LinuxC实现内存映射

LinuxC实现内存映射

代码如下：

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<fcntl.h>
#include<sys/mman.h>
#include<unistd.h>
#include<sys/types.h>
int count=0;
typedef struct
{
    char xuehao[40];
    char name[30];
}Student;

Student *insert(Student *student)
{
    int i;
    printf("请输入姓名，学号\n");
    scanf("%s%s",(student+count)->name,(student+count)->xuehao);
    count++;
    return student;
}

Student *delete(Student *student)
{
    int i,flag,j;
    char a[100];
    printf("请输入一个学号\n");
    scanf("%s",a);
    for(i=0;i<count;i++)
    {
        if(strcmp((student+i)->xuehao,a)==0)
        {
            for(j=i;j<count;j++)
            {
            strcpy((student+j)->name,(student+j+1)->name);
            strcpy((student+j)->xuehao,(student+j+1)->xuehao);
            }
            flag=0;
            count--;
            printf("delete success!!!\n");
            break;
        }
    }
    if(flag!=0)
        printf("delete failed\n");
    return student;
}

void chazhao(Student *student)
{
    int i;
    char b[100];
    printf("请输入一个学号\n");
    scanf("%s",b);
    for(i=0;i<count;i++)
    {
        if(strcmp((student+i)->xuehao,b)==0)
        {
            printf("已找到\n");
            printf("%s %s\n",(student+i)->name,(student+i)->xuehao);
            break;
        }
    }
    if(i==count)
        printf("没有找到信息\n");
}

Student *xiugai(Student *student)
{
    int i;
    char c[100];
    printf("请输入一个学号\n");
    scanf("%s",c);
    for(i=0;i<count;i++)
    {
        if(strcmp((student+i)->xuehao,c)==0)
        {
            printf("请输入要修改的信息\n");
            scanf("%s%s",(student+i)->name,(student+i)->xuehao);
            printf("修改成功\n");
            break;
        }
    }
    if(i==count)
        printf("修改未成功\n");
    return student;
}

int main(int argc,char** argv)
{
    int n,fd;
    Student *student;
    Student *wq=(Student *)malloc(sizeof(Student));
    fd=open(argv[1],O_RDWR|O_CREAT,0666);
    if(fd<0)
    {
        printf("open %s failed\n",argv[1]);
        exit(1);
    }
    write(fd,wq,sizeof(Student));
    lseek(fd,1000*sizeof(Student),SEEK_CUR);
    write(fd,wq,sizeof(Student));
    close(fd);
    fd=open(argv[1],O_RDWR);
    if(fd<0)
    {
        printf("open %s failed\n",argv[1]);
        exit(1);
    }
    if((student=(Student *)mmap(NULL,sizeof(Student)*1000,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0))==(Student*)-1);
    {
        perror("mmap\n");
    }
    close(fd);
    fd=open("test",O_RDWR|O_CREAT,0666);
    n=read(fd,&count,4);
    if(n<0)
        count=0;
    close(fd);
    while(1)
    {
    int number;
    printf("\t\t\t请选择：\n");
    printf("\t\t\t1.添加信息\n");
    printf("\t\t\t2.删除信息\n");
    printf("\t\t\t3.查找信息\n");
    printf("\t\t\t4.修改信息\n");
    printf("\t\t\t5.退出\n");
    scanf("%d",&number);
    switch(number)
    {
        case 1:
        student=insert(student);
        break;
        case 2:
        student=delete(student);
        break;
        case 3:
        chazhao(student);
        break;
        case 4:
        student=xiugai(student);
        break;
        case 5:
        exit(0);
    }
  }
    fd=open("test",O_RDWR);
    write(fd,&count,4);
    close(fd);
    munmap(student,sizeof(Student)*1000);
    return 0;
}