lib: make symbols in prio-head hidden
[babeltrace.git] / src / lib / object-pool.h
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1#ifndef BABELTRACE_OBJECT_POOL_INTERNAL_H
2#define BABELTRACE_OBJECT_POOL_INTERNAL_H
3
4/*
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5 * Copyright (c) 2018 Philippe Proulx <pproulx@efficios.com>
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
23 * SOFTWARE.
24 */
25
26/*
27 * This is a generic object pool to avoid memory allocation/deallocation
28 * for objects of which the lifespan is typically short, but which are
29 * created a lot.
30 *
31 * The object pool, thanks to two user functions, knows how to allocate
32 * a brand new object in memory when the pool is empty and how to
33 * destroy an object when we destroy the pool.
34 *
35 * The object pool's user is responsible for:
36 *
37 * * Setting whatever references the object needs to keep and reset some
38 * properties _after_ calling bt_object_pool_create_object(). This is
39 * typically done in the bt_*_create() function which calls
40 * bt_object_pool_create_object() (which could call the user-provided
41 * allocation function if the pool is empty) and then sets the
42 * appropriate properties on the possibly recycled object.
43 *
44 * * Releasing whatever references the object keeps _before_ calling
45 * bt_object_pool_recycle_object(). This is typically done in a custom
46 * bt_*_recycle() function which does the necessary before calling
47 * bt_object_pool_recycle_object() with an object ready to be reused
48 * at any time.
49 */
50
51#include <glib.h>
578e048b 52#include "lib/object.h"
312c056a 53
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54/* Protection: this file uses BT_LIB_LOG*() macros directly */
55#ifndef BT_LIB_LOG_SUPPORTED
56# error Please include "lib/logging.h" before including this file.
57#endif
58
312c056a 59typedef void *(*bt_object_pool_new_object_func)(void *data);
9c7f2f85 60typedef void (*bt_object_pool_destroy_object_func)(void *obj, void *data);
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61
62struct bt_object_pool {
63 /*
64 * Container of recycled objects, owned by this. The array's size
65 * is the pool's capacity.
66 */
67 GPtrArray *objects;
68
69 /*
70 * Pool's size, that is, number of elements in the array above,
71 * starting at index 0, which exist as recycled objects.
72 */
73 size_t size;
74
75 /* User functions */
76 struct {
77 /* Allocate a new object in memory */
78 bt_object_pool_new_object_func new_object;
79
80 /* Free direct and indirect memory occupied by object */
81 bt_object_pool_destroy_object_func destroy_object;
82 } funcs;
83
84 /* User data passed to user functions */
85 void *data;
86};
87
88/*
89 * Initializes an object pool which is already allocated.
90 */
91int bt_object_pool_initialize(struct bt_object_pool *pool,
92 bt_object_pool_new_object_func new_object_func,
93 bt_object_pool_destroy_object_func destroy_object_func,
94 void *data);
95
96/*
97 * Finalizes an object pool without deallocating it.
98 */
99void bt_object_pool_finalize(struct bt_object_pool *pool);
100
101/*
102 * Creates an object from an object pool. If the pool is empty, this
103 * function calls the "new" user function to allocate a new object
104 * before returning it. Otherwise this function returns a recycled
105 * object, removing it from the pool.
106 *
107 * The returned object is owned by the caller.
108 */
109static inline
110void *bt_object_pool_create_object(struct bt_object_pool *pool)
111{
112 struct bt_object *obj;
113
98b15851 114 BT_ASSERT_DBG(pool);
ef267d12 115 BT_LOGT("Creating object from pool: pool-addr=%p, pool-size=%zu, pool-cap=%u",
312c056a 116 pool, pool->size, pool->objects->len);
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117
118 if (pool->size > 0) {
119 /* Pick one from the pool */
120 pool->size--;
121 obj = pool->objects->pdata[pool->size];
122 pool->objects->pdata[pool->size] = NULL;
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123 goto end;
124 }
125
126 /* Pool is empty: create a brand new object */
3f7d4d90 127 BT_LOGD("Pool is empty: allocating new object: pool-addr=%p",
312c056a 128 pool);
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129 obj = pool->funcs.new_object(pool->data);
130
131end:
ef267d12 132 BT_LOGT("Created one object from pool: pool-addr=%p, obj-addr=%p",
312c056a 133 pool, obj);
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134 return obj;
135}
136
137/*
138 * Recycles an object, that is, puts it back into the pool.
139 *
140 * The pool becomes the sole owner of the object to recycle.
141 */
142static inline
143void bt_object_pool_recycle_object(struct bt_object_pool *pool, void *obj)
144{
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145 struct bt_object *bt_obj = obj;
146
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147 BT_ASSERT_DBG(pool);
148 BT_ASSERT_DBG(obj);
ef267d12 149 BT_LOGT("Recycling object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
312c056a 150 pool, pool->size, pool->objects->len, obj);
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151
152 if (pool->size == pool->objects->len) {
153 /* Backing array is full: make place for recycled object */
3f7d4d90 154 BT_LOGD("Object pool is full: increasing object pool capacity: "
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155 "pool-addr=%p, old-pool-cap=%u, new-pool-cap=%u",
156 pool, pool->objects->len, pool->objects->len + 1);
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157 g_ptr_array_set_size(pool->objects, pool->size + 1);
158 }
159
cdc4693d 160 /* Reset reference count to 1 since it could be 0 now */
3fea54f6 161 bt_obj->ref_count = 1;
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162
163 /* Back to the pool */
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164 pool->objects->pdata[pool->size] = obj;
165 pool->size++;
ef267d12 166 BT_LOGT("Recycled object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
312c056a 167 pool, pool->size, pool->objects->len, obj);
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168}
169
170#endif /* BABELTRACE_OBJECT_POOL_INTERNAL_H */
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