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// Archive/TarHeader.cpp
#include "StdAfx.h"
#include "TarHeader.h"
namespace NArchive {
namespace NTar {
namespace NFileHeader {
const char * const kLongLink = "././@LongLink";
const char * const kLongLink2 = "@LongLink";
// The magic field is filled with this if uname and gname are valid.
namespace NMagic
{
// const char * const kUsTar = "ustar"; // 5 chars
// const char * const kGNUTar = "GNUtar "; // 7 chars and a null
// const char * const kEmpty = "\0\0\0\0\0\0\0\0";
// 7-Zip used kUsTar_00 before 21.07:
const char k_Posix_ustar_00[8] = { 'u', 's', 't', 'a', 'r', 0, '0', '0' } ;
// GNU TAR uses such header:
const char k_GNU_ustar__[8] = { 'u', 's', 't', 'a', 'r', ' ', ' ', 0 } ;
}
/*
pre-POSIX.1-1988 (i.e. v7) tar header:
-----
Link indicator:
'0' or 0 : Normal file
'1' : Hard link
'2' : Symbolic link
Some pre-POSIX.1-1988 tar implementations indicated a directory by having
a trailing slash (/) in the name.
Numeric values : octal with leading zeroes.
For historical reasons, a final NUL or space character should also be used.
Thus only 11 octal digits can be stored from 12 bytes field.
2001 star : introduced a base-256 coding that is indicated by
setting the high-order bit of the leftmost byte of a numeric field.
GNU-tar and BSD-tar followed this idea.
versions of tar from before the first POSIX standard from 1988
pad the values with spaces instead of zeroes.
UStar
-----
UStar (Unix Standard TAR) : POSIX IEEE P1003.1 : 1988.
257 signature: "ustar", 0, "00"
265 32 Owner user name
297 32 Owner group name
329 8 Device major number
337 8 Device minor number
345 155 Filename prefix
POSIX.1-2001/pax
----
format is known as extended tar format or pax format
vendor-tagged vendor-specific enhancements.
tags Defined by the POSIX standard:
atime, mtime, path, linkpath, uname, gname, size, uid, gid, ...
PAX EXTENSION
-----------
Hard links
A further difference from the ustar header block is that data blocks
for files of typeflag 1 (hard link) may be included,
which means that the size field may be greater than zero.
Archives created by pax -o linkdata shall include these data
blocks with the hard links.
*
compatiblity
------------
7-Zip 16.03 supports "PaxHeader/"
7-Zip 20.01 supports "PaxHeaders.X/" with optional "./"
7-Zip 21.02 supports "@PaxHeader" with optional "./" "./"
GNU tar --format=posix uses "PaxHeaders/" in folder of file
GNU TAR format
==============
v7 - Unix V7
oldgnu - GNU tar <=1.12 : writes zero in last character in name
gnu - GNU tar 1.13 : doesn't write zero in last character in name
as 7-zip 21.07
ustar - POSIX.1-1988
posix (pax) - POSIX.1-2001
gnu tar:
if (S_ISCHR (st->stat.st_mode) || S_ISBLK (st->stat.st_mode)) {
major_t devmajor = major (st->stat.st_rdev);
minor_t devminor = minor (st->stat.st_rdev); }
*/
}}}
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