mirror of
https://git.savannah.gnu.org/git/tar.git
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400 lines
13 KiB
C
400 lines
13 KiB
C
/* GNU tar Archive Format description.
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Copyright 1988-2026 Free Software Foundation, Inc.
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This file is part of GNU tar.
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GNU tar is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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GNU tar is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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/* tar Header Block, from POSIX 1003.1-2024
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<https://pubs.opengroup.org/onlinepubs/9799919799/utilities/pax.html#tagtcjh_21> */
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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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enum
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{
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REGTYPE = '0', /* regular file */
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AREGTYPE = '\0', /* regular file */
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LNKTYPE = '1', /* link */
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SYMTYPE = '2', /* symbolic link */
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CHRTYPE = '3', /* character special */
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BLKTYPE = '4', /* block special */
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DIRTYPE = '5', /* directory */
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FIFOTYPE = '6', /* FIFO special */
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CONTTYPE = '7', /* contiguous; treated as a regular file */
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XHDTYPE = 'x', /* Extended header referring to the
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next file in the archive */
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XGLTYPE = 'g' /* Global extended header */
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};
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/* Bits used in the mode field, values in octal. */
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enum
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{
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TSUID = 04000, /* set UID on execution */
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TSGID = 02000, /* set GID on execution */
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TSVTX = 01000, /* reserved */
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/* file permissions */
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TUREAD = 00400, /* read by owner */
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TUWRITE = 00200, /* write by owner */
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TUEXEC = 00100, /* execute/search by owner */
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TGREAD = 00040, /* read by group */
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TGWRITE = 00020, /* write by group */
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TGEXEC = 00010, /* execute/search by group */
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TOREAD = 00004, /* read by other */
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TOWRITE = 00002, /* write by other */
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TOEXEC = 00001 /* execute/search by other */
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};
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/* tar Header Block, GNU extensions. */
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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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enum
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{
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SPARSES_IN_EXTRA_HEADER = 16,
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SPARSES_IN_OLDGNU_HEADER = 4,
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SPARSES_IN_SPARSE_HEADER = 21
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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 Incr. archive: atime of the file */
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char ctime[12]; /* 357 Incr. archive: ctime of the file */
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char offset[12]; /* 369 Multivolume archive: the offset of
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the start of this volume */
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char longnames[4]; /* 381 Not used */
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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 Sparse file: Extension sparse header
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follows */
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char realsize[12]; /* 483 Sparse file: Real size*/
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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. Letters in use in other implementations include:
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'A' Solaris Access Control List
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'E' Solaris Extended Attribute File
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'I' Inode only, as in 'star'
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'N' Obsolete GNU tar, for file names too long for main header. */
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enum
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{
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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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GNUTYPE_DUMPDIR = 'D',
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/* Identifies the *next* file on the tape as having a long linkname. */
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GNUTYPE_LONGLINK = 'K',
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/* Identifies the *next* file on the tape as having a long name. */
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GNUTYPE_LONGNAME = 'L',
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/* This is the continuation of a file that began on another volume. */
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GNUTYPE_MULTIVOL = 'M',
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/* This is for sparse files. */
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GNUTYPE_SPARSE = 'S',
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/* This file is a tape/volume header. Ignore it on extraction. */
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GNUTYPE_VOLHDR = 'V',
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/* Solaris extended header. */
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SOLARIS_XHDTYPE = 'X'
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};
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/* Jörg Schilling star header. */
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struct star_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[131]; /* 345 */
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char atime[12]; /* 476 */
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char ctime[12]; /* 488 */
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/* 500 */
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};
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enum
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{
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SPARSES_IN_STAR_HEADER = 4,
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SPARSES_IN_STAR_EXT_HEADER = 21
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};
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struct star_in_header
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{
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char fill[345]; /* 0 Everything that is before t_prefix */
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char prefix[1]; /* 345 t_name prefix */
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char fill2; /* 346 */
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char fill3[8]; /* 347 */
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char isextended; /* 355 */
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struct sparse sp[SPARSES_IN_STAR_HEADER]; /* 356 */
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char realsize[12]; /* 452 Actual size of the file */
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char offset[12]; /* 464 Offset of multivolume contents */
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char atime[12]; /* 476 */
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char ctime[12]; /* 488 */
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char mfill[8]; /* 500 */
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char xmagic[4]; /* 508 "tar" */
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};
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struct star_ext_header
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{
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struct sparse sp[SPARSES_IN_STAR_EXT_HEADER];
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char isextended;
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};
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/* END */
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/* tar Header Block, overall structure. */
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/* tar files are made in basic blocks of size BLOCKSIZE.
