Tom Lane wrote:
Andrew Chernow <[EMAIL PROTECTED]> writes:
Which callback do we use as the key? Currently, none are required (only the name was required). We have to choose one callback that must be provided.


What?  I thought what you wanted back was the void * pointer that had
been registered with a particular callback function.  So you use that
callback function.  If it's not actually registered, you get a NULL.

This is what is passed to PQaddObjectHooks, along with a conn:

This is all wrong IMHO, not least because it creates ABI problems if you
want to add another hook type later.  Register each hook separately, eg

typedef void (*PGCRHook) (PGconn *conn, void *passthrough);

void PQregisterConnResetHook(PGconn *conn, PQCRHook func, void *passthrough);

... repeat for each possible hook ...

                        regards, tom lane



One can make a case to break apart the obj hooks structure into individual register functions, but I think you have a different idea in your head than what is being proposed. For starters, there is no passthru pointer to register with a callback (there could be but that is different than hook data...your register looks more like a user_ptr). The passthru pointer, what we call hookData, is allocated with a PGconn (not provided by the user). This is the point of the initHookData callback.

typedef void *(*PGinitHookData)(const PGconn *conn);

PQregisterInitHookData((PGconn *)NULL, (PGinitHookData)func);
PQregisterConnResetHook((PGconn *)NULL, (PGCRHook)func);
//etc...
conn = PQconnectdb();

When connectdb returns, initHookData has already been called. So, a call to PQhookData(conn, ????) will work. BUT, what is still missing from the equation is how to uniquely reference hookData on a conn.

What I was previously suggesting was to use the address of initHookData, since w/o this address there wouldn't be any hook data to get. Seemed like a logical choice.

--
Andrew Chernow
eSilo, LLC
every bit counts
http://www.esilo.com/

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