FairCom ISAM for C

ctSysQueueMlen

Retrieves the length of the next available message in the queue.

Short Name

ctSysQueueMlen()

Type

ISAM function.

Declaration

NINT ctSysQueueMlen(NINT qhandle, LONG timeout)

Description

ctSysQueueMlen() returns the length of the next available message in the specified queue.

Parameter qhandle is a system queue handle returned by a call to ctSysQueueOpen(). Parameter timeout specifies a millisecond time that ctSysQueueMlen() will block if the queue is empty. A timeout value of ctWAITDFOREVER will cause ctSysQueueMlen() to block until data is available in the queue.

Use ctSysQueueMlen() to find out the appropriate size of a buffer before calling ctSysQueueRead().

Return

ctSysQueueMlen() returns the length of the next available message, or a negative value on error.

Value	Symbolic Constant	Explanation
-7	TUSR_ERR	Terminate user.
-90	NQUE_ERR	Could not create queue.
-514	CQUE_ERR	Queue has already been closed.

See FairCom DB Error Codes for a complete listing of valid FairCom DB error values.

Example

NINT len = ctSysQueueMlen(qhandle, ctWAITFOREVER);

if (len >= 0)

printf("The next message length is %d bytes\n", len);

else

printf("ctSysQueueMlen failed with code %d\n", -len);

Limitations

Client/Server mode only.