uC/OS-II 函数之内存管理相关函数

上文主要介绍了邮箱管理相关的函数，本文介绍内存管理相关的函数：OSMemCreate()内存块创建函数，OSMemGet()函数，OSMemPut()函数，OSMemQuery()函数.以前用过的uC/OS-II笔记分享到这里。

内存管理介绍

在ANSI C中可以用malloc()和free()两个函数动态地分配内存和释放内存。但是，在嵌入式实时操作系统中，多次这样做会把原来很大的一块连续内存区域，逐渐地分割成许多非常小而且彼此又不相邻的内存区域，也就是内存碎片。由于这些碎片的大量存在，使得程序到后来连非常小的内存也分配不到。另外，由于内存管理算法的原因，malloc()和free()函数执行时间是不确定的。
在μC/OS-II中，操作系统把连续的大块内存按分区来管理。每个分区中包含有整数个大小相同的内存块。利用这种机制，μC/OS-II 对malloc()和free()函数进行了改进，使得它们可以分配和释放固定大小的内存块。这样一来，malloc()和free()函数的执行时间也是固定的了。
在一个系统中可以有多个内存分区。这样，用户的应用程序就可以从不同的内存分区中得到不同大小的内存块。但是，特定的内存块在释放时必须重新放回它以前所属于的内存分区。显然，采用这样的内存管理算法，上面的内存碎片问题就得到了解决。

为了便于内存的管理，在μC/OS-II中使用内存控制块（memory control blocks）的数据结构来跟踪每一个内存分区，系统中的每个内存分区都有它自己的内存控制块。
内存控制块的定义如下：
typedef struct {
void *OSMemAddr; //指向内存分区起始地址的指针
void *OSMemFreeList; //是指向下一个空闲内存控制块或者下一个空闲的内存块的指针
INT32U OSMemBlkSize; //是内存分区中内存块的大小
INT32U OSMemNBlks; //内存分区中总的内存块数量
INT32U OSMemNFree; //内存分区中当前可以得空闲内存块数量
} OS_MEM;
如果要在μC/OS-II中使用内存管理，需要在OS_CFG.H文件中将开关量OS_MEM_EN设置为1。这样μC/OS-II 在启动时就会对内存管理器进行初始化[由OSInit()调用OSMemInit()实现]。常数OS_MAX_MEM_PART（见文件OS_CFG.H）定义了最大的内存分区数，该常数值最小应为2。

注意的事项

使用内存管理模块需要做的工作还有：
1．打开配置文件OS_CFG.H，将开关量OS_MEM_EN设置为1：
#define OS_MEM_EN 0
2．打开配置文件OS_CFG.H，设置系统要建立的任务分区的数量：
#define OS_MAX_MEM_PART 2

OSMemCreate()内存块创建函数

1 主要作用： 该函数建立并初始化一个用于动态内存分配的区域，该内存区域包含指定数目的、大小确定的内存块。应用可以动态申请这些内存块并在用完后将其释放回这个内存区域。该函数的返回值就是指向这个内存区域控制块的指针，并作为OSMemGet()，OSMemPut()，OSMemQuery() 等相关调用的参数。
2函数原型：OS_MEM *OSMemCreate( void *addr, INT32U nblks, INT32U blksize, INT8U *err );
3参数说明：addr 建立的内存区域的起始地址。可以使用静态数组或在系统初始化时使用 malloc() 函数来分配这个区域的空间。
nblks 内存块的数目。每一个内存区域最少需要定义两个内存块。
blksize 每个内存块的大小，最小应该能够容纳一个指针变量。
err 是指向包含错误码的变量的指针。Err可能是如下几种情况：
OS_NO_ERR ：成功建立内存区域。
OS_MEM_INVALID_ADDR ：非法地址，即地址为空指针。
OS_MEM_INVALID_PART ：没有空闲的内存区域。
OS_MEM_INVALID_BLKS ：没有为内存区域建立至少两个内存块。
OS_MEM_INVALID_SIZE ：内存块大小不足以容纳一个指针变量。
5、函数主体在os_men.c中
4返回值说明：
OSMemCreate() 函数返回指向所创建的内存区域控制块的指针。如果创建失败，函数返回空指针。

