Pass through poll_oneof

it's better than nothing

src/wasi_snapshot_preview1.rs

@@ -891,7 +891,49 @@ pub(crate) unsafe fn poll_oneoff<S: Storage>(
     out: *mut Event,
     nsubscriptions: u32,
 ) -> Result<Size, Error> {
-    Err(wasi::ERRNO_NOTSUP.into())
+    let in_ = slice::from_raw_parts(in_, nsubscriptions as usize);
+    let mut new_in = Vec::<Subscription>::new();
+    for sub in in_ {
+        match sub.u.tag {
+        0 /* EVENTTYPE_CLOCK */ => {
+            new_in.push(*sub);
+        }
+        1 | 2 /* EVENTTYPE_FD_READ | EVENTTYPE_FD_WRITE */ => {
+            let mut new_sub = *sub;
+            let fd = if sub.u.tag == 1 {
+                sub.u.u.fd_read.file_descriptor
+            } else {
+                sub.u.u.fd_write.file_descriptor
+            };
+            let fd = fs.get_backing_fd(fd)?;
+            let new_fd = match fd {
+                BackingFd::Virtual(_) => return Err(wasi::ERRNO_NOTSUP.into()),
+                BackingFd::Wasi(fd) => fd,
+            };
+
+            if sub.u.tag == 1 {
+                new_sub.u.u.fd_read.file_descriptor = new_fd;
+            } else {
+                new_sub.u.u.fd_write.file_descriptor = new_fd;
+            }
+
+            new_in.push(new_sub);
+        }
+        _ => return Err(wasi::ERRNO_INVAL.into()),
+        }
+    }
+    let mut rp0 = MaybeUninit::<Fdstat>::uninit();
+    let ret = wasi::wasi_snapshot_preview1::poll_oneoff(
+        new_in.as_ptr() as i32,
+        out as i32,
+        nsubscriptions as i32,
+        rp0.as_mut_ptr() as i32,
+    );
+
+    match ret {
+        0 => Ok(core::ptr::read(rp0.as_mut_ptr() as i32 as *const Size)),
+        _ => Err(Error(ret as u16)),
+    }
 }
 
 fn read_bytes<R: std::io::Read>(mut src: R, iovs: wasi::IovecArray) -> Result<usize, wasi::Errno> {

tests/run-make/polling/Makefile

@@ -0,0 +1,13 @@
+-include ../tools.mk
+
+objs = $(TMPDIR)/main.c.o
+
+check: $(objs)
+	$(CC) $(LDFLAGS) $(objs) $(LIB_WASI_VFS) -o $(TMPDIR)/main.wasm
+	$(WASI_VFS_CLI) pack $(TMPDIR)/main.wasm --mapdir /dev::./dev -o $(TMPDIR)/main.packed.wasm
+	$(WASI_RUN) --mapdir /dev::./dev $(TMPDIR)/main.wasm
+# TODO(katei): Currently, poll_oneoff is not supported for vfs fd
+#	$(WASI_RUN) --mapdir /dev::./dev $(TMPDIR)/main.packed.wasm
+
+clean:
+	rm -rf $(PROG) $(objs)

tests/run-make/polling/dev/polling

@@ -0,0 +1 @@
+hello

tests/run-make/polling/main.c

@@ -0,0 +1,20 @@
+#include <assert.h>
+#include <stdio.h>
+#include <time.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+
+int main(int argc, char *argv[]) {
+  int ret = clock_nanosleep(CLOCK_MONOTONIC, 0, 0, 0);
+  assert(ret == 0);
+
+  // Check ioctl(fd, FIONREAD, ...)
+  int fd = open("/dev/polling", O_RDONLY);
+  assert(fd >= 0);
+  int val = 0;
+  ret = ioctl(fd, FIONREAD, &val);
+  assert(ret == 0);
+  assert(val == 6); // "hello\n"
+
+  return 0;
+}