src/lib/object-pool.h

   1 #ifndef BABELTRACE_OBJECT_POOL_INTERNAL_H
   2 #define BABELTRACE_OBJECT_POOL_INTERNAL_H
   3
   4 /*
   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>
  52 #include "lib/object.h"
  53
  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
  59 typedef void *(*bt_object_pool_new_object_func)(void *data);
  60 typedef void (*bt_object_pool_destroy_object_func)(void *obj, void *data);
  61
  62 struct 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  */
  91 int 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  */
  99 void 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  */
 109 static inline
 110 void *bt_object_pool_create_object(struct bt_object_pool *pool)
 111 {
 112         struct bt_object *obj;
 113
 114         BT_ASSERT_DBG(pool);
 115         BT_LOGT("Creating object from pool: pool-addr=%p, pool-size=%zu, pool-cap=%u",
 116                 pool, pool->size, pool->objects->len);
 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         BT_LOGD("Pool is empty: allocating new object: pool-addr=%p",
 128                 pool);
 129         obj = pool->funcs.new_object(pool->data);
 130
 131 end:
 132         BT_LOGT("Created one object from pool: pool-addr=%p, obj-addr=%p",
 133                 pool, obj);
 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  */
 142 static inline
 143 void bt_object_pool_recycle_object(struct bt_object_pool *pool, void *obj)
 144 {
 145         struct bt_object *bt_obj = obj;
 146
 147         BT_ASSERT_DBG(pool);
 148         BT_ASSERT_DBG(obj);
 149         BT_LOGT("Recycling object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
 150                 pool, pool->size, pool->objects->len, obj);
 151
 152         if (pool->size == pool->objects->len) {
 153                 /* Backing array is full: make place for recycled object */
 154                 BT_LOGD("Object pool is full: increasing object pool capacity: "
 155                         "pool-addr=%p, old-pool-cap=%u, new-pool-cap=%u",
 156                         pool, pool->objects->len, pool->objects->len + 1);
 157                 g_ptr_array_set_size(pool->objects, pool->size + 1);
 158         }
 159
 160         /* Reset reference count to 1 since it could be 0 now */
 161         bt_obj->ref_count = 1;
 162
 163         /* Back to the pool */
 164         pool->objects->pdata[pool->size] = obj;
 165         pool->size++;
 166         BT_LOGT("Recycled object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
 167                 pool, pool->size, pool->objects->len, obj);
 168 }
 169
 170 #endif /* BABELTRACE_OBJECT_POOL_INTERNAL_H */