memheap.c

/*
 * File      : memheap.c
 * This file is part of RT-Thread RTOS
 * COPYRIGHT (C) 2012, RT-Thread Development Team
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rt-thread.org/license/LICENSE
 *
 * Change Logs:
 * Date           Author       Notes
 * 2012-04-10     Bernard      first implementation
 * 2012-10-16     Bernard      add the mutex lock for heap object.
 */

#include <rtthread.h>

#ifdef RT_USING_MEMHEAP

/* dynamic pool magic and mask */
#define RT_MEMHEAP_MAGIC        0x1ea01ea0
#define RT_MEMHEAP_MASK         0xfffffffe
#define RT_MEMHEAP_USED         0x01
#define RT_MEMHEAP_FREED        0x00

#define RT_MEMHEAP_IS_USED(i)   ((i)->magic & RT_MEMHEAP_USED)
#define RT_MEMHEAP_MINIALLOC    12

#define RT_MEMHEAP_SIZE     RT_ALIGN(sizeof(struct rt_memheap_item), RT_ALIGN_SIZE)

/*
 * The initialized memory pool will be:
 * +-----------------------------------+--------------------------+
 * | whole freed memory block          | Used Memory Block Tailer |
 * +-----------------------------------+--------------------------+
 *
 * block_list --> whole freed memory block
 *
 * The length of Used Memory Block Tailer is 0,
 * which is prevents block merging across list
 */
rt_err_t rt_memheap_init(struct rt_memheap *memheap,
                         const char        *name,
                         void              *start_addr,
                         rt_uint32_t        size)
{
    struct rt_memheap_item *item;

    RT_ASSERT(memheap != RT_NULL);

    /* initialize pool object */
    rt_object_init(&(memheap->parent), RT_Object_Class_MemHeap, name);

    memheap->start_addr     = start_addr;
    memheap->pool_size      = RT_ALIGN_DOWN(size, RT_ALIGN_SIZE);
    memheap->available_size = memheap->pool_size - (2 * RT_MEMHEAP_SIZE);

    /* initialize the free list header */
    item            = &(memheap->free_header);
    item->magic     = RT_MEMHEAP_MAGIC;
    item->pool_ptr  = memheap;
    item->next      = RT_NULL;
    item->prev      = RT_NULL;
    item->next_free = item;
    item->prev_free = item;

    /* set the free list to free list header */
    memheap->free_list = item;

    /* initialize the first big memory block */
    item            = (struct rt_memheap_item *)start_addr;
    item->magic     = RT_MEMHEAP_MAGIC;
    item->pool_ptr  = memheap;
    item->next      = RT_NULL;
    item->prev      = RT_NULL;
    item->next_free = item;
    item->prev_free = item;

    item->next = (struct rt_memheap_item *)
        ((rt_uint8_t *)item + memheap->available_size + RT_MEMHEAP_SIZE);
    item->prev = item->next;

    /* block list header */
    memheap->block_list = item;

    /* place the big memory block to free list */
    item->next_free = memheap->free_list->next_free;
    item->prev_free = memheap->free_list;
    memheap->free_list->next_free->prev_free = item;
    memheap->free_list->next_free            = item;

    /* move to the end of memory pool to build a small tailer block,
     * which prevents block merging
     */
    item = item->next;
    /* it's a used memory block */
    item->magic     = RT_MEMHEAP_MAGIC | RT_MEMHEAP_USED;
    item->pool_ptr  = memheap;
    item->next      = (struct rt_memheap_item *)start_addr;
    item->prev      = (struct rt_memheap_item *)start_addr;
    /* not in free list */
    item->next_free = item->prev_free = RT_NULL;

    /* initialize mutex lock */
    rt_mutex_init(&(memheap->lock), name, RT_IPC_FLAG_FIFO);

    RT_DEBUG_LOG(RT_DEBUG_MEMHEAP,
                 ("memory heap: start addr 0x%08x, size %d, free list header 0x%08x",
                  start_addr, size, &(memheap->free_header)));

    return RT_EOK;
}
RTM_EXPORT(rt_memheap_init);

rt_err_t rt_memheap_detach(struct rt_memheap *heap)
{
    RT_ASSERT(heap);

    rt_object_detach(&(heap->lock.parent.parent));
    rt_object_detach(&(heap->parent));

