/*************************************************************************

    > File Name: memory_map.c

    > Author: hailin.ma

    > Mail: mhl2018@126.com

    > Created Time: Thu 28 May 2015 08:20:50 AM CST

 ************************************************************************/

#include<stdio.h>

#include <sys/mman.h>

#include <fcntl.h>

#include <string.h>

#define MEM_MAP_SIZE 1000

int memory_map()

{

    char * pmap = NULL;

    int fd;

    char rdbuf[] = "\0";

    fd = open("memory.txt",O_RDWR|O_CREAT|O_TRUNC,);

    if(fd == -)

    {

        perror("open error");

        return -;

    }

    write(fd,"hello world!",MEM_MAP_SIZE);        //write data to file,the write size must as long as MEM_MAP_SIZE

    pmap = mmap(NULL,MEM_MAP_SIZE,PROT_READ|PROT_WRITE,MAP_SHARED,fd,);        //map memory with file

    printf("the memory is: %s\n",pmap);

    memset(pmap,'a',MEM_MAP_SIZE);

    memcpy(pmap,"this is memory map",);        //try to chang any charactor in memory

    lseek(fd,,SEEK_SET);            //move fd pointer to begin section

    memset(rdbuf,,sizeof(rdbuf));

    read(fd,rdbuf,);                //read the context in file

    printf("the file is: %s\n",rdbuf);

    munmap(pmap,);

    close(fd);

    return ;

}