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moby--moby/pkg/system/xattrs_linux.go

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package system
import (
"syscall"
"unsafe"
)
// 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 := syscall.BytePtrFromString(path)
if err != nil {
return nil, err
}
attrBytes, err := syscall.BytePtrFromString(attr)
if err != nil {
return nil, err
}
dest := make([]byte, 128)
destBytes := unsafe.Pointer(&dest[0])
sz, _, errno := syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
if errno == syscall.ENODATA {
return nil, nil
}
if errno == syscall.ERANGE {
dest = make([]byte, sz)
destBytes := unsafe.Pointer(&dest[0])
sz, _, errno = syscall.Syscall6(syscall.SYS_LGETXATTR, uintptr(unsafe.Pointer(pathBytes)), uintptr(unsafe.Pointer(attrBytes)), uintptr(destBytes), uintptr(len(dest)), 0, 0)
}
if errno != 0 {
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 := syscall.BytePtrFromString(path)
if err != nil {
return err
}
attrBytes, err := syscall.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 := syscall.Syscall6(syscall.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
}