myems.cpp

本项目是一款内存动态分区分配模拟程序。用户通过本程序可以了解动态分区分配方式中使用的数据结构和分配算法

// MyEMS.cpp: implementation of the MyEMS class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "EMSDSD.h"
#include "MyEMS.h"

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

MyEMS::MyEMS()
{

}

MyEMS::~MyEMS()
{
}

void MyEMS::Init(long totleEMS)
{
	num = 0;
	EMST = new struct EMSTable();
	EMST->start = 0;
	EMST->end = EMST->size = totleEMS;
	EMST->isFree = true;
	EMST->next = NULL;
	EMST->before = NULL;
	worklist = wlend = new struct WorkList();
	wlend->num = 0;
	wlend->position = NULL;
	wlend->size = 0;
	wlend->next = NULL;
	wlend->before = worklist;
}

bool MyEMS::Distribute(int arithmetic, long spaceneed)
{
	if(arithmetic == 1)
	{
		struct EMSTable * temp1 = EMST, * temp2;
		for(; temp1 != NULL; temp1 = temp1->next)
		{
			if(temp1->isFree && temp1->size >= spaceneed)
			{
				if(temp1->size != spaceneed)
				{
					temp2 = new struct EMSTable();
					temp2->start = temp1->start + spaceneed;
					temp2->end = temp1->end;
					temp2->next = temp1->next;
					temp2->before = temp1;
					temp2->size = temp1->size - spaceneed;
					temp1->next = temp2;
				}
				temp1->end = temp1->start + spaceneed - 1;
				temp1->isFree = false;
				temp1->size = spaceneed;
				num++;
				wlend->num = num;
				wlend->position = temp1;
				wlend->size = temp1->size;
				wlend->next = new struct WorkList();
				wlend->next->before=wlend;
				wlend = wlend->next;
				wlend->num = 0;
				wlend->position = NULL;
				wlend->size = 0;
				wlend->next = NULL;
				return true;
			}
		}
	}
	if(arithmetic == 2)
	{
		struct EMSTable * temp1, * temp2 = EMST;
		int n = 50000;
		for(; temp2 != NULL; temp2 = temp2->next)
		{
			if(temp2->isFree && temp2->size >= spaceneed)
			{
				if(temp2->size < n)
				{
					n = temp2->size;
					temp1 = temp2;
				}
			}
		}
		if(n < 50000)
		{
			if(temp1->size != spaceneed)
			{
				temp2 = new struct EMSTable();
				temp2->start = temp1->start + spaceneed;
				temp2->end = temp1->end;
				temp2->next = temp1->next;
				temp2->before = temp1;
				temp2->size = temp1->size - spaceneed;
				temp1->next = temp2;
			}
			temp1->end = temp1->start + spaceneed - 1;
			temp1->isFree = false;
			temp1->size = spaceneed;
			num++;
			wlend->num = num;
			wlend->position = temp1;
			wlend->size = temp1->size;
			wlend->next = new struct WorkList();
			wlend->next->before=wlend;
			wlend = wlend->next;
			wlend->num = 0;
			wlend->position = NULL;
			wlend->size = 0;
			wlend->next = NULL;
			return true;
		}
	}
	return false;
}