PxMsgEnvelop()

Envelops a data area in a newly created message object.

APPLIES TO

8.2.0

SYNOPSIS

PxMsg_t PxMsgEnvelop (PxMsgData_t data_area, PxSize_t msgsize, PxOpool_t opoolid);

ARGUMENTS

data_area: The data area to be enveloped (start address)

msgsize: The size of the enveloped data area

opoolid: Object pool where to take the message object from

RETURN VALUES

The recieved message handle

ERROR CODES

PXERR_OPOOL_ILLOPOOL

The passed object pool handle is invalid

PXERR_OBJ_NOOBJ

No free object is available

PXERR_OBJ_ABORTED

The request was aborted by an event

PXERR_OBJ_ILLOBJ

The passed object handle is not valid

PXERR_GLOBAL_ILLEGAL_CORE

The requested object pool is not on the same core

PXERR_EVENT_ZERO

The given event mask is 0 for awaiting events

PXERR_PROT_PERMISSION

The data area is not writeable for the calling task

PXERR_MSG_ILL_ALIGN

Illegal aligned data pointer

PXERR_MSG_ILLMSG

Illegal aligned data pointer

PXERR_MSG_ILL_SIZE

Illegal data size

PXERR_INTERNAL_INCONSISTENCY

Inconsistency of internal structures

DESCRIPTION

The PxMsgEnvelop function envelops a data area specified by arguments data_area (start address) and msgsize (size in bytes) in a new message object taken from object pool opool. The message object handle is returned. If there is no free object available, the PxMsgEnvelop waits until a free object is available.

In contrast to normal message object, The newly created envelope message object has implicitly set the await release flag. It is possible to wait for the message object release with function PxMsgAwaitRel or PxMsgAwaitRel_EvWait or check the release state by function PxMsgAwatRel_NoWait.

The task that called PxMsgEnvelop becomes the (permanent) owner and the (temporary) user of the created message. The task’s access rights to the data area is marked in the message object and can be read by calling PxMsgGetProtection. The owner may restrict the access right by calling PxMsgSetProtection.

IMPLEMENTATION GUIDELINES

Before call

data_area must be a pointer to a valid data area.
msgsize must be a plausible value given as a constant (V) or a variable (C).
opoolid must be a valid PXROS-HR object pool and the calling task must have the access right to take objects from this object pool (V). The validity of opoolid may also be checked by the PxOpoolIsValid macro (F). The object pool must be created on the same core as the caller runs on. The creator core id can be read with the macro PxOpoolCoreId and the own core id with PxGetCoreId (C). Typically the task’s default object pool PXOpoolTaskdefault is used for this purpose.

After call

The returned value is the id of type PxMsg_t. This id may be checked with one of the following macros:
- PxMsgIdIsValid() must be true.
- PxMsgIdGet() must not be _PXIllegalObjId.
- PxMsgIdError() must be PXERR_NOERROR otherwise the returned error code has to be interpreted (C).

Best Practice

PxMsgEnvelop may block, if no PXROS-HR object is available. If blocking calls are prohibited, PxMsgEnvelop_NoWait should be used instead.
If the message requested with PxMsgEnvelop is sent to another task, the data_area must not be accessed by the requesting task until the recipient releases the message. PxMsgAwaitRel may be used to await the message’s release.

SEE ALSO

USAGE

#include "pxdef.h"

char Buf[BUFFER_SIZE] PXMEM_ALIGNED; /* The buffer is aligned to 8 bytes */

PxMsg_t Msg = PxMsgEnvelop(Buf, sizeof(Buf), opoolid)

if (PxMsgIdIsValid (Msg)) {
    // Handle message
}
else {
    // Handle error
}