实验四 主存空间的分配与回收

#include <iostream>
#include <list>
#include <algorithm>
#include <vector>
#include <cstdlib>
#include <time.h>
using namespace std;
struct block{
    int begin,end;
};

struct free_place{
    int begin,length;
};

bool cmp(const block &b1,const block &b2){
    if(b1.begin<b2.begin)
        return true;
    return false;
}

bool cmp1(const free_place &f1,const free_place &f2){
    if(f1.begin<f2.begin)
        return true;
    return false;
}

vector<block> memory_tab;
list<free_place> free_list;
void init(){
    srand(time(0));
    cout<<"请输入初始状态"<<endl;
    cout<<"请输入内存占用情况"<<endl;
    block now;
    while(cin>>now.begin>>now.end,now.begin!=now.end){
        memory_tab.push_back(now);
    }
    vector<free_place> v;
    free_place now1;
    cout<<"请输入空闲区表"<<endl;
    while(cin>>now1.begin>>now1.length,now1.begin!=now1.length){
        v.push_back(now1);
    }
    sort(memory_tab.begin(),memory_tab.end(),cmp);
    sort(v.begin(),v.end(),cmp1);
    for(int i=0;i<v.size();i++)
        free_list.push_back(v[i]);
}
int  request(){
    cout<<"请输入要申请的内存空间"<<endl;
    int len;
    cin>>len;
    return len;
}

void print_page(){
    cout<<"内存空间占用"<<endl;
    for(int i=0;i<memory_tab.size();i++){
        cout<<i<<":"<<memory_tab[i].begin<<"--"<<memory_tab[i].end<<endl;
    }
    cout<<endl;
}
void print_free_table(){
    cout<<"空闲分区表"<<endl
        <<"起始长度      长度"<<endl;
    list<free_place>::iterator p=free_list.begin();
    while(p!=free_list.end()){
        cout<<(*p).begin<<"        "<<(*p).length<<endl;
        p++;
    }
    cout<<endl;
}
void print(){
    cout<<endl<<endl<<endl<<"分配结果"<<endl;
    print_page();
    print_free_table();
    cout<<endl;
}

bool mem_get_back(block &c){
    vector<block>::iterator sel;
    int t;
    if(memory_tab.size()!=0){
        t=rand()%memory_tab.size();
        while(t==0)
            t=rand()%memory_tab.size();
        sel=memory_tab.begin()+t;
        c=*sel;
        memory_tab.erase(sel);
        return true;
    }
    return false;
}
void mem_free(block c){
    free_place t;
    t.begin=c.begin;
    t.length=c.end-c.begin;
    if(free_list.size()==0){
        free_list.push_back(t);
        return ;
    }
    if(c.begin<(*free_list.begin()).begin){
        free_list.push_front(t);
    }
    else{
        list<free_place>::iterator p=free_list.begin();
        for(p++;p!=free_list.end();p++){
            if(c.begin<(*p).begin){
                free_list.insert(p,t);
            }
        }
        list<free_place>::iterator q;
        for(p=free_list.begin();p!=free_list.end();p++){
            q=p;
            ++q;
            if(q!=free_list.end()&&((*p).begin+(*p).length)==(*q).begin){
                (*p).length+=(*q).length;
                free_list.erase(q);
            }
        }
    }
}
bool memory_pack(int length){
    list<free_place>::iterator p=free_list.begin();
    while(p!=free_list.end()){
        if((*p).length>=length){
            block c;
            c.begin=(*p).begin;
            c.end=c.begin+length;
            memory_tab.push_back(c);
            if((*p).length>length)
                (*p).begin=c.end+1;
            else free_list.erase(p);
            sort(memory_tab.begin(),memory_tab.end(),cmp);
            return true;
        }
        p++;
    }
    return false;
}
int main(){
    init();
    int length;
    block c;
    while(1){
        length=request();
        if(length){
            if(mem_get_back(c))
                mem_free(c);
            if(memory_pack(length))
                print();
            else cout<<"内存不足"<<endl;
        }
    }
    return 0;
}