μcosii源码试读6- OS_MemInit ()；内存管理初始化函数

如果内存管理标志位使能，那么系统初始化内存管理功能

/*
*********************************************************************************************************
* INITIALIZE MEMORY PARTITION MANAGER
*
* Description : This function is called by uC/OS-II to initialize the memory partition manager. Your
* application MUST NOT call this function.
*
* Arguments : none
*
* Returns : none
*
* Note(s) : This function is INTERNAL to uC/OS-II and your application should not call it.
*********************************************************************************************************
*/

void OS_MemInit (void)
{
#if OS_MAX_MEM_PART == 1
    OS_MemClr((INT8U *)&OSMemTbl[0], sizeof(OSMemTbl)); /* Clear the memory partition table */
    OSMemFreeList = (OS_MEM *)&OSMemTbl[0]; /* Point to beginning of free list */
#if OS_MEM_NAME_SIZE > 1
    OSMemFreeList->OSMemName[0] = '?'; /* Unknown name */
    OSMemFreeList->OSMemName[1] = OS_ASCII_NUL;
#endif
#endif

#if OS_MAX_MEM_PART >= 2
    OS_MEM *pmem;
    INT16U i;


    OS_MemClr((INT8U *)&OSMemTbl[0], sizeof(OSMemTbl)); /* Clear the memory partition table */
    pmem = &OSMemTbl[0]; /* Point to memory control block (MCB) */
    for (i = 0; i < (OS_MAX_MEM_PART - 1); i++) { /* Init. list of free memory partitions */
        pmem->OSMemFreeList = (void *)&OSMemTbl[i+1]; /* Chain list of free partitions */
#if OS_MEM_NAME_SIZE > 1
        pmem->OSMemName[0] = '?'; /* Unknown name */
        pmem->OSMemName[1] = OS_ASCII_NUL;
#endif
        pmem++;
    }
    pmem->OSMemFreeList = (void *)0; /* Initialize last node */
#if OS_MEM_NAME_SIZE > 1
    pmem->OSMemName[0] = '?'; /* Unknown name */
    pmem->OSMemName[1] = OS_ASCII_NUL;
#endif

    OSMemFreeList = &OSMemTbl[0]; /* Point to beginning of free list */
#endif
}

核心数据结构为OSMemTbl[0]内存分区表

MCB内存控制数据块的结构如下所示

/*
*********************************************************************************************************
* MEMORY PARTITION DATA STRUCTURES
*********************************************************************************************************
*/

#if (OS_MEM_EN > 0) && (OS_MAX_MEM_PART > 0)
typedef struct os_mem { /* MEMORY CONTROL BLOCK */
    void *OSMemAddr; /* Pointer to beginning of memory partition */
    void *OSMemFreeList; /* Pointer to list of free memory blocks */
    INT32U OSMemBlkSize; /* Size (in bytes) of each block of memory */
    INT32U OSMemNBlks; /* Total number of blocks in this partition */
    INT32U OSMemNFree; /* Number of memory blocks remaining in this partition */
#if OS_MEM_NAME_SIZE > 1
    INT8U OSMemName[OS_MEM_NAME_SIZE]; /* Memory partition name */
#endif
} OS_MEM;


typedef struct os_mem_data {
    void *OSAddr; /* Pointer to the beginning address of the memory partition */
    void *OSFreeList; /* Pointer to the beginning of the free list of memory blocks */
    INT32U OSBlkSize; /* Size (in bytes) of each memory block */
    INT32U OSNBlks; /* Total number of blocks in the partition */
    INT32U OSNFree; /* Number of memory blocks free */
    INT32U OSNUsed; /* Number of memory blocks used */
} OS_MEM_DATA;
#endif

OSMemAddr指向内存分区头地址的void型指针

OSMemFreeList指向空闲内存分区列表的void型指针

OSMemBlkSize内存分区块以字节为单位的大小

OSMemNBlks内存分区中块的个数

OSMemNFree内存分区中未使用的块的个数

 

初始化函数中，当只有一个内存分区时，我们把OSMemTbl[0]赋值给OSMemFreeList就完成了

当有多个内存分区时，初始化OSMemTbl[0]链表，将未使用的MCB单元的指向内存分区地址的指针OSMemFreeList赋值数组的下一个元素，其本质与以前的链表初始化相同，只是只用了一个指针

最后一个节点的指针指向NULL指针

然后将OSMemTbl[0]数组返回给操作系统的OSMemFreeList值