236 lines
9.6 KiB
Plaintext
236 lines
9.6 KiB
Plaintext
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/* GNU tar Archive Format description.
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Copyright (C) 1988, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
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1997, 2000, 2001 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2, or (at your option) any later
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version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
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Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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/* If OLDGNU_COMPATIBILITY is not zero, tar produces archives which, by
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default, are readable by older versions of GNU tar. This can be
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overriden by using --posix; in this case, POSIXLY_CORRECT in environment
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may be set for enforcing stricter conformance. If OLDGNU_COMPATIBILITY
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is zero or undefined, tar will eventually produces archives which, by
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default, POSIX compatible; then either using --posix or defining
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POSIXLY_CORRECT enforces stricter conformance.
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This #define will disappear in a few years. FP, June 1995. */
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#define OLDGNU_COMPATIBILITY 1
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/* tar Header Block, from POSIX 1003.1-1990. */
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/* POSIX header. */
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struct posix_header
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@{ /* byte offset */
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char name[100]; /* 0 */
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char mode[8]; /* 100 */
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char uid[8]; /* 108 */
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char gid[8]; /* 116 */
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char size[12]; /* 124 */
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char mtime[12]; /* 136 */
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char chksum[8]; /* 148 */
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char typeflag; /* 156 */
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char linkname[100]; /* 157 */
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char magic[6]; /* 257 */
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char version[2]; /* 263 */
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char uname[32]; /* 265 */
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char gname[32]; /* 297 */
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char devmajor[8]; /* 329 */
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char devminor[8]; /* 337 */
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char prefix[155]; /* 345 */
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/* 500 */
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@};
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#define TMAGIC "ustar" /* ustar and a null */
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#define TMAGLEN 6
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#define TVERSION "00" /* 00 and no null */
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#define TVERSLEN 2
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/* Values used in typeflag field. */
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#define REGTYPE '0' /* regular file */
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#define AREGTYPE '\0' /* regular file */
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#define LNKTYPE '1' /* link */
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#define SYMTYPE '2' /* reserved */
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#define CHRTYPE '3' /* character special */
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#define BLKTYPE '4' /* block special */
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#define DIRTYPE '5' /* directory */
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#define FIFOTYPE '6' /* FIFO special */
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#define CONTTYPE '7' /* reserved */
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/* Bits used in the mode field, values in octal. */
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#define TSUID 04000 /* set UID on execution */
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#define TSGID 02000 /* set GID on execution */
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#define TSVTX 01000 /* reserved */
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/* file permissions */
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#define TUREAD 00400 /* read by owner */
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#define TUWRITE 00200 /* write by owner */
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#define TUEXEC 00100 /* execute/search by owner */
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#define TGREAD 00040 /* read by group */
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#define TGWRITE 00020 /* write by group */
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#define TGEXEC 00010 /* execute/search by group */
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#define TOREAD 00004 /* read by other */
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#define TOWRITE 00002 /* write by other */
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#define TOEXEC 00001 /* execute/search by other */
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/* tar Header Block, GNU extensions. */
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/* In GNU tar, SYMTYPE is for to symbolic links, and CONTTYPE is for
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contiguous files, so maybe disobeying the `reserved' comment in POSIX
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header description. I suspect these were meant to be used this way, and
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should not have really been `reserved' in the published standards. */
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/* *BEWARE* *BEWARE* *BEWARE* that the following information is still
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boiling, and may change. Even if the OLDGNU format description should be
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accurate, the so-called GNU format is not yet fully decided. It is
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surely meant to use only extensions allowed by POSIX, but the sketch
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below repeats some ugliness from the OLDGNU format, which should rather
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go away. Sparse files should be saved in such a way that they do *not*
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require two passes at archive creation time. Huge files get some POSIX
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fields to overflow, alternate solutions have to be sought for this. */
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/* Descriptor for a single file hole. */
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struct sparse
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@{ /* byte offset */
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char offset[12]; /* 0 */
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char numbytes[12]; /* 12 */
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/* 24 */
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@};
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/* Sparse files are not supported in POSIX ustar format. For sparse files
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with a POSIX header, a GNU extra header is provided which holds overall
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sparse information and a few sparse descriptors. When an old GNU header
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replaces both the POSIX header and the GNU extra header, it holds some
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sparse descriptors too. Whether POSIX or not, if more sparse descriptors
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are still needed, they are put into as many successive sparse headers as
