「 操作系统 」

实现程序内存的动态分配

首次适应算法：

找到第一个满足程序的内存块，并将其分配给程序

最佳适应算法：

找到所有的满足程序的内存块，并将其中最小的内存块分配给程序

#include <iostream>#include <string.h>#include <stdio.h>using namespace std;struct node{        int st,size,num;    bool work;    node *next,*pre;    node(){        work = false;        st = 0;        next = NULL;        pre = NULL;    }}*add,*mem;int work_num,oper,Size;void show(){        printf("------------------------------------------------------------------------\n\n");        printf("\t\t当前的内存分配情况如下:\n\n");        node *now = mem;        printf("\t起始地址\t空间大小\t工作状态\t作业号\t\n\n");        while(true){        printf("\t%d\t\t%d kb\t\t%s\t\t",now->st,now->size,now->work?"Busy":"Free");        if(now->work) printf("%d\t",now->num);        printf("\n\n");        if(now->next==NULL){            break;        }        now = now->next;    }        printf("------------------------------------------------------------------------\n\n");        }bool find1(){    //找最小的    node *now = mem;    node *get = NULL;    while(true){        if(!now->work){            if(now->size>=Size){                //找出所有的可放置内存块中内存最小的                if(get==NULL){                    get = now;                }else{                    if(get->size > now->size){                        get = now;                    }                }            }        }        if(now->next==NULL) break;        now = now->next;    }    // 若找不到放置位置 返回不可放置    if(get==NULL) return false;        // 更新内存情况    get->work = true;    get->num = work_num;    if(get->size>Size){        add = new node();        add->size = get->size - Size;        get->size = Size;        add->st = get->st + get->size;        add->next = get->next;        get->next = add;        add->pre = get;    }        return true;}bool find2(){    //找最前面的    node *now = mem;    while(true){        if(!now->work){            if(now->size>=Size){                //找到第一个可放置的内存空间 更新内存状况 返回分配结果                now->work = true;                now->num = work_num;                                if(now->size>Size){                    add = new node();                    add->size = now->size - Size;                    now->size = Size;                    add->st = now->st + now->size;                    add->next = now->next;                    now->next = add;                    add->pre = now;                                    }                return true;            }        }        if(now->next==NULL) break;        now = now->next;    }    return false;}bool find(int ope){        // 分配内存操作        if(ope){        //最佳适应算法        return find1();    }else{        //首次适应算法        return find2();    }}bool reget(){        // 回收内存操作        node *now = mem;    while(true){                if(now->num==work_num&&now->work){            //找到对应工作号且在工作的内存区                        node *pre = now,*next = now->next;            int pre_unused_memSize = 0,next_unused_memSize = 0;                        //将空闲的内存区合并            while(pre->pre!=NULL&&!pre->pre->work){                                pre_unused_memSize += pre->size;                pre = pre->pre;            }            while(next!=NULL&&!next->work){                next_unused_memSize += next->size;                next = next->next;            }            now = pre;            now->next = next;            now->size += pre_unused_memSize + next_unused_memSize;            now->work = false;            if(next!=NULL) next->pre = now;            return true;        }                if(now->next==NULL){            break;        }        now = now->next;    }        return false;}void work(int ope){        // 执行操作        while(true){        printf("\n\t1: 分配内存  2: 回收内存  0: 退出\n\n请输入操作:");        scanf("%d",&oper);        printf("\n");        if(oper==1){                        // 分配内存                        printf("请输入作业号: ");            scanf("%d",&work_num);            printf("\n");            printf("请输入需要分配的内存大小(kb): ");            scanf("%d",&Size);            printf("\n");            if(find(ope)){                printf("内存分配成功！\n\n");            }else{                printf("内存分配失败！\n\n");            }            show();        }else if(oper==2){                        // 回收内存                        printf("请输入作业号: ");            scanf("%d",&work_num);            printf("\n");            if(reget()){                printf("\t\t内存回收成功！\n\n");            }else{                printf("\t\t内存回收失败！\n\n");            }            show();        }else{            // 操作结束                        break;        }    }}void delete_mem(node *now){    // 清空内存    if(now->next!=NULL) delete_mem(now->next);    delete now;}int main(){        int ope;    while(true){        printf("\t\t请选择需要模拟的分配算法\n\n\t\t0\t首次适应算法\n\n\t\t1\t最佳适应算法\n\n");        printf("\t\t你的选择是 : ");        scanf("%d",&ope);        printf("\n");        mem = new node(); mem->size = 1000;        if(ope){            //最佳适应算法  找到最小可存储空间            work(ope);            printf("\t\t最佳适应算法模拟结束\n\n\n");            printf("-----------------------------------------------------------------------\n\n");        }else{            //首次适应算法  找到第一个可存储空间            work(ope);            printf("\t\t首次适应算法模拟结束\n\n\n");            printf("-----------------------------------------------------------------------\n\n");        }        delete_mem(mem);    }    return 0;}