OSMemGet()函数

1 主要作用： 该函数用于从内存区域分配一个内存块。用户程序必须知道所建立的内存块的大小，并必须在使用完内存块后释放它。可以多次调用 OSMemGet() 函数。它的返回值就是指向所分配内存块的指针，并作为 OSMemPut() 函数的参数。
2函数原型：void *OSMemGet(OS_MEM *pmem, INT8U *err);
3参数说明：pmem 是指向内存区域控制块的指针，可以从 OSMemCreate() 函数的返回值中得到。
err 是指向包含错误码的变量的指针。Err可能是如下情况：
OS_NO_ERR ：成功得到一个内存块。
OS_MEM_NO_FREE_BLKS ：内存区域中已经没有足够的内存块。
4返回值说明：
OSMemGet() 函数返回指向所分配内存块的指针。如果没有可分配的内存块，OSMemGet() 函数返回空指针。
5、函数主体在os_men.c中

OSMemPut()

1 主要作用：该函数用于释放一个内存块，内存块必须释放回它原先所在的内存区域，否则会造成系统错误。
2函数原型：INT8U OSMemPut (OS_MEM *pmem, void *pblk);
3参数说明：pmem 是指向内存区域控制块的指针，可以从 OSMemCreate() 函数的返回值中得到。
pblk 是指向将被释放的内存块的指针。
4返回值说明：
OSMemPut() 函数的返回值为下述之一：
OS_NO_ERR ：成功释放内存块
OS_MEM_FULL ：内存区域已满，不能再接受更多释放的内存块。这种情况说明用户程序出现了错误，释放了多于用 OSMemGet() 函数得到的内存块。
5、函数主体在os_men.c中

OSMemQuery()

1 主要作用：该函数用于得到内存区域的信息。
2函数原型：INT8U OSMemQuery(OS_MEM *pmem, OS_MEM_DATA pdata);
3参数说明：pmem 是指向内存区域控制块的指针，可以从 OSMemCreate() 函数的返回值中得到。
pdata 是一个指向 OS_MEM_DATA 数据结构的指针，该数据结构包含了以下的域：
void OSAddr; / 指向内存区域起始地址的指针 /
void OSFreeList; / 指向空闲内存块列表起始地址的指针 /
INT32U OSBlkSize; / 每个内存块的大小 /
INT32U OSNBlks; / 该内存区域中的内存块总数 /
INT32U OSNFree; / 空闲的内存块数目 /
INT32U OSNUsed; / 已使用的内存块数目 */
4返回值说明：函数返回值总是OS_NO_ERR。
5、函数主体在os_men.c中

附os_men.c代码

/*
*********************************************************************************************************
*                                                uC/OS-II
*                                          The Real-Time Kernel
*                                            MEMORY MANAGEMENT
*
*                              (c) Copyright 1992-2013, Micrium, Weston, FL
*                                           All Rights Reserved
*
* File    : OS_MEM.C
* By      : Jean J. Labrosse
* Version : V2.92.08
*
* LICENSING TERMS:
* ---------------
*   uC/OS-II is provided in source form for FREE evaluation, for educational use or for peaceful research.
* If you plan on using  uC/OS-II  in a commercial product you need to contact Micrium to properly license
* its use in your product. We provide ALL the source code for your convenience and to help you experience
* uC/OS-II.   The fact that the  source is provided does  NOT  mean that you can use it without  paying a
* licensing fee.
*********************************************************************************************************
*/

#define  MICRIUM_SOURCE

#ifndef  OS_MASTER_FILE
#include <ucos_ii.h>
#endif

#if (OS_MEM_EN > 0u) && (OS_MAX_MEM_PART > 0u)
/*
*********************************************************************************************************
*                                      CREATE A MEMORY PARTITION
*
* Description : Create a fixed-sized memory partition that will be managed by uC/OS-II.
*
* Arguments   : addr     is the starting address of the memory partition
*
*               nblks    is the number of memory blocks to create from the partition.
*
*               blksize  is the size (in bytes) of each block in the memory partition.
*
*               perr     is a pointer to a variable containing an error message which will be set by
*                        this function to either:
*
*                        OS_ERR_NONE              if the memory partition has been created correctly.
*                        OS_ERR_MEM_INVALID_ADDR  if you are specifying an invalid address for the memory
*                                                 storage of the partition or, the block does not align
*                                                 on a pointer boundary
*                        OS_ERR_MEM_INVALID_PART  no free partitions available
*                        OS_ERR_MEM_INVALID_BLKS  user specified an invalid number of blocks (must be >= 2)
*                        OS_ERR_MEM_INVALID_SIZE  user specified an invalid block size
*                                                   - must be greater than the size of a pointer
*                                                   - must be able to hold an integral number of pointers
* Returns    : != (OS_MEM *)0  is the partition was created
*              == (OS_MEM *)0  if the partition was not created because of invalid arguments or, no
*                              free partition is available.
*********************************************************************************************************
*/

