include/babeltrace/object-pool-internal.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 <babeltrace/object-internal.h>
  53
  54 typedef void *(*bt_object_pool_new_object_func)(void *data);
  55 typedef void *(*bt_object_pool_destroy_object_func)(void *obj, void *data);
  56
  57 struct bt_object_pool {
  58         /*
  59          * Container of recycled objects, owned by this. The array's size
  60          * is the pool's capacity.
  61          */
  62         GPtrArray *objects;
  63
  64         /*
  65          * Pool's size, that is, number of elements in the array above,
  66          * starting at index 0, which exist as recycled objects.
  67          */
  68         size_t size;
  69
  70         /* User functions */
  71         struct {
  72                 /* Allocate a new object in memory */
  73                 bt_object_pool_new_object_func new_object;
  74
  75                 /* Free direct and indirect memory occupied by object */
  76                 bt_object_pool_destroy_object_func destroy_object;
  77         } funcs;
  78
  79         /* User data passed to user functions */
  80         void *data;
  81 };
  82
  83 /*
  84  * Initializes an object pool which is already allocated.
  85  */
  86 int bt_object_pool_initialize(struct bt_object_pool *pool,
  87                 bt_object_pool_new_object_func new_object_func,
  88                 bt_object_pool_destroy_object_func destroy_object_func,
  89                 void *data);
  90
  91 /*
  92  * Finalizes an object pool without deallocating it.
  93  */
  94 void bt_object_pool_finalize(struct bt_object_pool *pool);
  95
  96 /*
  97  * Creates an object from an object pool. If the pool is empty, this
  98  * function calls the "new" user function to allocate a new object
  99  * before returning it. Otherwise this function returns a recycled
 100  * object, removing it from the pool.
 101  *
 102  * The returned object is owned by the caller.
 103  */
 104 static inline
 105 void *bt_object_pool_create_object(struct bt_object_pool *pool)
 106 {
 107         struct bt_object *obj;
 108
 109         BT_ASSERT(pool);
 110
 111 #ifdef BT_LOGV
 112         BT_LOGV("Creating object from pool: pool-addr=%p, pool-size=%zu, pool-cap=%u",
 113                 pool, pool->size, pool->objects->len);
 114 #endif
 115
 116         if (pool->size > 0) {
 117                 /* Pick one from the pool */
 118                 pool->size--;
 119                 obj = pool->objects->pdata[pool->size];
 120                 pool->objects->pdata[pool->size] = NULL;
 121                 goto end;
 122         }
 123
 124         /* Pool is empty: create a brand new object */
 125 #ifdef BT_LOGV
 126         BT_LOGV("Pool is empty: allocating new object: pool-addr=%p",
 127                 pool);
 128 #endif
 129
 130         obj = pool->funcs.new_object(pool->data);
 131
 132 end:
 133 #ifdef BT_LOGV
 134         BT_LOGV("Created one object from pool: pool-addr=%p, obj-addr=%p",
 135                 pool, obj);
 136 #endif
 137
 138         return obj;
 139 }
 140
 141 /*
 142  * Recycles an object, that is, puts it back into the pool.
 143  *
 144  * The pool becomes the sole owner of the object to recycle.
 145  */
 146 static inline
 147 void bt_object_pool_recycle_object(struct bt_object_pool *pool, void *obj)
 148 {
 149         struct bt_object *bt_obj = obj;
 150
 151         BT_ASSERT(pool);
 152         BT_ASSERT(obj);
 153
 154 #ifdef BT_LOGV
 155         BT_LOGV("Recycling object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
 156                 pool, pool->size, pool->objects->len, obj);
 157 #endif
 158
 159         if (pool->size == pool->objects->len) {
 160                 /* Backing array is full: make place for recycled object */
 161 #ifdef BT_LOGV
 162                 BT_LOGV("Object pool is full: increasing object pool capacity: "
 163                         "pool-addr=%p, old-pool-cap=%u, new-pool-cap=%u",
 164                         pool, pool->objects->len, pool->objects->len + 1);
 165 #endif
 166                 g_ptr_array_set_size(pool->objects, pool->size + 1);
 167         }
 168
 169         /* Reset reference count to 1 since it could be 0 now */
 170         bt_obj->ref_count = 1;
 171
 172         /* Back to the pool */
 173         pool->objects->pdata[pool->size] = obj;
 174         pool->size++;
 175
 176 #ifdef BT_LOGV
 177         BT_LOGV("Recycled object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
 178                 pool, pool->size, pool->objects->len, obj);
 179 #endif
 180 }
 181
 182 #endif /* BABELTRACE_OBJECT_POOL_INTERNAL_H */