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