OS_MEM  *OSMemCreate (void   *addr,
                      INT32U  nblks,
                      INT32U  blksize,
                      INT8U  *perr)
{
    OS_MEM    *pmem;
    INT8U     *pblk;
    void     **plink;
    INT32U     loops;
    INT32U     i;
#if OS_CRITICAL_METHOD == 3u                          /* Allocate storage for CPU status register      */
    OS_CPU_SR  cpu_sr = 0u;
#endif



#ifdef OS_SAFETY_CRITICAL
    if (perr == (INT8U *)0) {
        OS_SAFETY_CRITICAL_EXCEPTION();
        return ((OS_MEM *)0);
    }
#endif

#ifdef OS_SAFETY_CRITICAL_IEC61508
    if (OSSafetyCriticalStartFlag == OS_TRUE) {
        OS_SAFETY_CRITICAL_EXCEPTION();
        return ((OS_MEM *)0);
    }
#endif

#if OS_ARG_CHK_EN > 0u
    if (addr == (void *)0) {                          /* Must pass a valid address for the memory part.*/
        *perr = OS_ERR_MEM_INVALID_ADDR;
        return ((OS_MEM *)0);
    }
    if (((INT32U)addr & (sizeof(void *) - 1u)) != 0u){  /* Must be pointer size aligned                */
        *perr = OS_ERR_MEM_INVALID_ADDR;
        return ((OS_MEM *)0);
    }
    if (nblks < 2u) {                                 /* Must have at least 2 blocks per partition     */
        *perr = OS_ERR_MEM_INVALID_BLKS;
        return ((OS_MEM *)0);
    }
    if (blksize < sizeof(void *)) {                   /* Must contain space for at least a pointer     */
        *perr = OS_ERR_MEM_INVALID_SIZE;
        return ((OS_MEM *)0);
    }
#endif
    OS_ENTER_CRITICAL();
    pmem = OSMemFreeList;                             /* Get next free memory partition                */
    if (OSMemFreeList != (OS_MEM *)0) {               /* See if pool of free partitions was empty      */
        OSMemFreeList = (OS_MEM *)OSMemFreeList->OSMemFreeList;
    }
    OS_EXIT_CRITICAL();
    if (pmem == (OS_MEM *)0) {                        /* See if we have a memory partition             */
        *perr = OS_ERR_MEM_INVALID_PART;
        return ((OS_MEM *)0);
    }
    plink = (void **)addr;                            /* Create linked list of free memory blocks      */
    pblk  = (INT8U *)addr;
    loops  = nblks - 1u;
    for (i = 0u; i < loops; i++) {
        pblk +=  blksize;                             /* Point to the FOLLOWING block                  */
       *plink = (void  *)pblk;                        /* Save pointer to NEXT block in CURRENT block   */
        plink = (void **)pblk;                        /* Position to  NEXT      block                  */
    }
    *plink              = (void *)0;                  /* Last memory block points to NULL              */
    pmem->OSMemAddr     = addr;                       /* Store start address of memory partition       */
    pmem->OSMemFreeList = addr;                       /* Initialize pointer to pool of free blocks     */
    pmem->OSMemNFree    = nblks;                      /* Store number of free blocks in MCB            */
    pmem->OSMemNBlks    = nblks;
    pmem->OSMemBlkSize  = blksize;                    /* Store block size of each memory blocks        */
    *perr               = OS_ERR_NONE;
    return (pmem);
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                         GET A MEMORY BLOCK
*
* Description : Get a memory block from a partition
*
* Arguments   : pmem    is a pointer to the memory partition control block
*
*               perr    is a pointer to a variable containing an error message which will be set by this
*                       function to either:
*
*                       OS_ERR_NONE             if the memory partition has been created correctly.
*                       OS_ERR_MEM_NO_FREE_BLKS if there are no more free memory blocks to allocate to caller
*                       OS_ERR_MEM_INVALID_PMEM if you passed a NULL pointer for 'pmem'
*
* Returns     : A pointer to a memory block if no error is detected
*               A pointer to NULL if an error is detected
*********************************************************************************************************
*/

void  *OSMemGet (OS_MEM  *pmem,
                 INT8U   *perr)
{
    void      *pblk;
#if OS_CRITICAL_METHOD == 3u                          /* Allocate storage for CPU status register      */
    OS_CPU_SR  cpu_sr = 0u;
#endif



#ifdef OS_SAFETY_CRITICAL
    if (perr == (INT8U *)0) {
        OS_SAFETY_CRITICAL_EXCEPTION();
        return ((void *)0);
    }
#endif

