Re-introduces internal fsapi.File with non-blocking methods (#1613)

Signed-off-by: Adrian Cole <[email protected]>

experimental/sys/dir.go

@@ -61,16 +61,6 @@ func (DirFile) SetAppend(bool) Errno {
 	return EISDIR
 }
 
-// IsNonblock implements File.IsNonblock
-func (DirFile) IsNonblock() bool {
-	return false
-}
-
-// SetNonblock implements File.SetNonblock
-func (DirFile) SetNonblock(bool) Errno {
-	return EISDIR
-}
-
 // IsDir implements File.IsDir
 func (DirFile) IsDir() (bool, Errno) {
 	return true, 0
@@ -86,11 +76,6 @@ func (DirFile) Pread([]byte, int64) (int, Errno) {
 	return 0, EISDIR
 }
 
-// Poll implements File.Poll
-func (DirFile) Poll(Pflag, int32) (ready bool, errno Errno) {
-	return false, ENOSYS
-}
-
 // Write implements File.Write
 func (DirFile) Write([]byte) (int, Errno) {
 	return 0, EISDIR

experimental/sys/file.go

@@ -67,29 +67,6 @@ type File interface {
 	//   - Implementations should cache this result.
 	IsDir() (bool, Errno)
 
-	// IsNonblock returns true if the file was opened with O_NONBLOCK, or
-	// SetNonblock was successfully enabled on this file.
-	//
-	// # Notes
-	//
-	//   - This might not match the underlying state of the file descriptor if
-	//     the file was not opened via OpenFile.
-	IsNonblock() bool
-
-	// SetNonblock toggles the non-blocking mode (O_NONBLOCK) of this file.
-	//
-	// # Errors
-	//
-	// A zero Errno is success. The below are expected otherwise:
-	//   - ENOSYS: the implementation does not support this function.
-	//   - EBADF: the file or directory was closed.
-	//
-	// # Notes
-	//
-	//   - This is like syscall.SetNonblock and `fcntl` with O_NONBLOCK in
-	//     POSIX. See https://pubs.opengroup.org/onlinepubs/9699919799/functions/fcntl.html
-	SetNonblock(enable bool) Errno
-
 	// IsAppend returns true if the file was opened with O_APPEND, or
 	// SetAppend was successfully enabled on this file.
 	//
@@ -200,37 +177,6 @@ type File interface {
 	//     of io.Seeker. See https://pubs.opengroup.org/onlinepubs/9699919799/functions/fseek.html
 	Seek(offset int64, whence int) (newOffset int64, errno Errno)
 
-	// Poll returns if the file has data ready to be read or written.
-	//
-	// # Parameters
-	//
-	// The `flag` parameter determines which event to await, such as POLLIN,
-	// POLLOUT, or a combination like `POLLIN|POLLOUT`.
-	//
-	// The `timeoutMillis` parameter is how long to block for an event, or
-	// interrupted, in milliseconds. There are two special values:
-	//   - zero returns immediately
-	//   - any negative value blocks any amount of time
-	//
-	// # Results
-	//
-	// `ready` means there was data ready to read or written. False can mean no
-	// event was ready or `errno` is not zero.
-	//
-	// A zero `errno` is success. The below are expected otherwise:
-	//   - ENOSYS: the implementation does not support this function.
-	//   - ENOTSUP: the implementation does not the flag combination.
-	//   - EINTR: the call was interrupted prior to an event.
-	//
-	// # Notes
-	//
-	//   - This is like `poll` in POSIX, for a single file.
-	//     See https://pubs.opengroup.org/onlinepubs/9699919799/functions/poll.html
-	//   - No-op files, such as those which read from /dev/null, should return
-	//     immediately true, as data will never become available.
-	//   - See /RATIONALE.md for detailed notes including impact of blocking.
-	Poll(flag Pflag, timeoutMillis int32) (ready bool, errno Errno)
-
 	// Readdir reads the contents of the directory associated with file and
 	// returns a slice of up to n Dirent values in an arbitrary order. This is
 	// a stateful function, so subsequent calls return any next values.

experimental/sys/unimplemented.go

@@ -101,16 +101,6 @@ func (UnimplementedFile) SetAppend(bool) Errno {
 	return ENOSYS
 }
 
