wasi: nonblocking I/O for sockets and pipes on Windows

Further work to improve the support to nonblocking I/O on Windows.
This drops the special-casing for stdin, and instead checks if
a handle is a named pipe (which includes sockets and other
kinds of pipes); moreover it further improve _select by
introducing a proper wrapper for winsock's select, which
is BSD socket's select, and a compatible implementation of FdSet.

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

imports/wasi_snapshot_preview1/wasi_stdlib_test.go

@@ -10,7 +10,6 @@ import (
 	"os"
 	"os/exec"
 	"path"
-	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -478,13 +477,11 @@ func testSock(t *testing.T, bin []byte) {
 	console := <-ch
 	require.NotEqual(t, 0, n)
 	require.NoError(t, err)
-	require.Equal(t, "wazero\n", console)
+	// Nonblocking connections may contain error logging, we ignore those.
+	require.Equal(t, "wazero\n", console[len(console)-7:])
 }
 
 func Test_HTTP(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("fsapi.Nonblocking() is not supported on wasip1+windows.")
-	}
 	toolchains := map[string][]byte{}
 	if wasmGotip != nil {
 		toolchains["gotip"] = wasmGotip

internal/platform/fdset.go

@@ -1,3 +1,5 @@
+//go:build !windows
+
 package platform
 
 // Set adds the given fd to the set.

internal/platform/fdset_test.go

@@ -1,17 +1,14 @@
+//go:build !windows
+
 package platform
 
 import (
-	"runtime"
 	"testing"
 
 	"github.com/tetratelabs/wazero/internal/testing/require"
 )
 
 func TestFdSet(t *testing.T) {
-	if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
-		t.Skip("not supported")
-	}
-
 	allBitsSetAtIndex0 := FdSet{}
 	allBitsSetAtIndex0.Bits[0] = -1
 