#if OS_ARG_CHK_EN > 0u
    if (pmem == (OS_MEM *)0) {                        /* Must point to a valid memory partition        */
        *perr = OS_ERR_MEM_INVALID_PMEM;
        return ((void *)0);
    }
#endif
    OS_ENTER_CRITICAL();
    if (pmem->OSMemNFree > 0u) {                      /* See if there are any free memory blocks       */
        pblk                = pmem->OSMemFreeList;    /* Yes, point to next free memory block          */
        pmem->OSMemFreeList = *(void **)pblk;         /*      Adjust pointer to new free list          */
        pmem->OSMemNFree--;                           /*      One less memory block in this partition  */
        OS_EXIT_CRITICAL();
        *perr = OS_ERR_NONE;                          /*      No error                                 */
        return (pblk);                                /*      Return memory block to caller            */
    }
    OS_EXIT_CRITICAL();
    *perr = OS_ERR_MEM_NO_FREE_BLKS;                  /* No,  Notify caller of empty memory partition  */
    return ((void *)0);                               /*      Return NULL pointer to caller            */
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                 GET THE NAME OF A MEMORY PARTITION
*
* Description: This function is used to obtain the name assigned to a memory partition.
*
* Arguments  : pmem      is a pointer to the memory partition
*
*              pname     is a pointer to a pointer to an ASCII string that will receive the name of the memory partition.
*
*              perr      is a pointer to an error code that can contain one of the following values:
*
*                        OS_ERR_NONE                if the name was copied to 'pname'
*                        OS_ERR_MEM_INVALID_PMEM    if you passed a NULL pointer for 'pmem'
*                        OS_ERR_PNAME_NULL          You passed a NULL pointer for 'pname'
*                        OS_ERR_NAME_GET_ISR        You called this function from an ISR
*
* Returns    : The length of the string or 0 if 'pmem' is a NULL pointer.
*********************************************************************************************************
*/

#if OS_MEM_NAME_EN > 0u
INT8U  OSMemNameGet (OS_MEM   *pmem,
                     INT8U   **pname,
                     INT8U    *perr)
{
    INT8U      len;
#if OS_CRITICAL_METHOD == 3u                     /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr = 0u;
#endif



#ifdef OS_SAFETY_CRITICAL
    if (perr == (INT8U *)0) {
        OS_SAFETY_CRITICAL_EXCEPTION();
        return (0u);
    }
#endif

#if OS_ARG_CHK_EN > 0u
    if (pmem == (OS_MEM *)0) {                   /* Is 'pmem' a NULL pointer?                          */
        *perr = OS_ERR_MEM_INVALID_PMEM;
        return (0u);
    }
    if (pname == (INT8U **)0) {                  /* Is 'pname' a NULL pointer?                         */
        *perr = OS_ERR_PNAME_NULL;
        return (0u);
    }
#endif
    if (OSIntNesting > 0u) {                     /* See if trying to call from an ISR                  */
        *perr = OS_ERR_NAME_GET_ISR;
        return (0u);
    }
    OS_ENTER_CRITICAL();
    *pname = pmem->OSMemName;
    len    = OS_StrLen(*pname);
    OS_EXIT_CRITICAL();
    *perr  = OS_ERR_NONE;
    return (len);
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                 ASSIGN A NAME TO A MEMORY PARTITION
*
* Description: This function assigns a name to a memory partition.
*
* Arguments  : pmem      is a pointer to the memory partition
*
*              pname     is a pointer to an ASCII string that contains the name of the memory partition.
*
*              perr      is a pointer to an error code that can contain one of the following values:
*
*                        OS_ERR_NONE                if the name was copied to 'pname'
*                        OS_ERR_MEM_INVALID_PMEM    if you passed a NULL pointer for 'pmem'
*                        OS_ERR_PNAME_NULL          You passed a NULL pointer for 'pname'
*                        OS_ERR_MEM_NAME_TOO_LONG   if the name doesn't fit in the storage area
*                        OS_ERR_NAME_SET_ISR        if you called this function from an ISR
*
* Returns    : None
*********************************************************************************************************
*/

#if OS_MEM_NAME_EN > 0u
void  OSMemNameSet (OS_MEM  *pmem,
                    INT8U   *pname,
                    INT8U   *perr)
{
#if OS_CRITICAL_METHOD == 3u                     /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr = 0u;
#endif



#ifdef OS_SAFETY_CRITICAL
    if (perr == (INT8U *)0) {
        OS_SAFETY_CRITICAL_EXCEPTION();
        return;
    }
#endif

