rbheap: API changes and documentation

1 files changed, 163 insertions, 24 deletions

diff --git a/cpukit/sapi/include/rtems/rbheap.h b/cpukit/sapi/include/rtems/rbheap.h
index be1eec6b66..5481e8954f 100644
--- a/cpukit/sapi/include/rtems/rbheap.h
+++ b/cpukit/sapi/include/rtems/rbheap.h
@@ -36,60 +36,191 @@ extern "C" {
  *
  * @brief Red-Black Tree Heap API.
  *
- * In the Red-Black Tree Heap the administration data structures are not
- * contained in the managed memory area.  This can be used for example in a
- * task stack allocator which protects the task stacks from access by other
- * tasks.
+ * The red-black tree heap provides a memory allocator suitable to implement
+ * the malloc() and free() interface.  It uses a first-fit allocation strategy.
+ * In the red-black tree heap the administration data structures are not
+ * contained in the managed memory area.  Thus writing beyond the boundaries of
+ * a chunk does not damage the data to maintain the heap.  This can be used for
+ * example in a task stack allocator which protects the task stacks from access
+ * by other tasks.  The allocated and free memory parts of the managed area are
+ * called chunks.  Each chunk needs a descriptor which is stored outside of the
+ * managed area.
  *
  * @{
  */
 
+/**
+ * @brief Red-black heap chunk descriptor.
+ */
 typedef struct {
+  /**
+   * This chain node can be used in two chains
+   *  - the chain of spare chunk descriptors and
+   *  - the chain of free chunks in the managed memory area.
+   *
+   * In case this chain node is not part of a chain, the chunk represents a
+   * used chunk in the managed memory area.
+   */
   rtems_chain_node chain_node;
+
+  /**
+   * Tree node for chunks that represent a part of the managed memory area.
+   * These chunks are either free or used.
+   */
   rtems_rbtree_node tree_node;
+
+  /**
+   * Begin address of the chunk.  The address alignment it specified in the
+   * @ref rtems_rbheap_control.
+   */
   uintptr_t begin;
+
+  /**
+   * Size of the chunk in bytes.
+   */
   uintptr_t size;
-} rtems_rbheap_page;
+} rtems_rbheap_chunk;
 
 typedef struct rtems_rbheap_control rtems_rbheap_control;
 
-typedef void (*rtems_rbheap_extend_page_pool)(rtems_rbheap_control *control);
+/**
+ * @brief Handler to extend the available chunk descriptors.
+ *
+ * This handler is called when no more chunk descriptors are available.  An
+ * example implementation is this:
+ *
+ * @code
+ * void extend_descriptors_with_malloc(rtems_rbheap_control *control)
+ * {
+ *   rtems_rbheap_chunk *chunk = malloc(sizeof(*chunk));
+ *
+ *   if (chunk != NULL) {
+ *     rtems_rbheap_add_to_spare_descriptor_chain(control, chunk);
+ *   }
+ * }
+ * @endcode
+ *
+ * @see rtems_rbheap_extend_descriptors_never() and
+ * rtems_rbheap_extend_descriptors_with_malloc().
+ */
+typedef void (*rtems_rbheap_extend_descriptors)(rtems_rbheap_control *control);
 
+/**
+ * @brief Red-black heap control.
+ */
 struct rtems_rbheap_control {
-  rtems_chain_control free_chain;
-  rtems_chain_control pool_chain;
-  rtems_rbtree_control page_tree;
-  uintptr_t page_alignment;
-  rtems_rbheap_extend_page_pool extend_page_pool;
+  /**
+   * Chain of free chunks in the managed memory area.
+   */
+  rtems_chain_control free_chunk_chain;
+
+  /**
+   * Chain of free chunk descriptors.  Descriptors are consumed during
+   * allocation and may be produced during free if contiguous chunks can be
+   * coalesced.  In case of descriptor starvation the @ref extend_descriptors
+   * handler will be called.
+   */
+  rtems_chain_control spare_descriptor_chain;
+
+  /**
+   * Tree of chunks representing the state of the managed memory area.
+   */
+  rtems_rbtree_control chunk_tree;
+
+  /**
+   * Minimum chunk begin alignment in bytes.
+   */
+  uintptr_t alignment;
+
+  /**
+   * Handler to extend the available chunk descriptors.
+   */
+  rtems_rbheap_extend_descriptors extend_descriptors;
+
+  /**
+   * User specified argument handler for private handler data.
+   */
   void *handler_arg;
 };
 
