lib: make trace IR API const-correct
[babeltrace.git] / include / babeltrace / object-pool-internal.h
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1#ifndef BABELTRACE_OBJECT_POOL_INTERNAL_H
2#define BABELTRACE_OBJECT_POOL_INTERNAL_H
3
4/*
5 * Copyright (c) 2018 EfficiOS Inc. and Linux Foundation
6 * Copyright (c) 2018 Philippe Proulx <pproulx@efficios.com>
7 *
8 * Permission is hereby granted, free of charge, to any person obtaining a copy
9 * of this software and associated documentation files (the "Software"), to deal
10 * in the Software without restriction, including without limitation the rights
11 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
12 * copies of the Software, and to permit persons to whom the Software is
13 * furnished to do so, subject to the following conditions:
14 *
15 * The above copyright notice and this permission notice shall be included in
16 * all copies or substantial portions of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
21 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
22 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
23 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
24 * SOFTWARE.
25 */
26
27/*
28 * This is a generic object pool to avoid memory allocation/deallocation
29 * for objects of which the lifespan is typically short, but which are
30 * created a lot.
31 *
32 * The object pool, thanks to two user functions, knows how to allocate
33 * a brand new object in memory when the pool is empty and how to
34 * destroy an object when we destroy the pool.
35 *
36 * The object pool's user is responsible for:
37 *
38 * * Setting whatever references the object needs to keep and reset some
39 * properties _after_ calling bt_object_pool_create_object(). This is
40 * typically done in the bt_*_create() function which calls
41 * bt_object_pool_create_object() (which could call the user-provided
42 * allocation function if the pool is empty) and then sets the
43 * appropriate properties on the possibly recycled object.
44 *
45 * * Releasing whatever references the object keeps _before_ calling
46 * bt_object_pool_recycle_object(). This is typically done in a custom
47 * bt_*_recycle() function which does the necessary before calling
48 * bt_object_pool_recycle_object() with an object ready to be reused
49 * at any time.
50 */
51
52#include <glib.h>
53#include <babeltrace/object-internal.h>
54
55typedef void *(*bt_object_pool_new_object_func)(void *data);
56typedef void *(*bt_object_pool_destroy_object_func)(void *obj, void *data);
57
58struct bt_object_pool {
59 /*
60 * Container of recycled objects, owned by this. The array's size
61 * is the pool's capacity.
62 */
63 GPtrArray *objects;
64
65 /*
66 * Pool's size, that is, number of elements in the array above,
67 * starting at index 0, which exist as recycled objects.
68 */
69 size_t size;
70
71 /* User functions */
72 struct {
73 /* Allocate a new object in memory */
74 bt_object_pool_new_object_func new_object;
75
76 /* Free direct and indirect memory occupied by object */
77 bt_object_pool_destroy_object_func destroy_object;
78 } funcs;
79
80 /* User data passed to user functions */
81 void *data;
82};
83
84/*
85 * Initializes an object pool which is already allocated.
86 */
87int bt_object_pool_initialize(struct bt_object_pool *pool,
88 bt_object_pool_new_object_func new_object_func,
89 bt_object_pool_destroy_object_func destroy_object_func,
90 void *data);
91
92/*
93 * Finalizes an object pool without deallocating it.
94 */
95void bt_object_pool_finalize(struct bt_object_pool *pool);
96
97/*
98 * Creates an object from an object pool. If the pool is empty, this
99 * function calls the "new" user function to allocate a new object
100 * before returning it. Otherwise this function returns a recycled
101 * object, removing it from the pool.
102 *
103 * The returned object is owned by the caller.
104 */
105static inline
106void *bt_object_pool_create_object(struct bt_object_pool *pool)
107{
108 struct bt_object *obj;
109
110 BT_ASSERT(pool);
111
112#ifdef BT_LOGV
113 BT_LOGV("Creating object from pool: pool-addr=%p, pool-size=%zu, pool-cap=%u",
114 pool, pool->size, pool->objects->len);
115#endif
116
117 if (pool->size > 0) {
118 /* Pick one from the pool */
119 pool->size--;
120 obj = pool->objects->pdata[pool->size];
121 pool->objects->pdata[pool->size] = NULL;
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122 goto end;
123 }
124
125 /* Pool is empty: create a brand new object */
126#ifdef BT_LOGV
127 BT_LOGV("Pool is empty: allocating new object: pool-addr=%p",
128 pool);
129#endif
130
131 obj = pool->funcs.new_object(pool->data);
132
133end:
134#ifdef BT_LOGV
135 BT_LOGV("Created one object from pool: pool-addr=%p, obj-addr=%p",
136 pool, obj);
137#endif
138
139 return obj;
140}
141
142/*
143 * Recycles an object, that is, puts it back into the pool.
144 *
145 * The pool becomes the sole owner of the object to recycle.
146 */
147static inline
148void bt_object_pool_recycle_object(struct bt_object_pool *pool, void *obj)
149{
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150 struct bt_object *bt_obj = obj;
151
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152 BT_ASSERT(pool);
153 BT_ASSERT(obj);
154
155#ifdef BT_LOGV
156 BT_LOGV("Recycling object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
157 pool, pool->size, pool->objects->len, obj);
158#endif
159
160 if (pool->size == pool->objects->len) {
161 /* Backing array is full: make place for recycled object */
162#ifdef BT_LOGV
163 BT_LOGV("Object pool is full: increasing object pool capacity: "
164 "pool-addr=%p, old-pool-cap=%u, new-pool-cap=%u",
165 pool, pool->objects->len, pool->objects->len + 1);
166#endif
167 g_ptr_array_set_size(pool->objects, pool->size + 1);
168 }
169
cdc4693d 170 /* Reset reference count to 1 since it could be 0 now */
3fea54f6 171 bt_obj->ref_count = 1;
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172
173 /* Back to the pool */
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174 pool->objects->pdata[pool->size] = obj;
175 pool->size++;
176
177#ifdef BT_LOGV
178 BT_LOGV("Recycled object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
179 pool, pool->size, pool->objects->len, obj);
180#endif
181}
182
183#endif /* BABELTRACE_OBJECT_POOL_INTERNAL_H */
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