Try #671:

lib/wasi-tests/tests/wasitests/mod.rs

@@ -18,6 +18,7 @@ mod mapdir;
 mod path_link;
 mod path_rename;
 mod path_symlink;
+mod poll_oneoff;
 mod quine;
 mod readlink;
 mod wasi_sees_virtual_root;

lib/wasi-tests/tests/wasitests/poll_oneoff.rs

@@ -0,0 +1,14 @@
+#[test]
+fn test_poll_oneoff() {
+    assert_wasi_output!(
+        "../../wasitests/poll_oneoff.wasm",
+        "poll_oneoff",
+        vec![],
+        vec![(
+            "hamlet".to_string(),
+            ::std::path::PathBuf::from("wasitests/test_fs/hamlet")
+        ),],
+        vec![],
+        "../../wasitests/poll_oneoff.out"
+    );
+}

lib/wasi-tests/wasitests/poll_oneoff.out

@@ -0,0 +1 @@
+__wasi_event_t { userdata: 1193046, error: 0, type_: 1, u: __wasi_event_u { __wasi_event_fd_readwrite_t { nbytes: 2259, flags: 0 } } }

lib/wasi-tests/wasitests/poll_oneoff.rs

@@ -0,0 +1,150 @@
+// Args:
+// mapdir: hamlet:wasitests/test_fs/hamlet
+
+use std::fs;
+use std::io::{Read, Seek, SeekFrom};
+#[cfg(target_os = "wasi")]
+use std::os::wasi::prelude::AsRawFd;
+use std::path::PathBuf;
+
+#[cfg(target_os = "wasi")]
+#[link(wasm_import_module = "wasi_unstable")]
+extern "C" {
+    fn poll_oneoff(subscriptons: u32, events: u32, nsubscriptons: u32, nevents: u32) -> u16;
+}
+
+#[derive(Debug, Copy, Clone)]
+#[repr(C)]
+pub struct __wasi_event_t {
+    pub userdata: u64,
+    pub error: u16,
+    pub type_: __wasi_eventtype_t,
+    pub u: __wasi_event_u,
+}
+
+impl Default for __wasi_event_t {
+    fn default() -> Self {
+        __wasi_event_t {
+            userdata: 0,
+            error: 0,
+            type_: 0,
+            u: __wasi_event_u {
+                fd_readwrite: __wasi_event_fd_readwrite_t {
+                    nbytes: 0,
+                    flags: 0,
+                },
+            },
+        }
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[repr(C)]
+pub struct __wasi_event_fd_readwrite_t {
+    pub nbytes: u64,
+    pub flags: u16,
+}
+
+#[derive(Copy, Clone)]
+#[repr(C)]
+pub union __wasi_event_u {
+    pub fd_readwrite: __wasi_event_fd_readwrite_t,
+}
+
+impl std::fmt::Debug for __wasi_event_u {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "__wasi_event_u {{ ")?;
+        write!(f, "{:?} }}", unsafe { self.fd_readwrite })
+    }
+}
+
+pub type __wasi_eventtype_t = u8;
+pub const __WASI_EVENTTYPE_CLOCK: u8 = 0;
+pub const __WASI_EVENTTYPE_FD_READ: u8 = 1;
+pub const __WASI_EVENTTYPE_FD_WRITE: u8 = 2;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[repr(C)]
+pub struct __wasi_subscription_clock_t {
+    pub userdata: u64,
+    pub clock_id: u32,
+    pub timeout: u64,
+    pub precision: u64,
+    pub flags: u16,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[repr(C)]
+pub struct __wasi_subscription_fs_readwrite_t {
+    pub fd: u32,
+}
+
+#[derive(Copy, Clone)]
+#[repr(C)]
+pub union __wasi_subscription_u {
+    clock: __wasi_subscription_clock_t,
+    fd_readwrite: __wasi_subscription_fs_readwrite_t,
+}
+
+#[derive(Copy, Clone)]
+#[repr(C)]
+pub struct __wasi_subscription_t {
+    pub userdata: u64,
+    pub type_: __wasi_eventtype_t,
+    pub u: __wasi_subscription_u,
+}
+
+#[cfg(target_os = "wasi")]
+fn poll_read(fds: &[u32]) -> Result<Vec<__wasi_event_t>, u16> {
+    let mut in_ = fds
+        .iter()
+        .map(|n| __wasi_subscription_t {
+            userdata: 0x123456,
+            type_: __WASI_EVENTTYPE_FD_READ,
+            u: __wasi_subscription_u {
+                fd_readwrite: __wasi_subscription_fs_readwrite_t { fd: *n as u32 },
+            },
+        })
+        .collect::<Vec<_>>();
+    let mut out_ = vec![Default::default(); in_.len()];
+    let mut nsubscriptions: u32 = 0;
+    let result = unsafe {
+        poll_oneoff(
+            in_.as_ptr() as usize as u32,
+            out_.as_mut_ptr() as usize as u32,
+            in_.len() as u32,
+            (&mut nsubscriptions as *mut u32) as usize as u32,
+        )
+    };
+
+    if result == 0 {
+        Ok(out_)
+    } else {
+        Err(result)
+    }
+}
+
+fn main() {
+    #[cfg(not(target_os = "wasi"))]
+    let mut base = PathBuf::from("wasitests/test_fs");
+    #[cfg(target_os = "wasi")]
+    let mut base = PathBuf::from("/");
+
+    let path = base.join("hamlet/act4/scene1.txt");
+    let mut file = fs::File::open(&path).expect("Could not open file");
+    let mut buffer = [0u8; 64];
+
+    #[cfg(target_os = "wasi")]
+    {
+        let fds = vec![file.as_raw_fd()];
+        let mut result = poll_read(fds.as_slice()).expect("First poll");
+        while result[0].error != 0 {
+            result = poll_read(fds.as_slice()).expect("subsequent polls");
+        }
+        println!("{:?}", result[0]);
+    }
+    #[cfg(not(target_os = "wasi"))]
+    {
+        println!("{}", "__wasi_event_t { userdata: 1193046, error: 0, type_: 1, u: __wasi_event_u { __wasi_event_fd_readwrite_t { nbytes: 2259, flags: 0 } } }");
+    }
+}