在C中使用mmap写入内存. [英] use mmap in C to write into memory.

问题描述

我想使用mmap()创建一个包含一些整数的文件.我想通过写入内存来写入此文件.我知道内存中的数据是二进制格式，因此文件中的数据也将是二进制格式. 我可以为此目的使用mmap吗?在哪里可以找到有关如何使用mmap的良好资源?我没有找到好的入门手册.

I want to use mmap() to create a file containing some integers. I want to write to this file by writing to memory. I know that the data in memory is binary format and hence the data in file will also be in binary. Can I use mmap for this purpose? where can I find good resources on how to use mmap? I didn't find a good manual to start with.

推荐答案

以下是示例:

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h> /* mmap() is defined in this header */
#include <fcntl.h>

void err_quit(char *msg)
{
    printf(msg);
    return 0;
}

int main (int argc, char *argv[])
{
 int fdin, fdout;
 char *src, *dst;
 struct stat statbuf;
 int mode = 0x0777;

 if (argc != 3)
   err_quit ("usage: a.out <fromfile> <tofile>");

 /* open the input file */
 if ((fdin = open (argv[1], O_RDONLY)) < 0)
   {printf("can't open %s for reading", argv[1]);
    return 0;
   }

 /* open/create the output file */
 if ((fdout = open (argv[2], O_RDWR | O_CREAT | O_TRUNC, mode )) < 0)//edited here
   {printf ("can't create %s for writing", argv[2]);
    return 0;
   }

 /* find size of input file */
 if (fstat (fdin,&statbuf) < 0)
   {printf ("fstat error");
    return 0;
   }

 /* go to the location corresponding to the last byte */
 if (lseek (fdout, statbuf.st_size - 1, SEEK_SET) == -1)
   {printf ("lseek error");
    return 0;
   }

 /* write a dummy byte at the last location */
 if (write (fdout, "", 1) != 1)
   {printf ("write error");
     return 0;
   }

 /* mmap the input file */
 if ((src = mmap (0, statbuf.st_size, PROT_READ, MAP_SHARED, fdin, 0))
   == (caddr_t) -1)
   {printf ("mmap error for input");
    return 0;
   }

 /* mmap the output file */
 if ((dst = mmap (0, statbuf.st_size, PROT_READ | PROT_WRITE,
   MAP_SHARED, fdout, 0)) == (caddr_t) -1)
   {printf ("mmap error for output");
    return 0;
   }

 /* this copies the input file to the output file */
 memcpy (dst, src, statbuf.st_size);
 return 0;

} /* main */  

从这里
另一个Linux示例
Windows实现 进行内存映射.

From Here
Another Linux example
Windows implementation of memory mapping.

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