include/babeltrace2/ctf-writer/object-pool-internal.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 #include <babeltrace2/ctf-writer/object-internal.h>
  54
  55 typedef void *(*bt_ctf_object_pool_new_object_func)(void *data);
  56 typedef void *(*bt_ctf_object_pool_destroy_object_func)(void *obj, void *data);
  57
  58 struct bt_ctf_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_ctf_object_pool_new_object_func new_object;
  75
  76                 /* Free direct and indirect memory occupied by object */
  77                 bt_ctf_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  */
  87 int bt_ctf_object_pool_initialize(struct bt_ctf_object_pool *pool,
  88                 bt_ctf_object_pool_new_object_func new_object_func,
  89                 bt_ctf_object_pool_destroy_object_func destroy_object_func,
  90                 void *data);
  91
  92 /*
  93  * Finalizes an object pool without deallocating it.
  94  */
  95 void bt_ctf_object_pool_finalize(struct bt_ctf_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  */
 105 static inline
 106 void *bt_ctf_object_pool_create_object(struct bt_ctf_object_pool *pool)
 107 {
 108         struct bt_ctf_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;
 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
 133 end:
 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  */
 147 static inline
 148 void bt_ctf_object_pool_recycle_object(struct bt_ctf_object_pool *pool, void *obj)
 149 {
 150         struct bt_ctf_object *bt_obj = obj;
 151
 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
 170         /* Reset reference count to 1 since it could be 0 now */
 171         bt_obj->ref_count = 1;
 172
 173         /* Back to the pool */
 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_CTF_WRITER_OBJECT_POOL_INTERNAL_H */