moby/vendor/github.com/containerd/continuity/devices/devices_unix.go

// +build linux darwin freebsd solaris

/*
   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 devices

import (
	"fmt"
	"os"
	"syscall"

	"golang.org/x/sys/unix"
)

func DeviceInfo(fi os.FileInfo) (uint64, uint64, error) {
	sys, ok := fi.Sys().(*syscall.Stat_t)
	if !ok {
		return 0, 0, fmt.Errorf("cannot extract device from os.FileInfo")
	}

	dev := uint64(sys.Rdev)
	return uint64(unix.Major(dev)), uint64(unix.Minor(dev)), nil
}

// mknod provides a shortcut for syscall.Mknod
func Mknod(p string, mode os.FileMode, maj, min int) error {
	var (
		m   = syscallMode(mode.Perm())
		dev uint64
	)

	if mode&os.ModeDevice != 0 {
		dev = unix.Mkdev(uint32(maj), uint32(min))

		if mode&os.ModeCharDevice != 0 {
			m |= unix.S_IFCHR
		} else {
			m |= unix.S_IFBLK
		}
	} else if mode&os.ModeNamedPipe != 0 {
		m |= unix.S_IFIFO
	}

	return unix.Mknod(p, m, int(dev))
}

// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
func syscallMode(i os.FileMode) (o uint32) {
	o |= uint32(i.Perm())
	if i&os.ModeSetuid != 0 {
		o |= unix.S_ISUID
	}
	if i&os.ModeSetgid != 0 {
		o |= unix.S_ISGID
	}
	if i&os.ModeSticky != 0 {
		o |= unix.S_ISVTX
	}
	return
}