/* Portability and helper wrappers.
   Copyright (C) 2019-2024 Free Software Foundation, Inc.

   This file is part of libctf.

   libctf 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, 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; see the file COPYING.  If not see
   <http://www.gnu.org/licenses/>.  */

#include <ctf-impl.h>
#ifdef HAVE_MMAP
#include <sys/mman.h>
#endif
#include <sys/types.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>

/* Private, read-only mmap from a file, with fallback to copying.

   No handling of page-offset issues at all: the caller must allow for that. */

_libctf_malloc_ void *
ctf_mmap (size_t length, size_t offset, int fd)
{
  void *data;

#ifdef HAVE_MMAP
  data = mmap (NULL, length, PROT_READ, MAP_PRIVATE, fd, offset);
  if (data == MAP_FAILED)
    data = NULL;
#else
  if ((data = malloc (length)) != NULL)
    {
      if (ctf_pread (fd, data, length, offset) <= 0)
	{
	  free (data);
	  data = NULL;
	}
    }
#endif
  return data;
}

void
ctf_munmap (void *buf, size_t length _libctf_unused_)
{
#ifdef HAVE_MMAP
  (void) munmap (buf, length);
#else
  free (buf);
#endif
}

/* pread() implementation, retrying on short reads.  */

ssize_t
ctf_pread (int fd, void *buf, ssize_t count, off_t offset)
{
  ssize_t len;
  size_t acc = 0;
  char *data = (char *) buf;

#ifdef HAVE_PREAD
  while (count > 0)
    {
      errno = 0;
      if (((len = pread (fd, data, count, offset)) < 0) &&
	  errno != EINTR)
	  return len;
      if (errno == EINTR)
	continue;

      acc += len;
      if (len == 0)				/* EOF.  */
	return acc;

      count -= len;
      offset += len;
      data += len;
    }
  return acc;
#else
  off_t orig_off;

  if ((orig_off = lseek (fd, 0, SEEK_CUR)) < 0)
    return -1;
  if ((lseek (fd, offset, SEEK_SET)) < 0)
    return -1;

  while (count > 0)
    {
      errno = 0;
      if (((len = read (fd, data, count)) < 0) &&
	  errno != EINTR)
	  return len;
      if (errno == EINTR)
	continue;

      acc += len;
      if (len == 0)				/* EOF.  */
	break;

      count -= len;
      data += len;
    }
  if ((lseek (fd, orig_off, SEEK_SET)) < 0)
    return -1;					/* offset is smashed.  */
#endif

  return acc;
}