wasi: nonblocking pipes on Windows (#1570)

Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>

imports/wasi_snapshot_preview1/wasi_stdlib_test.go

@@ -498,18 +498,42 @@ func Test_Stdin(t *testing.T) {
 }
 
 func testStdin(t *testing.T, bin []byte) {
-	r, w, err := os.Pipe()
+	stdinReader, stdinWriter, err := os.Pipe()
+	require.NoError(t, err)
+	stdoutReader, stdoutWriter, err := os.Pipe()
+	require.NoError(t, err)
+	defer func() {
+		stdinReader.Close()
+		stdinWriter.Close()
+		stdoutReader.Close()
+		stdoutReader.Close()
+	}()
 	require.NoError(t, err)
 	moduleConfig := wazero.NewModuleConfig().
 		WithSysNanotime(). // poll_oneoff requires nanotime.
 		WithArgs("wasi", "stdin").
-		WithStdin(r)
-	ch := make(chan string, 1)
+		WithStdin(stdinReader).
+		WithStdout(stdoutWriter)
+	ch := make(chan struct{}, 1)
 	go func() {
-		ch <- compileAndRun(t, testCtx, moduleConfig, bin)
+		defer close(ch)
+
+		r := wazero.NewRuntime(testCtx)
+		defer r.Close(testCtx)
+		_, err := wasi_snapshot_preview1.Instantiate(testCtx, r)
+		require.NoError(t, err)
+		_, err = r.InstantiateWithConfig(testCtx, bin, moduleConfig)
+		require.NoError(t, err)
 	}()
+
 	time.Sleep(1 * time.Second)
-	_, _ = w.WriteString("foo")
-	s := <-ch
-	require.Equal(t, "waiting for stdin...\nfoo", s)
+	buf := make([]byte, 21)
+	_, _ = stdoutReader.Read(buf)
+	require.Equal(t, "waiting for stdin...\n", string(buf))
+	_, _ = stdinWriter.WriteString("foo")
+	_ = stdinWriter.Close()
+	buf = make([]byte, 3)
+	_, _ = stdoutReader.Read(buf)
+	require.Equal(t, "foo", string(buf))
+	<-ch
 }

internal/sysfs/file_test.go

@@ -87,11 +87,7 @@ func TestReadFdNonblock(t *testing.T) {
 	// Read from the file without ever writing to it should not block.
 	buf := make([]byte, 8)
 	_, e := readFd(fd, buf)
-	if runtime.GOOS == "windows" {
-		require.EqualErrno(t, syscall.ENOSYS, e)
-	} else {
 	require.EqualErrno(t, syscall.EAGAIN, e)
-	}
 }
 
 func TestFileSetAppend(t *testing.T) {

internal/sysfs/file_unsupported.go

@@ -1,4 +1,4 @@
-//go:build !unix && !linux && !darwin
+//go:build !unix && !linux && !darwin && !windows
 
 package sysfs
 

internal/sysfs/file_windows.go

@@ -0,0 +1,61 @@
+package sysfs
+
+import (
+	"syscall"
+	"unsafe"
+
+	"github.com/tetratelabs/wazero/internal/platform"
+)
+
+const NonBlockingFileIoSupported = true
+
+var kernel32 = syscall.NewLazyDLL("kernel32.dll")
+
+// procPeekNamedPipe is the syscall.LazyProc in kernel32 for PeekNamedPipe
+var procPeekNamedPipe = kernel32.NewProc("PeekNamedPipe")
+
+// readFd returns ENOSYS on unsupported platforms.
+//
+// PeekNamedPipe: https://learn.microsoft.com/en-us/windows/win32/api/namedpipeapi/nf-namedpipeapi-peeknamedpipe
+// "GetFileType can assist in determining what device type the handle refers to. A console handle presents as FILE_TYPE_CHAR."
+// https://learn.microsoft.com/en-us/windows/console/console-handles
+func readFd(fd uintptr, buf []byte) (int, syscall.Errno) {
+	handle := syscall.Handle(fd)
+	fileType, err := syscall.GetFileType(syscall.Stdin)
+	if err != nil {
+		return 0, platform.UnwrapOSError(err)
+	}
+	if fileType&syscall.FILE_TYPE_CHAR == 0 {
+		return -1, syscall.ENOSYS
+	}
+	n, err := peekNamedPipe(handle)
+	if err != nil {
+		errno := platform.UnwrapOSError(err)
+		if errno == syscall.ERROR_BROKEN_PIPE {
+			return 0, 0
+		}
+	}
+	if n == 0 {
+		return -1, syscall.EAGAIN
+	}
+	un, err := syscall.Read(handle, buf[0:n])
+	return un, platform.UnwrapOSError(err)
+}
+
+// peekNamedPipe partially exposes PeekNamedPipe from the Win32 API
+// see https://learn.microsoft.com/en-us/windows/win32/api/namedpipeapi/nf-namedpipeapi-peeknamedpipe
+func peekNamedPipe(handle syscall.Handle) (uint32, error) {
+	var totalBytesAvail uint32
+	totalBytesPtr := unsafe.Pointer(&totalBytesAvail)
+	_, _, err := procPeekNamedPipe.Call(
+		uintptr(handle),        // [in]            HANDLE  hNamedPipe,
+		0,                      // [out, optional] LPVOID  lpBuffer,
+		0,                      // [in]            DWORD   nBufferSize,
+		0,                      // [out, optional] LPDWORD lpBytesRead
+		uintptr(totalBytesPtr), // [out, optional] LPDWORD lpTotalBytesAvail,
+		0)                      // [out, optional] LPDWORD lpBytesLeftThisMessage
+	if err == syscall.Errno(0) {
+		return totalBytesAvail, nil
+	}
+	return totalBytesAvail, err
+}

