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system: Use symlink xattr functions from x/sys/unix 

Use the symlink xattr syscall wrappers Lgetxattr and Lsetxattr from
x/sys/unix (introduced in golang/sys@b90f89a) instead of providing own
wrappers. Leave the functionality of system.Lgetxattr intact with
respect to the retry with a larger buffer, but switch it to use
unix.Lgetxattr. Also leave system.Lsetxattr intact (even though it's
just a wrapper around the corresponding function from unix) in order to
keep moby building for !linux.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
This commit is contained in:
Tobias Klauser 2017-06-08 08:52:39 +02:00
parent ef5252fc5d
commit 4d966409bc
1 changed files with 5 additions and 40 deletions
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45
pkg/system/xattrs_linux.go
View File

@ -1,64 +1,29 @@
package system
import (
"unsafe"
"golang.org/x/sys/unix"
)
import "golang.org/x/sys/unix"
// Lgetxattr retrieves the value of the extended attribute identified by attr
// and associated with the given path in the file system.
// It will returns a nil slice and nil error if the xattr is not set.
func Lgetxattr(path string, attr string) ([]byte, error) {
pathBytes, err := unix.BytePtrFromString(path)
if err != nil {
return nil, err
}
attrBytes, err := unix.BytePtrFromString(attr)
if err != nil {
return nil, err
}
dest := make([]byte, 128)
destBytes := unsafe.Pointer(&dest[0])
sz, _, errno := unix.Syscall6(unix.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
sz, errno := unix.Lgetxattr(path, attr, dest)
if errno == unix.ENODATA {
return nil, nil
}
if errno == unix.ERANGE {
dest = make([]byte, sz)
destBytes := unsafe.Pointer(&dest[0])
sz, _, errno = unix.Syscall6(unix.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
sz, errno = unix.Lgetxattr(path, attr, dest)
}
if errno != 0 {
if errno != nil {
return nil, errno
}
return dest[:sz], nil
}
var _zero uintptr
// Lsetxattr sets the value of the extended attribute identified by attr
// and associated with the given path in the file system.
func Lsetxattr(path string, attr string, data []byte, flags int) error {
pathBytes, err := unix.BytePtrFromString(path)
if err != nil {
return err
}
attrBytes, err := unix.BytePtrFromString(attr)
if err != nil {
return err
}
var dataBytes unsafe.Pointer
if len(data) > 0 {
dataBytes = unsafe.Pointer(&data[0])
} else {
dataBytes = unsafe.Pointer(&_zero)
}
_, _, errno := unix.Syscall6(unix.SYS_LSETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(dataBytes), uintptr(len(data)), uintptr(flags), 0)
if errno != 0 {
return errno
}
return nil
return unix.Lsetxattr(path, attr, data, flags)
}