rom/dos/attemptlockdoslist.c

   1 /*
   2     Copyright © 1995-2010, 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 *****************************************************************************/
  49 {
  50     AROS_LIBFUNC_INIT
  51
  52     struct DosInfo *di = BADDR(DOSBase->dl_Root->rn_Info);
  53     struct DosList *dl = (struct DosList *)&di->di_DevInfo;
  54     ULONG DevSem = FALSE, EntrySem = FALSE, DelSem = FALSE;
  55
  56     D(bug("AttemptLockDosList: flags = $%lx\n", flags));
  57
  58     if (((flags & (LDF_READ|LDF_WRITE)) != LDF_READ &&
  59          (flags & (LDF_READ|LDF_WRITE)) != LDF_WRITE) ||
  60         (flags & ~(LDF_READ|LDF_WRITE|LDF_DEVICES|LDF_VOLUMES|LDF_ASSIGNS|LDF_ENTRY|LDF_DELETE)))
  61         return NULL;
  62
  63     if (flags & LDF_ALL)
  64     {
  65         if (flags & LDF_WRITE)
  66             DevSem = AttemptSemaphore(&di->di_DevLock);
  67         else
  68             DevSem = AttemptSemaphoreShared(&di->di_DevLock);
  69         if (!DevSem)
  70             dl = NULL;
  71     }
  72
  73     if (flags & LDF_ENTRY)
  74     {
  75         if (flags & LDF_WRITE)
  76             EntrySem = AttemptSemaphore(&di->di_EntryLock);
  77         else
  78             EntrySem = AttemptSemaphoreShared(&di->di_EntryLock);
  79         if (!EntrySem)
  80             dl = NULL;
  81     }
  82
  83     if (flags & LDF_DELETE)
  84     {
  85         if (flags & LDF_WRITE)
  86             DelSem = AttemptSemaphore(&di->di_DeleteLock);
  87         else
  88             DelSem = AttemptSemaphoreShared(&di->di_DeleteLock);
  89         if (!DelSem)
  90             dl = NULL;
  91     }
  92
  93 /* This came from MorphOS source code, however looks strange.
  94    Commented out but left for reference.
  95     if (dl)
  96         Forbid(); */
  97     if (!dl) {
  98         if (DevSem)
  99             ReleaseSemaphore(&di->di_DevLock);
 100         if (EntrySem)
 101             ReleaseSemaphore(&di->di_EntryLock);
 102         if (DelSem)
 103             ReleaseSemaphore(&di->di_DeleteLock);
 104     }
 105
 106     D(bug("AttemptLockDosList: result = $%lx\n", dl));
 107
 108     return dl;
 109
 110     AROS_LIBFUNC_EXIT
 111 } /* AttemptLockDosList */