static void child(int n)
{
// Only first 2 children participate in first pingpong test
cprintf("in child %d\n", n);
if (n < 2) {
int i;
for (i = 0; i < 10; i++) {
cprintf("in child %d count %d\n", n, i);
while (pingpong != n)
pause();
xchg(&pingpong, !pingpong);
}
sys_ret();
}
// Second test, round-robin pingpong between all 4 children
int i;
for (i = 0; i < 10; i++) {
cprintf("in child %d count %d\n", n, i);
while (pingpong != n)
pause();
xchg(&pingpong, (pingpong + 1) % 4);
}
sys_ret();
// Only "child 0" (or the proc that thinks it's child 0), trap check...
if (n == 0) {
assert(recovargs == NULL);
trap_check(&recovargs);
assert(recovargs == NULL);
sys_ret();
}
panic("child(): shouldn't have gotten here");
}
// Flush any outstanding writes on this file to our parent process.
// (XXX should flushes propagate across multiple levels?)
int
fileino_flush(int ino)
{
assert(fileino_isvalid(ino));
if (files->fi[ino].size > files->fi[ino].rlen)
sys_ret(); // synchronize and reconcile with parent
return 0;
}
void gcc_noreturn
exit(int status)
{
// To exit a PIOS user process, by convention,
// we just set our exit status in our filestate area
// and return to our parent process.
files->status = status;
files->exited = 1;
sys_ret();
panic("exit: sys_ret shouldn't have returned");
}
// Read up to 'count' data elements each of size 'eltsize',
// starting at absolute byte offset 'ofs' within the file in inode 'ino'.
// Returns the number of elements (NOT the number of bytes!) actually read,
// or if an error occurs, returns -1 and sets errno appropriately.
// The number of elements returned is normally equal to the 'count' parameter,
// but may be less (without resulting in an error)
// if the file is not large enough to read that many elements.
ssize_t
fileino_read(int ino, off_t ofs, void *buf, size_t eltsize, size_t count)
{
assert(fileino_isreg(ino));
assert(ofs >= 0);
assert(eltsize > 0);
fileinode *fi = &files->fi[ino];
#if LAB >= 9
// XXX hack: allow reading init-files bigger than 4MB
#else
assert(fi->size <= FILE_MAXSIZE);
#endif
#if SOL >= 4
ssize_t actual = 0;
while (count > 0) {
// Read as many elements as we can from the file.
// Note: fd->ofs could well point beyond the end of file,
// which means that avail will be negative - but that's OK.
ssize_t avail = MIN(count, (fi->size - ofs) / eltsize);
if (ofs >= fi->size)
avail = 0;
if (avail > 0) {
memmove(buf, FILEDATA(ino) + ofs, avail * eltsize);
buf += avail * eltsize;
actual += avail;
count -= avail;
}
// If there's no more we can read, stop now.
if (count == 0 || !(fi->mode & S_IFPART))
break;
// Wait for our parent to extend (or close) the file.
#if LAB >= 99
cprintf("fileino_read: waiting for input on file %d\n",
fd - files->fd);
#endif
sys_ret();
}
return actual;
#else // ! SOL >= 4
// Lab 4: insert your file reading code here.
warn("fileino_read() not implemented");
errno = EINVAL;
return -1;
#endif // ! SOL >= 4
}