//BY 简单的元清
//部分内容引用了其他博主的文章，对这些博主表示感谢，时间关系就不一一指出了。
//如有转载，请说明，谢谢
/*
/*
*********************************************************************************************************
* uC/OS-II
* The Real-Time Kernel
* MEMORY MANAGEMENT
*
* (c) Copyright 1992-1998, Jean J. Labrosse, Plantation, FL
* All Rights Reserved
*
* V2.00
*
* File : OS_MEM.C
* By : Jean J. Labrosse
*********************************************************************************************************
*/
#ifndef OS_MASTER_FILE
#include "software\includes.h"
#endif
#if OS_MEM_EN && OS_MAX_MEM_PART >= 2
/*
*********************************************************************************************************
* LOCAL GLOBAL VARIABLES
*********************************************************************************************************
*/
static OS_MEM *OSMemFreeList; /* Pointer to free list of memory partitions */
static OS_MEM OSMemTbl[OS_MAX_MEM_PART];/* Storage for memory partition manager */
/*$PAGE*/
/*
*********************************************************************************************************
* 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.
*
* err is a pointer to a variable containing an error message which will be set by
* this function to either:
*
* OS_NO_ERR if the memory partition has been created correctly.
* OS_MEM_INVALID_PART no free partitions available
* OS_MEM_INVALID_BLKS user specified an invalid number of blocks (must be >= 2)
* OS_MEM_INVALID_SIZE user specified an invalid block size
* (must be greater than the size of a pointer)
* 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.
*********************************************************************************************************
*/
//建立一个内存分区
OS_MEM *OSMemCreate (void *addr, INT32U nblks, INT32U blksize, INT8U *err) reentrant
{
OS_MEM *pmem;
INT8U *pblk;
void **plink;
INT32U i;
if (nblks < 2) { /* Must have at least 2 blocks per partition */
*err = OS_MEM_INVALID_BLKS;
return ((OS_MEM *)0);
}
//块的数目必须大于2
if (blksize < sizeof(void *)) { /* Must contain space for at least a pointer */
*err = OS_MEM_INVALID_SIZE;
return ((OS_MEM *)0);
}
//块的大于必须大于一个指针的大小
OS_ENTER_CRITICAL();
//进入临界区
pmem = OSMemFreeList; /* Get next free memory partition */
//从空列表中摘下一个块
if (OSMemFreeList != (OS_MEM *)0) { /* See if pool of free partitions was empty */
OSMemFreeList = (OS_MEM *)OSMemFreeList->OSMemFreeList;
//如果这个块是零，OSMemFreeList指向OSMemFreeList->OSMemFreeList
}
OS_EXIT_CRITICAL();
//退出临界区
if (pmem == (OS_MEM *)0) { /* See if we have a memory partition */
*err = OS_MEM_INVALID_PART;
return ((OS_MEM *)0);
//如果pmem是零，发送错误码并返回0
}
plink = (void **)addr; /* Create linked list of free memory blocks */
pblk = (INT8U *)addr + blksize;
for (i = 0; i < (nblks - 1); i++) {
*plink = (void *)pblk;
plink = (void **)pblk;
pblk = pblk + blksize;
}
//所要建立的内存分区内的所有内存块被链接成一个单向的链表
OS_ENTER_CRITICAL();
//进入临界区
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 */
//填写相应的信息
OS_EXIT_CRITICAL();
*err = OS_NO_ERR;
return (pmem);
//退出并返回错误码
}
/*$PAGE*/
/*
*********************************************************************************************************
* GET A MEMORY BLOCK
*
* Description : Get a memory block from a partition
*
* Arguments : pmem is a pointer to the memory partition control block
*
* err is a pointer to a variable containing an error message which will be set by this
* function to either:
*
* OS_NO_ERR if the memory partition has been created correctly.
