handlers.c

eXtremeDB数据库在Linux平台下的使用源码。内含多个示例程序

/************************************************************
 *                                                          *
 * Copyright (c) 2001-2007 McObject LLC. All Right Reserved.*
 *                                                          *
 ************************************************************/

/* Event handlers (call back functions) implementaions */

#include "platform.h"
#include <stdio.h>
#include <stdlib.h>

#include "evdb.h"
#include "handlers.h"

int unregister_events(mco_db_h db) {
	MCO_RET rc;
	mco_trans_h t;
	mco_trans_start(db, MCO_READ_WRITE, MCO_TRANS_FOREGROUND, &t);

	mco_unregister_newEvent_handler( t, & new_handler);
	mco_unregister_deleteEvent_handler( t, & delete_handler);
	mco_unregister_updateEvent_handler( t, & update_handler1);
	mco_unregister_updateEvent_handler( t, & update_handler2);

	rc = mco_trans_commit(t);
	return rc;
}


int register_events(mco_db_h db) {
	MCO_RET rc;
	mco_trans_h t;

	mco_trans_start(db, MCO_READ_WRITE, MCO_TRANS_FOREGROUND, &t);

	mco_register_newEvent_handler( t, & new_handler, (void*)0 );
	mco_register_deleteEvent_handler(t, & delete_handler, (void * )0);
	mco_register_updateEvent_handler( t, & update_handler1, (void *)0,  MCO_BEFORE_UPDATE );
	mco_register_updateEvent_handler( t, & update_handler2, (void *)0,  MCO_AFTER_UPDATE );

	rc = mco_trans_commit(t);

	return rc;
}


/* Handler for the "<new>" event. Reads the autoid and prints it out
 */
MCO_RET new_handler(mco_trans_h t,  MyClass * obj, MCO_EVENT_TYPE et, /*INOUT */void *param) {
	int8 u8;

	param = (int *)1;

	MyClass_autoid_get( obj, &u8);
#ifdef	MCO_CFG_QUAD_STRUCT
	printf("Event \"Object New\" : object (%ld,%ld) is created\n",u8.lo, u8.hi);
#else  /* MCO_CFG_QUAD_STRUCT */
	printf("Event \"Object New\" : object (%lld) is created\n",u8);
#endif /* MCO_CFG_QUAD_STRUCT */

	return MCO_S_OK;
}


/* Handler for the "<delete>" event. Note that the handler is called before
 * the current transaction is committed. Therefore, the object is still
 * valid; the object handle is passed back to the handler and is used to obtain the
 * autoid of the object.
 * The event's handler return value is passed into the "delete" function and is
 * later examined by the mco_trans_commit(). If the value is anything but
 * MCO_S_OK, the transaction is rollbacked. In this sample every other delete
 * transaction is rolled back.
 */
MCO_RET delete_handler( mco_trans_h t,  MyClass * obj,  MCO_EVENT_TYPE et, /*INOUT*/ void *user_param) {
	int8 u8;

	MyClass_autoid_get( obj, &u8);

#ifdef	MCO_CFG_QUAD_STRUCT
	printf("Event \"Object Delete\": object (%ld,%ld) is being deleted...",	u8.lo, u8.hi);
	return (((u8.lo + u8.hi) %2) ? 1: MCO_S_OK);

#else  /* MCO_CFG_QUAD_STRUCT */

	printf("Event \"Object Delete\": object (%lld) is being deleted...",	u8 );
	return (((u8) %2) ? 1: MCO_S_OK);
#endif /* MCO_CFG_QUAD_STRUCT */

}


/* Handler for the "update" event.This handler is called before the update transaction
 * was commited - hence the value of the field being changed is reported unchanged yet.
 */
MCO_RET update_handler1( mco_trans_h t,  MyClass * obj,  MCO_EVENT_TYPE et, /*INOUT*/ void *param) {
	uint4 u4;
	int8 u8;

	MyClass_autoid_get( obj, &u8);
	MyClass_u4_get(obj, &u4);
#ifdef	MCO_CFG_QUAD_STRUCT
	printf("Event \"Object Update\" (before commit): object (%ld,%ld) value %d\n",u8.lo, u8.hi, u4);
#else  /* MCO_CFG_QUAD_STRUCT */
	printf("Event \"Object Update\" (before commit): object (%lld) value %d\n",u8, u4);
#endif /* MCO_CFG_QUAD_STRUCT */
	return MCO_S_OK;
}


/* Another handler for the "<update>" event, only this time it is called after the
 * transaction was committed. So, the updated field value is already commited to
 * the database.
 */
MCO_RET update_handler2( mco_trans_h t,  MyClass * obj,  MCO_EVENT_TYPE et, /*INOUT*/ void *param) {
	uint4 u4;
	int8 u8;

	MyClass_autoid_get( obj, &u8);
	MyClass_u4_get(obj, &u4);
#ifdef	MCO_CFG_QUAD_STRUCT
	printf("Event \"Object Update\" (after commit): object (%ld,%ld) value %d\n",u8.lo, u8.hi, u4);
#else  /* MCO_CFG_QUAD_STRUCT */
	printf("Event \"Object Update\" (after commit): object (%lld) value %d\n",u8, u4);
#endif /* MCO_CFG_QUAD_STRUCT */
	return MCO_S_OK;
}