一个简单的内存管理程序

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
#define PROCESS_NAME_LEN 32   /*进程名长度*/
#define MIN_SLICE    10             /*最小碎片的大小*/
#define DEFAULT_MEM_SIZE 1024     /*内存大小*/
#define DEFAULT_MEM_START 0       /*起始位置*/
/* 内存分配算法 */
#define MA_FF 1
#define MA_BF 2
#define MA_WF 3
int mem_size=DEFAULT_MEM_SIZE; /*内存大小*/
int ma_algorithm = MA_FF;           /*当前分配算法*/
static int pid = 0;                                      /*初始pid*/
int flag = 0;                                    /*设置内存大小标志*/
/*描述每一个空闲块的数据结构*/
struct free_block_type{
    int size;
    int start_addr;
    struct free_block_type *next;
}; 

/*指向内存中空闲块链表的首指针*/
struct free_block_type *free_block;
/*每个进程分配到的内存块的描述*/
struct allocated_block{
    int pid;   
 int size;
    int start_addr;
    char process_name[PROCESS_NAME_LEN];
    struct allocated_block *next;
};
/*进程分配内存块链表的首指针*/
struct allocated_block *allocated_block_head = NULL;
/*初始化空闲块，默认为一块，可以指定大小及起始地址*/
struct free_block_type* init_free_block(int mem_size){
    struct free_block_type *fb;
 struct allocated_block *p=allocated_block_head;
 
    fb=(struct free_block_type *)malloc(sizeof(struct free_block_type));
    if(fb==NULL){
        printf("No mem\n");
        return NULL;
 }
    fb->size = mem_size;
 while(p)
  p=p->next;
 if(p==allocated_block_head)
  fb->start_addr = mem_size;
 else
  fb->start_addr=mem_size-(p->size+p->start_addr);
 // fb->start_addr = DEFAULT_MEM_START;
    fb->next = NULL;
    return fb;
}
display_menu();

int set_mem_size();

set_algorithm();

rearrange(int algorithm);

rearrange_FF();

rearrange_BF();

rearrange_WF();

new_process();

kill_process();

do_exit();

struct allocated_block *find_process(int pid);

int allocate_mem(struct allocated_block *ab);

int free_mem(struct allocated_block *ab);

int dispose(struct allocated_block *free_ab);

display_mem_usage();

display_menu(){
    printf("\n");
    printf("1 - Set memory size (default=%d)\n", DEFAULT_MEM_SIZE);
    printf("2 - Select memory allocation algorithm\n");
    printf("3 - New process \n");
    printf("4 - Terminate a process \n");
    printf("5 - Display memory usage \n");
    printf("0 - Exit\n");
}
/*设置内存的大小*/
int set_mem_size(){
    int size;
    if(flag!=0){  //防止重复设置
        printf("Cannot set memory size again\n");
        return 0;
 }
    printf("Total memory size =");
    scanf("%d", &size);
    if(size>0) {
        mem_size = size;
        free_block->size = mem_size;
  free_block->start_addr=mem_size;
  flag=1; 
  return 1;
 }
 else
 {
  printf("the size is erro!\n");
  return 0;
 }
}
/* 设置当前的分配算法 */
set_algorithm(){
    int algorithm;
    printf("\t1 - First Fit\n");
    printf("\t2 - Best Fit \n");
    printf("\t3 - Worst Fit \n");
    scanf("%d", &algorithm);
    if(algorithm>=1 && algorithm <=3) 
  ma_algorithm=algorithm;
 //按指定算法重新排列空闲区链表
    rearrange(ma_algorithm);
}
/*按指定的算法整理内存空闲块链表*/
rearrange(int algorithm){
    switch(algorithm){
 case MA_FF:  rearrange_FF(); break;
 case MA_BF:  rearrange_BF(); break;
 case MA_WF: rearrange_WF(); break;
 }
}
/*按FF算法重新整理内存空闲块链表*/
rearrange_FF(){
 int size;
    int start_addr;
 struct free_block_type *p, *q; //*free_block
 p=q=free_block;
 while(p)
 {
  while(q)
  {
   if(p->size>q->size)
   {
    size=p->size;
    start_addr=p->start_addr;
    p->size=q->size;
    p->start_addr=q->start_addr;
    q->size=size;
    q->start_addr=start_addr;
   }
   q=q->next;
  }
  p=p->next;
 }
 //请自行补充
}
/*按BF算法重新整理内存空闲块链表*/
rearrange_BF(){
 int size;
    int start_addr;
 struct free_block_type *p, *q; //*free_block
 p=q=free_block;
 while(p)
 {
  while(q)
  {
   if(p->size>q->size)
   {
    size=p->size;
    start_addr=p->start_addr;
    p->size=q->size;
    p->start_addr=q->start_addr;
    q->size=size;
    q->start_addr=start_addr;
   }
   q=q->next;
  }
  p=p->next;
 }
 //请自行补充
 
