Design of the Browse sample program

 

The program opens the target queue using the MQOPEN call with the MQOO_BROWSE option. If it cannot open the queue, the program outputs an error message containing the reason code returned by the MQOPEN call.

For each message on the queue, the program uses the MQGET call to copy the message from the queue, then displays the data contained in the message. The MQGET call uses these options:

MQGMO_BROWSE_NEXT

After the MQOPEN call, the browse cursor is positioned logically before the first message in the queue, so this option causes the first message to be returned when the call is first made.

MQGMO_NO_WAIT

The program does not wait if there are no messages on the queue.

MQGMO_ACCEPT_TRUNCATED_MSG

The MQGET call specifies a buffer of fixed size. If a message is longer than this buffer, the program displays the truncated message, together with a warning that the message has been truncated.

The program demonstrates how clear the MsgId and CorrelId fields of the MQMD structure after each MQGET call, because the call sets these fields to the values contained in the message it retrieves. Clearing these fields means that successive MQGET calls retrieve messages in the order in which the messages are held in the queue.

The program continues to the end of the queue; at this point the MQGET call returns the MQRC_NO_MSG_AVAILABLE reason code and the program displays a warning message. If the MQGET call fails, the program displays an error message that contains the reason code.

The program then closes the queue using the MQCLOSE call.

 

Parent topic:

The Browse sample programs

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