books/apue/mmap.c

   1 /*
   2  * cp example using mmap()
   3  */
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <unistd.h>
   8 #include <fcntl.h>
   9 #include <sys/types.h>
  10 #include <sys/stat.h>
  11 #include <sys/mman.h>
  12
  13 int main(int argc, char *argv[])
  14 {
  15         char *src, *dst;
  16         int err, fdin, fdout;
  17         struct stat statbuf;
  18
  19         if (argc != 3) {
  20                 fprintf(stderr, "usage: 12.14 <fromfile> <tofile>\n");
  21                 exit(EXIT_FAILURE);
  22         }
  23
  24         fdin = open(argv[1], O_RDONLY);
  25         if (fdin < 0) {
  26                 fprintf(stderr, "can't open %s for reading", argv[1]);
  27                 exit(EXIT_FAILURE);
  28         }
  29
  30         fdout = open(argv[2], O_RDWR | O_CREAT | O_TRUNC, 0666);
  31         if (fdin < 0) {
  32                 fprintf(stderr, "can't open %s for reading", argv[2]);
  33                 exit(EXIT_FAILURE);
  34         }
  35
  36         err = fstat(fdin, &statbuf);
  37         if (err) {
  38                 perror("fstat()");
  39                 exit(EXIT_FAILURE);
  40         }
  41
  42         /* Allocates the space needed */
  43         err = lseek(fdout, statbuf.st_size -1, SEEK_SET);
  44         if (err == (off_t) -1) {
  45                 perror("lseek()");
  46                 exit(EXIT_FAILURE);
  47         }
  48
  49         err = write(fdout, "", 1);
  50         if (err != 1) {
  51                 perror("write()");
  52                 exit(EXIT_FAILURE);
  53         }
  54
  55         src = (char *) mmap((void *) 0, statbuf.st_size,
  56                             PROT_READ, MAP_SHARED, fdin, 0);
  57         if (src == MAP_FAILED) {
  58                 perror("first mmap()");
  59                 exit(EXIT_FAILURE);
  60         }
  61
  62         dst = (char *) mmap((void *) 0, statbuf.st_size,
  63                             PROT_READ | PROT_WRITE, MAP_SHARED, fdout, 0);
  64         if (dst == MAP_FAILED) {
  65                 perror("second mmap()");
  66                 exit(EXIT_FAILURE);
  67         }
  68
  69         memcpy(dst, src, statbuf.st_size);
  70
  71         munmap(src, statbuf.st_size);
  72         munmap(dst, statbuf.st_size);
  73
  74         return 0;
  75 }