internal/sysfs/nonblock_unix.go

@@ -2,8 +2,16 @@
 
 package sysfs
 
-import "syscall"
+import (
+	"syscall"
+
+	"github.com/tetratelabs/wazero/internal/fsapi"
+)
 
 func setNonblock(fd uintptr, enable bool) error {
 	return syscall.SetNonblock(int(fd), enable)
 }
+
+func isNonblock(f *osFile) bool {
+	return f.flag&fsapi.O_NONBLOCK == fsapi.O_NONBLOCK
+}

internal/sysfs/nonblock_windows.go

@@ -2,8 +2,24 @@
 
 package sysfs
 
-import "syscall"
+import (
+	"io/fs"
+	"syscall"
+
+	"github.com/tetratelabs/wazero/internal/fsapi"
+)
 
 func setNonblock(fd uintptr, enable bool) error {
+	// We invoke the syscall, but this is currently no-op.
 	return syscall.SetNonblock(syscall.Handle(fd), enable)
 }
+
+func isNonblock(f *osFile) bool {
+	// On Windows, we support non-blocking reads only on named pipes.
+	isValid := false
+	st, errno := f.Stat()
+	if errno == 0 {
+		isValid = st.Mode&fs.ModeNamedPipe != 0
+	}
+	return isValid && f.flag&fsapi.O_NONBLOCK == fsapi.O_NONBLOCK
+}

internal/sysfs/osfile.go

@@ -106,7 +106,7 @@ func (f *osFile) reopen() (errno syscall.Errno) {
 
 // IsNonblock implements the same method as documented on fsapi.File
 func (f *osFile) IsNonblock() bool {
-	return f.flag&fsapi.O_NONBLOCK == fsapi.O_NONBLOCK
+	return isNonblock(f)
 }
 
 // SetNonblock implements the same method as documented on fsapi.File

internal/sysfs/select_windows.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"syscall"
 	"time"
-	"unsafe"
 
 	"github.com/tetratelabs/wazero/internal/platform"
 )
@@ -16,11 +15,6 @@ const wasiFdStdin = 0
 // pollInterval is the interval between each calls to peekNamedPipe in pollNamedPipe
 const pollInterval = 100 * time.Millisecond
 
-var kernel32 = syscall.NewLazyDLL("kernel32.dll")
-
-// procPeekNamedPipe is the syscall.LazyProc in kernel32 for PeekNamedPipe
-var procPeekNamedPipe = kernel32.NewProc("PeekNamedPipe")
-
 // syscall_select emulates the select syscall on Windows for two, well-known cases, returns syscall.ENOSYS for all others.
 // If r contains fd 0, and it is a regular file, then it immediately returns 1 (data ready on stdin)
 // and r will have the fd 0 bit set.
@@ -72,7 +66,8 @@ func syscall_select(n int, r, w, e *platform.FdSet, timeout *time.Duration) (int
 func pollNamedPipe(ctx context.Context, pipeHandle syscall.Handle, duration *time.Duration) (bool, error) {
 	// Short circuit when the duration is zero.
 	if duration != nil && *duration == time.Duration(0) {
-		return peekNamedPipe(pipeHandle)
+		bytes, err := peekNamedPipe(pipeHandle)
+		return bytes > 0, err
 	}
 
 	// Ticker that emits at every pollInterval.
@@ -101,27 +96,9 @@ func pollNamedPipe(ctx context.Context, pipeHandle syscall.Handle, duration *tim
 			if err != nil {
 				return false, err
 			}
-			if res {
+			if res > 0 {
 				return true, nil
 			}
 		}
 	}
 }
-
-// peekNamedPipe partially exposes PeekNamedPipe from the Win32 API
-// see https://learn.microsoft.com/en-us/windows/win32/api/namedpipeapi/nf-namedpipeapi-peeknamedpipe
-func peekNamedPipe(handle syscall.Handle) (bool, error) {
-	var totalBytesAvail uint32
-	totalBytesPtr := unsafe.Pointer(&totalBytesAvail)
-	_, _, err := procPeekNamedPipe.Call(
-		uintptr(handle),        // [in]            HANDLE  hNamedPipe,
-		0,                      // [out, optional] LPVOID  lpBuffer,
-		0,                      // [in]            DWORD   nBufferSize,
-		0,                      // [out, optional] LPDWORD lpBytesRead
-		uintptr(totalBytesPtr), // [out, optional] LPDWORD lpTotalBytesAvail,
-		0)                      // [out, optional] LPDWORD lpBytesLeftThisMessage
-	if err == syscall.Errno(0) {
-		return totalBytesAvail > 0, nil
-	}
-	return totalBytesAvail > 0, err
-}

internal/sysfs/select_windows_test.go

@@ -33,9 +33,9 @@ func TestSelect_Windows(t *testing.T) {
 		wh := syscall.Handle(w.Fd())
 
 		// Ensure the pipe has data.
-		hasData, err := peekNamedPipe(rh)
+		n, err := peekNamedPipe(rh)
 		require.NoError(t, err)
-		require.False(t, hasData)
+		require.NotEqual(t, 0, n)
 
 		// Write to the channel.
 		msg, err := syscall.ByteSliceFromString("test\n")
@@ -44,9 +44,9 @@ func TestSelect_Windows(t *testing.T) {
 		require.NoError(t, err)
 
 		// Ensure the pipe has data.
-		hasData, err = peekNamedPipe(rh)
+		n, err = peekNamedPipe(rh)
 		require.NoError(t, err)
-		require.True(t, hasData)
+		require.NotEqual(t, 0, n)
 	})
 
 	t.Run("pollNamedPipe should return immediately when duration is nil (no data)", func(t *testing.T) {