}
37
38// Setxattr calls syscall setxattr
39func Setxattr(path string, attr string, data []byte, flags int) (err error) {
40	return unix.Setxattr(path, attr, data, flags)
41}
42
43// Getxattr calls syscall getxattr
44func Getxattr(path, attr string) ([]byte, error) {
45	return getxattrAll(path, attr, unix.Getxattr)
46}
47
48// LListxattr lists xattrs, not following symlinks
49func LListxattr(path string) ([]string, error) {
50	return listxattrAll(path, unix.Llistxattr)
51}
52
53// LRemovexattr removes an xattr, not following symlinks
54func LRemovexattr(path string, attr string) (err error) {
55	return unix.Lremovexattr(path, attr)
56}
57
58// LSetxattr sets an xattr, not following symlinks
59func LSetxattr(path string, attr string, data []byte, flags int) (err error) {
60	return unix.Lsetxattr(path, attr, data, flags)
61}
62
63// LGetxattr gets an xattr, not following symlinks
64func LGetxattr(path, attr string) ([]byte, error) {
65	return getxattrAll(path, attr, unix.Lgetxattr)
66}
67
68const defaultXattrBufferSize = 128
69
70type listxattrFunc func(path string, dest []byte) (int, error)
71
72func listxattrAll(path string, listFunc listxattrFunc) ([]string, error) {
73	buf := make([]byte, defaultXattrBufferSize)
74	n, err := listFunc(path, buf)
75	for err == unix.ERANGE {
76		// Buffer too small, use zero-sized buffer to get the actual size
77		n, err = listFunc(path, []byte{})
78		if err != nil {
79			return nil, err
80		}
81		buf = make([]byte, n)
82		n, err = listFunc(path, buf)
83	}
84	if err != nil {
85		return nil, err
86	}
87
88	ps := bytes.Split(bytes.TrimSuffix(buf[:n], []byte{0}), []byte{0})
89	var entries []string
90	for _, p := range ps {
91		if len(p) > 0 {
92			entries = append(entries, string(p))
93		}
94	}
95
96	return entries, nil
97}
98
99type getxattrFunc func(string, string, []byte) (int, error)
100
101func getxattrAll(path, attr string, getFunc getxattrFunc) ([]byte, error) {
102	buf := make([]byte, defaultXattrBufferSize)
103	n, err := getFunc(path, attr, buf)
104	for err == unix.ERANGE {
105		// Buffer too small, use zero-sized buffer to get the actual size
106		n, err = getFunc(path, attr, []byte{})
107		if err != nil {
108			return nil, err
109		}
110		buf = make([]byte, n)
111		n, err = getFunc(path, attr, buf)
112	}
113	if err != nil {
114		return nil, err
115	}
116	return buf[:n], nil
117}
118