/*
*********************************************************************************************************
* uC/OS-II
* The Real-Time Kernel
* MEMORY MANAGEMENT
*
* (c) Copyright 1992-2002, Jean J. Labrosse, Weston, FL
* All Rights Reserved
*
* File : OS_MEM.C
* By : Jean J. Labrosse
*********************************************************************************************************
*/
#ifndef OS_MASTER_FILE
#include "includes.h"
#endif
#if (OS_MEM_EN > 0) && (OS_MAX_MEM_PART > 0)
/*
*********************************************************************************************************
* 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/分区
*
* 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_ADDR you are specifying an invalid address for the memory
* storage of the partition.
* 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.
*********************************************************************************************************
*/
//创建内存分区
OS_MEM *OSMemCreate (void *addr, INT32U nblks, INT32U blksize, INT8U *err)
{
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif
OS_MEM *pmem;
INT8U *pblk;
void **plink;
INT32U i;
#if OS_ARG_CHK_EN > 0
//内存分区的起始地址是否有效
if (addr == (void *)0) { /* Must pass a valid address for the memory part. */
*err = OS_MEM_INVALID_ADDR;
return ((OS_MEM *)0);
}
//创建的内存分区中是否指定只有一个内存块
if (nblks < 2) { /* Must have at least 2 blocks per partition */
*err = OS_MEM_INVALID_BLKS;
return ((OS_MEM *)0);
}
//每个内存块至少要能容下一个指针
if (blksize < sizeof(void *)) { /* Must contain space for at least a pointer */
*err = OS_MEM_INVALID_SIZE;
return ((OS_MEM *)0);
}
#endif
OS_ENTER_CRITICAL();
//OSMemFreeList是一个全局变量
pmem = OSMemFreeList; /* Get next free memory partition */
//See if pool of free partitions was empty 成立 OSMemFreeList指向下一个空闲内存分区
if (OSMemFreeList != (OS_MEM *)0) { /* See if pool of free partitions was empty */
OSMemFreeList = (OS_MEM *)OSMemFreeList->OSMemFreeList;
}
OS_EXIT_CRITICAL();
//没有有效的分区时
if (pmem == (OS_MEM *)0) { /* See if we have a memory partition */
*err = OS_MEM_INVALID_PART;
return ((OS_MEM *)0);
}
//开始进行分区管理
//plink获取内存分区的首地址
plink = (void **)addr; /* Create linked list of free memory blocks */
//pblk获取内存分区的第一块的地址
pblk = (INT8U *)addr + blksize;
//开始构建单向的空闲内存块的链表
for (i = 0; i < (nblks - 1); i++) {
*plink = (void *)pblk; //当前块的第一个元素中存储下一个块的地址
plink = (void **)pblk; //指向下一块
pblk = pblk + blksize;//pblk指向下一块
}
//Last memory block points to NULL
*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 */
*err = OS_NO_ERR; //create success
return (pmem);
}
/*$PAGE*/
/*
*********************************************************************************************************
* GET A MEMORY BLOCK
*
* Description : Get a memory block from a partition
*
* Arguments : pmem is a pointer to the memory partition control block
*
* err is a pointer to a variable containing an error message which will be set by this
* function to either:
*
* OS_NO_ERR if the memory partition has been created correctly.
* OS_MEM_NO_FREE_BLKS if there are no more free memory blocks to allocate to caller
* OS_MEM_INVALID_PMEM if you passed a NULL pointer for 'pmem'
*
* Returns : A pointer to a memory block if no error is detected
* A pointer to NULL if an error is detected
*********************************************************************************************************
*/
//Get a memory block from a partition/分区 pmem--创建分区函数所返回的内存控制块的指针；
void *OSMemGet (OS_MEM *pmem, INT8U *err)
{
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif
void *pblk;
#if OS_ARG_CHK_EN > 0
//a valid memory partition
if (pmem == (OS_MEM *)0) { /* Must point to a valid memory partition */
*err = OS_MEM_INVALID_PMEM;
return ((OS_MEM *)0);
}
#endif
OS_ENTER_CRITICAL();
//See if there are any free memory blocks
if (pmem->OSMemNFree > 0) { /* See if there are any free memory blocks */
pblk = pmem->OSMemFreeList; /* Yes, point to next free memory block */
//相当于从链表头中摘下表头
pmem->OSMemFreeList = *(void **)pblk; /* Adjust pointer to new free list */
pmem->OSMemNFree--; /* One less memory block in this partition */
OS_EXIT_CRITICAL();
*err = OS_NO_ERR; /* No error */
return (pblk); /* Return memory block to caller */
}
OS_EXIT_CRITICAL();
*err = OS_MEM_NO_FREE_BLKS; /* No, Notify caller of empty memory partition */
return ((void *)0); /* Return NULL pointer to caller */
}
/*$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!)
