github.com/sealerio/sealer@v0.11.1-0.20240507115618-f4f89c5853ae/utils/archive/attr.go (about)

     1  // Copyright © 2021 Alibaba Group Holding Ltd.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // This file is extracted from "github.com/docker/docker/pkg/system"
    16  
    17  package archive
    18  
    19  import "golang.org/x/sys/unix"
    20  
    21  // Lgetxattr retrieves the value of the extended attribute identified by attr
    22  // and associated with the given path in the file system.
    23  // It will return a nil slice and nil error if the xattr is not set.
    24  func Lgetxattr(path string, attr string) ([]byte, error) {
    25  	// Start with a 128 length byte array
    26  	dest := make([]byte, 128)
    27  	sz, errno := unix.Lgetxattr(path, attr, dest)
    28  
    29  	switch {
    30  	case errno == unix.ENODATA:
    31  		return nil, nil
    32  	case errno == unix.ERANGE:
    33  		// 128 byte array might just not be good enough. A dummy buffer is used
    34  		// to get the real size of the xattrs on disk
    35  		sz, errno = unix.Lgetxattr(path, attr, []byte{})
    36  		if errno != nil {
    37  			return nil, errno
    38  		}
    39  		dest = make([]byte, sz)
    40  		sz, errno = unix.Lgetxattr(path, attr, dest)
    41  		if errno != nil {
    42  			return nil, errno
    43  		}
    44  	case errno != nil:
    45  		return nil, errno
    46  	}
    47  	return dest[:sz], nil
    48  }
    49  
    50  // Lsetxattr sets the value of the extended attribute identified by attr
    51  // and associated with the given path in the file system.
    52  func Lsetxattr(path string, attr string, data []byte, flags int) error {
    53  	return unix.Lsetxattr(path, attr, data, flags)
    54  }