hurd/alloc-fd.c

   1 /* Copyright (C) 1994, 1995 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <hurd.h>
  20 #include <hurd/fd.h>
  21 #include <hurd/resource.h>
  22 #include <stdlib.h>
  23 #include "hurdmalloc.h"         /* XXX */
  24
  25 /* Allocate a new file descriptor and return it, locked.  The new
  26    descriptor number will be no less than FIRST_FD.  If the table is full,
  27    set errno to EMFILE and return NULL.  If FIRST_FD is negative or bigger
  28    than the size of the table, set errno to EINVAL and return NULL.  */
  29
  30 struct hurd_fd *
  31 _hurd_alloc_fd (int *fd, int first_fd)
  32 {
  33   int i;
  34   void *crit;
  35   long int rlimit;
  36
  37   if (first_fd < 0)
  38     {
  39       errno = EINVAL;
  40       return NULL;
  41     }
  42
  43   crit = _hurd_critical_section_lock ();
  44
  45   __mutex_lock (&_hurd_dtable_lock);
  46
  47  search:
  48   for (i = first_fd; i < _hurd_dtablesize; ++i)
  49     {
  50       struct hurd_fd *d = _hurd_dtable[i];
  51       if (d == NULL)
  52         {
  53           /* Allocate a new descriptor structure for this slot,
  54              initializing its port cells to nil.  The test below will catch
  55              and return this descriptor cell after locking it.  */
  56           d = _hurd_new_fd (MACH_PORT_NULL, MACH_PORT_NULL);
  57           if (d == NULL)
  58             {
  59               __mutex_unlock (&_hurd_dtable_lock);
  60               _hurd_critical_section_unlock (crit);
  61               return NULL;
  62             }
  63           _hurd_dtable[i] = d;
  64         }
  65
  66       __spin_lock (&d->port.lock);
  67       if (d->port.port == MACH_PORT_NULL)
  68         {
  69           __mutex_unlock (&_hurd_dtable_lock);
  70           _hurd_critical_section_unlock (crit);
  71           if (fd != NULL)
  72             *fd = i;
  73           return d;
  74         }
  75       else
  76         __spin_unlock (&d->port.lock);
  77     }
  78
  79   __mutex_lock (&_hurd_rlimit_lock);
  80   rlimit = _hurd_rlimits[RLIMIT_OFILE].rlim_cur;
  81   __mutex_unlock (&_hurd_rlimit_lock);
  82
  83   if (first_fd < rlimit)
  84     {
  85       /* The descriptor table is full.  Check if we have reached the
  86          resource limit, or only the allocated size.  */
  87       if (_hurd_dtablesize < rlimit)
  88         {
  89           /* Enlarge the table.  */
  90           int save = errno;
  91           struct hurd_fd **new;
  92           /* Try to double the table size, but don't exceed the limit,
  93              and make sure it exceeds FIRST_FD.  */
  94           int size = _hurd_dtablesize * 2;
  95           if (size > rlimit)
  96             size = rlimit;
  97           else if (size <= first_fd)
  98             size = first_fd + 1;
  99
 100           /* If we fail to allocate that, decrement the desired size
 101              until we succeed in allocating it.  */
 102           do
 103             new = realloc (_hurd_dtable, size * sizeof (*_hurd_dtable));
 104           while (new == NULL && size-- > first_fd);
 105
 106           if (new != NULL)
 107             {
 108               /* We managed to allocate a new table.  Now install it.  */
 109               errno = save;
 110               if (first_fd < _hurd_dtablesize)
 111                 first_fd = _hurd_dtablesize;
 112               /* Initialize the new slots.  */
 113               for (i = _hurd_dtablesize; i < size; ++i)
 114                 new[i] = NULL;
 115               _hurd_dtablesize = size;
 116               _hurd_dtable = new;
 117               /* Go back to the loop to initialize the first new slot.  */
 118               goto search;
 119             }
 120         }
 121       else
 122         errno = EMFILE;
 123     }
 124   else
 125     errno = EINVAL;             /* Bogus FIRST_FD value.  */
 126
 127   __mutex_unlock (&_hurd_dtable_lock);
 128   _hurd_critical_section_unlock (crit);
 129
 130   return NULL;
 131 }