* OS_MEM_NO_FREE_BLKS if there are no more free memory blocks to allocate to caller
*
* Returns : A pointer to a memory block if no error is detected
* A pointer to NULL if an error is detected
*********************************************************************************************************
*/
//获得一个内存块
void *OSMemGet (OS_MEM *pmem, INT8U *err) reentrant
{
void *pblk;
OS_ENTER_CRITICAL();
//进入临界区
if (pmem->OSMemNFree > 0) { /* See if there are any free memory blocks */
//如果有空闲的内存块
pblk = pmem->OSMemFreeList; /* Yes, point to next free memory block */
//从空闲内存块链表中删除第一个内存块
pmem->OSMemFreeList = *(void **)pblk; /* Adjust pointer to new free list */
//对空闲内存块链表作相应的修改
pmem->OSMemNFree--; /* One less memory block in this partition */
//链表头指针后移一个元素和空闲内存块数减1
OS_EXIT_CRITICAL();
*err = OS_NO_ERR; /* No error */
////退出并返回错误码
return (pblk); /* Return memory block to caller */
//返回指向被分配内存块的指针
} else {
OS_EXIT_CRITICAL();
*err = OS_MEM_NO_FREE_BLKS; /* No, Notify caller of empty memory partition */
return ((void *)0); /* Return NULL pointer to caller */
//退出并返回错误码
}
}
/*$PAGE*/
/*
*********************************************************************************************************
* INITIALIZE MEMORY PARTITION MANAGER
*
* Description : This function is called by uC/OS-II to initialize the memory partition manager. Your
* application MUST NOT call this function.
*
* Arguments : none
*
* Returns : none
*********************************************************************************************************
*/
//初始化内存分区
void OSMemInit (void) reentrant
{
OS_MEM *pmem;
INT16U i;
pmem = (OS_MEM *)&OSMemTbl[0]; /* Point to memory control block (MCB) */
//内存块链接表指向内存块首地址
for (i = 0; i < (OS_MAX_MEM_PART - 1); i++) { /* Init. list of free memory partitions */
pmem->OSMemFreeList = (void *)&OSMemTbl[i+1]; /* Chain list of free partitions */
pmem->OSMemAddr = (void *)0; /* Store start address of memory partition */
pmem->OSMemNFree = 0; /* No free blocks */
pmem->OSMemNBlks = 0; /* No blocks */
pmem->OSMemBlkSize = 0; /* Zero size */
pmem++;
}
//对内存的设置
OSMemTbl[OS_MAX_MEM_PART - 1].OSMemFreeList = (void *)0;
OSMemFreeList = (OS_MEM *)&OSMemTbl[0];
////回到开始的内存块链接表
}
/*$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_NO_ERR if the memory block was inserted into the partition
* OS_MEM_FULL if you are returning a memory block to an already FULL memory partition
* (You freed more blocks than you allocated!)
*********************************************************************************************************
*/
//释放一个内存块
INT8U OSMemPut (OS_MEM *pmem, void *pblk) reentrant
{
OS_ENTER_CRITICAL();
//退出临界区
if (pmem->OSMemNFree >= pmem->OSMemNBlks) { /* Make sure all blocks not already returned */
OS_EXIT_CRITICAL();
return (OS_MEM_FULL);
//检查内存分区是否已满
}
*(void **)pblk = pmem->OSMemFreeList; /* Insert released block into free block list */
//释放的内存块被插入到该分区的空闲内存块链表中
pmem->OSMemFreeList = pblk;
//？？？？
pmem->OSMemNFree++; /* One more memory block in this partition */
//空闲内存块加一
OS_EXIT_CRITICAL();
//退出临界区
return (OS_NO_ERR); /* 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
*
* pdata is a pointer to a structure that will contain information about the memory
* partition.
*
* Returns : OS_NO_ERR Always returns no error.
*********************************************************************************************************
*/
//查询一个内存分区的状态
INT8U OSMemQuery (OS_MEM *pmem, OS_MEM_DATA *ppdata) reentrant
{
OS_ENTER_CRITICAL();
//进入临界区
ppdata->OSAddr = pmem->OSMemAddr;
ppdata->OSFreeList = pmem->OSMemFreeList;
ppdata->OSBlkSize = pmem->OSMemBlkSize;
ppdata->OSNBlks = pmem->OSMemNBlks;
ppdata->OSNFree = pmem->OSMemNFree;
//复制pmem信息到ppdata
OS_EXIT_CRITICAL();
//退出临界区
ppdata->OSNUsed = ppdata->OSNBlks - ppdata->OSNFree;
//计算使用量
return (OS_NO_ERR);
//返回错误码
}
#endif
逐字逐句解析ucos ii 源代码-》OS_MEM.C
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