MQCBD - Callback descriptor

The MQCBD structure is used to specify a callback function and the options controlling its use by the queue manager. The structure is an input parameter on the MQCB call.

Availability

The MQCBD structure is available on the following platforms:

AIX®
IBM® i
Linux®
Solaris
Windows
z/OS®

and for IBM MQ MQI clients connected to these systems.

Version

The current version of MQCBD is MQCBD_VERSION_1.

Character set and encoding

Data in MQCBD must be in the character set given by the CodedCharSetId queue manager attribute and encoding of the local queue manager given by MQENC_NATIVE. However, if the application is running as an MQ MQI client, the structure must be in the character set and encoding of the client.

Fields

Note: In the following table, the fields are grouped by usage rather than alphabetically. The child topics follow the same sequence.

Table 1. Fields in MQCBD
Field name and description	Name of constant	Initial value (if any) of constant
StrucID (structure identifier)	MQCBD_STRUC_ID	`'CBD¬'`
Version (structure version number)	MQCBD_VERSION_1	`1`
CallbackType (type of callback function)	MQCBT_MESSAGE_CONSUMER	`1`
Options (options controlling message consumption)	MQCBDO_NONE	0
CallbackArea (field for callback function to use)	None	Null pointer or null blanks
CallbackFunction (whether the function is invoked as an API call)	None	Null pointer or null blanks
CallbackName (whether the function is invoked as a dynamically-linked program)	None	Null string or blanks
MaxMsgLength (length of longest message that can be read)	MQCBD_FULL_MSG_LENGTH	`-1`
Notes: The symbol `¬` represents a single blank character. The value Null string or blanks denotes the null sting in the C programming language, and blank characters in other programming languages. In the C programming language, the macro variable MQCBD_DEFAULT contains the values that are listed in the table. Use it in the following way to provide initial values for the fields in the structure: `MQCBD MyCBD = {MQCBD_DEFAULT};`

Language declarations

C declaration for MQCBD


typedef struct tagMQCBD MQCBD;
 struct tagMQCBD {
   MQCHAR4    StrucId;                 /* Structure identifier */
   MQLONG     Version;                 /* Structure version number */
   MQLONG     CallBackType;            /* Callback function type */
   MQLONG     Options;                 /* Options controlling message
                                          consumption */
   MQPTR      CallbackArea;            /* User data passed to the function */
   MQPTR      CallbackFunction;        /* Callback function pointer */
   MQCHAR128  CallbackName;            /* Callback name */
   MQLONG     MaxMsgLength;            /* Maximum message length */
 };

COBOL declaration for MQCBD


** MQCBCD structure
 10  MQCBD.
** Structure Identifier
 15  MQCBD-STRUCID                      PIC X(4).
** Structure Version
 15  MQCBD-VERSION                      PIC S9(9) BINARY.
 ** Callback Type
 15  MQCBD-CALLBACKTYPE                 PIC S9(9) BINARY.
** Options
 15  MQCBD-OPTIONS                      PIC S9(9) BINARY.
** Callback User Area
 15  MQCBD-CALLBACKAREA                 POINTER
** Callback Function Pointer
 15  MQCBD-CALLBACKFUNCTION             FUNCTION-POINTER
** Callback Program Name
 15  MQCBD-CALLBACKNAME                 PIC X(128)
** Maximum Message Length
 15  MQCDB-MAXMSGLENGTH                 PIC S9(9) BINARY.

PL/I declaration for MQCBD


dcl
 1 MQCBD based,
  3 StrucId             char(4),       /* Structure identifier*/
  3 Version             fixed bin(31), /* Structure version*/
  3 CallbackType        fixed bin(31), /* Callback function type */
  3 Options             fixed bin(31), /* Options */
  3 CallbackArea        pointer,       /* User area passed to the function */
  3 CallbackFunction    pointer,       /* Callback Function Pointer */
  3 CallbackName        char(128),     /* Callback Program Name */
  3 MaxMsgLength        fixed bin(31); /* Maximum Message Length */