rom/exec/getmsg.c

   1 /*
   2     Copyright © 1995-2017, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Get a message from a message port.
   6     Lang: english
   7 */
   8
   9 #define DEBUG 0
  10 #include <aros/debug.h>
  11
  12 #include <exec/execbase.h>
  13 #include <exec/ports.h>
  14 #include <aros/libcall.h>
  15 #include <proto/exec.h>
  16
  17 #include "exec_intern.h"
  18
  19 /*****************************************************************************
  20
  21     NAME */
  22
  23         AROS_LH1(struct Message *, GetMsg,
  24
  25 /*  SYNOPSIS */
  26         AROS_LHA(struct MsgPort *, port, A0),
  27
  28 /*  LOCATION */
  29         struct ExecBase *, SysBase, 62, Exec)
  30
  31 /*  FUNCTION
  32         Get a message from a given messageport. This function doesn't wait
  33         and returns NULL if the messageport is empty. Therefore it's
  34         generally a good idea to WaitPort() or Wait() on the given port first.
  35
  36     INPUTS
  37         port - Pointer to messageport
  38
  39     RESULT
  40         Pointer to message removed from the port.
  41
  42     NOTES
  43
  44     EXAMPLE
  45
  46     BUGS
  47
  48     SEE ALSO
  49         WaitPort(), PutMsg()
  50
  51     INTERNALS
  52
  53 ******************************************************************************/
  54 {
  55     AROS_LIBFUNC_INIT
  56
  57     struct Message *msg;
  58
  59     D(bug("[Exec] GetMsg(0x%p)\n", port);)
  60
  61     ASSERT_VALID_PTR(port);
  62
  63     /*
  64      * Protect the message list, and get the first node.
  65      */
  66     Disable();
  67 #if defined(__AROSEXEC_SMP__)
  68     EXEC_SPINLOCK_LOCK(&port->mp_SpinLock, NULL, SPINLOCK_MODE_WRITE);
  69 #endif
  70     msg=(struct Message *)RemHead(&port->mp_MsgList);
  71 #if defined(__AROSEXEC_SMP__)
  72     EXEC_SPINLOCK_UNLOCK(&port->mp_SpinLock);
  73 #endif
  74     Enable();
  75
  76     /* All done. */
  77     ASSERT_VALID_PTR_OR_NULL(msg);
  78
  79     return msg;
  80     AROS_LIBFUNC_EXIT
  81 } /* GetMsg() */
  82