bfd/format.c

   1 /* Generic BFD support for file formats.
   2    Copyright (C) 1990-1991 Free Software Foundation, Inc.
   3    Written by Cygnus Support.
   4
   5 This file is part of BFD, the Binary File Descriptor library.
   6
   7 This program is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2 of the License, or
  10 (at your option) any later version.
  11
  12 This program is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with this program; if not, write to the Free Software
  19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  20
  21 /*
  22 SECTION
  23         File Formats
  24
  25         A format is a BFD concept of high level file contents type. The
  26         formats supported by BFD are:
  27
  28         o <<bfd_object>>
  29
  30         The BFD may contain data, symbols, relocations and debug info.
  31
  32         o <<bfd_archive>>
  33
  34         The BFD contains other BFDs and an optional index.
  35
  36         o <<bfd_core>>
  37
  38         The BFD contains the result of an executable core dump.
  39
  40
  41 */
  42
  43 #include "bfd.h"
  44 #include "sysdep.h"
  45 #include "libbfd.h"
  46
  47 extern bfd_target *target_vector[];
  48 extern bfd_target *default_vector[];
  49
  50
  51 /*
  52 FUNCTION
  53         bfd_check_format
  54
  55 SYNOPSIS
  56         boolean bfd_check_format(bfd *abfd, bfd_format format);
  57
  58 DESCRIPTION
  59         Verify if the file attached to the BFD @var{abfd} is compatible
  60         with the format @var{format} (i.e., one of <<bfd_object>>,
  61         <<bfd_archive>> or <<bfd_core>>).
  62
  63         If the BFD has been set to a specific target before the
  64         call, only the named target and format combination is
  65         checked. If the target has not been set, or has been set to
  66         <<default>>, then all the known target backends is
  67         interrogated to determine a match.  If the default target
  68         matches, it is used.  If not, exactly one target must recognize
  69         the file, or an error results.
  70
  71         The function returns <<true>> on success, otherwise <<false>>
  72         with one of the following error codes:
  73
  74         o invalid_operation -
  75         if <<format>> is not one of <<bfd_object>>, <<bfd_archive>> or
  76         <<bfd_core>>.
  77
  78         o system_call_error -
  79         if an error occured during a read - even some file mismatches
  80         can cause system_call_errors.
  81
  82         o file_not_recognised -
  83         none of the backends recognised the file format.
  84
  85         o file_ambiguously_recognized -
  86         more than one backend recognised the file format.
  87
  88 */
  89
  90 boolean
  91 DEFUN(bfd_check_format,(abfd, format),
  92       bfd *abfd AND
  93       bfd_format format)
  94 {
  95   bfd_target **target, *save_targ, *right_targ;
  96   int match_count;
  97
  98   if (!bfd_read_p (abfd) ||
  99       ((int)(abfd->format) < (int)bfd_unknown) ||
 100       ((int)(abfd->format) >= (int)bfd_type_end)) {
 101     bfd_error = invalid_operation;
 102     return false;
 103   }
 104
 105   if (abfd->format != bfd_unknown)
 106     return (abfd->format == format)? true: false;
 107
 108
 109   /* Since the target type was defaulted, check them
 110      all in the hope that one will be uniquely recognized.  */
 111
 112   save_targ = abfd->xvec;
 113   match_count = 0;
 114   right_targ = 0;
 115
 116
 117   /* presume the answer is yes */
 118   abfd->format = format;
 119
 120   /* If the target type was explicitly specified, just check that target.  */
 121
 122   if (!abfd->target_defaulted) {
 123     bfd_seek (abfd, (file_ptr)0, SEEK_SET);     /* rewind! */
 124
 125     right_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 126     if (right_targ) {
 127       abfd->xvec = right_targ;          /* Set the target as returned */
 128       return true;                      /* File position has moved, BTW */
 129     }
 130   }
 131
 132   for (target = target_vector; *target != NULL; target++) {
 133     bfd_target *temp;
 134
 135     abfd->xvec = *target;       /* Change BFD's target temporarily */
 136     bfd_seek (abfd, (file_ptr)0, SEEK_SET);
 137     /* If _bfd_check_format neglects to set bfd_error, assume wrong_format.
