mymemory.cpp

模拟64M的内存的动态管理,包括分配.回收.操作系统实验课程设计题目

#include "StdAfx.h"
#include "Block.h"
#include "MyMemory.h"
#include <fstream>

const int MEM_SIZE = 64*1024*1024; //64 M

CMyMemory::CMyMemory(void)
{
	pMem = NULL;

	/*pMem = new char[MEM_SIZE];
	if(!pMem)
	{
	cerr<<"alloc memory failed.";
	}*/

	EmptyList.Insert(Block(0,MEM_SIZE),EmptyList.ListSize());

} 

CMyMemory::~CMyMemory(void)
{
	if(pMem)
		delete pMem;
}

//[功能]察看内存的详细使用情况
//[参数]NULL
void CMyMemory::ShowDetail(void)
{
	cout<<"Block List:"<<endl;
    cout<<"-----------------------------------------------------------------------"<<endl;
	for(int i=0;i<EmptyList.ListSize();i++)
	{
		Block & data = EmptyList.GetData(i);
		cout<<"start["<<data.start<<"]\t\tsize["<<data.size<<"]\t\tstate["<<data.flag<<"]\t"<<"No["<<i<<"]"<<endl;
	}
	cout<<"-----------------------------------------------------------------------"<<endl;
}

//[功能]采用首次适应算法，将分配的内存块插入到空闲分区的前面
//[参数]out[1]成功分配，out[0]分配失败
int CMyMemory::Allocation(int size)
{
	int i;
	for(i=0;i<EmptyList.ListSize();i++)
	{
		Block & block =  EmptyList.GetData(i);

		if(block.size >= size && block.flag == 0)
		{
			//insert a node to the EmptyList
			block.start += size;
			block.size -= size;

			if(i>=0)
			{
				Block  newBlock(EmptyList.GetData(i-1).size + EmptyList.GetData(i-1).start,size,1);
				EmptyList.Insert(newBlock,i);
			/*}
			else
			{
				Block  newBlock(EmptyList.GetData(-1).size,size,1);
				EmptyList.Insert(newBlock,i);*/
			}

			return 1;
		}
	}
	return 0;
}

//[功能]释放由pos标识的内存快
//[参数]in[pos]为内存块的标号
//      out[0]failed
//      out[1]sucess
int CMyMemory::Release(int pos)
{
	//参数有效性检查，失败返回0
	if(pos <0 || pos > EmptyList.ListSize())
	{
		return 0;
	}

	//释放内存区，只需要将内存区域标记为未用（flag = 0）即可
	if(pos>=0 && pos<EmptyList.ListSize())
	{
		Block & block = EmptyList.GetData(pos);
		block.flag = 0;
	}

	//若有必要可以在这里调用Merge()合并为用的空暇区块
    //Merge();
	return 1;
}

//[功能]合并连续未用的内存块为一块
//[参数]NULL
int CMyMemory::Merge(void)
{
	int start = 0,size = 0;
	int flag = 0,temp = 0;
	int i;

	for(i=0;i< EmptyList.ListSize();i++)
	{
		Block & block = EmptyList.GetData(i);

		if(! block.flag)
		{
			//记录连续未用段的开始段的起始地址
			if(!flag)
			{
				start = block.start;
				temp = i;
				flag = 1;
			}

			size += block.size;
			EmptyList.Delete(i);
			i--;
		}
		else
		{

			//向链表中插入一块空白的空间大小为连续未用的空间的总和
			if(flag)
			{
				flag = 0;
				Block  newBlock(start,size,0);
				EmptyList.Insert(newBlock,temp);
				i = temp;
			}
		}
	}

	//合并最后一块连续未用的空间
	if(flag)
	{
		if(size == 0)
		{
			return 0;
		}

		Block  newBlock(start,size,0);
		EmptyList.Insert(newBlock,temp);
	}

	return 1;
}