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	const (
    15		blockSize = 512
    16	
    17		// Types
    18		TypeReg           = '0'
    19		TypeRegA          = '\x00'
    20		TypeLink          = '1'
    21		TypeSymlink       = '2'
    22		TypeChar          = '3'
    23		TypeBlock         = '4'
    24		TypeDir           = '5'
    25		TypeFifo          = '6'
    26		TypeCont          = '7'
    27		TypeXHeader       = 'x'
    28		TypeXGlobalHeader = 'g'
    29	)
    30	
    31	// A Header represents a single header in a tar archive.
    32	// Some fields may not be populated.
    33	type Header struct {
    34		Name     string
    35		Mode     int64
    36		Uid      int
    37		Gid      int
    38		Size     int64
    39		Mtime    int64
    40		Typeflag byte
    41		Linkname string
    42		Uname    string
    43		Gname    string
    44		Devmajor int64
    45		Devminor int64
    46		Atime    int64
    47		Ctime    int64
    48	}
    49	
    50	var zeroBlock = make([]byte, blockSize)
    51	
    52	// POSIX specifies a sum of the unsigned byte values, but the Sun tar uses signed byte values.
    53	// We compute and return both.
    54	func checksum(header []byte) (unsigned int64, signed int64) {
    55		for i := 0; i < len(header); i++ {
    56			if i == 148 {
    57				// The chksum field (header[148:156]) is special: it should be treated as space bytes.
    58				unsigned += ' ' * 8
    59				signed += ' ' * 8
    60				i += 7
    61				continue
    62			}
    63			unsigned += int64(header[i])
    64			signed += int64(int8(header[i]))
    65		}
    66		return
    67	}
    68	
    69	type slicer []byte
    70	
    71	func (sp *slicer) next(n int) (b []byte) {
    72		s := *sp
    73		b, *sp = s[0:n], s[n:]
    74		return
    75	}
The Go Programming Language

Source file src/pkg/archive/tar/common.go
