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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package tar implements access to tar archives.
// It aims to cover most of the variations, including those produced
// by GNU and BSD tars.
//
// References:
// http://www.freebsd.org/cgi/man.cgi?query=tar&sektion=5
// http://www.gnu.org/software/tar/manual/html_node/Standard.html
// http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html
package tar
import (
"errors"
"fmt"
"os"
"path"
"time"
)
// BUG: Use of the Uid and Gid fields in Header could overflow on 32-bit
// architectures. If a large value is encountered when decoding, the result
// stored in Header will be the truncated version.
// Header type flags.
const (
TypeReg = '0' // regular file
TypeRegA = '\x00' // regular file
TypeLink = '1' // hard link
TypeSymlink = '2' // symbolic link
TypeChar = '3' // character device node
TypeBlock = '4' // block device node
TypeDir = '5' // directory
TypeFifo = '6' // fifo node
TypeCont = '7' // reserved
TypeXHeader = 'x' // extended header
TypeXGlobalHeader = 'g' // global extended header
TypeGNULongName = 'L' // Next file has a long name
TypeGNULongLink = 'K' // Next file symlinks to a file w/ a long name
TypeGNUSparse = 'S' // sparse file
)
// A Header represents a single header in a tar archive.
// Some fields may not be populated.
type Header struct {
Name string // name of header file entry
Mode int64 // permission and mode bits
Uid int // user id of owner
Gid int // group id of owner
Size int64 // length in bytes
ModTime time.Time // modified time
Typeflag byte // type of header entry
Linkname string // target name of link
Uname string // user name of owner
Gname string // group name of owner
Devmajor int64 // major number of character or block device
Devminor int64 // minor number of character or block device
AccessTime time.Time // access time
ChangeTime time.Time // status change time
Xattrs map[string]string
}
// FileInfo returns an os.FileInfo for the Header.
func (h *Header) FileInfo() os.FileInfo {
return headerFileInfo{h}
}
// headerFileInfo implements os.FileInfo.
type headerFileInfo struct {
h *Header
}
func (fi headerFileInfo) Size() int64 { return fi.h.Size }
func (fi headerFileInfo) IsDir() bool { return fi.Mode().IsDir() }
func (fi headerFileInfo) ModTime() time.Time { return fi.h.ModTime }
func (fi headerFileInfo) Sys() interface{} { return fi.h }
// Name returns the base name of the file.
func (fi headerFileInfo) Name() string {
if fi.IsDir() {
return path.Base(path.Clean(fi.h.Name))
}
return path.Base(fi.h.Name)
}
// Mode returns the permission and mode bits for the headerFileInfo.
func (fi headerFileInfo) Mode() (mode os.FileMode) {
// Set file permission bits.
mode = os.FileMode(fi.h.Mode).Perm()
// Set setuid, setgid and sticky bits.
if fi.h.Mode&c_ISUID != 0 {
// setuid
mode |= os.ModeSetuid
}
if fi.h.Mode&c_ISGID != 0 {
// setgid
mode |= os.ModeSetgid
}
if fi.h.Mode&c_ISVTX != 0 {
// sticky
mode |= os.ModeSticky
}
// Set file mode bits.
// clear perm, setuid, setgid and sticky bits.
m := os.FileMode(fi.h.Mode) &^ 07777
if m == c_ISDIR {
// directory
mode |= os.ModeDir
}
if m == c_ISFIFO {
// named pipe (FIFO)
mode |= os.ModeNamedPipe
}
if m == c_ISLNK {
// symbolic link
mode |= os.ModeSymlink
}
if m == c_ISBLK {
// device file
mode |= os.ModeDevice
}
if m == c_ISCHR {
// Unix character device
mode |= os.ModeDevice
mode |= os.ModeCharDevice
}
if m == c_ISSOCK {
// Unix domain socket
mode |= os.ModeSocket
}
switch fi.h.Typeflag {
case TypeSymlink:
// symbolic link
mode |= os.ModeSymlink
case TypeChar:
// character device node
mode |= os.ModeDevice
mode |= os.ModeCharDevice
case TypeBlock:
// block device node
mode |= os.ModeDevice
case TypeDir:
// directory
mode |= os.ModeDir
case TypeFifo:
// fifo node
mode |= os.ModeNamedPipe
}
return mode
}
// sysStat, if non-nil, populates h from system-dependent fields of fi.
