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 /* SPDX-License-Identifier: BSD-2-Clause */
 
 /**
  * @file
  *
  * @ingroup RTEMSAPIRBHeap
  *
  * @brief This header file provides the Red-Black Tree Heap API.
  */
 
 /*
  * Copyright (c) 2012 embedded brains GmbH & Co. KG
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef _RTEMS_RBHEAP_H
 #define _RTEMS_RBHEAP_H
 
 #include <rtems.h>
 #include <rtems/chain.h>
 #include <rtems/rbtree.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /**
  * @defgroup RTEMSAPIRBHeap Red-Black Tree Heap
  *
  * @ingroup RTEMSAPI
  *
  * @brief The red-black tree heap provides a memory allocator using a red-black
  *   tree to maintain blocks of memory.
  *
  * 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_chunk;
 
 typedef struct rtems_rbheap_control rtems_rbheap_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 {
   /**
    * 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_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 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_spare_descriptor_chain(
   rtems_rbheap_control *control
 )
 {
   return &control->spare_descriptor_chain;
 }
 
 static inline void rtems_rbheap_add_to_spare_descriptor_chain(
   rtems_rbheap_control *control,
   rtems_rbheap_chunk *chunk
 )
 {
   rtems_chain_control *chain =
     rtems_rbheap_get_spare_descriptor_chain(control);
 
   rtems_chain_initialize_node(&chunk->chain_node);
   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(
   const rtems_rbheap_control *control
 )
 {
   return control->handler_arg;
 }
 
 static inline void rtems_rbheap_set_handler_arg(
   rtems_rbheap_control *control,
   void *handler_arg
 )
 {
   control->handler_arg = handler_arg;
 }
 
 /**
  * @brief Chunk descriptor extend handler that does nothing.
  */
 void rtems_rbheap_extend_descriptors_never(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_chunk_of_node(node) \
   RTEMS_CONTAINER_OF(node, rtems_rbheap_chunk, tree_node)
 
 static inline bool rtems_rbheap_is_chunk_free(const rtems_rbheap_chunk *chunk)
 {
   return !rtems_chain_is_node_off_chain(&chunk->chain_node);
 }
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif /* _RTEMS_RBHEAP_H */

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