test.c

高效内存管理函数实现。VC＋＋实现

#include <stdio.h>
#include <stdlib.h>

#define TOTALMEMORY 1048
char MEMSpace[TOTALMEMORY];

void MEMInit(void);
void *MyAlloc(int size);
void  MyFree(void *p);

typedef struct list
{
  struct list * pre;//上一块空闲区或使用区指针，NULL表示为第一块空闲区或使用区
  int size;//空闲区或使用区大小
  struct list * next;//下一块空闲区或使用区指针，NULL表示为最后一块空闲区或使用区
}MCB;

struct memory
{
   char *memorybase;		//内存区首地址 
   long memorysize;			//内存区大小
   struct list * AllocList;	//使用链
   struct list * FreeList;	//空链
};
struct memory sMEM;
//****************************main()*************************//
void main()
{  
    char *ch[20];
	int Choice;
	int Volume;
	int Num;
	for (Num = 0; Num<20; Num++) 
		ch[Num] = NULL;

	MEMInit();
	while(1)
	{
		printf("Please select Fuct: 1.分配空间，2.释放空间\n");
		scanf("%d",&Choice);
		if(Choice == 1)
		{
			printf("输入要分区的区序号和大小: 序号 大小\n");
			scanf("%d %d",&Num,&Volume);
			if(ch[Num] != NULL)
			{
				printf("该块已经被占用，选择其他块\n");
				continue;

			}
			if(Volume >0 && Volume <=1000)
			{
				if(Num<20 )
				{
					 ch[Num] = (char *)MyAlloc(Volume);	
					 printf("第 %d个分块获得%d字节内存\n地址为%8x\n",Num,Volume,ch[Num]);
				}
				else
				{
					printf("块数应小于20\n");
					break;
				}
			}
			else
			{
				printf("空间太大\n");
			}


		}
		else if (Choice == 2)
		{
			printf("请输入要释放的块的序号\n");
			scanf("%d",&Num);
			if(Num>=0 && Num<=20)
			{
				MyFree(ch[Num]);
				ch[Num]=NULL;
			}			
		}	
	}
}

void MEMInit(void)
{
    sMEM.memorybase = MEMSpace;
    sMEM.memorysize = TOTALMEMORY;
    sMEM.AllocList = NULL;
    sMEM.FreeList = (MCB *)MEMSpace;
    sMEM.FreeList->size = TOTALMEMORY - sizeof(MCB);
    sMEM.FreeList->next = NULL;
    sMEM.FreeList->pre = NULL; 
    printf("Mem Inited success, test begin......\n管理1000字节空间(%8x---%8x)\n",MEMSpace,&MEMSpace[TOTALMEMORY]);
}


void * MyAlloc(int size)
{
 struct list *CurList; 
 struct list *AllocMCB;
 struct list *NextList;//NextList ==>TmpList
 AllocMCB = sMEM.FreeList;//初始化AllocMCB
 NextList = sMEM.FreeList;//初始化NextList
 if (size <= 0)
 {
 printf("您分配的空间的大小是无意义的！");
	 return(NULL);
 }

 for(CurList = sMEM.FreeList; CurList!=NULL; CurList = CurList->next)
 {
          if (size<=(CurList->size)) //最先适应，找到就给它
          {   
			  if(size<=(CurList->size-sizeof(MCB)))//一分为二
              { 
                 AllocMCB = CurList; //printf("-----%8x\n\n", CurList);
			     CurList =(struct list*) ((int)CurList+(int)size+sizeof(MCB));

				 CurList->size = AllocMCB->size-size-sizeof(struct list);
				 CurList->next = AllocMCB->next;
                 CurList->pre = AllocMCB->pre;

				 if(AllocMCB->pre!=NULL)
					 (AllocMCB->pre)->next = CurList;
				 else sMEM.FreeList = CurList;// printf("-----%8x\n\n", sMEM.FreeList);
				 AllocMCB->size = size;
				 printf("分到%d字节的一块内存，余下的可划分为一块！\n",size);
              }
			  else
			  {     
					if(CurList->size==size) printf("刚好分到%d块内存！\n",size);
					else 
						printf("分到%d字节内存,余下的不能划分为一块！\n",size);
					AllocMCB = CurList;
					NextList = CurList->pre;
					CurList = CurList->next;
					if(CurList!=NULL) 
						CurList->pre = NextList;
					if(NextList!=NULL) 
						NextList->next = CurList;
					else 
						sMEM.FreeList = CurList;
			  }    // 加入 sMEM.AllocList,直接放到头就可以
			  NextList = sMEM.AllocList;
              sMEM.AllocList = AllocMCB;
			  sMEM.AllocList->pre = NULL;
			  sMEM.AllocList->next = NextList;
			  if(NextList!=NULL) 
				  NextList->pre = sMEM.AllocList;
			   return (char*) ((int)AllocMCB + sizeof(MCB));//实际数据空间