#if OS_ARG_CHK_EN > 0u
    if (pmem == (OS_MEM *)0) {                   /* Is 'pmem' a NULL pointer?                          */
        *perr = OS_ERR_MEM_INVALID_PMEM;
        return;
    }
    if (pname == (INT8U *)0) {                   /* Is 'pname' a NULL pointer?                         */
        *perr = OS_ERR_PNAME_NULL;
        return;
    }
#endif
    if (OSIntNesting > 0u) {                     /* See if trying to call from an ISR                  */
        *perr = OS_ERR_NAME_SET_ISR;
        return;
    }
    OS_ENTER_CRITICAL();
    pmem->OSMemName = pname;
    OS_EXIT_CRITICAL();
    *perr           = OS_ERR_NONE;
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                       RELEASE A MEMORY BLOCK
*
* Description : Returns a memory block to a partition
*
* Arguments   : pmem    is a pointer to the memory partition control block
*
*               pblk    is a pointer to the memory block being released.
*
* Returns     : OS_ERR_NONE              if the memory block was inserted into the partition
*               OS_ERR_MEM_FULL          if you are returning a memory block to an already FULL memory
*                                        partition (You freed more blocks than you allocated!)
*               OS_ERR_MEM_INVALID_PMEM  if you passed a NULL pointer for 'pmem'
*               OS_ERR_MEM_INVALID_PBLK  if you passed a NULL pointer for the block to release.
*********************************************************************************************************
*/

INT8U  OSMemPut (OS_MEM  *pmem,
                 void    *pblk)
{
#if OS_CRITICAL_METHOD == 3u                     /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr = 0u;
#endif



#if OS_ARG_CHK_EN > 0u
    if (pmem == (OS_MEM *)0) {                   /* Must point to a valid memory partition             */
        return (OS_ERR_MEM_INVALID_PMEM);
    }
    if (pblk == (void *)0) {                     /* Must release a valid block                         */
        return (OS_ERR_MEM_INVALID_PBLK);
    }
#endif
    OS_ENTER_CRITICAL();
    if (pmem->OSMemNFree >= pmem->OSMemNBlks) {  /* Make sure all blocks not already returned          */
        OS_EXIT_CRITICAL();
        return (OS_ERR_MEM_FULL);
    }
    *(void **)pblk      = pmem->OSMemFreeList;   /* Insert released block into free block list         */
    pmem->OSMemFreeList = pblk;
    pmem->OSMemNFree++;                          /* One more memory block in this partition            */
    OS_EXIT_CRITICAL();
    return (OS_ERR_NONE);                        /* Notify caller that memory block was released       */
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                       QUERY MEMORY PARTITION
*
* Description : This function is used to determine the number of free memory blocks and the number of
*               used memory blocks from a memory partition.
*
* Arguments   : pmem        is a pointer to the memory partition control block
*
*               p_mem_data  is a pointer to a structure that will contain information about the memory
*                           partition.
*
* Returns     : OS_ERR_NONE               if no errors were found.
*               OS_ERR_MEM_INVALID_PMEM   if you passed a NULL pointer for 'pmem'
*               OS_ERR_MEM_INVALID_PDATA  if you passed a NULL pointer to the data recipient.
*********************************************************************************************************
*/

#if OS_MEM_QUERY_EN > 0u
INT8U  OSMemQuery (OS_MEM       *pmem,
                   OS_MEM_DATA  *p_mem_data)
{
#if OS_CRITICAL_METHOD == 3u                     /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr = 0u;
#endif



#if OS_ARG_CHK_EN > 0u
    if (pmem == (OS_MEM *)0) {                   /* Must point to a valid memory partition             */
        return (OS_ERR_MEM_INVALID_PMEM);
    }
    if (p_mem_data == (OS_MEM_DATA *)0) {        /* Must release a valid storage area for the data     */
        return (OS_ERR_MEM_INVALID_PDATA);
    }
#endif
    OS_ENTER_CRITICAL();
    p_mem_data->OSAddr     = pmem->OSMemAddr;
    p_mem_data->OSFreeList = pmem->OSMemFreeList;
    p_mem_data->OSBlkSize  = pmem->OSMemBlkSize;
    p_mem_data->OSNBlks    = pmem->OSMemNBlks;
    p_mem_data->OSNFree    = pmem->OSMemNFree;
    OS_EXIT_CRITICAL();
    p_mem_data->OSNUsed    = p_mem_data->OSNBlks - p_mem_data->OSNFree;
    return (OS_ERR_NONE);
}
#endif                                           /* OS_MEM_QUERY_EN                                    */
/*$PAGE*/
/*
*********************************************************************************************************
*                                 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 == 1u
    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_EN > 0u
    OSMemFreeList->OSMemName    = (INT8U *)"?";           /* Unknown name                              */
#endif
#endif

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


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

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