    /* Return a successful completion. */
    return RT_EOK;
}
RTM_EXPORT(rt_memheap_detach);

void *rt_memheap_alloc(struct rt_memheap *heap, rt_uint32_t size)
{
    rt_err_t result;
    rt_uint32_t free_size;
    struct rt_memheap_item *header_ptr;

    RT_ASSERT(heap != RT_NULL);

    /* align allocated size */
    size = RT_ALIGN(size, RT_ALIGN_SIZE);
    if (size < RT_MEMHEAP_MINIALLOC)
        size = RT_MEMHEAP_MINIALLOC;

    RT_DEBUG_LOG(RT_DEBUG_MEMHEAP, ("allocate %d", size));

    if (size < heap->available_size)
    {
        /* search on free list */
        free_size = 0;

        /* lock memheap */
        result = rt_mutex_take(&(heap->lock), RT_WAITING_FOREVER);
        if (result != RT_EOK)
        {
            rt_set_errno(result);

            return RT_NULL;
        }

        /* get the first free memory block */
        header_ptr = heap->free_list->next_free;
        while (header_ptr != heap->free_list && free_size < size)
        {
            /* get current freed memory block size */
            free_size = (rt_uint32_t)(header_ptr->next) -
                        (rt_uint32_t)header_ptr -
                        RT_MEMHEAP_SIZE;

            if (free_size < size)
            {
                /* move to next free memory block */
                header_ptr = header_ptr->next_free;
            }
        }

        /* determine if the memory is available. */
        if (free_size >= size)
        {
            /* a block that satisfies the request has been found. */

            /* determine if the block needs to be split. */
            if (free_size >= (size + RT_MEMHEAP_SIZE + RT_MEMHEAP_MINIALLOC))
            {
                struct rt_memheap_item *new_ptr;

                /* split the block. */
                new_ptr = (struct rt_memheap_item *)
                          (((rt_uint8_t *)header_ptr) + size + RT_MEMHEAP_SIZE);

                RT_DEBUG_LOG(RT_DEBUG_MEMHEAP,
                             ("split: h[0x%08x] nm[0x%08x] pm[0x%08x] to n[0x%08x]",
                              header_ptr,
                              header_ptr->next,
                              header_ptr->prev,
                              new_ptr));

                /* mark the new block as a memory block and freed. */
                new_ptr->magic = RT_MEMHEAP_MAGIC;

                /* put the pool pointer into the new block. */
                new_ptr->pool_ptr = heap;

                /* break down the block list */
                new_ptr->prev          = header_ptr;
                new_ptr->next          = header_ptr->next;
                header_ptr->next->prev = new_ptr;
                header_ptr->next       = new_ptr;

                /* remove header ptr from free list */
                header_ptr->next_free->prev_free = header_ptr->prev_free;
                header_ptr->prev_free->next_free = header_ptr->next_free;
                header_ptr->next_free = RT_NULL;
                header_ptr->prev_free = RT_NULL;

                /* insert new_ptr to free list */
                new_ptr->next_free = heap->free_list->next_free;
                new_ptr->prev_free = heap->free_list;
                heap->free_list->next_free->prev_free = new_ptr;
                heap->free_list->next_free            = new_ptr;
                RT_DEBUG_LOG(RT_DEBUG_MEMHEAP, ("new ptr: nf 0x%08x, pf 0x%08x",
                                                new_ptr->next_free,
                                                new_ptr->prev_free));

                /* decrement the available byte count.  */
                heap->available_size = heap->available_size -
                                       size -
                                       RT_MEMHEAP_SIZE;
            }
            else
            {
                /* decrement the entire free size from the available bytes count. */
                heap->available_size = heap->available_size - free_size;

                /* remove header_ptr from free list */
                RT_DEBUG_LOG(RT_DEBUG_MEMHEAP,
                             ("one block: h[0x%08x], nf 0x%08x, pf 0x%08x",
                              header_ptr,
                              header_ptr->next_free,
                              header_ptr->prev_free));

                header_ptr->next_free->prev_free = header_ptr->prev_free;
                header_ptr->prev_free->next_free = header_ptr->next_free;
                header_ptr->next_free = RT_NULL;
                header_ptr->prev_free = RT_NULL;
            }

            /* release lock */
            rt_mutex_release(&(heap->lock));
            
            /* Mark the allocated block as not available. */
            header_ptr->magic |= RT_MEMHEAP_USED;

