rom/dos/attemptlockdoslist.c

   1 /*
   2     Copyright © 1995-2007, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc:
   6     Lang: English
   7 */
   8 #include <aros/debug.h>
   9 #include <proto/exec.h>
  10 #include "dos_intern.h"
  11
  12 /*****************************************************************************
  13
  14     NAME */
  15 #include <proto/dos.h>
  16
  17         AROS_LH1(struct DosList *, AttemptLockDosList,
  18
  19 /*  SYNOPSIS */
  20         AROS_LHA(ULONG, flags, D1),
  21
  22 /*  LOCATION */
  23         struct DosLibrary *, DOSBase, 111, Dos)
  24
  25 /*  FUNCTION
  26         Tries to get a lock on some of the dos lists. If all went
  27         well a handle is returned that can be used for FindDosEntry().
  28         Don't try to busy wait until the lock can be granted - use
  29         LockDosList() instead.
  30
  31     INPUTS
  32         flags  --  what lists to lock
  33
  34     RESULT
  35         Handle to the dos list or NULL. This is not a direct pointer
  36         to the first list element but to a pseudo element instead.
  37
  38     NOTES
  39
  40     EXAMPLE
  41
  42     BUGS
  43
  44     SEE ALSO
  45
  46     INTERNALS
  47
  48     HISTORY
  49         04-06-07    sonic   merged back from MorphOS source code
  50         29-10-95    digulla automatically created from
  51                             dos_lib.fd and clib/dos_protos.h
  52
  53 *****************************************************************************/
  54 {
  55     AROS_LIBFUNC_INIT
  56
  57     struct DosInfo *di = BADDR(DOSBase->dl_Root->rn_Info);
  58     struct DosList *dl = (struct DosList *)&DOSBase->dl_DevInfo;
  59     ULONG DevSem, EntrySem, DelSem;
  60
  61     D(bug("AttemptLockDosList: flags = $%lx\n", flags));
  62
  63     if (((flags & (LDF_READ|LDF_WRITE)) != LDF_READ &&
  64          (flags & (LDF_READ|LDF_WRITE)) != LDF_WRITE) ||
  65         (flags & ~(LDF_READ|LDF_WRITE|LDF_DEVICES|LDF_VOLUMES|LDF_ASSIGNS|LDF_ENTRY|LDF_DELETE)))
  66         return NULL;
  67
  68     if (flags & LDF_ALL)
  69     {
  70         if (flags & LDF_WRITE)
  71             DevSem = AttemptSemaphore(&di->di_DevLock);
  72         else
  73             DevSem = AttemptSemaphoreShared(&di->di_DevLock);
  74         if (!DevSem)
  75             dl = NULL;
  76     }
  77
  78     if (flags & LDF_ENTRY)
  79     {
  80         if (flags & LDF_WRITE)
  81             EntrySem = AttemptSemaphore(&di->di_EntryLock);
  82         else
  83             EntrySem = AttemptSemaphoreShared(&di->di_EntryLock);
  84         if (!EntrySem)
  85             dl = NULL;
  86     }
  87
  88     if (flags & LDF_DELETE)
  89     {
  90         if (flags & LDF_WRITE)
  91             DelSem = AttemptSemaphore(&di->di_DeleteLock);
  92         else
  93             DelSem = AttemptSemaphoreShared(&di->di_DeleteLock);
  94         if (!DelSem)
  95             dl = NULL;
  96     }
  97
  98 /* This came from MorphOS source code, however looks strange.
  99    Commented out but left for reference.
 100     if (dl)
 101         Forbid(); */
 102     if (!dl) {
 103         if (DevSem)
 104             ReleaseSemaphore(&di->di_DevLock);
 105         if (EntrySem)
 106             ReleaseSemaphore(&di->di_EntryLock);
 107         if (DelSem)
 108             ReleaseSemaphore(&di->di_DeleteLock);
 109     }
 110
 111     D(bug("AttemptLockDosList: result = $%lx\n", dl));
 112
 113     return dl;
 114
 115     AROS_LIBFUNC_EXIT
 116 } /* AttemptLockDosList */