-// IsNonblock implements File.IsNonblock
-func (UnimplementedFile) IsNonblock() bool {
-	return false
-}
-
-// SetNonblock implements File.SetNonblock
-func (UnimplementedFile) SetNonblock(bool) Errno {
-	return ENOSYS
-}
-
 // Stat implements File.Stat
 func (UnimplementedFile) Stat() (sys.Stat_t, Errno) {
 	return sys.Stat_t{}, ENOSYS
@@ -136,11 +126,6 @@ func (UnimplementedFile) Readdir(int) (dirents []Dirent, errno Errno) {
 	return nil, ENOSYS
 }
 
-// Poll implements File.Poll
-func (UnimplementedFile) Poll(Pflag, int32) (ready bool, errno Errno) {
-	return false, ENOSYS
-}
-
 // Write implements File.Write
 func (UnimplementedFile) Write([]byte) (int, Errno) {
 	return 0, ENOSYS

imports/wasi_snapshot_preview1/fs_test.go

@@ -17,6 +17,7 @@ import (
 	"github.com/tetratelabs/wazero"
 	"github.com/tetratelabs/wazero/api"
 	experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
+	"github.com/tetratelabs/wazero/internal/fsapi"
 	"github.com/tetratelabs/wazero/internal/fstest"
 	"github.com/tetratelabs/wazero/internal/platform"
 	"github.com/tetratelabs/wazero/internal/sys"
@@ -247,7 +248,7 @@ func Test_fdFdstatGet(t *testing.T) {
 	}}}).OpenFile("stdin", 0, 0)
 	require.EqualErrno(t, 0, errno)
 
-	stdin.File = stdinFile
+	stdin.File = fsapi.Adapt(stdinFile)
 
 	// Make this file writeable, to ensure flags read-back correctly.
 	fileFD, errno := fsc.OpenFile(preopen, file, experimentalsys.O_RDWR, 0)

imports/wasi_snapshot_preview1/poll.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/tetratelabs/wazero/api"
 	"github.com/tetratelabs/wazero/experimental/sys"
+	"github.com/tetratelabs/wazero/internal/fsapi"
 	internalsys "github.com/tetratelabs/wazero/internal/sys"
 	"github.com/tetratelabs/wazero/internal/wasip1"
 	"github.com/tetratelabs/wazero/internal/wasm"
@@ -177,7 +178,7 @@ func pollOneoffFn(_ context.Context, mod api.Module, params []uint64) sys.Errno
 	}
 	// Wait for the timeout to expire, or for some data to become available on Stdin.
 
-	if stdinReady, errno := stdin.File.Poll(sys.POLLIN, int32(timeout.Milliseconds())); errno != 0 {
+	if stdinReady, errno := stdin.File.Poll(fsapi.POLLIN, int32(timeout.Milliseconds())); errno != 0 {
 		return errno
 	} else if stdinReady {
 		// stdin has data ready to for reading, write back all the events

imports/wasi_snapshot_preview1/poll_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/tetratelabs/wazero"
 	"github.com/tetratelabs/wazero/api"
 	experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
+	"github.com/tetratelabs/wazero/internal/fsapi"
 	"github.com/tetratelabs/wazero/internal/sys"
 	"github.com/tetratelabs/wazero/internal/testing/require"
 	"github.com/tetratelabs/wazero/internal/wasip1"
@@ -161,7 +162,7 @@ func Test_pollOneoff_Stdin(t *testing.T) {
 		name                                   string
 		in, out, nsubscriptions, resultNevents uint32
 		mem                                    []byte // at offset in
-		stdin                                  experimentalsys.File
+		stdin                                  fsapi.File
 		expectedErrno                          wasip1.Errno
 		expectedMem                            []byte // at offset out
 		expectedLog                            string
@@ -442,7 +443,7 @@ func Test_pollOneoff_Stdin(t *testing.T) {
 	}
 }
 
-func setStdin(t *testing.T, mod api.Module, stdin experimentalsys.File) {
+func setStdin(t *testing.T, mod api.Module, stdin fsapi.File) {
 	fsc := mod.(*wasm.ModuleInstance).Sys.FS()
 	f, ok := fsc.LookupFile(sys.FdStdin)
 	require.True(t, ok)
@@ -613,8 +614,8 @@ type neverReadyTtyStdinFile struct {
 }
 
