主存储器空间的分配和回收

主存储器空间的分配和回收直接进行源代码的编写:/*作业名用1，2，3,···表示*/#include<iostream>#include<list>using namespace std;#define TOTLE_LEFT 108 //除系统占用内存外的剩余内存#define first_free 14 //第一块空闲区的起始地址#define first_size 12 //第一块空闲区的大小#define sec_free 32 //第二块空闲区的起始地址#define sec_size 96 //第二块空闲区的大小#define first_job_size 3#define sec_job_size 23#define third_job_size 3//空闲分区表结点struct Free{int start;int length;Free(int s,int l);};Free::Free(int s,int l){start = s;length = 1;}//已分配分区表结点struct Task{int name;int start;int length;Task(int n,int s,int l); };Task::Task(int n,int s,int l) {name = n;start = s;length = l;}//声明空闲分区表list<Free*>free_list;list<Task*>Task_list;//分配可用的起始地址int get_free(int size){int start = -1;//查找适当的空闲分区list<Free*>::iterator it = free_list.begin();bool find = false;while(it!=free_list.end()){if((*it)->length>=size){find = true;start = (*it)->start;//大于，就分割，把低地址分配出去if((*it)->length>size){(*it)->start += size;(*it)->length -= size;}//等于，就从空闲区中删除elsefree_list.erase(it);break; //找到就跳出循环}it ++;}return start;}void do_request(int name,int size){if(name==0){cout<<”申请不合法!非法的作业名!”<<endl;return;}if(size>TOTLE_LEFT){cout<<”申请不合法!超出了最大可用内存!”<<endl;return;}//查找是否已存在同名作业bool find = false;list<Task*>::iterator it = task_list.begin();while(it!=task_list.end()){if((*it)->name ==name){find = true;break;}it++;}if(find){cout<<”此作业已存在!”<<endl;return;}//从空闲分区选择合适的空间int start = get_free(size);//未找到合适空间if(start ==-1){cout<<”系统内存不足!作业等待!”<<endl;return;}Task * ta = new Task(name,start,size);task_list.push_back(ta);cout<<”作业申请内存成功!”<<endl;}//插入到空闲分区表，起始地址从小到大void free_task(int start,int length){//查找要插入的位置list<Free*>::iterator init_it,last_it;last_it = init_it;list<Free*>::iterator it = free_list.begin();while(it! = free_list.end()){if((*it)->start>start) break;last_it = it;it ++;}bool link_prev = false;bool link_next = false;//有前一个小时if(last_it! = init_it){if((*last_it)->start+(*last_it)->length == start) link_prev = true;}//有后一个小时if(it! = free_list.end()){if(start + length ==(*it)->start)link_next = true;}//与前后都相连if(link_prev&&link_next){(*last_it)->length += length + (*it) ->length;free_list.erase(it);}//只与前相连else if(link_prev){(*last_it)->length += length;//只与后相连else if(link_next){(*it)->start = start;(*it)->length += length;}//前后都不相连else{Free *fr = new Free(start,length);Free_list.insert(it,fr);}}void do_revoke(int name){if(name ==0){cout<<”错误!不能回收系统内存!”<<endl;return;}//查找要回收的作业是否存在bool find = false;list<Task*>::iterator it = task_list.begin();while(it! = task_list,end()){if((*it)->name == name){find = true;break;}it ++;}if(!find){cout<<”错误!要回收的作业不存在!”<<endl;return;}free_task((*it)->start,(*it)->length);task_list.erase(it);cout<<”回收作业占用内存成功!”<<endl;}void print_task(){cout<<”作业名称起始地址大小”<<endl;for(list<Task*>::iterator it = task_list.begin();it!=task_list.end();it++){cout<<(*it)->name<<””<<(*it)->start<<””<<(*it)->length<<endl;}}void print_free(){cout<<”以下是空闲分区表的状态”<<endl;<<”起始地址大小”<<endl;for(list<Free*>::iterator it = free_list.begin();it! = free_list.end();it ++){cout<<(*it)->start<<””<<(*it)->length<<endl;}}int main(0{//把系统占用后剩余的内存空间计入空闲分区表Free *fr1 = new Free(first_free,first_size);free_list.push_back(fr1);Free *fr = new Free(sec_free,sec_size);free_list.push_back(fr);Task *ta = new Task(1,26,first_job_size);task_list.push_back(ta);Task *ta1 = new Task(3,29,third_job_size);task_list.push_back(ta1);Task *ta2 = new Task(2,128,sec_job_size);task_list.push_back(ta2);print_free():bool quit = false;while(!quit){cout<<”选择要进行的操作:1.申请内存2.回收内存3.查看作业”;int op;cin>>op;if(op==1){int name;int size;cout<<”请输入作业名及占用空间大小:”;cin>>name;cin>>size;do_request(name,size);print_free();}else if(op==2){ int name;cout<<”请输入要回收的作业名:”;cin>>name;do_revoke(name);print_free();}else if(op==3){print_task();}else{cout<<”非法操作!”<<endl;}cout<<”***********************”<<endl; char con;cout<<继续(y/n):”;cin>>con;if(con ==’n’||con == ‘N’){quit = true;}}return 0 ;}。