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NAME: dbsetbusy
FUNCTION:
Call a user-supplied function when DB-Library is reading from
SQL Server.
SYNTAX:
void dbsetbusy(dbproc, busyfunc)
DBPROCESS *dbproc;
void (*(*busyfunc)())();
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COMMENTS:
o This routine associates a user-supplied function with the
specified dbproc. The user-supplied function will automati-
cally be called whenever DB-Library is reading or waiting to
read output from SQL Server. For example, an application may
want to print a message whenever SQL Server is accessed.
dbsetbusy() will cause the user-supplied function busyfunc() to
be called in this case.
o Similarly, dbsetidle() may also be used to associate a user-
supplied function, idlefunc(), with a dbproc. idlefunc() will
automatically be called whenever DB-Library has finished read-
ing output from SQL Server.
o The server sends result data to the application in packets of
512 bytes. (The final packet in a set of results may be less
than 512 bytes.) DB-Library calls busyfunc() at the beginning
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of each packet and idlefunc() at the end of each packet. If
the output from the server spans multiple packets, busyfunc()
and idlefunc() will be called multiple times.
o Here's an example of installing and defining busyfunc() and
idlefunc():
int (*busyfunc())(); /* busyfunc is a function which returns
* a pointer to a function which returns
* an integer.
*/
void idlefunc();
int counterfunc();
...
main()
{
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DBPROCESS *dbproc;
...
dbproc = dbopen(login, NULL);
/* Now that we have a DBPROCESS, install the busy-function
* and the idle-function.
*/
dbsetbusy(dbproc, busyfunc);
dbsetidle(dbproc, idlefunc);
dbcmd(dbproc, "select * from sysdatabases");
dbcmd(dbproc, " select * from sysobjects");
dbsqlexec(dbproc);
/* DB-Library calls busyfunc() for the first time during
* dbsqlexec(). Depending on the size of the results,
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* it may call busyfunc() again during processing of
* the results. */
while (dbresults(dbproc) != NO_MORE_RESULTS)
dbprrow(dbproc);
/* DB-Library calls idlefunc() each time a packet of results
* has been received. Depending on the size of the results,
* it may call idlefunc() multiple times during processing of
the results. */
...
}
int (*busyfunc(dbproc))()
DBPROCESS *dbproc;
{
printf("Waiting for data...\n");
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/* busyfunc returns a pointer to a routine which returns an integer. */
return(counterfunc);
}
void idlefunc(procptr, dbproc)
int (*procptr)(); /* idlefunc's first parameter is a pointer
* to a routine which returns an integer.
* This is the same pointer that busyfunc
* returns.
*/
DBPROCESS *dbproc;
{
int count;
printf("Data is ready.\n");
count = (*procptr)();
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printf
("Counterfunc has been called %d %s.\n",
count, (count == 1 ? "time" : "times"));
}
int counterfunc()
{
static int counter = 0;
return(++counter);
}
PARAMETERS:
dbproc - A pointer to the DBPROCESS structure that provides the
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connection for a particular front-end/SQL Server process. It
contains all the information that DB-Library uses to manage
communications and data between the front end and SQL Server.
busyfunc - The user-supplied function that DB-Library will call
whenever it accesses SQL Server. DB-Library calls busyfunc()
with a single parameter-a pointer to the DBPROCESS from the
dbsetbusy() call.
busyfunc() returns a pointer to a function that returns an
integer.
RETURNS:
None.
SEE ALSO:
dbsetidle