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| Clone a message using C from a exit |
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| HenriqueS |
 Posted: Tue Sep 25, 2007 2:33 pm Post subject: Clone a message using C from a exit |
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Master
Joined: 22 Sep 2006
Posts: 235
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Hello, let´s say I want to clone a message, as it flows through a channel, into a specific queue, as given in the following exit funciton:
void MQENTRY MsgExit (PMQCXP pExitParms
,PMQCD pChannelDef
,PMQLONG pDataLength
,PMQLONG pAgentBufferLength
,PMQCHAR pAgentBuffer
,PMQLONG pExitBufferLength
,PMQCHAR *pExitBuffer
)
{
PMQXQH pMQXQH;
pMQXQH = (PMQXQH) pAgentBuffer;
/* clone message descriptor data */
PMQMD pMQMD;
pMQMD = &pMQXQH->MsgDesc;
memcpy( &md, pMQMD, sizeof( md ) );
...
MQPUT(Hconn, Hobj, &md, &pmo, *pDataLength, pAgentBuffer, &CompCode, &Reason);
...
}
The code above produces a message slightly different from the message that actually flows in the channel. Particularly the data below is NOT COPIED (or overwritten at a later step by MQ?):
a) UserIdentifier
b) PutApplName
c) PutApplType
d) ApplIdentityData
e) AccountingToken
Also, an interesting fact is that the message data itself is filled with the whole MQXQH (message data + several fields) structure (passing pAgentBuffer to MQPUT).
a) How can I make a real clone and put it into a queue? Is it possible?
b) How can I take only the message 'user'-data to the pAgentBuffer makes this happen, how can I cast it in a way only to recover the message and pass only it to the MQPUT paramater instead of the whole MQXQH structure?.
Hard topic, I know 
_________________
HenriqueS
Certified Websphere MQ 6.0 System Administrator |
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| jefflowrey |
| Posted: Tue Sep 25, 2007 2:37 pm Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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it would be a hard topic, if mirrorq didn't already solve it from an API Exit point of view.
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I am *not* the model of the modern major general. |
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| Nigelg |
| Posted: Tue Sep 25, 2007 7:01 pm Post subject: |
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Grand Master
Joined: 02 Aug 2004
Posts: 1046
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a. You probably need one of the CONTEXT options on the put.
b. Read the data from an offset:
char *ptr = (char *)pMQXQH;
char *msgdata = ptr + sizeof(MQXQH);
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| HenriqueS |
| Posted: Mon Nov 05, 2007 11:06 am Post subject: |
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Master
Joined: 22 Sep 2006
Posts: 235
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Thanks Nigelg for the input. It gives the exact code to jump the message header and get to the message payload.
I had access to the production system here (using RFHUTIL to browse messages) and found out that actually the message is not really cloned. It is just encapsulated into a new datagram message, making the things easier.
_________________
HenriqueS
Certified Websphere MQ 6.0 System Administrator |
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