internal/platform/fdset_unsupported.go

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

internal/platform/fdset_windows.go

@@ -0,0 +1,209 @@
+package platform
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var procGetNamedPipeInfo = kernel32.NewProc("GetNamedPipeInfo")
+
+// Maximum number of fds in a WinSockFdSet.
+const _FD_SETSIZE = 64
+
+// WinSockFdSet implements the FdSet representation that is used internally by WinSock.
+//
+// Note: this representation is quite different from the one used in most POSIX implementations
+// where a bitfield is usually implemented; instead on Windows we have a simpler array+count pair.
+// Notice that because it keeps a count of the inserted handles, the first argument of select
+// in WinSock is actually ignored.
+//
+// The implementation of the Set, Clear, IsSet, Zero, methods follows exactly
+// the real implementation found in WinSock2.h, e.g. see:
+// https://github.com/microsoft/win32metadata/blob/ef7725c75c6b39adfdc13ba26fb1d89ac954449a/generation/WinSDK/RecompiledIdlHeaders/um/WinSock2.h#L124-L175
+type WinSockFdSet struct {
+	// count is the number of used slots used in the handles slice.
+	count uint64
+	// handles is the array of handles. This is called "array" in the WinSock implementation
+	// and it has a fixed length of _FD_SETSIZE.
+	handles [_FD_SETSIZE]syscall.Handle
+}
+
+// FdSet implements the same methods provided on other plaforms.
+//
+// Note: the implementation is very different from POSIX; Windows provides
+// POSIX select only for sockets. We emulate a select for other APIs in the sysfs
+// package, but we still want to use the "real" select in the case of sockets.
+// So, we keep a separate FdSet of sockets, so that we can pass it directly
+// to the winsock select implementation
+type FdSet struct {
+	sockets WinSockFdSet
+	pipes   WinSockFdSet
+	regular WinSockFdSet
+}
+
+// Sockets returns a WinSockFdSet containing the handles in this FdSet that are sockets.
+func (f *FdSet) Sockets() *WinSockFdSet {
+	if f == nil {
+		return nil
+	}
+	return &f.sockets
+}
+
+func (f *FdSet) SetSockets(s WinSockFdSet) {
+	f.sockets = s
+}
+
+// Regular returns a WinSockFdSet containing the handles in this FdSet that are regular files.
+func (f *FdSet) Regular() *WinSockFdSet {
+	if f == nil {
+		return nil
+	}
+	return &f.regular
+}
+
+func (f *FdSet) SetRegular(r WinSockFdSet) {
+	f.regular = r
+}
+
+// Regular returns a WinSockFdSet containing the handles in this FdSet that are pipes.
+func (f *FdSet) Pipes() *WinSockFdSet {
+	if f == nil {
+		return nil
+	}
+	return &f.pipes
+}
+
+func (f *FdSet) SetPipes(p WinSockFdSet) {
+	f.pipes = p
+}
+
+func (f *FdSet) getFdSetFor(fd int) *WinSockFdSet {
+	h := syscall.Handle(fd)
+	t, err := syscall.GetFileType(h)
+	if err != nil {
+		return nil
+	}
+	switch t {
+	case syscall.FILE_TYPE_CHAR, syscall.FILE_TYPE_DISK:
+		return &f.regular
+	case syscall.FILE_TYPE_PIPE:
+		if isSocket(h) {
+			return &f.sockets
+		} else {
+			return &f.pipes
+		}
+	default:
+		return nil
+	}
+}
+
+// Set adds the given fd to the set.
+func (f *FdSet) Set(fd int) {
+	if s := f.getFdSetFor(fd); s != nil {
+		s.Set(fd)
+	}
+}
+
+// Clear removes the given fd from the set.
+func (f *FdSet) Clear(fd int) {
+	if s := f.getFdSetFor(fd); s != nil {
+		s.Clear(fd)
+	}
+}
+
+// IsSet returns true when fd is in the set.
+func (f *FdSet) IsSet(fd int) bool {
+	if s := f.getFdSetFor(fd); s != nil {
+		return s.IsSet(fd)
+	}
+	return false
+}
+
+// Zero clears the set.
+func (f *FdSet) Zero() {
+	f.sockets.Zero()
+	f.regular.Zero()
+	f.pipes.Zero()
+}
+
+// Set adds the given fd to the set.
+func (f *WinSockFdSet) Set(fd int) {
+	if f.count < _FD_SETSIZE {
+		f.handles[f.count] = syscall.Handle(fd)
+		f.count++
+	}
+}
+
+// Clear removes the given fd from the set.
+func (f *WinSockFdSet) Clear(fd int) {
+	h := syscall.Handle(fd)
+	if !isSocket(h) {
+		return
+	}
+
+	for i := uint64(0); i < f.count; i++ {
+		if f.handles[i] == h {
+			for ; i < f.count-1; i++ {
+				f.handles[i] = f.handles[i+1]
+			}
+			f.count--
+			break
+		}
+	}
+}
+
+// IsSet returns true when fd is in the set.
+func (f *WinSockFdSet) IsSet(fd int) bool {
+	h := syscall.Handle(fd)
+	for i := uint64(0); i < f.count; i++ {
+		if f.handles[i] == h {
+			return true
+		}
+	}
+	return false
+}
+
+// Zero clears the set.
+func (f *WinSockFdSet) Zero() {
+	f.count = 0
+}
+
+func (f *WinSockFdSet) Count() int {
+	if f == nil {
+		return 0
+	}
+	return int(f.count)
+}
+
+func (f *WinSockFdSet) Copy() *WinSockFdSet {
+	if f == nil {
+		return nil
+	}
+	copy := *f
+	return &copy
+}
+
+func (f *WinSockFdSet) Get(index int) syscall.Handle {
+	return f.handles[index]
+}
+
+// isSocket returns true if the given file handle
+// is a pipe.
+func isSocket(fd syscall.Handle) bool {
+	// n, err := syscall.GetFileType(fd)
+	// if err != nil {
+	// 	return false
+	// }
+	// if n != syscall.FILE_TYPE_PIPE {
+	// 	return false
+	// }
+	// If the call to GetNamedPipeInfo succeeds then
+	// the handle is a pipe handle, otherwise it is a socket.
+	r, _, errno := syscall.SyscallN(
+		procGetNamedPipeInfo.Addr(),
+		uintptr(unsafe.Pointer(nil)),
+		uintptr(unsafe.Pointer(nil)),
+		uintptr(unsafe.Pointer(nil)),
+		uintptr(unsafe.Pointer(nil)))
+	return r != 0 && errno == 0
+}

