refactor(sampledconn): Add Windows OSPeekConn impl

p2p/transport/tcpreuse/internal/sampledconn/sampledconn_other.go

@@ -1,4 +1,4 @@
-//go:build !unix
+//go:build !unix && !windows
 
 package sampledconn
 

p2p/transport/tcpreuse/internal/sampledconn/sampledconn_windows.go

@@ -0,0 +1,44 @@
+//go:build windows
+
+package sampledconn
+
+import (
+	"errors"
+	"io"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+func OSPeekConn(conn syscall.Conn) (PeekedBytes, error) {
+	s := PeekedBytes{}
+
+	rawConn, err := conn.SyscallConn()
+	if err != nil {
+		return s, err
+	}
+
+	var readErr error
+	var n uint32
+	err = rawConn.Read(func(fd uintptr) bool {
+		flags := uint32(windows.MSG_PEEK | windows.MSG_WAITALL)
+		wsabuf := windows.WSABuf{
+			Len: uint32(len(s)),
+			Buf: &s[0],
+		}
+
+		readErr = windows.WSARecv(windows.Handle(fd), &wsabuf, 1, &n, &flags, nil, nil)
+		return !errors.Is(readErr, windows.WSAEWOULDBLOCK)
+	})
+	if err != nil {
+		return s, err
+	}
+	if readErr != nil {
+		return s, readErr
+	}
+	if n < peekSize {
+		return s, io.EOF
+	}
+
+	return s, nil
+}