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