 // Poll implements the same method as documented on sys.File
-func (neverReadyTtyStdinFile) Poll(flag experimentalsys.Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno) {
-	if flag != experimentalsys.POLLIN {
+func (neverReadyTtyStdinFile) Poll(flag fsapi.Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno) {
+	if flag != fsapi.POLLIN {
 		return false, experimentalsys.ENOTSUP
 	}
 	switch {
@@ -632,8 +633,8 @@ type pollStdinFile struct {
 }
 
 // Poll implements the same method as documented on sys.File
-func (p *pollStdinFile) Poll(flag experimentalsys.Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno) {
-	if flag != experimentalsys.POLLIN {
+func (p *pollStdinFile) Poll(flag fsapi.Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno) {
+	if flag != fsapi.POLLIN {
 		return false, experimentalsys.ENOTSUP
 	}
 	return p.ready, 0

imports/wasi_snapshot_preview1/wasi_stdlib_test.go

@@ -20,8 +20,8 @@ import (
 	"github.com/tetratelabs/wazero"
 	"github.com/tetratelabs/wazero/api"
 	experimentalsock "github.com/tetratelabs/wazero/experimental/sock"
-	experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
 	"github.com/tetratelabs/wazero/imports/wasi_snapshot_preview1"
+	"github.com/tetratelabs/wazero/internal/fsapi"
 	"github.com/tetratelabs/wazero/internal/fstest"
 	internalsys "github.com/tetratelabs/wazero/internal/sys"
 	"github.com/tetratelabs/wazero/internal/testing/require"
@@ -329,7 +329,7 @@ func Test_Poll(t *testing.T) {
 	tests := []struct {
 		name            string
 		args            []string
-		stdin           experimentalsys.File
+		stdin           fsapi.File
 		expectedOutput  string
 		expectedTimeout time.Duration
 	}{

internal/fsapi/file.go

@@ -0,0 +1,69 @@
+package fsapi
+
+import experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
+
+// File includes methods not yet ready to document for end users, notably
+// non-blocking functionality.
+//
+// Particularly, Poll is subject to debate. For example, whether a user should
+// be able to choose how to implement timeout or not. Currently, this interface
+// allows the user to choose to sleep or use native polling, and which choice
+// they make impacts thread behavior as summarized here:
+// https://github.com/tetratelabs/wazero/pull/1606#issuecomment-1665475516
+type File interface {
+	experimentalsys.File
+
+	// IsNonblock returns true if the file was opened with O_NONBLOCK, or
+	// SetNonblock was successfully enabled on this file.
+	//
+	// # Notes
+	//
+	//   - This might not match the underlying state of the file descriptor if
+	//     the file was not opened via OpenFile.
+	IsNonblock() bool
+
+	// SetNonblock toggles the non-blocking mode (O_NONBLOCK) of this file.
+	//
+	// # Errors
+	//
+	// A zero Errno is success. The below are expected otherwise:
+	//   - ENOSYS: the implementation does not support this function.
+	//   - EBADF: the file or directory was closed.
+	//
+	// # Notes
+	//
+	//   - This is like syscall.SetNonblock and `fcntl` with O_NONBLOCK in
+	//     POSIX. See https://pubs.opengroup.org/onlinepubs/9699919799/functions/fcntl.html
+	SetNonblock(enable bool) experimentalsys.Errno
+
+	// Poll returns if the file has data ready to be read or written.
+	//
+	// # Parameters
+	//
+	// The `flag` parameter determines which event to await, such as POLLIN,
+	// POLLOUT, or a combination like `POLLIN|POLLOUT`.
+	//
+	// The `timeoutMillis` parameter is how long to block for an event, or
+	// interrupted, in milliseconds. There are two special values:
+	//   - zero returns immediately
+	//   - any negative value blocks any amount of time
+	//
+	// # Results
+	//
+	// `ready` means there was data ready to read or written. False can mean no
+	// event was ready or `errno` is not zero.
+	//
+	// A zero `errno` is success. The below are expected otherwise:
+	//   - ENOSYS: the implementation does not support this function.
+	//   - ENOTSUP: the implementation does not the flag combination.
+	//   - EINTR: the call was interrupted prior to an event.
+	//
+	// # Notes
+	//
+	//   - This is like `poll` in POSIX, for a single file.
+	//     See https://pubs.opengroup.org/onlinepubs/9699919799/functions/poll.html
+	//   - No-op files, such as those which read from /dev/null, should return
+	//     immediately true, as data will never become available.
+	//   - See /RATIONALE.md for detailed notes including impact of blocking.
+	Poll(flag Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno)
+}

