操作系统实验-可变分区存储管理

作业一实验一：可变分区存储管理（一）

实验题目编写一个C程序，用char*malloc(unsignedsize函数向系统申请一次内存空间（如size=1000，单位为字节），模拟可变分区内存管理，实现对该内存区的分配和释放管理。（二）

实验目的1．加深对可变分区的存储管理的理解；2．提高用C语言编制大型系统程序的能力，特别是掌握C语言编程的难点：指针和指针作为函数参数；3．掌握用指针实现链表和在链表上的基本操作。图2-9释放区与前后空闲区相邻的情况（三）程序代码#include#include#include#definenew(type(type*malloc(sizeof(typetypedefstruct_map{unsignedintsize;char*address;struct_map*next;struct_map*prev;}map;typedefmap*pmap;typedefstruct_mem{unsignedinttotalSize;char*space;pmaphead;pmapcMap;}mem;typedefmem*pmem;pmemcreateMem(unsignedintto_size//创建内存区域{pmemnewMem=new(mem;pmapnewHead=new(map;newMem->totalSize=to_size;newHead->size=to_size;newHead->address=newMem->space;newHead->next=newHead;newHead->prev=newHead;newMem->head=newHead;newMem->cMap=newHead;returnnewMem;}voidfreeMem(pmemm{pmapmap,cMap;pmaphead=m->head;free(map->address;for(map=head;map->next!=head;{cMap=map;map=cMap->next;free(cMap;}free(m;}char*lmalloc(pmemcMem,unsignedintsize//分配函数{if(size>1000{printf("内存容量超出范围!\n";//当需要分配的内存空间已经大于实际空间时出错}else{pmapp=cMem->cMap;char*rAddr;if(size==0returnNULL;while(p->size{if(p->next==cMem->cMapreturnNULL;p=p->next;}rAddr=p->address;p->size-=size;p->address+=size;if(p->size==0{p->prev->next=p->next;p->next->prev=p->prev;cMem->cMap=p->next;if(cMem->head==pcMem->head=p->next;if(p->next!=cMem->headfree(p;}else{cMem->cMap=p;}returnrAddr;}}voidlfree(pmemm,unsignedintsize,char*addr//释放函数{pmapnextMap,prevMap,newMap;if(addrspace||addr>=m->space+m->totalSize{fprintf(stderr,"地址越界\n";//释放空间时，大小输入出错return;}nextMap=m->head;while(nextMap->address{nextMap=nextMap->next;if(nextMap==m->headbreak;}prevMap=nextMap->prev;if(nextMap!=m->head&&prevMap->address+prevMap->size==addr//第一种情况{prevMap->size+=size;if(addr+size==nextMap->address//第二种情况{prevMap->size+=nextMap->size;prevMap->next=nextMap->next;prevMap->next->prev=prevMap;if(nextMap==m->cMap{m->cMap=prevMap;}free(nextMap;nextMap=NULL;}}else{if(addr+size==nextMap->address//第三种情况{nextMap->address-=size;nextMap->size+=size;}else//第四种情况{newMap=new(map;newMap->address=addr;newMap->size=size;prevMap->next=newMap;newMap->prev=prevMap;newMap->next=nextMap;nextMap->prev=newMap;if(nextMap==m->headm->head=newMap;}}}voidprintMem(pmemm//打印函数{pmapmap=m->head;printf("\空闲内存空间:\n\-----------------------\n\大小起始地址\n";do{if(map==m->cMapprintf("->";elseprintf("";printf("%10u%10u\n",map->size,map->address;map=map->next;}while(map!=m->head;printf("-----------------------\n";}voidmain(//主函数{printf("--------------------------------------------------------\n";printf("请选择操作：分配内存(mor释放内存(for打印内存表(p\n";printf("--------------------------------------------------------\n";typedefenum{cmdMalloc,cmdFree,cmdPrint,cmdHelp,cmdQuit,cmdInvalid}cmdType;pmemm=createMem(1000;charcmd[20];char*addr;unsignedintsize;cmdTypetype;while(1{scanf("%s",cmd;if(cmd[1]=='\0'{switch(cmd[0]{case'm':case'M':type=cmdMalloc;break;case'f':case'F':type=cmdFree;break;case'p':case'P':type=cmdPrint;break;}}else{if(!strcmp(cmd,"malloc"type=cmdMalloc;elseif(!strcmp(cmd,"free"type=cmdFree;elseif(!strcmp(cmd,"print"type=cmdPrint;}switch(type{casecmdMalloc:scan