--- /dev/null
+#ifndef BABELTRACE_CTF_WRITER_OBJECT_POOL_INTERNAL_H
+#define BABELTRACE_CTF_WRITER_OBJECT_POOL_INTERNAL_H
+
+/*
+ * Copyright (c) 2018 EfficiOS Inc. and Linux Foundation
+ * Copyright (c) 2018 Philippe Proulx <pproulx@efficios.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+/*
+ * This is a generic object pool to avoid memory allocation/deallocation
+ * for objects of which the lifespan is typically short, but which are
+ * created a lot.
+ *
+ * The object pool, thanks to two user functions, knows how to allocate
+ * a brand new object in memory when the pool is empty and how to
+ * destroy an object when we destroy the pool.
+ *
+ * The object pool's user is responsible for:
+ *
+ * * Setting whatever references the object needs to keep and reset some
+ * properties _after_ calling bt_ctf_object_pool_create_object(). This is
+ * typically done in the bt_*_create() function which calls
+ * bt_ctf_object_pool_create_object() (which could call the user-provided
+ * allocation function if the pool is empty) and then sets the
+ * appropriate properties on the possibly recycled object.
+ *
+ * * Releasing whatever references the object keeps _before_ calling
+ * bt_ctf_object_pool_recycle_object(). This is typically done in a custom
+ * bt_*_recycle() function which does the necessary before calling
+ * bt_ctf_object_pool_recycle_object() with an object ready to be reused
+ * at any time.
+ */
+
+#include <glib.h>
+#include <babeltrace/ctf-writer/object-internal.h>
+
+typedef void *(*bt_ctf_object_pool_new_object_func)(void *data);
+typedef void *(*bt_ctf_object_pool_destroy_object_func)(void *obj, void *data);
+
+struct bt_ctf_object_pool {
+ /*
+ * Container of recycled objects, owned by this. The array's size
+ * is the pool's capacity.
+ */
+ GPtrArray *objects;
+
+ /*
+ * Pool's size, that is, number of elements in the array above,
+ * starting at index 0, which exist as recycled objects.
+ */
+ size_t size;
+
+ /* User functions */
+ struct {
+ /* Allocate a new object in memory */
+ bt_ctf_object_pool_new_object_func new_object;
+
+ /* Free direct and indirect memory occupied by object */
+ bt_ctf_object_pool_destroy_object_func destroy_object;
+ } funcs;
+
+ /* User data passed to user functions */
+ void *data;
+};
+
+/*
+ * Initializes an object pool which is already allocated.
+ */
+int bt_ctf_object_pool_initialize(struct bt_ctf_object_pool *pool,
+ bt_ctf_object_pool_new_object_func new_object_func,
+ bt_ctf_object_pool_destroy_object_func destroy_object_func,
+ void *data);
+
+/*
+ * Finalizes an object pool without deallocating it.
+ */
+void bt_ctf_object_pool_finalize(struct bt_ctf_object_pool *pool);
+
+/*
+ * Creates an object from an object pool. If the pool is empty, this
+ * function calls the "new" user function to allocate a new object
+ * before returning it. Otherwise this function returns a recycled
+ * object, removing it from the pool.
+ *
+ * The returned object is owned by the caller.
+ */
+static inline
+void *bt_ctf_object_pool_create_object(struct bt_ctf_object_pool *pool)
+{
+ struct bt_ctf_object *obj;
+
+ BT_ASSERT(pool);
+
+#ifdef BT_LOGV
+ BT_LOGV("Creating object from pool: pool-addr=%p, pool-size=%zu, pool-cap=%u",
+ pool, pool->size, pool->objects->len);
+#endif
+
+ if (pool->size > 0) {
+ /* Pick one from the pool */
+ pool->size--;
+ obj = pool->objects->pdata[pool->size];
+ pool->objects->pdata[pool->size] = NULL;
+ goto end;
+ }
+
+ /* Pool is empty: create a brand new object */
+#ifdef BT_LOGV
+ BT_LOGV("Pool is empty: allocating new object: pool-addr=%p",
+ pool);
+#endif
+
+ obj = pool->funcs.new_object(pool->data);
+
+end:
+#ifdef BT_LOGV
+ BT_LOGV("Created one object from pool: pool-addr=%p, obj-addr=%p",
+ pool, obj);
+#endif
+
+ return obj;
+}
+
+/*
+ * Recycles an object, that is, puts it back into the pool.
+ *
+ * The pool becomes the sole owner of the object to recycle.
+ */
+static inline
+void bt_ctf_object_pool_recycle_object(struct bt_ctf_object_pool *pool, void *obj)
+{
+ struct bt_ctf_object *bt_obj = obj;
+
+ BT_ASSERT(pool);
+ BT_ASSERT(obj);
+
+#ifdef BT_LOGV
+ BT_LOGV("Recycling object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
+ pool, pool->size, pool->objects->len, obj);
+#endif
+
+ if (pool->size == pool->objects->len) {
+ /* Backing array is full: make place for recycled object */
+#ifdef BT_LOGV
+ BT_LOGV("Object pool is full: increasing object pool capacity: "
+ "pool-addr=%p, old-pool-cap=%u, new-pool-cap=%u",
+ pool, pool->objects->len, pool->objects->len + 1);
+#endif
+ g_ptr_array_set_size(pool->objects, pool->size + 1);
+ }
+
+ /* Reset reference count to 1 since it could be 0 now */
+ bt_obj->ref_count = 1;
+
+ /* Back to the pool */
+ pool->objects->pdata[pool->size] = obj;
+ pool->size++;
+
+#ifdef BT_LOGV
+ BT_LOGV("Recycled object: pool-addr=%p, pool-size=%zu, pool-cap=%u, obj-addr=%p",
+ pool, pool->size, pool->objects->len, obj);
+#endif
+}
+
+#endif /* BABELTRACE_CTF_WRITER_OBJECT_POOL_INTERNAL_H */
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