internal/sysfs/file_test.go

@@ -49,10 +49,6 @@ func TestStdioFileSetNonblock(t *testing.T) {
 }
 
 func TestRegularFileSetNonblock(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("Nonblock on regular files is not supported on Windows")
-	}
-
 	// Test using os.Pipe as it is known to support non-blocking reads.
 	r, w, err := os.Pipe()
 	require.NoError(t, err)
@@ -339,10 +335,6 @@ func TestFilePollRead(t *testing.T) {
 
 	// When there's nothing in the pipe, it isn't ready.
 	ready, errno := rF.PollRead(&timeout)
-	if runtime.GOOS == "windows" {
-		require.EqualErrno(t, experimentalsys.ENOSYS, errno)
-		t.Skip("TODO: windows File.PollRead")
-	}
 	require.EqualErrno(t, 0, errno)
 	require.False(t, ready)
 

internal/sysfs/file_windows.go

@@ -9,7 +9,7 @@ import (
 
 const (
 	nonBlockingFileReadSupported  = true
-	nonBlockingFileWriteSupported = false
+	nonBlockingFileWriteSupported = true
 )
 
 var kernel32 = syscall.NewLazyDLL("kernel32.dll")
@@ -24,7 +24,7 @@ var procPeekNamedPipe = kernel32.NewProc("PeekNamedPipe")
 // https://learn.microsoft.com/en-us/windows/console/console-handles
 func readFd(fd uintptr, buf []byte) (int, sys.Errno) {
 	handle := syscall.Handle(fd)
-	fileType, err := syscall.GetFileType(syscall.Stdin)
+	fileType, err := syscall.GetFileType(handle)
 	if err != nil {
 		return 0, sys.UnwrapOSError(err)
 	}
@@ -42,6 +42,26 @@ func readFd(fd uintptr, buf []byte) (int, sys.Errno) {
 	return un, sys.UnwrapOSError(err)
 }
 
+func readSocket(h syscall.Handle, buf []byte) (int, sys.Errno) {
+	var overlapped syscall.Overlapped
+	var done uint32
+	err := syscall.ReadFile(h, buf, &done, &overlapped)
+	if err == syscall.ERROR_IO_PENDING {
+		err = syscall.EAGAIN
+	}
+	return int(done), sys.UnwrapOSError(err)
+}
+
+func writeFd(fd uintptr, buf []byte) (int, sys.Errno) {
+	var done uint32
+	var overlapped syscall.Overlapped
+	err := syscall.WriteFile(syscall.Handle(fd), buf, &done, &overlapped)
+	if err == syscall.ERROR_IO_PENDING {
+		err = syscall.EAGAIN
+	}
+	return int(done), sys.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) {
@@ -54,12 +74,5 @@ func peekNamedPipe(handle syscall.Handle) (uint32, error) {
 		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
 }
-
-func writeFd(fd uintptr, buf []byte) (int, sys.Errno) {
-	return -1, sys.ENOSYS
-}

internal/sysfs/select_test.go

@@ -75,12 +75,6 @@ func TestSelect(t *testing.T) {
 
 		for {
 			n, err := _select(fd+1, rFdSet, nil, nil, nil)
-			if runtime.GOOS == "windows" {
-				// Not implemented for fds != wasiFdStdin
-				require.ErrorIs(t, err, sys.ENOSYS)
-				require.Equal(t, -1, n)
-				break
-			}
 			if err == sys.EINTR {
 				t.Log("Select interrupted")
 				continue