rt-thread中动态内存分配之小内存管理模块方法的一点理解

@2019-01-18

【小记】

rt-thread中动态内存分配之小内存管理模块方法的一点理解

> 内存初始化后的布局示意

lfree指向内存空闲区首地址

 /**

  * @ingroup SystemInit

  *

  * This function will initialize system heap memory.

  *

  * @param begin_addr the beginning address of system heap memory.

  * @param end_addr the end address of system heap memory.

  */

 void rt_system_heap_init(void *begin_addr, void *end_addr)

 {

     struct heap_mem *mem;

     rt_ubase_t begin_align = RT_ALIGN((rt_ubase_t)begin_addr, RT_ALIGN_SIZE);

     rt_ubase_t end_align   = RT_ALIGN_DOWN((rt_ubase_t)end_addr, RT_ALIGN_SIZE);

     RT_DEBUG_NOT_IN_INTERRUPT;

     /* alignment addr */

     if ((end_align > ( * SIZEOF_STRUCT_MEM)) &&

         ((end_align -  * SIZEOF_STRUCT_MEM) >= begin_align))

     {

         /* calculate the aligned memory size */

         mem_size_aligned = end_align - begin_align -  * SIZEOF_STRUCT_MEM;

     }

     else

     {

         rt_kprintf("mem init, error begin address 0x%x, and end address 0x%x\n",

                    (rt_ubase_t)begin_addr, (rt_ubase_t)end_addr);

         return;

     }

     /* point to begin address of heap */

     heap_ptr = (rt_uint8_t *)begin_align;

     RT_DEBUG_LOG(RT_DEBUG_MEM, ("mem init, heap begin address 0x%x, size %d\n",

                                 (rt_ubase_t)heap_ptr, mem_size_aligned));

     /* initialize the start of the heap */

     mem        = (struct heap_mem *)heap_ptr;

     mem->magic = HEAP_MAGIC;

     mem->next  = mem_size_aligned + SIZEOF_STRUCT_MEM;

     mem->prev  = ;

     mem->used  = ;

 #ifdef RT_USING_MEMTRACE

     rt_mem_setname(mem, "INIT");

 #endif

     /* initialize the end of the heap */

     heap_end        = (struct heap_mem *)&heap_ptr[mem->next];

     heap_end->magic = HEAP_MAGIC;

     heap_end->used  = ;

     heap_end->next  = mem_size_aligned + SIZEOF_STRUCT_MEM;

     heap_end->prev  = mem_size_aligned + SIZEOF_STRUCT_MEM;

 #ifdef RT_USING_MEMTRACE

     rt_mem_setname(heap_end, "INIT");

 #endif

     rt_sem_init(&heap_sem, "heap", , RT_IPC_FLAG_FIFO);

     /* initialize the lowest-free pointer to the start of the heap */

     lfree = (struct heap_mem *)heap_ptr;

 }

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