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LG_BLOCKSIZE is the log base 2 of BLOCKSIZE. */
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enum { LG_BLOCKSIZE = 9, BLOCKSIZE = 1 << LG_BLOCKSIZE };
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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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USTAR_FORMAT, /* POSIX.1-1988 (ustar) format */
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POSIX_FORMAT, /* POSIX.1-2001 format */
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STAR_FORMAT, /* Star format defined in 1994 */
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GNU_FORMAT /* Same as OLDGNU_FORMAT with one exception:
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see FIXME note for to_chars() function
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(create.c:189) */
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};
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/* Information about a sparse file. */
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struct sp_array
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{
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off_t offset;
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off_t numbytes;
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};
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struct xheader
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{
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struct obstack *stk;
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idx_t size;
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char *buffer;
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idx_t string_length;
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};
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/* Information about xattrs for a file. */
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struct xattr_array
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{
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char *xkey;
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char *xval_ptr;
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idx_t xval_len;
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};
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struct xattr_map
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{
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struct xattr_array *xm_map;
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idx_t xm_size; /* Size of the xattr map */
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idx_t xm_max; /* Max. number of entries in xattr_map */
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};
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struct tar_stat_info
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{
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char *orig_file_name; /* name of file read from the archive header */
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char *file_name; /* name of file for the current archive entry
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after being normalized. */
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bool had_trailing_slash; /* true if the current archive entry had a
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trailing slash before it was normalized. */
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char *link_name; /* name of link for the current archive entry. */
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char *uname; /* user name of owner */
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char *gname; /* group name of owner */
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char *cntx_name; /* SELinux context for the current archive entry. */
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char *acls_a_ptr; /* Access ACLs for the current archive entry. */
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idx_t acls_a_len; /* Access ACLs for the current archive entry. */
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char *acls_d_ptr; /* Default ACLs for the current archive entry. */
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idx_t acls_d_len; /* Default ACLs for the current archive entry. */
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struct stat stat; /* regular filesystem stat */
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/* STAT doesn't always have access, data modification, and status
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change times in a convenient form, so store them separately. */
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struct timespec atime;
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struct timespec mtime;
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struct timespec ctime;
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off_t archive_file_size; /* Size of file as stored in the archive.
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Equals stat.st_size for non-sparse files */
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bool is_sparse; /* Is the file sparse */
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/* For sparse files: */
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intmax_t sparse_major;
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intmax_t sparse_minor;
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idx_t sparse_map_avail; /* Index to the first unused element in
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sparse_map array. Zero if the file is
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not sparse */
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idx_t sparse_map_size; /* Size of the sparse map */
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struct sp_array *sparse_map;
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off_t real_size; /* The real size of sparse file */
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bool real_size_set; /* True when GNU.sparse.realsize is set in
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archived file */
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bool sparse_name_done; /* Set to true if 'GNU.sparse.name' header was
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processed pax header parsing. Following 'path'
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header (lower priority) will be ignored. */
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struct xattr_map xattr_map;
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/* Extended headers */
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struct xheader xhdr;
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/* For dumpdirs */
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bool is_dumpdir; /* Is the member a dumpdir? */
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bool skipped; /* The member contents are already read. */
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char *dumpdir; /* Contents of the dump directory */
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/* Parent directory, if creating an archive. This is null if the
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file is at the top level. */
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struct tar_stat_info *parent;
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/* Directory stream. If this is not null, it is in control of FD,
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and should be closed instead of FD. */
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DIR *dirstream;
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/* File descriptor, if creating an archive, and if a directory or a
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regular file or a contiguous file.
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It is zero if no file descriptor is available, either because it
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was never needed or because it was open and then closed to
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conserve on file descriptors. (Standard input is never used
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here, so zero cannot be a valid file descriptor.)
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It is negative if it could not be reopened after it was closed.
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Negate it to find out what errno was when the reopen failed. */
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int fd;
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/* Exclusion list */
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struct exclist *exclude_list;
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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 star_header star_header;
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struct oldgnu_header oldgnu_header;
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struct sparse_header sparse_header;
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struct star_in_header star_in_header;
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struct star_ext_header star_ext_header;
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};
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