+/**
+ * @brief Initializes the red-black tree heap @a control.
+ *
+ * @param[in, out] control The red-black tree heap.
+ * @param[in] area_begin The managed memory area begin.
+ * @param[in] area_size The managed memory area size.
+ * @param[in] alignment The minimum chunk alignment.
+ * @param[in] extend_descriptors The handler to extend the available chunk
+ * descriptors.
+ * @param[in] handler_arg The handler argument.
+ *
+ * @retval RTEMS_SUCCESSFUL Successful operation.
+ * @retval RTEMS_INVALID_NUMBER The alignment is not positive.
+ * @retval RTEMS_INVALID_ADDRESS The memory area is invalid.
+ * @retval RTEMS_NO_MEMORY Not enough chunk descriptors.
+ */
 rtems_status_code rtems_rbheap_initialize(
   rtems_rbheap_control *control,
   void *area_begin,
   uintptr_t area_size,
-  uintptr_t page_alignment,
-  rtems_rbheap_extend_page_pool extend_page_pool,
+  uintptr_t alignment,
+  rtems_rbheap_extend_descriptors extend_descriptors,
   void *handler_arg
 );
 
+/**
+ * @brief Allocates a chunk of memory of at least @a size bytes from the
+ * red-black tree heap @a control.
+ *
+ * The chunk begin is aligned by the value specified in
+ * rtems_rbheap_initialize().
+ *
+ * @param[in, out] control The red-black tree heap.
+ * @param[in] size The requested chunk size in bytes.
+ *
+ * @retval NULL Not enough free space in the heap.
+ * @retval otherwise Pointer to allocated chunk of memory.
+ */
 void *rtems_rbheap_allocate(rtems_rbheap_control *control, size_t size);
 
+/**
+ * @brief Frees a chunk of memory @a ptr allocated from the red-black tree heap
+ * @a control.
+ *
+ * @param[in, out] control The red-black tree heap.
+ * @param[in] ptr The pointer to the chunk of memory.
+ *
+ * @retval RTEMS_SUCCESSFUL Successful operation.
+ * @retval RTEMS_INVALID_ID The chunk of memory is not a valid chunk in the
+ * red-black tree heap.
+ * @retval RTEMS_INCORRECT_STATE The chunk of memory is not in the right state.
+ */
 rtems_status_code rtems_rbheap_free(rtems_rbheap_control *control, void *ptr);
 
-static inline rtems_chain_control *rtems_rbheap_get_pool_chain(
+static inline rtems_chain_control *rtems_rbheap_get_spare_descriptor_chain(
   rtems_rbheap_control *control
 )
 {
-  return &control->pool_chain;
+  return &control->spare_descriptor_chain;
 }
 
-static inline void rtems_rbheap_set_extend_page_pool(
+static inline void rtems_rbheap_add_to_spare_descriptor_chain(
   rtems_rbheap_control *control,
-  rtems_rbheap_extend_page_pool extend_page_pool
+  rtems_rbheap_chunk *chunk
 )
 {
-  control->extend_page_pool = extend_page_pool;
+  rtems_chain_control *chain =
+    rtems_rbheap_get_spare_descriptor_chain(control);
+
+  rtems_chain_prepend_unprotected(chain, &chunk->chain_node);
+}
+
+static inline void rtems_rbheap_set_extend_descriptors(
+  rtems_rbheap_control *control,
+  rtems_rbheap_extend_descriptors extend_descriptors
+)
+{
+  control->extend_descriptors = extend_descriptors;
 }
 
 static inline void *rtems_rbheap_get_handler_arg(
@@ -107,20 +238,28 @@ static inline void rtems_rbheap_set_handler_arg(
   control->handler_arg = handler_arg;
 }
 
-void rtems_rbheap_extend_page_pool_never(rtems_rbheap_control *control);
+/**
+ * @brief Chunk descriptor extend handler that does nothing.
+ */
+void rtems_rbheap_extend_descriptors_never(rtems_rbheap_control *control);
 
-void rtems_rbheap_extend_page_pool_with_malloc(rtems_rbheap_control *control);
+/**
+ * @brief Chunk descriptor extend handler that uses malloc().
+ */
+void rtems_rbheap_extend_descriptors_with_malloc(
+  rtems_rbheap_control *control
+);
 
 /** @} */
 
 /* Private API */
 
-#define rtems_rbheap_page_of_node(node) \
-  rtems_rbtree_container_of(node, rtems_rbheap_page, tree_node)
+#define rtems_rbheap_chunk_of_node(node) \
+  rtems_rbtree_container_of(node, rtems_rbheap_chunk, tree_node)
 
-static inline bool rtems_rbheap_is_page_free(const rtems_rbheap_page *page)
+static inline bool rtems_rbheap_is_chunk_free(const rtems_rbheap_chunk *chunk)
 {
-  return !rtems_chain_is_node_off_chain(&page->chain_node);
+  return !rtems_chain_is_node_off_chain(&chunk->chain_node);
 }
 
 #ifdef __cplusplus