github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/archive/tar/stat_unix.go (about)

     1  // Copyright 2012 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build aix || linux || darwin || dragonfly || freebsd || openbsd || netbsd || solaris
     6  // +build aix linux darwin dragonfly freebsd openbsd netbsd solaris
     7  
     8  package tar
     9  
    10  import (
    11  	"io/fs"
    12  	"os/user"
    13  	"runtime"
    14  	"strconv"
    15  	"sync"
    16  	"syscall"
    17  )
    18  
    19  func init() {
    20  	sysStat = statUnix
    21  }
    22  
    23  // userMap and groupMap caches UID and GID lookups for performance reasons.
    24  // The downside is that renaming uname or gname by the OS never takes effect.
    25  var userMap, groupMap sync.Map // map[int]string
    26  
    27  func statUnix(fi fs.FileInfo, h *Header) error {
    28  	sys, ok := fi.Sys().(*syscall.Stat_t)
    29  	if !ok {
    30  		return nil
    31  	}
    32  	h.Uid = int(sys.Uid)
    33  	h.Gid = int(sys.Gid)
    34  
    35  	// Best effort at populating Uname and Gname.
    36  	// The os/user functions may fail for any number of reasons
    37  	// (not implemented on that platform, cgo not enabled, etc).
    38  	if u, ok := userMap.Load(h.Uid); ok {
    39  		h.Uname = u.(string)
    40  	} else if u, err := user.LookupId(strconv.Itoa(h.Uid)); err == nil {
    41  		h.Uname = u.Username
    42  		userMap.Store(h.Uid, h.Uname)
    43  	}
    44  	if g, ok := groupMap.Load(h.Gid); ok {
    45  		h.Gname = g.(string)
    46  	} else if g, err := user.LookupGroupId(strconv.Itoa(h.Gid)); err == nil {
    47  		h.Gname = g.Name
    48  		groupMap.Store(h.Gid, h.Gname)
    49  	}
    50  
    51  	h.AccessTime = statAtime(sys)
    52  	h.ChangeTime = statCtime(sys)
    53  
    54  	// Best effort at populating Devmajor and Devminor.
    55  	if h.Typeflag == TypeChar || h.Typeflag == TypeBlock {
    56  		dev := uint64(sys.Rdev) // May be int32 or uint32
    57  		switch runtime.GOOS {
    58  		case "aix":
    59  			var major, minor uint32
    60  			major = uint32((dev & 0x3fffffff00000000) >> 32)
    61  			minor = uint32((dev & 0x00000000ffffffff) >> 0)
    62  			h.Devmajor, h.Devminor = int64(major), int64(minor)
    63  		case "linux":
    64  			// Copied from golang.org/x/sys/unix/dev_linux.go.
    65  			major := uint32((dev & 0x00000000000fff00) >> 8)
    66  			major |= uint32((dev & 0xfffff00000000000) >> 32)
    67  			minor := uint32((dev & 0x00000000000000ff) >> 0)
    68  			minor |= uint32((dev & 0x00000ffffff00000) >> 12)
    69  			h.Devmajor, h.Devminor = int64(major), int64(minor)
    70  		case "darwin", "ios":
    71  			// Copied from golang.org/x/sys/unix/dev_darwin.go.
    72  			major := uint32((dev >> 24) & 0xff)
    73  			minor := uint32(dev & 0xffffff)
    74  			h.Devmajor, h.Devminor = int64(major), int64(minor)
    75  		case "dragonfly":
    76  			// Copied from golang.org/x/sys/unix/dev_dragonfly.go.
    77  			major := uint32((dev >> 8) & 0xff)
    78  			minor := uint32(dev & 0xffff00ff)
    79  			h.Devmajor, h.Devminor = int64(major), int64(minor)
    80  		case "freebsd":
    81  			// Copied from golang.org/x/sys/unix/dev_freebsd.go.
    82  			major := uint32((dev >> 8) & 0xff)
    83  			minor := uint32(dev & 0xffff00ff)
    84  			h.Devmajor, h.Devminor = int64(major), int64(minor)
    85  		case "netbsd":
    86  			// Copied from golang.org/x/sys/unix/dev_netbsd.go.
    87  			major := uint32((dev & 0x000fff00) >> 8)
    88  			minor := uint32((dev & 0x000000ff) >> 0)
    89  			minor |= uint32((dev & 0xfff00000) >> 12)
    90  			h.Devmajor, h.Devminor = int64(major), int64(minor)
    91  		case "openbsd":
    92  			// Copied from golang.org/x/sys/unix/dev_openbsd.go.
    93  			major := uint32((dev & 0x0000ff00) >> 8)
    94  			minor := uint32((dev & 0x000000ff) >> 0)
    95  			minor |= uint32((dev & 0xffff0000) >> 8)
    96  			h.Devmajor, h.Devminor = int64(major), int64(minor)
    97  		default:
    98  			// TODO: Implement solaris (see https://golang.org/issue/8106)
    99  		}
   100  	}
   101  	return nil
   102  }