var sysStat func(fi os.FileInfo, h *Header) error
// Mode constants from the tar spec.
const (
c_ISUID = 04000 // Set uid
c_ISGID = 02000 // Set gid
c_ISVTX = 01000 // Save text (sticky bit)
c_ISDIR = 040000 // Directory
c_ISFIFO = 010000 // FIFO
c_ISREG = 0100000 // Regular file
c_ISLNK = 0120000 // Symbolic link
c_ISBLK = 060000 // Block special file
c_ISCHR = 020000 // Character special file
c_ISSOCK = 0140000 // Socket
)
// Keywords for the PAX Extended Header
const (
paxAtime = "atime"
paxCharset = "charset"
paxComment = "comment"
paxCtime = "ctime" // please note that ctime is not a valid pax header.
paxGid = "gid"
paxGname = "gname"
paxLinkpath = "linkpath"
paxMtime = "mtime"
paxPath = "path"
paxSize = "size"
paxUid = "uid"
paxUname = "uname"
paxXattr = "SCHILY.xattr."
paxNone = ""
)
// FileInfoHeader creates a partially-populated Header from fi.
// If fi describes a symlink, FileInfoHeader records link as the link target.
// If fi describes a directory, a slash is appended to the name.
// Because os.FileInfo's Name method returns only the base name of
// the file it describes, it may be necessary to modify the Name field
// of the returned header to provide the full path name of the file.
func FileInfoHeader(fi os.FileInfo, link string) (*Header, error) {
if fi == nil {
return nil, errors.New("tar: FileInfo is nil")
}
fm := fi.Mode()
h := &Header{
Name: fi.Name(),
ModTime: fi.ModTime(),
Mode: int64(fm.Perm()), // or'd with c_IS* constants later
}
switch {
case fm.IsRegular():
h.Mode |= c_ISREG
h.Typeflag = TypeReg
h.Size = fi.Size()
case fi.IsDir():
h.Typeflag = TypeDir
h.Mode |= c_ISDIR
h.Name += "/"
case fm&os.ModeSymlink != 0:
h.Typeflag = TypeSymlink
h.Mode |= c_ISLNK
h.Linkname = link
case fm&os.ModeDevice != 0:
if fm&os.ModeCharDevice != 0 {
h.Mode |= c_ISCHR
h.Typeflag = TypeChar
} else {
h.Mode |= c_ISBLK
h.Typeflag = TypeBlock
}
case fm&os.ModeNamedPipe != 0:
h.Typeflag = TypeFifo
h.Mode |= c_ISFIFO
case fm&os.ModeSocket != 0:
h.Mode |= c_ISSOCK
default:
return nil, fmt.Errorf("archive/tar: unknown file mode %v", fm)
}
if fm&os.ModeSetuid != 0 {
h.Mode |= c_ISUID
}
if fm&os.ModeSetgid != 0 {
h.Mode |= c_ISGID
}
if fm&os.ModeSticky != 0 {
h.Mode |= c_ISVTX
}
// If possible, populate additional fields from OS-specific
// FileInfo fields.
if sys, ok := fi.Sys().(*Header); ok {
// This FileInfo came from a Header (not the OS). Use the
// original Header to populate all remaining fields.
h.Uid = sys.Uid
h.Gid = sys.Gid
h.Uname = sys.Uname
h.Gname = sys.Gname
h.AccessTime = sys.AccessTime
h.ChangeTime = sys.ChangeTime
if sys.Xattrs != nil {
h.Xattrs = make(map[string]string)
for k, v := range sys.Xattrs {
h.Xattrs[k] = v
}
}
if sys.Typeflag == TypeLink {
// hard link
h.Typeflag = TypeLink
h.Size = 0
h.Linkname = sys.Linkname
}
}
if sysStat != nil {
return h, sysStat(fi, h)
}
return h, nil
}
// isHeaderOnlyType checks if the given type flag is of the type that has no
// data section even if a size is specified.
func isHeaderOnlyType(flag byte) bool {
switch flag {
case TypeLink, TypeSymlink, TypeChar, TypeBlock, TypeDir, TypeFifo:
return true
default:
return false
}
}