gdb/dwarf2/leb.c

   1 /* Low-level DWARF 2 reading code
   2
   3    Copyright (C) 1994-2020 Free Software Foundation, Inc.
   4
   5    Adapted by Gary Funck (gary@intrepid.com), Intrepid Technology,
   6    Inc.  with support from Florida State University (under contract
   7    with the Ada Joint Program Office), and Silicon Graphics, Inc.
   8    Initial contribution by Brent Benson, Harris Computer Systems, Inc.,
   9    based on Fred Fish's (Cygnus Support) implementation of DWARF 1
  10    support.
  11
  12    This file is part of GDB.
  13
  14    This program is free software; you can redistribute it and/or modify
  15    it under the terms of the GNU General Public License as published by
  16    the Free Software Foundation; either version 3 of the License, or
  17    (at your option) any later version.
  18
  19    This program is distributed in the hope that it will be useful,
  20    but WITHOUT ANY WARRANTY; without even the implied warranty of
  21    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22    GNU General Public License for more details.
  23
  24    You should have received a copy of the GNU General Public License
  25    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  26
  27 #include "defs.h"
  28 #include "dwarf2/leb.h"
  29
  30 ULONGEST
  31 read_unsigned_leb128 (bfd *abfd, const gdb_byte *buf,
  32                           unsigned int *bytes_read_ptr)
  33 {
  34   ULONGEST result;
  35   unsigned int num_read;
  36   int shift;
  37   unsigned char byte;
  38
  39   result = 0;
  40   shift = 0;
  41   num_read = 0;
  42   while (1)
  43     {
  44       byte = bfd_get_8 (abfd, buf);
  45       buf++;
  46       num_read++;
  47       result |= ((ULONGEST) (byte & 127) << shift);
  48       if ((byte & 128) == 0)
  49         {
  50           break;
  51         }
  52       shift += 7;
  53     }
  54   *bytes_read_ptr = num_read;
  55   return result;
  56 }
  57
  58 LONGEST
  59 read_signed_leb128 (bfd *abfd, const gdb_byte *buf,
  60                     unsigned int *bytes_read_ptr)
  61 {
  62   ULONGEST result;
  63   int shift, num_read;
  64   unsigned char byte;
  65
  66   result = 0;
  67   shift = 0;
  68   num_read = 0;
  69   while (1)
  70     {
  71       byte = bfd_get_8 (abfd, buf);
  72       buf++;
  73       num_read++;
  74       result |= ((ULONGEST) (byte & 127) << shift);
  75       shift += 7;
  76       if ((byte & 128) == 0)
  77         {
  78           break;
  79         }
  80     }
  81   if ((shift < 8 * sizeof (result)) && (byte & 0x40))
  82     result |= -(((ULONGEST) 1) << shift);
  83   *bytes_read_ptr = num_read;
  84   return result;
  85 }
  86
  87 /* See leb.h.  */
  88
  89 LONGEST
  90 read_initial_length (bfd *abfd, const gdb_byte *buf, unsigned int *bytes_read,
  91                      bool handle_nonstd)
  92 {
  93   LONGEST length = bfd_get_32 (abfd, buf);
  94
  95   if (length == 0xffffffff)
  96     {
  97       length = bfd_get_64 (abfd, buf + 4);
  98       *bytes_read = 12;
  99     }
 100   else if (handle_nonstd && length == 0)
 101     {
 102       /* Handle the (non-standard) 64-bit DWARF2 format used by IRIX.  */
 103       length = bfd_get_64 (abfd, buf);
 104       *bytes_read = 8;
 105     }
 106   else
 107     {
 108       *bytes_read = 4;
 109     }
 110
 111   return length;
 112 }
 113
 114 /* See leb.h.  */
 115
 116 LONGEST
 117 read_offset (bfd *abfd, const gdb_byte *buf, unsigned int offset_size)
 118 {
 119   LONGEST retval = 0;
 120
 121   switch (offset_size)
 122     {
 123     case 4:
 124       retval = bfd_get_32 (abfd, buf);
 125       break;
 126     case 8:
 127       retval = bfd_get_64 (abfd, buf);
 128       break;
 129     default:
 130       internal_error (__FILE__, __LINE__,
 131                       _("read_offset_1: bad switch [in module %s]"),
 132                       bfd_get_filename (abfd));
 133     }
 134
 135   return retval;
 136 }