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[babeltrace.git] / src / ctf-writer / object-pool.h
1 #ifndef BABELTRACE_CTF_WRITER_OBJECT_POOL_INTERNAL_H
2 #define BABELTRACE_CTF_WRITER_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_ctf_object_pool_create_object(). This is
40 * typically done in the bt_*_create() function which calls
41 * bt_ctf_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_ctf_object_pool_recycle_object(). This is typically done in a custom
47 * bt_*_recycle() function which does the necessary before calling
48 * bt_ctf_object_pool_recycle_object() with an object ready to be reused
49 * at any time.
50 */
51
52 #include <glib.h>
53
54 #include "object.h"
55
56 typedef void *(*bt_ctf_object_pool_new_object_func)(void *data);
57 typedef void *(*bt_ctf_object_pool_destroy_object_func)(void *obj, void *data);
58
59 struct bt_ctf_object_pool {
60 /*
61 * Container of recycled objects, owned by this. The array's size
62 * is the pool's capacity.
63 */
64 GPtrArray *objects;
65
66 /*
67 * Pool's size, that is, number of elements in the array above,
68 * starting at index 0, which exist as recycled objects.
69 */
70 size_t size;
71
72 /* User functions */
73 struct {
74 /* Allocate a new object in memory */
75 bt_ctf_object_pool_new_object_func new_object;
76
77 /* Free direct and indirect memory occupied by object */
78 bt_ctf_object_pool_destroy_object_func destroy_object;
79 } funcs;
80
81 /* User data passed to user functions */
82 void *data;
83 };
84
85 /*
86 * Initializes an object pool which is already allocated.
87 */
88 int bt_ctf_object_pool_initialize(struct bt_ctf_object_pool *pool,
89 bt_ctf_object_pool_new_object_func new_object_func,
90 bt_ctf_object_pool_destroy_object_func destroy_object_func,
91 void *data);
92
93 /*
94 * Finalizes an object pool without deallocating it.
95 */
96 void bt_ctf_object_pool_finalize(struct bt_ctf_object_pool *pool);
97
98 /*
99 * Creates an object from an object pool. If the pool is empty, this
100 * function calls the "new" user function to allocate a new object
101 * before returning it. Otherwise this function returns a recycled
102 * object, removing it from the pool.
103 *
104 * The returned object is owned by the caller.
105 */
106 static inline
107 void *bt_ctf_object_pool_create_object(struct bt_ctf_object_pool *pool)
108 {
109 struct bt_ctf_object *obj;
110
111 BT_ASSERT(pool);
112
113 #ifdef BT_LOGV
114 BT_LOGV("Creating object from pool: pool-addr=%p, pool-size=%zu, pool-cap=%u",
115 pool, pool->size, pool->objects->len);
116 #endif
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;
123 goto end;
124 }
125
126 /* Pool is empty: create a brand new object */
127 #ifdef BT_LOGV
128 BT_LOGV("Pool is empty: allocating new object: pool-addr=%p",
129 pool);
130 #endif
131
132 obj = pool->funcs.new_object(pool->data);
133
134 end:
135 #ifdef BT_LOGV
136 BT_LOGV("Created one object from pool: pool-addr=%p, obj-addr=%p",
137 pool, obj);
138 #endif
139
140 return obj;
141 }
142
143 /*
144 * Recycles an object, that is, puts it back into the pool.
145 *
146 * The pool becomes the sole owner of the object to recycle.
147 */
148 static inline
149 void bt_ctf_object_pool_recycle_object(struct bt_ctf_object_pool *pool, void *obj)
150 {
151 struct bt_ctf_object *bt_obj = obj;
152
153 BT_ASSERT(pool);
154 BT_ASSERT(obj);
155
156 #ifdef BT_LOGV
157 BT_LOGV("Recycling object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
158 pool, pool->size, pool->objects->len, obj);
159 #endif
160
161 if (pool->size == pool->objects->len) {
162 /* Backing array is full: make place for recycled object */
163 #ifdef BT_LOGV
164 BT_LOGV("Object pool is full: increasing object pool capacity: "
165 "pool-addr=%p, old-pool-cap=%u, new-pool-cap=%u",
166 pool, pool->objects->len, pool->objects->len + 1);
167 #endif
168 g_ptr_array_set_size(pool->objects, pool->size + 1);
169 }
170
171 /* Reset reference count to 1 since it could be 0 now */
172 bt_obj->ref_count = 1;
173
174 /* Back to the pool */
175 pool->objects->pdata[pool->size] = obj;
176 pool->size++;
177
178 #ifdef BT_LOGV
179 BT_LOGV("Recycled object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
180 pool, pool->size, pool->objects->len, obj);
181 #endif
182 }
183
184 #endif /* BABELTRACE_CTF_WRITER_OBJECT_POOL_INTERNAL_H */
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