 138        We didn't used to even pay any attention to bfd_error, so I suspect
 139        that some _bfd_check_format might have this problem.  */
 140     bfd_error = wrong_format;
 141     temp = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 142     if (temp) {                         /* This format checks out as ok! */
 143       right_targ = temp;
 144       match_count++;
 145       /* If this is the default target, accept it, even if other targets
 146          might match.  People who want those other targets have to set
 147          the GNUTARGET variable.  */
 148       if (temp == default_vector[0])
 149         {
 150           match_count = 1;
 151           break;
 152         }
 153 #ifdef GNU960
 154       /* Big- and little-endian b.out archives look the same, but it doesn't
 155        * matter: there is no difference in their headers, and member file byte
 156        * orders will (I hope) be handled appropriately by bfd.  Ditto for big
 157        * and little coff archives.  And the 4 coff/b.out object formats are
 158        * unambiguous.  So accept the first match we find.
 159        */
 160       break;
 161 #endif
 162     } else if (bfd_error != wrong_format) {
 163       abfd->xvec = save_targ;
 164       abfd->format = bfd_unknown;
 165       return false;
 166     }
 167   }
 168
 169   if (match_count == 1) {
 170     abfd->xvec = right_targ;            /* Change BFD's target permanently */
 171     return true;                        /* File position has moved, BTW */
 172   }
 173
 174   abfd->xvec = save_targ;               /* Restore original target type */
 175   abfd->format = bfd_unknown;           /* Restore original format */
 176   bfd_error = ((match_count == 0) ? file_not_recognized :
 177                file_ambiguously_recognized);
 178   return false;
 179 }
 180
 181
 182 /*
 183 FUNCTION
 184         bfd_set_format
 185
 186 SYNOPSIS
 187         boolean bfd_set_format(bfd *abfd, bfd_format format);
 188
 189 DESCRIPTION
 190         This function sets the file format of the BFD @var{abfd} to the
 191         format @var{format}. If the target set in the BFD does not
 192         support the format requested, the format is invalid, or the BFD
 193         is not open for writing, then an error occurs.
 194
 195 */
 196
 197 boolean
 198 DEFUN(bfd_set_format,(abfd, format),
 199       bfd *abfd AND
 200       bfd_format format)
 201 {
 202
 203   if (bfd_read_p (abfd) ||
 204       ((int)abfd->format < (int)bfd_unknown) ||
 205       ((int)abfd->format >= (int)bfd_type_end)) {
 206     bfd_error = invalid_operation;
 207     return false;
 208   }
 209
 210   if (abfd->format != bfd_unknown)
 211     return (abfd->format == format) ? true:false;
 212
 213   /* presume the answer is yes */
 214   abfd->format = format;
 215
 216   if (!BFD_SEND_FMT (abfd, _bfd_set_format, (abfd))) {
 217     abfd->format = bfd_unknown;
 218     return false;
 219   }
 220
 221   return true;
 222 }
 223
 224
 225 /*
 226 FUNCTION
 227         bfd_format_string
 228
 229 SYNOPSIS
 230         CONST char *bfd_format_string(bfd_format format);
 231
 232 DESCRIPTION
 233         Return a pointer to a const string
 234         <<invalid>>, <<object>>, <<archive>>, <<core>>, or <<unknown>>,
 235         depending upon the value of @var{format}.
 236 */
 237
 238 CONST char *
 239 DEFUN(bfd_format_string,(format),
 240      bfd_format format)
 241 {
 242   if (((int)format <(int) bfd_unknown)
 243       || ((int)format >=(int) bfd_type_end))
 244     return "invalid";
 245
 246   switch (format) {
 247   case bfd_object:
 248     return "object";            /* linker/assember/compiler output */
 249   case bfd_archive:
 250     return "archive";           /* object archive file */
 251   case bfd_core:
 252     return "core";              /* core dump */
 253   default:
 254     return "unknown";
 255   }
 256 }