1#ifndef MYSQL_SERVICE_THD_SPECIFICS_INCLUDED
2/* Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; version 2 of the License.
7
8 This program is distributed in the hope that it will be useful,
9 but WITHOUT ANY WARRANTY; without even the implied warranty of
10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 GNU General Public License for more details.
12
13 You should have received a copy of the GNU General Public License
14 along with this program; if not, write to the Free Software
15 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
16
17/**
18 @file
19
20 THD specific for plugin(s)
21
22 This API provides pthread_getspecific like functionality to plugin authors.
23 This is a functional alternative to the declarative MYSQL_THDVAR
24
25 A plugin should at init call thd_key_create that create a key that
26 will have storage in each THD. The key should be used by all threads
27 and can be used concurrently from all threads.
28
29 A plugin should at deinit call thd_key_delete.
30
31 Alternatively, a plugin can use thd_key_create_from_var(K,V) to create
32 a key that corresponds to a named MYSQL_THDVAR variable.
33
34 This API is also safe when using pool-of-threads in which case
35 pthread_getspecific is not, because the actual OS thread may change.
36
37 @note
38
39 Normally one should prefer MYSQL_THDVAR declarative API.
40
41 The benefits are:
42
43 - It supports typed variables (int, char*, enum, etc), not only void*.
44 - The memory allocated for MYSQL_THDVAR is free'd automatically
45 (if PLUGIN_VAR_MEMALLOC is specified).
46 - Continuous loading and unloading of the same plugin does not allocate
47 memory for same variables over and over again.
48
49 An example of using MYSQL_THDVAR for a thd local storage:
50
51 MYSQL_THDVAR_STR(my_tls,
52 PLUGIN_VAR_MEMALLOC | PLUGIN_VAR_NOSYSVAR | PLUGIN_VAR_NOCMDOPT,
53 "thd local storage example", 0, 0, 0);
54*/
55
56#ifdef __cplusplus
57extern "C" {
58#endif
59
60typedef int MYSQL_THD_KEY_T;
61
62extern struct thd_specifics_service_st {
63 int (*thd_key_create_func)(MYSQL_THD_KEY_T *key);
64 void (*thd_key_delete_func)(MYSQL_THD_KEY_T *key);
65 void *(*thd_getspecific_func)(MYSQL_THD thd, MYSQL_THD_KEY_T key);
66 int (*thd_setspecific_func)(MYSQL_THD thd, MYSQL_THD_KEY_T key, void *value);
67} *thd_specifics_service;
68
69#define thd_key_create_from_var(K, V) do { *(K)= MYSQL_SYSVAR_NAME(V).offset; } while(0)
70
71#ifdef MYSQL_DYNAMIC_PLUGIN
72
73#define thd_key_create(K) (thd_specifics_service->thd_key_create_func(K))
74#define thd_key_delete(K) (thd_specifics_service->thd_key_delete_func(K))
75#define thd_getspecific(T, K) (thd_specifics_service->thd_getspecific_func(T, K))
76#define thd_setspecific(T, K, V) (thd_specifics_service->thd_setspecific_func(T, K, V))
77
78#else
79
80/**
81 * create THD specific storage
82 * @return 0 on success
83 * else errno is returned
84 */
85int thd_key_create(MYSQL_THD_KEY_T *key);
86
87/**
88 * delete THD specific storage
89 */
90void thd_key_delete(MYSQL_THD_KEY_T *key);
91
92/**
93 * get/set thd specific storage
94 * - first time this is called from a thread it will return 0
95 * - this call is thread-safe in that different threads may call this
96 * simultaneously if operating on different THDs.
97 * - this call acquires no mutexes and is implemented as an array lookup
98 */
99void* thd_getspecific(MYSQL_THD thd, MYSQL_THD_KEY_T key);
100int thd_setspecific(MYSQL_THD thd, MYSQL_THD_KEY_T key, void *value);
101
102#endif
103
104#ifdef __cplusplus
105}
106#endif
107
108#define MYSQL_SERVICE_THD_SPECIFICS_INCLUDED
109#endif
110
111