gdb/dwarf2/leb.c

/* Low-level DWARF 2 reading code

   Copyright (C) 1994-2021 Free Software Foundation, Inc.

   Adapted by Gary Funck (gary@intrepid.com), Intrepid Technology,
   Inc.  with support from Florida State University (under contract
   with the Ada Joint Program Office), and Silicon Graphics, Inc.
   Initial contribution by Brent Benson, Harris Computer Systems, Inc.,
   based on Fred Fish's (Cygnus Support) implementation of DWARF 1
   support.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "dwarf2/leb.h"

ULONGEST
read_unsigned_leb128 (bfd *abfd, const gdb_byte *buf,
			  unsigned int *bytes_read_ptr)
{
  ULONGEST result;
  unsigned int num_read;
  int shift;
  unsigned char byte;

  result = 0;
  shift = 0;
  num_read = 0;
  while (1)
    {
      byte = bfd_get_8 (abfd, buf);
      buf++;
      num_read++;
      result |= ((ULONGEST) (byte & 127) << shift);
      if ((byte & 128) == 0)
	{
	  break;
	}
      shift += 7;
    }
  *bytes_read_ptr = num_read;
  return result;
}

LONGEST
read_signed_leb128 (bfd *abfd, const gdb_byte *buf,
		    unsigned int *bytes_read_ptr)
{
  ULONGEST result;
  int shift, num_read;
  unsigned char byte;

  result = 0;
  shift = 0;
  num_read = 0;
  while (1)
    {
      byte = bfd_get_8 (abfd, buf);
      buf++;
      num_read++;
      result |= ((ULONGEST) (byte & 127) << shift);
      shift += 7;
      if ((byte & 128) == 0)
	{
	  break;
	}
    }
  if ((shift < 8 * sizeof (result)) && (byte & 0x40))
    result |= -(((ULONGEST) 1) << shift);
  *bytes_read_ptr = num_read;
  return result;
}

/* See leb.h.  */

LONGEST
read_initial_length (bfd *abfd, const gdb_byte *buf, unsigned int *bytes_read,
		     bool handle_nonstd)
{
  LONGEST length = bfd_get_32 (abfd, buf);

  if (length == 0xffffffff)
    {
      length = bfd_get_64 (abfd, buf + 4);
      *bytes_read = 12;
    }
  else if (handle_nonstd && length == 0)
    {
      /* Handle the (non-standard) 64-bit DWARF2 format used by IRIX.  */
      length = bfd_get_64 (abfd, buf);
      *bytes_read = 8;
    }
  else
    {
      *bytes_read = 4;
    }

  return length;
}

/* See leb.h.  */

LONGEST
read_offset (bfd *abfd, const gdb_byte *buf, unsigned int offset_size)
{
  LONGEST retval = 0;

  switch (offset_size)
    {
    case 4:
      retval = bfd_get_32 (abfd, buf);
      break;
    case 8:
      retval = bfd_get_64 (abfd, buf);
      break;
    default:
      internal_error (__FILE__, __LINE__,
		      _("read_offset_1: bad switch [in module %s]"),
		      bfd_get_filename (abfd));
    }

  return retval;
}