            /* Return a memory address to the caller.  */
            RT_DEBUG_LOG(RT_DEBUG_MEMHEAP,
                         ("am: m[0x%08x], h[0x%08x], size: %d",
                          (void *)((rt_uint8_t *)header_ptr + RT_MEMHEAP_SIZE),
                          header_ptr,
                          size);

            return (void *)((rt_uint8_t *)header_ptr + RT_MEMHEAP_SIZE));
        }

        /* release lock */
        rt_mutex_release(&(heap->lock));
    }

    RT_DEBUG_LOG(RT_DEBUG_MEMHEAP, ("allocate memory: failed\n"));

    /* Return the completion status.  */
    return RT_NULL;
}
RTM_EXPORT(rt_memheap_alloc);

void rt_memheap_free(void *ptr)
{
    rt_err_t result;
    struct rt_memheap *heap;
    struct rt_memheap_item *header_ptr, *new_ptr;
    rt_uint32_t insert_header;

    /* set initial status as OK */
    insert_header = 1;
    new_ptr       = RT_NULL;
    header_ptr    = (struct rt_memheap_item *)((rt_uint8_t *)ptr -
                                               RT_MEMHEAP_SIZE);

    RT_DEBUG_LOG(RT_DEBUG_MEMHEAP, ("free memory: m[0x%08x], h[0x%08x]",
                                    ptr, header_ptr));

    /* check magic */
    RT_ASSERT((header_ptr->magic & RT_MEMHEAP_MASK) == RT_MEMHEAP_MAGIC);

    /* get pool ptr */
    heap = header_ptr->pool_ptr;

    /* lock memheap */
    result = rt_mutex_take(&(heap->lock), RT_WAITING_FOREVER);
    if (result != RT_EOK)
    {
        rt_set_errno(result);

        return ;
    }

    /* Mark the memory as available. */
    header_ptr->magic &= ~RT_MEMHEAP_USED;

    /* Adjust the available number of bytes. */
    heap->available_size =
        heap->available_size +
        ((rt_uint32_t)(header_ptr->next) - (rt_uint32_t)header_ptr) -
        RT_MEMHEAP_SIZE;

    /* Determine if the block can be merged with the previous neighbor. */
    if (!RT_MEMHEAP_IS_USED(header_ptr->prev))
    {
        RT_DEBUG_LOG(RT_DEBUG_MEMHEAP, ("merge: left node 0x%08x",
                                        header_ptr->prev));

        /* adjust the available number of bytes. */
        heap->available_size = heap->available_size + RT_MEMHEAP_SIZE;

        /* yes, merge block with previous neighbor. */
        (header_ptr->prev)->next = header_ptr->next;
        (header_ptr->next)->prev = header_ptr->prev;

        /* move header pointer to previous. */
        header_ptr = header_ptr->prev;
        /* don't insert header to free list */
        insert_header = 0;
    }

    /* determine if the block can be merged with the next neighbor. */
    if (!RT_MEMHEAP_IS_USED(header_ptr->next))
    {
        /* adjust the available number of bytes. */
        heap->available_size = heap->available_size + RT_MEMHEAP_SIZE;

        /* merge block with next neighbor. */
        new_ptr = header_ptr->next;

        RT_DEBUG_LOG(RT_DEBUG_MEMHEAP,
                     ("merge: right node 0x%08x, nf 0x%08x, pf 0x%08x",
                      new_ptr, new_ptr->next_free, new_ptr->prev_free));

        new_ptr->next->prev = header_ptr;
        header_ptr->next    = new_ptr->next;

        /* remove new ptr from free list */
        new_ptr->next_free->prev_free = new_ptr->prev_free;
        new_ptr->prev_free->next_free = new_ptr->next_free;
    }

    if (insert_header)
    {
        /* no left merge, insert to free list */
        header_ptr->next_free = heap->free_list->next_free;
        header_ptr->prev_free = heap->free_list;
        heap->free_list->next_free->prev_free = header_ptr;
        heap->free_list->next_free            = header_ptr;

        RT_DEBUG_LOG(RT_DEBUG_MEMHEAP,
                     ("insert to free list: nf 0x%08x, pf 0x%08x",
                      header_ptr->next_free, header_ptr->prev_free));
    }

    /* release lock */
    rt_mutex_release(&(heap->lock));
}
RTM_EXPORT(rt_memheap_free);

#endif