}
/*按WF算法重新整理内存空闲块链表*/
rearrange_WF(){
 int size;
    int start_addr;
 struct free_block_type *p, *q; //*free_block
 p=q=free_block;
 while(p)
 {
  while(q)
  {
   if(p->size<q->size)
   {
    size=p->size;
    start_addr=p->start_addr;
    p->size=q->size;
    p->start_addr=q->start_addr;
    q->size=size;
    q->start_addr=start_addr;
   }
   q=q->next;
  }
  p=p->next;
 }
 //请自行补充
 
}
/*创建新的进程，主要是获取内存的申请数量*/
new_process(){
    struct allocated_block *ab;
    int size;    int ret;
 int j=0;
    ab=(struct allocated_block *)malloc(sizeof(struct allocated_block));
    if(!ab) exit(-5);
    ab->next = NULL;
    pid++;
    sprintf(ab->process_name, "PROCESS-%02d", pid);
    ab->pid = pid;   
    printf("Memory for %s:", ab->process_name);
    scanf("%d", &size);
    if(size>0) ab->size=size;
    ret = allocate_mem(ab);  /* 从空闲区分配内存，ret==1表示分配ok*/
 
 /*如果此时allocated_block_head尚未赋值，则赋值*/
    if((ret==1) &&(allocated_block_head == NULL)){
        allocated_block_head=ab;
        return 1;        }
    /*分配成功，将该已分配块的描述插入已分配链表*/
    else if (ret==1) {
        ab->next=allocated_block_head;
        allocated_block_head=ab;
        return 2;        }
    else if(ret==-1){ /*分配不成功*/
        printf("Allocation fail\n");
        free(ab);
        return -1;      
 }
 //ab->start_addr=++j;
    return 3;
}
/*分配内存模块*/
int allocate_mem(struct allocated_block *ab){
    struct free_block_type *fbt, *pre;
    int request_size=ab->size;
 struct allocated_block *p,*q;
 p=q=allocated_block_head;
 fbt = pre = free_block;

 while(q)
 {
  q=q->next;
 }
 
 while(fbt)
 {  
  pre=fbt->next;
  if(fbt->size-request_size<10&&fbt->size-request_size>0)
  {
   if(fbt==free_block)
   {
    ab->size=request_size;
    if(q==allocated_block_head)
     ab->start_addr=0;
    else
     ab->start_addr=p->start_addr+p->size;
    free_block=free_block->next;
    free(fbt);
    return 1;
   }
   else
   {
    ab->size=request_size;
    if(q==allocated_block_head)
     ab->start_addr=0;
    else
     ab->start_addr=p->start_addr+p->size;
    pre->next=fbt->next;
    free(fbt);
    return 1;
    break;
   }
  }
  else if(fbt->size-request_size>10)
  {
   ab->size=request_size;
   if(q==allocated_block_head)
    ab->start_addr=0;
   else
    ab->start_addr=p->start_addr+p->size;
   fbt->size-=request_size;
   switch(ma_algorithm)
   {
   case 1:
    {
     rearrange_FF();
     break;
    }
   case 2:
    {
     rearrange_BF();
     break;
    }
   case 3:
    {
     rearrange_WF();
     break;
    }
   }
   return 1;
  }
  fbt=fbt->next;
 }
 if(!fbt)
 {
  // printf("没有合适的空间!\n");
  return -1;
 }
  return 0;
}
/*删除进程，归还分配的存储空间，并删除描述该进程内存分配的节点*/
struct allocated_block *find_process(int pid)
{
 struct  allocated_block *p=allocated_block_head;
 // p=allocated_block_head;struct allocated_block *allocated_block_head = NULL
 while(p)          
  //判断条件必须是p是否为空不能是p->next,因为如果只有一个节点时p->next=NULL，此时不能返回要删除的节点
 {
  if(p->pid==pid)
  {
   return p;
  }
  p=p->next;
 }
 return NULL;
}
kill_process(){
    struct allocated_block *ab;
    int pid;
    printf("Kill Process, pid=");
    scanf("%d", &pid);
    ab=find_process(pid);
    if(ab!=NULL){
        free_mem(ab); /*释放ab所表示的分配区*/
        dispose(ab);  /*释放ab数据结构节点*/
 }
}
/*将ab所表示的已分配区归还，并进行可能的合并*/
void sort()
{
 int size;
    int start_addr;
 struct free_block_type *p, *q; //*free_block
 p=q=free_block;
 while(p)
 {
  while(q)
  {
   if(p->start_addr >q->start_addr)
   {
    size=p->size;
    start_addr=p->start_addr;
    p->size=q->size;
    p->start_addr=q->start_addr;
    q->size=size;
    q->start_addr=start_addr;
   }
   q=q->next;
  }
  p=p->next;
 }
 
