MQSCAN CALLBACK

Data Type : Message Queues

MQSCAN_CALLBACK - Action routine invoked by MQScan().

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#include <mq.h>

Definition :

typedef STATUS (LNCALLBACKPTR MQSCAN_CALLBACK)(
   const char far *pBuffer,
   WORD            Length,
   WORD            Priority,
   void far *      Ctx);

Description :

This type defines the prototype of the user-written callback routine that will be invoked by the function MQScan() for each message in a message queue. The address of a routine with this prototype is supplied as an argument to MQScan().

The Action routine may return one of the following values to affect the behavior of MQScan:

NOERROR - process the next message.
ERR_MQSCAN_ABORT - return from MQScan immediately without dequeueing a message. Note that MQScan returns ERR_MQSCAN_ABORT.
ERR_MQSCAN_DEQUEUE - remove the message from the queue, terminate the enumeration, and return the current message to the caller of MQScan. If the Buffer is smaller than the message, MQScan can return ERR_MQ_BFR_TOO_SMALL.
ERR_MQSCAN_DELETE - remove the current message from the message queue and continue the enumeration.

The arguments to the MQSCAN_CALLBACK are as follows:

pBuffer - a pointer to a buffer containing the current message.
Length - the length of the message in the buffer.
Priority - the priority of this message, from 1(highest) to MAXWORD (lowest).
Ctx - a pointer to user-defined data. This allows non-global data to be shared between MQScan() and the callback function.

Under Windows, the action routine must be present in an EXPORT statement in the application's .DEF file.

See Also : MQScan

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