Sends a high-priority data message to the given low-level mailbox and places it at the head of the queue. 

BOOLEAN knSendRtPriorityData(
    KNHANDLE hMailbox,   // handle for low-level mailbox
    LPVOID lpData,       // pointer to data message
    DWORD cbBytesSent       // number of bytes in message
);

Parameters

hMailbox

Handle for low-level mailbox, previously created with knCreateRtMailbox.

lpData

Pointer to the area containing the message to be sent.

cbBytesSent

Number of bytes in the message to be sent. The value can be no greater than the maximum message size specified when the mailbox was created.

Remarks

If a task is waiting at the mailbox, it receives the message; otherwise, the message is queued. If the mailbox is full, then an error is returned.

Mailboxes normally store messages in a FIFO queue. A series of knSendRtPriorityData calls results in messages queued in LIFO order.

When you create a low-level mailbox with knCreateRtMailbox, you can specify one of the slots in its queue as reserved for a high-priority message. knSendRtPriorityData can then use that slot.

Note:   If you use this call from an interrupt handler, use knStopRtScheduler before making the call.

Return Values

TRUE

Success

FALSE

To determine the status, call GetLastRtError

Status

E_OK

The mailbox accepted the message.

E_KN_LIMIT_EXCEEDED

The message was rejected because the mailbox was full.

Requirements

See Also

Mailbox system calls, knCreateRtMailbox, knStopRtScheduler