* OS_MEM_INVALID_PMEM if you passed a NULL pointer for 'pmem'
* OS_MEM_INVALID_PBLK if you passed a NULL pointer for the block to release.
*********************************************************************************************************
*/
//内存分区的释放-也就是将内存块归还给空闲内存块链表
INT8U OSMemPut (OS_MEM *pmem, void *pblk)
{
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif
#if OS_ARG_CHK_EN > 0
if (pmem == (OS_MEM *)0) { /* Must point to a valid memory partition */
return (OS_MEM_INVALID_PMEM);
}
if (pblk == (void *)0) { /* Must release a valid block */
return (OS_MEM_INVALID_PBLK);
}
#endif
OS_ENTER_CRITICAL();
//如果空闲的快数大于等于最大块数，说明分区已满不能释放
if (pmem->OSMemNFree >= pmem->OSMemNBlks) { /* Make sure all blocks not already returned */
OS_EXIT_CRITICAL();
return (OS_MEM_FULL);
}
//否则 将释放的块归还给空闲内存块链表 插入到表头
*(void **)pblk = pmem->OSMemFreeList; /* Insert released block into free block list */
pmem->OSMemFreeList = pblk;
//空闲块数加加
pmem->OSMemNFree++; /* One more memory block in this partition */
OS_EXIT_CRITICAL();
return (OS_NO_ERR); /* Notify caller that memory block was released */
}
/*$PAGE*/
/*
*********************************************************************************************************
* QUERY MEMORY PARTITION
*
* Description : This function is used to determine the number of free memory blocks and the number of
* used memory blocks from a memory partition.
*
* Arguments : pmem is a pointer to the memory partition control block
*
* pdata is a pointer to a structure that will contain information about the memory
* partition.
*
* Returns : OS_NO_ERR If no errors were found.
* OS_MEM_INVALID_PMEM if you passed a NULL pointer for 'pmem'
* OS_MEM_INVALID_PDATA if you passed a NULL pointer for the block to release.
*********************************************************************************************************
*/
// This function is used to determine the number of free memory blocks and the number of
// used memory blocks from a memory partition. 也就是查询内存分区的状态
#if OS_MEM_QUERY_EN > 0
INT8U OSMemQuery (OS_MEM *pmem, OS_MEM_DATA *pdata)
{
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif
#if OS_ARG_CHK_EN > 0
// a valid memory partition
if (pmem == (OS_MEM *)0) { /* Must point to a valid memory partition */
return (OS_MEM_INVALID_PMEM);
}
// a valid storage area for the data
if (pdata == (OS_MEM_DATA *)0) { /* Must release a valid storage area for the data */
return (OS_MEM_INVALID_PDATA);
}
#endif
//各种保存
OS_ENTER_CRITICAL();
//保存内存分区的首地址
pdata->OSAddr = pmem->OSMemAddr;
//保存空闲内存块链表地址
pdata->OSFreeList = pmem->OSMemFreeList;
pdata->OSBlkSize = pmem->OSMemBlkSize;
pdata->OSNBlks = pmem->OSMemNBlks;
pdata->OSNFree = pmem->OSMemNFree;
OS_EXIT_CRITICAL();
pdata->OSNUsed = pdata->OSNBlks - pdata->OSNFree;
return (OS_NO_ERR);
}
#endif /* OS_MEM_QUERY_EN */
/*$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.
*********************************************************************************************************
*/
// initialize the memory partition manager
void OS_MemInit (void)
{
#if OS_MAX_MEM_PART == 1 //最大内存分区数量为1
OSMemFreeList = (OS_MEM *)&OSMemTbl[0]; /* Point to beginning of free list */
OSMemFreeList->OSMemFreeList = (void *)0; /* Initialize last node */
OSMemFreeList->OSMemAddr = (void *)0; /* Store start address of memory partition */
OSMemFreeList->OSMemNFree = 0; /* No free blocks */
OSMemFreeList->OSMemNBlks = 0; /* No blocks */
OSMemFreeList->OSMemBlkSize = 0; /* Zero size */
#endif
#if OS_MAX_MEM_PART >= 2
OS_MEM *pmem;
INT16U i;
//
pmem = (OS_MEM *)&OSMemTbl[0]; /* Point to memory control block (MCB) */
for (i = 0; i < (OS_MAX_MEM_PART - 1); i++) { /* Init. list of free memory partitions */
// 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++;
}
//最后一项指向空地址
pmem->OSMemFreeList = (void *)0; /* Initialize last node */
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 */
//空闲内存控制块指针指向空闲内存控制块的第一项
OSMemFreeList = (OS_MEM *)&OSMemTbl[0]; /* Point to beginning of free list */
#endif
}
#endif /* OS_MEM_EN */