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alloc-fd.c

/* Copyright (C) 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <hurd.h>
#include <hurd/fd.h>
#include <hurd/resource.h>
#include <stdlib.h>
#include "hurdmalloc.h"       /* XXX */

/* Allocate a new file descriptor and return it, locked.  The new
   descriptor number will be no less than FIRST_FD.  If the table is full,
   set errno to EMFILE and return NULL.  If FIRST_FD is negative or bigger
   than the size of the table, set errno to EINVAL and return NULL.  */

struct hurd_fd *
_hurd_alloc_fd (int *fd, int first_fd)
{
  int i;
  void *crit;
  long int rlimit;

  if (first_fd < 0)
    {
      errno = EINVAL;
      return NULL;
    }

  crit = _hurd_critical_section_lock ();

  __mutex_lock (&_hurd_dtable_lock);

 search:
  for (i = first_fd; i < _hurd_dtablesize; ++i)
    {
      struct hurd_fd *d = _hurd_dtable[i];
      if (d == NULL)
      {
        /* Allocate a new descriptor structure for this slot,
           initializing its port cells to nil.  The test below will catch
           and return this descriptor cell after locking it.  */
        d = _hurd_new_fd (MACH_PORT_NULL, MACH_PORT_NULL);
        if (d == NULL)
          {
            __mutex_unlock (&_hurd_dtable_lock);
            _hurd_critical_section_unlock (crit);
            return NULL;
          }
        _hurd_dtable[i] = d;
      }

      __spin_lock (&d->port.lock);
      if (d->port.port == MACH_PORT_NULL)
      {
        __mutex_unlock (&_hurd_dtable_lock);
        _hurd_critical_section_unlock (crit);
        if (fd != NULL)
          *fd = i;
        return d;
      }
      else
      __spin_unlock (&d->port.lock);
    }

  __mutex_lock (&_hurd_rlimit_lock);
  rlimit = _hurd_rlimits[RLIMIT_OFILE].rlim_cur;
  __mutex_unlock (&_hurd_rlimit_lock);

  if (first_fd < rlimit)
    {
      /* The descriptor table is full.  Check if we have reached the
       resource limit, or only the allocated size.  */
      if (_hurd_dtablesize < rlimit)
      {
        /* Enlarge the table.  */
        int save = errno;
        struct hurd_fd **new;
        /* Try to double the table size, but don't exceed the limit,
           and make sure it exceeds FIRST_FD.  */
        int size = _hurd_dtablesize * 2;
        if (size > rlimit)
          size = rlimit;
        else if (size <= first_fd)
          size = first_fd + 1;

        if (size * sizeof (*_hurd_dtable) < size)
          {
            /* Integer overflow! */
            errno = ENOMEM;
            goto out;
          }

        /* If we fail to allocate that, decrement the desired size
           until we succeed in allocating it.  */
        do
          new = realloc (_hurd_dtable, size * sizeof (*_hurd_dtable));
        while (new == NULL && size-- > first_fd);

        if (new != NULL)
          {
            /* We managed to allocate a new table.  Now install it.  */
            errno = save;
            if (first_fd < _hurd_dtablesize)
            first_fd = _hurd_dtablesize;
            /* Initialize the new slots.  */
            for (i = _hurd_dtablesize; i < size; ++i)
            new[i] = NULL;
            _hurd_dtablesize = size;
            _hurd_dtable = new;
            /* Go back to the loop to initialize the first new slot.  */
            goto search;
          }
        else
          errno = ENOMEM;
      }
      else
      errno = EMFILE;
    }
  else
    errno = EINVAL;           /* Bogus FIRST_FD value.  */

 out:
  __mutex_unlock (&_hurd_dtable_lock);
  _hurd_critical_section_unlock (crit);

  return NULL;
}

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