/* Routines for vectors of uids/gids

   Copyright (C) 1995, 1996 Free Software Foundation, Inc.

   Written by Miles Bader <miles@gnu.ai.mit.edu>

   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 2, 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */

#include <malloc.h>
#include <string.h>
#include <idvec.h>

typedef uid_t id_t;

/* Return a new, empty, idvec, or NULL if there wasn't enough memory.  */
struct idvec *
make_idvec ()
{
  struct idvec *idvec = malloc (sizeof (struct idvec));
  if (idvec)
    {
      idvec->alloced = idvec->num = 0;
      idvec->ids = 0;
    }
  return idvec;
}

/* Free's IDVEC, but not the storage pointed to by the IDS field.  */
void
idvec_free_wrapper (struct idvec *idvec)
{
  free (idvec);
}

void 
idvec_free (struct idvec *idvec)
{
  if (idvec->alloced)
    free (idvec->ids);
  free (idvec);
}

/* Ensure that IDVEC has enough spaced allocated to hold NUM ids, thus
   ensuring that any subsequent ids added won't return a memory allocation
   error unless it would result in more ids that NUM.  ENOMEM is returned if
   a memory allocation error occurs.  */
error_t
idvec_ensure (struct idvec *idvec, unsigned num)
{
  if (num > idvec->alloced)
    {
      id_t *_ids = realloc (idvec->ids, num * sizeof (id_t));
      if (! _ids)
	return ENOMEM;
      idvec->ids = _ids;
      idvec->alloced = num;
    }
  return 0;
}

/* Like idvec_ensure(), but takes INC, the increment of the number of ids
   already in IDVEC as an argument.  */
error_t
idvec_grow (struct idvec *idvec, unsigned inc)
{
  return idvec_ensure (idvec, idvec->num + inc);
}

/* Returns true if IDVEC contains ID, at or after position POS.  */
int
idvec_tail_contains (struct idvec *idvec, unsigned pos, id_t id)
{
  while (pos < idvec->num)
    if (idvec->ids[pos++] == id)
      return  1;
  return 0;
}

/* Returns true if IDVEC contains ID.  */
int
idvec_contains (struct idvec *idvec, id_t id)
{
  return idvec_tail_contains (idvec, 0, id);
}

/* Insert ID into IDVEC at position POS, returning ENOMEM if there wasn't
   enough memory, or 0.  */
error_t
idvec_insert (struct idvec *idvec, unsigned pos, id_t id)
{
  error_t err = 0;
  unsigned num = idvec->num;

  if (idvec->alloced == num)
    /* If we seem to be growing by just one, actually prealloc some more. */
    err = idvec_grow (idvec, num + 1);
  else
    err = idvec_grow (idvec, 1);

  if (! err)
    {
      id_t *ids = idvec->ids;
      if (pos < num)
	bcopy (ids + pos, ids + pos + 1, (num - pos) * sizeof (id_t));
      else if (pos > num)
	bzero (ids + num, (pos - num) * sizeof (id_t));
      ids[pos] = id;
      idvec->num = num + 1;
    }

  return err;
}

/* Add ID onto the end of IDVEC, returning ENOMEM if there's not enough memory,
   or 0.  */
error_t
idvec_add (struct idvec *idvec, id_t id)
{
  return idvec_insert (idvec, idvec->num, id);
}

/* If IDVEC doesn't contain ID, add it onto the end, returning ENOMEM if
   there's not enough memory; otherwise, do nothing.  */
error_t
idvec_add_new (struct idvec *idvec, id_t id)
{
  if (idvec_contains (idvec, id))
    return 0;
  else
    return idvec_add (idvec, id);
}

/* If IDVEC doesn't contain ID at position POS or after, insert it at POS,
   returning ENOMEM if there's not enough memory; otherwise, do nothing.  */
error_t
idvec_insert_new (struct idvec *idvec, unsigned pos, id_t id)
{
  if (idvec_tail_contains (idvec, pos, id))
    return 0;
  else
    return idvec_insert (idvec, pos, id);
}

