Dogcows Code - chaz/tar/blob - src/tar.h

   1 /* Format of tar archives.
   2    Copyright (C) 1988, 92, 93, 94, 96, 97 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify it
   5    under the terms of the GNU General Public License as published by the
   6    Free Software Foundation; either version 2, or (at your option) any later
   7    version.
   8
   9    This program is distributed in the hope that it will be useful, but
  10    WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
  12    Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, write to the Free Software Foundation, Inc.,
  16    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* GNU tar Archive Format description.  */
  19
  20 /* If OLDGNU_COMPATIBILITY is not zero, tar produces archives which, by
  21    default, are readable by older versions of GNU tar.  This can be
  22    overriden by using --posix; in this case, POSIXLY_CORRECT in environment
  23    may be set for enforcing stricter conformance.  If OLDGNU_COMPATIBILITY
  24    is zero or undefined, tar will eventually produces archives which, by
  25    default, POSIX compatible; then either using --posix or defining
  26    POSIXLY_CORRECT enforces stricter conformance.
  27
  28    This #define will disappear in a few years.  FP, June 1995.  */
  29 #define OLDGNU_COMPATIBILITY 1
  30
  31 /*---------------------------------------------.
  32 | `tar' Header Block, from POSIX 1003.1-1990.  |
  33 `---------------------------------------------*/
  34
  35 /* POSIX header.  */
  36
  37 struct posix_header
  38 {                               /* byte offset */
  39   char name[100];               /*   0 */
  40   char mode[8];                 /* 100 */
  41   char uid[8];                  /* 108 */
  42   char gid[8];                  /* 116 */
  43   char size[12];                /* 124 */
  44   char mtime[12];               /* 136 */
  45   char chksum[8];               /* 148 */
  46   char typeflag;                /* 156 */
  47   char linkname[100];           /* 157 */
  48   char magic[6];                /* 257 */
  49   char version[2];              /* 263 */
  50   char uname[32];               /* 265 */
  51   char gname[32];               /* 297 */
  52   char devmajor[8];             /* 329 */
  53   char devminor[8];             /* 337 */
  54   char prefix[155];             /* 345 */
  55                                 /* 500 */
  56 };
  57
  58 #define TMAGIC   "ustar"        /* ustar and a null */
  59 #define TMAGLEN  6
  60 #define TVERSION "00"           /* 00 and no null */
  61 #define TVERSLEN 2
  62
  63 /* Values used in typeflag field.  */
  64 #define REGTYPE  '0'            /* regular file */
  65 #define AREGTYPE '\0'           /* regular file */
  66 #define LNKTYPE  '1'            /* link */
  67 #define SYMTYPE  '2'            /* reserved */
  68 #define CHRTYPE  '3'            /* character special */
  69 #define BLKTYPE  '4'            /* block special */
  70 #define DIRTYPE  '5'            /* directory */
  71 #define FIFOTYPE '6'            /* FIFO special */
  72 #define CONTTYPE '7'            /* reserved */
  73
  74 /* Bits used in the mode field, values in octal.  */
  75 #define TSUID    04000          /* set UID on execution */
  76 #define TSGID    02000          /* set GID on execution */
  77 #define TSVTX    01000          /* reserved */
  78                                 /* file permissions */
  79 #define TUREAD   00400          /* read by owner */
  80 #define TUWRITE  00200          /* write by owner */
  81 #define TUEXEC   00100          /* execute/search by owner */
  82 #define TGREAD   00040          /* read by group */
  83 #define TGWRITE  00020          /* write by group */
  84 #define TGEXEC   00010          /* execute/search by group */
  85 #define TOREAD   00004          /* read by other */
  86 #define TOWRITE  00002          /* write by other */
  87 #define TOEXEC   00001          /* execute/search by other */
  88
  89 /*-------------------------------------.
