Source file src/pkg/archive/tar/common.go
1 // Copyright 2009 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 // Package tar implements access to tar archives. 6 // It aims to cover most of the variations, including those produced 7 // by GNU and BSD tars. 8 // 9 // References: 10 // http://www.freebsd.org/cgi/man.cgi?query=tar&sektion=5 11 // http://www.gnu.org/software/tar/manual/html_node/Standard.html 12 package tar 13 14 import "time" 15 16 const ( 17 blockSize = 512 18 19 // Types 20 TypeReg = '0' // regular file 21 TypeRegA = '\x00' // regular file 22 TypeLink = '1' // hard link 23 TypeSymlink = '2' // symbolic link 24 TypeChar = '3' // character device node 25 TypeBlock = '4' // block device node 26 TypeDir = '5' // directory 27 TypeFifo = '6' // fifo node 28 TypeCont = '7' // reserved 29 TypeXHeader = 'x' // extended header 30 TypeXGlobalHeader = 'g' // global extended header 31 ) 32 33 // A Header represents a single header in a tar archive. 34 // Some fields may not be populated. 35 type Header struct { 36 Name string // name of header file entry 37 Mode int64 // permission and mode bits 38 Uid int // user id of owner 39 Gid int // group id of owner 40 Size int64 // length in bytes 41 ModTime time.Time // modified time 42 Typeflag byte // type of header entry 43 Linkname string // target name of link 44 Uname string // user name of owner 45 Gname string // group name of owner 46 Devmajor int64 // major number of character or block device 47 Devminor int64 // minor number of character or block device 48 AccessTime time.Time // access time 49 ChangeTime time.Time // status change time 50 } 51 52 var zeroBlock = make([]byte, blockSize) 53 54 // POSIX specifies a sum of the unsigned byte values, but the Sun tar uses signed byte values. 55 // We compute and return both. 56 func checksum(header []byte) (unsigned int64, signed int64) { 57 for i := 0; i < len(header); i++ { 58 if i == 148 { 59 // The chksum field (header[148:156]) is special: it should be treated as space bytes. 60 unsigned += ' ' * 8 61 signed += ' ' * 8 62 i += 7 63 continue 64 } 65 unsigned += int64(header[i]) 66 signed += int64(int8(header[i])) 67 } 68 return 69 } 70 71 type slicer []byte 72 73 func (sp *slicer) next(n int) (b []byte) { 74 s := *sp 75 b, *sp = s[0:n], s[n:] 76 return 77 }