}
int free_mem(struct allocated_block *ab){
    int algorithm = ma_algorithm;
    struct free_block_type *fbt, *pre;//*work;
 fbt=(struct free_block_type*) malloc(sizeof(struct free_block_type));
    if(!fbt) return -1;
 else
 {
  pre=free_block;
  fbt->size=ab->size;
  fbt->start_addr=ab->start_addr;
  while(pre->next)
   pre=pre->next;
  fbt->next=NULL;
  pre->next=fbt;
  switch(algorithm)
  {
  case 1:
   {
    sort();
    rearrange_FF();
    break;
   }
  case 2:
   {
    sort();
    rearrange_BF();
    break;
   }
  case 3:
   {
    sort();
    rearrange_WF();
    break;
   }
  }
 }
    return 1;
}
/*释放ab数据结构节点*/
int dispose(struct allocated_block *free_ab){
    struct allocated_block *pre, *ab;
 if(free_ab == allocated_block_head) { /*如果要释放第一个节点*/
  allocated_block_head = allocated_block_head->next;
        free(free_ab);
        return 1;
 }
 else
 {
  pre = allocated_block_head; 
  ab = allocated_block_head->next;
  while(ab!=free_ab){ pre = ab;  ab = ab->next; }
  pre->next = ab->next;
  free(ab);
  return 2;
 }
}

/* 显示当前内存的使用情况，包括空闲区的情况和已经分配的情况 */
display_mem_usage(){
    struct free_block_type *fbt=free_block;
    struct allocated_block *ab=allocated_block_head;
    if(fbt==NULL) return(-1);
    printf("----------------------------------------------------------\n");
 
    /* 显示空闲区 */
    printf("Free Memory:\n");
    printf("%20s %20s\n", "      start_addr", "       size");
    while(fbt!=NULL){
        printf("%20d %20d\n", fbt->start_addr, fbt->size);
        fbt=fbt->next;
 }   
 /* 显示已分配区 */
    printf("\nUsed Memory:\n");
    printf("%10s %20s %10s %10s\n", "PID", "ProcessName", "start_addr", " size");
    while(ab!=NULL){
        printf("%10d %20s %10d %10d\n", ab->pid, ab->process_name, ab->start_addr, ab->size);
        ab=ab->next;
 }
    printf("----------------------------------------------------------\n");
    return 0;
}
do_exit()
{
 printf("操作完毕，退出系统!\n");
}
main(){
    char choice;      pid=0;
    free_block = init_free_block(mem_size); //初始化空闲区
    while(1) {
  display_menu(); //显示菜单
  fflush(stdin);
  choice=getchar(); //获取用户输入
  switch(choice)
  {
  case '1': {
   set_mem_size();  
   break;  
      }//设置内存大小
        case '2':
   {
    set_algorithm();flag=1;
    break;
   } //设置算法
        case '3':
   {
    new_process();
    flag=1;
    break;
   } //创建新进程
        case '4':
   {
    kill_process();
    flag=1; 
    break;
   }  //删除进程
        case '5':
   {
    display_mem_usage();  
    flag=1;
    break; 
   }    //显示内存使用
        case '0':
   {
    do_exit();
    exit(0);
   }//释放链表并退出
        default: break;    
  }   
 }
}