net: add FileListener for WASI

Signed-off-by: Roman Volosatovs <roman@profian.com>

Author: rvolosatovs

src/net/fd_wasi.go

@@ -4,7 +4,6 @@
 package net
 
 import (
-	"io"
 	"os"
 	"syscall"
 	"time"
@@ -21,13 +20,13 @@ type netFD struct {
 
 // Read implements the Conn Read method.
 func (c *netFD) Read(b []byte) (int, error) {
-    // TODO: Handle EAGAIN and perform poll
+	// TODO: Handle EAGAIN and perform poll
 	return c.File.Read(b)
 }
 
 // Write implements the Conn Write method.
 func (c *netFD) Write(b []byte) (int, error) {
-    // TODO: Handle EAGAIN and perform poll
+	// TODO: Handle EAGAIN and perform poll
 	return c.File.Write(b)
 }
 
@@ -55,3 +54,25 @@ func (*netFD) SetReadDeadline(t time.Time) error {
 func (*netFD) SetWriteDeadline(t time.Time) error {
 	return ErrNotImplemented
 }
+
+type listener struct {
+	*os.File
+}
+
+// Accept implements the Listener Accept method.
+func (l *listener) Accept() (Conn, error) {
+	fd, err := syscall.SockAccept(int(l.File.Fd()), syscall.O_NONBLOCK)
+	if err != nil {
+		return nil, wrapSyscallError("sock_accept", err)
+	}
+	return &netFD{File: os.NewFile(uintptr(fd), "conn"), net: "file+net", laddr: nil, raddr: nil}, nil
+}
+
+// Addr implements the Listener Addr method.
+func (*listener) Addr() Addr {
+	return nil
+}
+
+func fileListener(f *os.File) (Listener, error) {
+	return &listener{File: f}, nil
+}

src/net/file.go

@@ -0,0 +1,31 @@
+//go:build wasi
+// +build wasi
+
+// The following is copied from Go 1.18 official implementation.
+
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+)
+
+type fileAddr string
+
+func (fileAddr) Network() string  { return "file+net" }
+func (f fileAddr) String() string { return string(f) }
+
+// FileListener returns a copy of the network listener corresponding
+// to the open file f.
+// It is the caller's responsibility to close ln when finished.
+// Closing ln does not affect f, and closing f does not affect ln.
+func FileListener(f *os.File) (ln Listener, err error) {
+	ln, err = fileListener(f)
+	if err != nil {
+		err = &OpError{Op: "file", Net: "file+net", Source: nil, Addr: fileAddr(f.Name()), Err: err}
+	}
+	return
+}