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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
package tar
const (
blockSize = 512
// Types
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.
)
// 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.
Mtime int64 // modified time; seconds since epoch.
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.
Atime int64 // access time; seconds since epoch.
Ctime int64 // status change time; seconds since epoch.
}
var zeroBlock = make([]byte, blockSize)
// POSIX specifies a sum of the unsigned byte values, but the Sun tar uses signed byte values.
// We compute and return both.
func checksum(header []byte) (unsigned int64, signed int64) {
for i := 0; i < len(header); i++ {
if i == 148 {
// The chksum field (header[148:156]) is special: it should be treated as space bytes.
unsigned += ' ' * 8
signed += ' ' * 8
i += 7
continue
}
unsigned += int64(header[i])
signed += int64(int8(header[i]))
}
return
}
type slicer []byte
func (sp *slicer) next(n int) (b []byte) {
s := *sp
b, *sp = s[0:n], s[n:]
return
}
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