  90 | `tar' Header Block, GNU extensions.  |
  91 `-------------------------------------*/
  92
  93 /* In GNU tar, SYMTYPE is for to symbolic links, and CONTTYPE is for
  94    contiguous files, so maybe disobeying the `reserved' comment in POSIX
  95    header description.  I suspect these were meant to be used this way, and
  96    should not have really been `reserved' in the published standards.  */
  97
  98 /* *BEWARE* *BEWARE* *BEWARE* that the following information is still
  99    boiling, and may change.  Even if the OLDGNU format description should be
 100    accurate, the so-called GNU format is not yet fully decided.  It is
 101    surely meant to use only extensions allowed by POSIX, but the sketch
 102    below repeats some ugliness from the OLDGNU format, which should rather
 103    go away.  Sparse files should be saved in such a way that they do *not*
 104    require two passes at archive creation time.  Huge files get some POSIX
 105    fields to overflow, alternate solutions have to be sought for this.  */
 106
 107 /* Descriptor for a single file hole.  */
 108
 109 struct sparse
 110 {                               /* byte offset */
 111   char offset[12];              /*   0 */
 112   char numbytes[12];            /*  12 */
 113                                 /*  24 */
 114 };
 115
 116 /* Sparse files are not supported in POSIX ustar format.  For sparse files
 117    with a POSIX header, a GNU extra header is provided which holds overall
 118    sparse information and a few sparse descriptors.  When an old GNU header
 119    replaces both the POSIX header and the GNU extra header, it holds some
 120    sparse descriptors too.  Whether POSIX or not, if more sparse descriptors
 121    are still needed, they are put into as many successive sparse headers as
 122    necessary.  The following constants tell how many sparse descriptors fit
 123    in each kind of header able to hold them.  */
 124
 125 #define SPARSES_IN_EXTRA_HEADER  16
 126 #define SPARSES_IN_OLDGNU_HEADER 4
 127 #define SPARSES_IN_SPARSE_HEADER 21
 128
 129 /* The GNU extra header contains some information GNU tar needs, but not
 130    foreseen in POSIX header format.  It is only used after a POSIX header
 131    (and never with old GNU headers), and immediately follows this POSIX
 132    header, when typeflag is a letter rather than a digit, so signaling a GNU
 133    extension.  */
 134
 135 struct extra_header
 136 {                               /* byte offset */
 137   char atime[12];               /*   0 */
 138   char ctime[12];               /*  12 */
 139   char offset[12];              /*  24 */
 140   char realsize[12];            /*  36 */
 141   char longnames[4];            /*  48 */
 142   char unused_pad1[68];         /*  52 */
 143   struct sparse sp[SPARSES_IN_EXTRA_HEADER];
 144                                 /* 120 */
 145   char isextended;              /* 504 */
 146                                 /* 505 */
 147 };
 148
 149 /* Extension header for sparse files, used immediately after the GNU extra
 150    header, and used only if all sparse information cannot fit into that
 151    extra header.  There might even be many such extension headers, one after
 152    the other, until all sparse information has been recorded.  */
 153
 154 struct sparse_header
 155 {                               /* byte offset */
 156   struct sparse sp[SPARSES_IN_SPARSE_HEADER];
 157                                 /*   0 */
 158   char isextended;              /* 504 */
 159                                 /* 505 */
 160 };
 161
 162 /* The old GNU format header conflicts with POSIX format in such a way that
 163    POSIX archives may fool old GNU tar's, and POSIX tar's might well be
 164    fooled by old GNU tar archives.  An old GNU format header uses the space
 165    used by the prefix field in a POSIX header, and cumulates information
 166    normally found in a GNU extra header.  With an old GNU tar header, we
 167    never see any POSIX header nor GNU extra header.  Supplementary sparse
 168    headers are allowed, however.  */
 169
 170 struct oldgnu_header
 171 {                               /* byte offset */
 172   char unused_pad1[345];        /*   0 */
 173   char atime[12];               /* 345 */
 174   char ctime[12];               /* 357 */
 175   char offset[12];              /* 369 */
 176   char longnames[4];            /* 381 */
 177   char unused_pad2;             /* 385 */
 178   struct sparse sp[SPARSES_IN_OLDGNU_HEADER];
 179                                 /* 386 */
 180   char isextended;              /* 482 */
 181   char realsize[12];            /* 483 */
 182                                 /* 495 */
 183 };
 184
 185 /* OLDGNU_MAGIC uses both magic and version fields, which are contiguous.
 186    Found in an archive, it indicates an old GNU header format, which will be
 187    hopefully become obsolescent.  With OLDGNU_MAGIC, uname and gname are
 188    valid, though the header is not truly POSIX conforming.  */
 189 #define OLDGNU_MAGIC "ustar  "  /* 7 chars and a null */
 190
 191 /* The standards committee allows only capital A through capital Z for
 192    user-defined expansion.  */
 193
 194 /* This is a dir entry that contains the names of files that were in the
 195    dir at the time the dump was made.  */
 196 #define GNUTYPE_DUMPDIR 'D'
 197
 198 /* Identifies the *next* file on the tape as having a long linkname.  */
 199 #define GNUTYPE_LONGLINK 'K'
 200
 201 /* Identifies the *next* file on the tape as having a long name.  */
 202 #define GNUTYPE_LONGNAME 'L'
 203
 204 /* This is the continuation of a file that began on another volume.  */
 205 #define GNUTYPE_MULTIVOL 'M'
 206
 207 /* For storing filenames that do not fit into the main header.  */
 208 #define GNUTYPE_NAMES 'N'
 209
 210 /* This is for sparse files.  */
 211 #define GNUTYPE_SPARSE 'S'
 212
 213 /* This file is a tape/volume header.  Ignore it on extraction.  */
 214 #define GNUTYPE_VOLHDR 'V'
 215
 216 /*--------------------------------------.
 217 | tar Header Block, overall structure.  |
 218 `--------------------------------------*/
 219
 220 /* tar files are made in basic blocks of this size.  */
 221 #define BLOCKSIZE 512
 222
 223 enum archive_format
 224 {
 225   DEFAULT_FORMAT,               /* format to be decided later */
 226   V7_FORMAT,                    /* old V7 tar format */
 227   OLDGNU_FORMAT,                /* GNU format as per before tar 1.12 */
 228   POSIX_FORMAT,                 /* restricted, pure POSIX format */
 229   GNU_FORMAT                    /* POSIX format with GNU extensions */
 230 };
 231
 232 union block
 233 {
 234   char buffer[BLOCKSIZE];
 235   struct posix_header header;
 236   struct extra_header extra_header;
 237   struct oldgnu_header oldgnu_header;
 238   struct sparse_header sparse_header;
 239 };
 240
 241 /* End of Format description.  */