experimental/sys/poll.go → internal/fsapi/poll.go

@@ -1,4 +1,4 @@
-package sys
+package fsapi
 
 // Pflag are bit flags used for File.Poll. Values, including zero, should not
 // be interpreted numerically. Instead, use by constants prefixed with 'POLL'.

internal/fsapi/unimplemented.go

@@ -0,0 +1,27 @@
+package fsapi
+
+import experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
+
+func Adapt(f experimentalsys.File) File {
+	if f, ok := f.(File); ok {
+		return f
+	}
+	return unimplementedFile{f}
+}
+
+type unimplementedFile struct{ experimentalsys.File }
+
+// IsNonblock implements File.IsNonblock
+func (unimplementedFile) IsNonblock() bool {
+	return false
+}
+
+// SetNonblock implements File.SetNonblock
+func (unimplementedFile) SetNonblock(bool) experimentalsys.Errno {
+	return experimentalsys.ENOSYS
+}
+
+// Poll implements File.Poll
+func (unimplementedFile) Poll(Pflag, int32) (ready bool, errno experimentalsys.Errno) {
+	return false, experimentalsys.ENOSYS
+}

internal/sys/fs.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/tetratelabs/wazero/experimental/sys"
 	"github.com/tetratelabs/wazero/internal/descriptor"
+	"github.com/tetratelabs/wazero/internal/fsapi"
 	socketapi "github.com/tetratelabs/wazero/internal/sock"
 	"github.com/tetratelabs/wazero/internal/sysfs"
 )
@@ -50,7 +51,7 @@ type FileEntry struct {
 	FS sys.FS
 
 	// File is always non-nil.
-	File sys.File
+	File fsapi.File
 
 	// direntCache is nil until DirentCache was called.
 	direntCache *DirentCache
@@ -287,7 +288,7 @@ func (c *FSContext) OpenFile(fs sys.FS, path string, flag sys.Oflag, perm fs.Fil
 	if f, errno := fs.OpenFile(path, flag, perm); errno != 0 {
 		return 0, errno
 	} else {
-		fe := &FileEntry{FS: fs, File: f}
+		fe := &FileEntry{FS: fs, File: fsapi.Adapt(f)}
 		if path == "/" || path == "." {
 			fe.Name = ""
 		} else {
@@ -339,18 +340,20 @@ func (c *FSContext) SockAccept(sockFD int32, nonblock bool) (int32, sys.Errno) {
 		return 0, sys.EBADF // Not a sock
 	}
 
-	var conn socketapi.TCPConn
-	var errno sys.Errno
-	if conn, errno = sock.Accept(); errno != 0 {
+	conn, errno := sock.Accept()
+	if errno != 0 {
 		return 0, errno
-	} else if nonblock {
-		if errno = conn.SetNonblock(true); errno != 0 {
+	}
+
+	fe := &FileEntry{File: fsapi.Adapt(conn)}
+
+	if nonblock {
+		if errno = fe.File.SetNonblock(true); errno != 0 {
 			_ = conn.Close()
 			return 0, errno
 		}
 	}
 
-	fe := &FileEntry{File: conn}
 	if newFD, ok := c.openedFiles.Insert(fe); !ok {
 		return 0, sys.EBADF
 	} else {
@@ -426,7 +429,7 @@ func (c *Context) InitFSContext(
 	}
 
 	for _, tl := range tcpListeners {
-		c.fsc.openedFiles.Insert(&FileEntry{IsPreopen: true, File: sysfs.NewTCPListenerFile(tl)})
+		c.fsc.openedFiles.Insert(&FileEntry{IsPreopen: true, File: fsapi.Adapt(sysfs.NewTCPListenerFile(tl))})
 	}
 	return nil
 }