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 +1,97 @@
+//go:build windows
+
+package sampledconn
+
+import (
+	"errors"
+	"io"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+const fionbio = 0x8004667e
+
+// updateBlocking updates the blocking mode of the file descriptor.
+// It returns true if the blocking mode was changed, and false if it was already in the desired mode.
+// If an error occurs, it returns the error.
+func updateBlocking(fd windows.Handle, blocking bool) (bool, error) {
+	// Determine the desired mode
+	var desiredMode uint32
+	if !blocking {
+		desiredMode = 1
+	} else {
+		desiredMode = 0
+	}
+
+	// Query the current mode
+	var currentMode uint32
+	err := windows.WSAIoctl(fd, fionbio, (*byte)(unsafe.Pointer(&currentMode)), 4, nil, 0, nil, nil, 0)
+	if err != nil {
+		return false, err
+	}
+
+	if currentMode == desiredMode {
+		return false, nil
+	}
+
+	// Update to the desired mode
+	err = windows.WSAIoctl(fd, fionbio, (*byte)(unsafe.Pointer(&desiredMode)), 4, nil, 0, nil, nil, 0)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func OSPeekConn(conn syscall.Conn) (PeekedBytes, error) {
+	s := PeekedBytes{}
+
+	rawConn, err := conn.SyscallConn()
+	if err != nil {
+		return s, err
+	}
+
+	var updatedBlocking bool
+	ctlErr := rawConn.Control(func(fd uintptr) {
+		updatedBlocking, err = updateBlocking(windows.Handle(fd), true)
+	})
+	if ctlErr != nil {
+		return s, ctlErr
+	}
+	if err != nil {
+		return s, err
+	}
+	if updatedBlocking {
+		defer func() {
+			_ = rawConn.Control(func(fd uintptr) {
+				_, _ = updateBlocking(windows.Handle(fd), false)
+			})
+		}()
+	}
+
+	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
+}