          }
	 }
	 printf("内存不够，没有分到%d块内存！\n",size);
	 return NULL;
}
void MyFree(void *p)
{   int mark1 = 0;
    int mark2 = 0,size;
	struct list *NextList; 
	struct list *CurCtlList;
    struct list *PreList;
    CurCtlList = sMEM.FreeList;//初始化CurCtlList
    PreList = sMEM.FreeList;//初始化PreList 
	if(p==NULL) 
		printf("此变量内存已经释放了，不要再释放！\n");
	else
	{
		for(NextList = sMEM.AllocList;NextList!=NULL;NextList = NextList->next)
		{
			  if(p == ((int)NextList+sizeof(MCB)))//在 sMEM.AllocList找到了
			  {		  
					CurCtlList = NextList;
					size = NextList->size;
					if(NextList->pre==NULL && NextList->next==NULL)
					{
						mark1 = 1;
						sMEM.AllocList=NULL;
						break;
					}
					else if(NextList->pre==NULL && NextList->next!=NULL)
					{
						sMEM.AllocList = (sMEM.AllocList)->next;
						(sMEM.AllocList)->pre =NULL;
						mark1 = 1;
						break;
					}
					else if(NextList->pre!=NULL && NextList->next==NULL)
					{
						(NextList->pre)->next=NULL;
						mark1 = 1;
						break;
					}
					else//中间的块
					{
						  PreList = NextList->pre;
						  NextList = NextList->next; 
						  if(NextList!=NULL) 
							  NextList->pre = PreList;
						  if(PreList!=NULL)
							  PreList->next = NextList;
						  mark1 = 1;
						  break;
					} 
			  }
		}
		if(mark1!=1) 
			printf("错误：要释放的内存块不是本函数分配的！\n");
		else
		{
		if(sMEM.FreeList==NULL) 
			sMEM.FreeList = CurCtlList;
		else
		{
			for(NextList = sMEM.FreeList; NextList!=NULL; NextList = NextList->next)
			{
			   if(CurCtlList<NextList)//插在NextList的前面
			   {
				 PreList = NextList->pre;
				 if(PreList!=NULL)
					 PreList->next = CurCtlList;
				 else 
					 sMEM.FreeList = CurCtlList;
				 CurCtlList->pre = PreList;
				 CurCtlList->next = NextList;
				 NextList->pre = CurCtlList;
				 break;
			   }
			}
		}// 再检查相临的是否需要合并,先检查和前面的是否能合并
		if(PreList!=NULL)
		{
			if(((int)PreList + PreList->size + sizeof(MCB))==(int)CurCtlList)
			{		  //合并
				PreList->size = PreList->size + CurCtlList->size + sizeof(MCB);
				PreList->next = NextList;
				NextList->pre = PreList;
				CurCtlList = PreList;
				mark1 = 1;
			}
		} 	//再检查跟后面的是否能合并
		if(CurCtlList->next!=NULL)
		{
			if(((int)CurCtlList + CurCtlList->size + sizeof(MCB)) == (int)NextList)
			{            //合并
				CurCtlList->size = CurCtlList->size + NextList->size + sizeof(MCB) ;
				CurCtlList->next = NextList->next;
				if(NextList->next!=NULL)(NextList->next)->pre = CurCtlList;
				mark2 = 1;
			}
		}
		if(mark1==0 && mark2==0) 
			printf("释放%d块内存成功，没有合并\n",size);
		else if(mark1==0 && mark2==1) 
			printf("释放%d块内存成功，释放块与后面块合并\n",size);

		else if(mark1==1 && mark2==0) 
			printf("释放%d块内存成功，释放块与前面块合并\n",size);
		else 
			printf("释放%d块内存成功，释放块与前，后块合并\n",size);
		}
	}
}