/* Adds each id in the vector IDS (NUM elements long) to IDVEC, as long as it
   wasn't previously in IDVEC.  */
error_t
idvec_merge_ids (struct idvec *idvec, id_t *ids, unsigned num)
{
  error_t err = 0;
  unsigned num_old = idvec->num;
  while (num-- > 0 && !err)
    {
      int i;
      for (i = 0; i < num_old; i++)
	if (idvec->ids[i] == *ids)
	  break;
      if (i == num_old)
	err = idvec_add (idvec, *ids);
      ids++;
    }
  return err;
}

/* Adds each id from  NEW to IDVEC, as if with idvec_add_new().  */
error_t
idvec_merge (struct idvec *idvec, struct idvec *new)
{
  return idvec_merge_ids (idvec, new->ids, new->num);
}

/* Remove any occurances of ID in IDVEC after position POS>  Returns true if
   anything was done.  */
int
idvec_remove (struct idvec *idvec, unsigned pos, id_t id)
{
  int left = idvec->num - pos;
  id_t *ids = idvec->ids + pos, *targ = ids;
  while (left--)
    {
      if (*ids != id)
	{
	  if (ids != targ)
	    *targ = *ids;
	  targ++;
	}
      ids++;
    }
  if (ids == targ)
    return 0;
  idvec->num = targ - idvec->ids;
  return 1;
}

/* Deleted the id at position POS in IDVEC.  */
void
idvec_delete (struct idvec *idvec, unsigned pos)
{
  unsigned num = idvec->num;
  if (pos < num)
    {
      id_t *ids = idvec->ids;
      idvec->num = --num;
      if (num > pos)
	bcopy (ids + pos + 1, ids + pos, (num - pos) * sizeof (id_t));
    }
}

/* Insert ID at position POS in IDVEC, remoint any instances of ID previously
   present at POS or after.  ENOMEM is returned if there's not enough memory,
   otherwise 0.  */
error_t
idvec_insert_only (struct idvec *idvec, unsigned pos, id_t id)
{
  if (idvec->ids[pos] == id)
    return 0;
  else
    {
      idvec_remove (idvec, pos, id);
      return idvec_insert (idvec, pos, id);
    }
}

/* EFF and AVAIL should be idvec's corresponding to a processes effective and
   available ids.  ID replaces the first id in EFF, and what it replaces is
   preserved by adding it to AVAIL (if not already present).  If SECURE is
   non-NULL, and ID was not previously present in either EFF or AVAIL, then
   *SECURE is set to true.  ENOMEM is returned if a malloc fails, otherwise
   0.  The return parameters are only touched if this call succeeds.  */
error_t
idvec_setid (struct idvec *eff, struct idvec *avail, id_t id, int *secure)
{
  error_t err;
  /* True if ID was not previously present in either EFF or AVAIL.  */
  int _secure = !idvec_contains (eff, id) &&  !idvec_contains (avail, id);

  if (eff->num > 0)
    /* If there are any old effective ids, we replace eff[0] with ID, and try
       to preserve the old eff[0] by putting it in AVAIL list if necessary.  */
    {
      if (avail->num == 0)
	/* The old eff[0] becomes avail[0] (the posix real id).  */
	err = idvec_add (avail, eff->ids[0]);
      else
	/* We preserve the old real id, and add eff[0] to the list of saved
	   ids (if necessary).  Inserting it means that the latest id saved
	   will correspond to the (single) posix saved id.  */
	err = idvec_insert_only (avail, 1, eff->ids[0]);

      /* Replace eff[0] with the new id.  */
      eff->ids[0] = id;
    }
  else
    /* No previous effective ids, just make ID the first one.  */
    err = idvec_add (eff, id);

  if (err)
    return err;

  if (_secure && secure && !*secure)
    *secure = 1;

  return 0;
}