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necessary. The following constants tell how many sparse descriptors fit
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in each kind of header able to hold them. */
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#define SPARSES_IN_EXTRA_HEADER 16
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#define SPARSES_IN_OLDGNU_HEADER 4
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#define SPARSES_IN_SPARSE_HEADER 21
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/* The GNU extra header contains some information GNU tar needs, but not
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foreseen in POSIX header format. It is only used after a POSIX header
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(and never with old GNU headers), and immediately follows this POSIX
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header, when typeflag is a letter rather than a digit, so signaling a GNU
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extension. */
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struct extra_header
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@{ /* byte offset */
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char atime[12]; /* 0 */
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char ctime[12]; /* 12 */
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char offset[12]; /* 24 */
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char realsize[12]; /* 36 */
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char longnames[4]; /* 48 */
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char unused_pad1[68]; /* 52 */
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struct sparse sp[SPARSES_IN_EXTRA_HEADER];
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/* 120 */
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char isextended; /* 504 */
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/* 505 */
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@};
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/* Extension header for sparse files, used immediately after the GNU extra
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header, and used only if all sparse information cannot fit into that
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extra header. There might even be many such extension headers, one after
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the other, until all sparse information has been recorded. */
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struct sparse_header
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@{ /* byte offset */
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struct sparse sp[SPARSES_IN_SPARSE_HEADER];
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/* 0 */
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char isextended; /* 504 */
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/* 505 */
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@};
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/* The old GNU format header conflicts with POSIX format in such a way that
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POSIX archives may fool old GNU tar's, and POSIX tar's might well be
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fooled by old GNU tar archives. An old GNU format header uses the space
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used by the prefix field in a POSIX header, and cumulates information
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normally found in a GNU extra header. With an old GNU tar header, we
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never see any POSIX header nor GNU extra header. Supplementary sparse
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headers are allowed, however. */
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struct oldgnu_header
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@{ /* byte offset */
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char unused_pad1[345]; /* 0 */
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char atime[12]; /* 345 */
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char ctime[12]; /* 357 */
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char offset[12]; /* 369 */
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char longnames[4]; /* 381 */
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char unused_pad2; /* 385 */
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struct sparse sp[SPARSES_IN_OLDGNU_HEADER];
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/* 386 */
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char isextended; /* 482 */
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char realsize[12]; /* 483 */
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/* 495 */
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@};
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/* OLDGNU_MAGIC uses both magic and version fields, which are contiguous.
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Found in an archive, it indicates an old GNU header format, which will be
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hopefully become obsolescent. With OLDGNU_MAGIC, uname and gname are
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valid, though the header is not truly POSIX conforming. */
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#define OLDGNU_MAGIC "ustar " /* 7 chars and a null */
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/* The standards committee allows only capital A through capital Z for
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user-defined expansion. */
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/* This is a dir entry that contains the names of files that were in the
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dir at the time the dump was made. */
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#define GNUTYPE_DUMPDIR 'D'
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/* Identifies the *next* file on the tape as having a long linkname. */
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#define GNUTYPE_LONGLINK 'K'
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/* Identifies the *next* file on the tape as having a long name. */
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#define GNUTYPE_LONGNAME 'L'
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/* This is the continuation of a file that began on another volume. */
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#define GNUTYPE_MULTIVOL 'M'
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/* For storing filenames that do not fit into the main header. */
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#define GNUTYPE_NAMES 'N'
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/* This is for sparse files. */
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#define GNUTYPE_SPARSE 'S'
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/* This file is a tape/volume header. Ignore it on extraction. */
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#define GNUTYPE_VOLHDR 'V'
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/* tar Header Block, overall structure. */
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/* tar files are made in basic blocks of this size. */
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#define BLOCKSIZE 512
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enum archive_format
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@{
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DEFAULT_FORMAT, /* format to be decided later */
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V7_FORMAT, /* old V7 tar format */
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OLDGNU_FORMAT, /* GNU format as per before tar 1.12 */
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POSIX_FORMAT, /* restricted, pure POSIX format */
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GNU_FORMAT /* POSIX format with GNU extensions */
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@};
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union block
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@{
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char buffer[BLOCKSIZE];
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struct posix_header header;
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struct extra_header extra_header;
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struct oldgnu_header oldgnu_header;
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struct sparse_header sparse_header;
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@};
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/* End of Format description. */
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