src/ctf-writer/object-pool.h

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (c) 2018 EfficiOS Inc. and Linux Foundation
   5  * Copyright (c) 2018 Philippe Proulx <pproulx@efficios.com>
   6  */
   7
   8 #ifndef BABELTRACE_CTF_WRITER_OBJECT_POOL_INTERNAL_H
   9 #define BABELTRACE_CTF_WRITER_OBJECT_POOL_INTERNAL_H
  10
  11 /*
  12  * This is a generic object pool to avoid memory allocation/deallocation
  13  * for objects of which the lifespan is typically short, but which are
  14  * created a lot.
  15  *
  16  * The object pool, thanks to two user functions, knows how to allocate
  17  * a brand new object in memory when the pool is empty and how to
  18  * destroy an object when we destroy the pool.
  19  *
  20  * The object pool's user is responsible for:
  21  *
  22  * * Setting whatever references the object needs to keep and reset some
  23  *   properties _after_ calling bt_ctf_object_pool_create_object(). This is
  24  *   typically done in the bt_*_create() function which calls
  25  *   bt_ctf_object_pool_create_object() (which could call the user-provided
  26  *   allocation function if the pool is empty) and then sets the
  27  *   appropriate properties on the possibly recycled object.
  28  *
  29  * * Releasing whatever references the object keeps _before_ calling
  30  *   bt_ctf_object_pool_recycle_object(). This is typically done in a custom
  31  *   bt_*_recycle() function which does the necessary before calling
  32  *   bt_ctf_object_pool_recycle_object() with an object ready to be reused
  33  *   at any time.
  34  */
  35
  36 #include <glib.h>
  37
  38 #include "object.h"
  39
  40 typedef void *(*bt_ctf_object_pool_new_object_func)(void *data);
  41 typedef void *(*bt_ctf_object_pool_destroy_object_func)(void *obj, void *data);
  42
  43 struct bt_ctf_object_pool {
  44         /*
  45          * Container of recycled objects, owned by this. The array's size
  46          * is the pool's capacity.
  47          */
  48         GPtrArray *objects;
  49
  50         /*
  51          * Pool's size, that is, number of elements in the array above,
  52          * starting at index 0, which exist as recycled objects.
  53          */
  54         size_t size;
  55
  56         /* User functions */
  57         struct {
  58                 /* Allocate a new object in memory */
  59                 bt_ctf_object_pool_new_object_func new_object;
  60
  61                 /* Free direct and indirect memory occupied by object */
  62                 bt_ctf_object_pool_destroy_object_func destroy_object;
  63         } funcs;
  64
  65         /* User data passed to user functions */
  66         void *data;
  67 };
  68
  69 /*
  70  * Initializes an object pool which is already allocated.
  71  */
  72 int bt_ctf_object_pool_initialize(struct bt_ctf_object_pool *pool,
  73                 bt_ctf_object_pool_new_object_func new_object_func,
  74                 bt_ctf_object_pool_destroy_object_func destroy_object_func,
  75                 void *data);
  76
  77 /*
  78  * Finalizes an object pool without deallocating it.
  79  */
  80 void bt_ctf_object_pool_finalize(struct bt_ctf_object_pool *pool);
  81
  82 /*
  83  * Creates an object from an object pool. If the pool is empty, this
  84  * function calls the "new" user function to allocate a new object
  85  * before returning it. Otherwise this function returns a recycled
  86  * object, removing it from the pool.
  87  *
  88  * The returned object is owned by the caller.
  89  */
  90 static inline
  91 void *bt_ctf_object_pool_create_object(struct bt_ctf_object_pool *pool)
  92 {
  93         struct bt_ctf_object *obj;
  94
  95         BT_ASSERT_DBG(pool);
  96
  97 #ifdef BT_LOGT
  98         BT_LOGT("Creating object from pool: pool-addr=%p, pool-size=%zu, pool-cap=%u",
  99                 pool, pool->size, pool->objects->len);
 100 #endif
 101
 102         if (pool->size > 0) {
 103                 /* Pick one from the pool */
 104                 pool->size--;
 105                 obj = pool->objects->pdata[pool->size];
 106                 pool->objects->pdata[pool->size] = NULL;
 107                 goto end;
 108         }
 109
 110         /* Pool is empty: create a brand new object */
 111 #ifdef BT_LOGT
 112         BT_LOGT("Pool is empty: allocating new object: pool-addr=%p",
 113                 pool);
 114 #endif
 115
 116         obj = pool->funcs.new_object(pool->data);
 117
 118 end:
 119 #ifdef BT_LOGT
 120         BT_LOGT("Created one object from pool: pool-addr=%p, obj-addr=%p",
 121                 pool, obj);
 122 #endif
 123
 124         return obj;
 125 }
 126
 127 /*
 128  * Recycles an object, that is, puts it back into the pool.
 129  *
 130  * The pool becomes the sole owner of the object to recycle.
 131  */
 132 static inline
 133 void bt_ctf_object_pool_recycle_object(struct bt_ctf_object_pool *pool, void *obj)
 134 {
 135         struct bt_ctf_object *bt_obj = obj;
 136
 137         BT_ASSERT_DBG(pool);
 138         BT_ASSERT_DBG(obj);
 139
 140 #ifdef BT_LOGT
 141         BT_LOGT("Recycling object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
 142                 pool, pool->size, pool->objects->len, obj);
 143 #endif
 144
 145         if (pool->size == pool->objects->len) {
 146                 /* Backing array is full: make place for recycled object */
 147 #ifdef BT_LOGT
 148                 BT_LOGT("Object pool is full: increasing object pool capacity: "
 149                         "pool-addr=%p, old-pool-cap=%u, new-pool-cap=%u",
 150                         pool, pool->objects->len, pool->objects->len + 1);
 151 #endif
 152                 g_ptr_array_set_size(pool->objects, pool->size + 1);
 153         }
 154
 155         /* Reset reference count to 1 since it could be 0 now */
 156         bt_obj->ref_count = 1;
 157
 158         /* Back to the pool */
 159         pool->objects->pdata[pool->size] = obj;
 160         pool->size++;
 161
 162 #ifdef BT_LOGT
 163         BT_LOGT("Recycled object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
 164                 pool, pool->size, pool->objects->len, obj);
 165 #endif
 166 }
 167
 168 #endif /* BABELTRACE_CTF_WRITER_OBJECT_POOL_INTERNAL_H */