????
Current Path : /usr/include/mysql/server/mysql/ |
Current File : //usr/include/mysql/server/mysql/service_thd_specifics.h |
#ifndef MYSQL_SERVICE_THD_SPECIFICS_INCLUDED /* Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */ /** @file THD specific for plugin(s) This API provides pthread_getspecific like functionality to plugin authors. This is a functional alternative to the declarative MYSQL_THDVAR A plugin should at init call thd_key_create that create a key that will have storage in each THD. The key should be used by all threads and can be used concurrently from all threads. A plugin should at deinit call thd_key_delete. Alternatively, a plugin can use thd_key_create_from_var(K,V) to create a key that corresponds to a named MYSQL_THDVAR variable. This API is also safe when using pool-of-threads in which case pthread_getspecific is not, because the actual OS thread may change. @note Normally one should prefer MYSQL_THDVAR declarative API. The benefits are: - It supports typed variables (int, char*, enum, etc), not only void*. - The memory allocated for MYSQL_THDVAR is free'd automatically (if PLUGIN_VAR_MEMALLOC is specified). - Continuous loading and unloading of the same plugin does not allocate memory for same variables over and over again. An example of using MYSQL_THDVAR for a thd local storage: MYSQL_THDVAR_STR(my_tls, PLUGIN_VAR_MEMALLOC | PLUGIN_VAR_NOSYSVAR | PLUGIN_VAR_NOCMDOPT, "thd local storage example", 0, 0, 0); */ #ifdef __cplusplus extern "C" { #endif typedef int MYSQL_THD_KEY_T; extern struct thd_specifics_service_st { int (*thd_key_create_func)(MYSQL_THD_KEY_T *key); void (*thd_key_delete_func)(MYSQL_THD_KEY_T *key); void *(*thd_getspecific_func)(MYSQL_THD thd, MYSQL_THD_KEY_T key); int (*thd_setspecific_func)(MYSQL_THD thd, MYSQL_THD_KEY_T key, void *value); } *thd_specifics_service; #define thd_key_create_from_var(K, V) do { *(K)= MYSQL_SYSVAR_NAME(V).offset; } while(0) #ifdef MYSQL_DYNAMIC_PLUGIN #define thd_key_create(K) (thd_specifics_service->thd_key_create_func(K)) #define thd_key_delete(K) (thd_specifics_service->thd_key_delete_func(K)) #define thd_getspecific(T, K) (thd_specifics_service->thd_getspecific_func(T, K)) #define thd_setspecific(T, K, V) (thd_specifics_service->thd_setspecific_func(T, K, V)) #else /** * create THD specific storage * @return 0 on success * else errno is returned */ int thd_key_create(MYSQL_THD_KEY_T *key); /** * delete THD specific storage */ void thd_key_delete(MYSQL_THD_KEY_T *key); /** * get/set thd specific storage * - first time this is called from a thread it will return 0 * - this call is thread-safe in that different threads may call this * simultaneously if operating on different THDs. * - this call acquires no mutexes and is implemented as an array lookup */ void* thd_getspecific(MYSQL_THD thd, MYSQL_THD_KEY_T key); int thd_setspecific(MYSQL_THD thd, MYSQL_THD_KEY_T key, void *value); #endif #ifdef __cplusplus } #endif #define MYSQL_SERVICE_THD_SPECIFICS_INCLUDED #endif