i386/MIT/course/src/git.lab/user/testfdsharing.c

   1 #include <inc/x86.h>
   2 #include <inc/lib.h>
   3
   4 char buf[512], buf2[512];
   5
   6 void
   7 umain(int argc, char **argv)
   8 {
   9         int fd, r, n, n2;
  10
  11         if ((fd = open("motd", O_RDONLY)) < 0)
  12                 panic("open motd: %e", fd);
  13         seek(fd, 0);
  14         if ((n = readn(fd, buf, sizeof buf)) <= 0)
  15                 panic("readn: %e", n);
  16
  17         if ((r = fork()) < 0)
  18                 panic("fork: %e", r);
  19         if (r == 0) {
  20                 seek(fd, 0);
  21                 cprintf("going to read in child (might page fault if your sharing is buggy)\n");
  22                 if ((n2 = readn(fd, buf2, sizeof buf2)) != n)
  23                         panic("read in parent got %d, read in child got %d", n, n2);
  24                 if (memcmp(buf, buf2, n) != 0)
  25                         panic("read in parent got different bytes from read in child");
  26                 cprintf("read in child succeeded\n");
  27                 seek(fd, 0);
  28                 close(fd);
  29                 exit();
  30         }
  31         wait(r);
  32         if ((n2 = readn(fd, buf2, sizeof buf2)) != n)
  33                 panic("read in parent got %d, then got %d", n, n2);
  34         cprintf("read in parent succeeded\n");
  35         close(fd);
  36
  37         if ((fd = open("newmotd", O_RDWR)) < 0)
  38                 panic("open newmotd: %e", fd);
  39         seek(fd, 0);
  40         if ((n = write(fd, "hello", 5)) != 5)
  41                 panic("write: %e", n);
  42
  43         if ((r = fork()) < 0)
  44                 panic("fork: %e", r);
  45         if (r == 0) {
  46                 seek(fd, 0);
  47                 cprintf("going to write in child\n");
  48                 if ((n = write(fd, "world", 5)) != 5)
  49                         panic("write in child: %e", n);
  50                 cprintf("write in child finished\n");
  51                 close(fd);
  52                 exit();
  53         }
  54         wait(r);
  55         seek(fd, 0);
  56         if ((n = readn(fd, buf, 5)) != 5)
  57                 panic("readn: %e", n);
  58         buf[5] = 0;
  59         if (strcmp(buf, "hello") == 0)
  60                 cprintf("write to file failed; got old data\n");
  61         else if (strcmp(buf, "world") == 0)
  62                 cprintf("write to file succeeded\n");
  63         else
  64                 cprintf("write to file failed; got %s\n", buf);
  65
  66         breakpoint();
  67 }