From 1b32e598713681cbac2986178ce88fe926d32190 Mon Sep 17 00:00:00 2001
From: Frank Palazzolo <frank@avoidspikes.com>
Date: Mon, 14 Nov 2022 08:58:11 -0500
Subject: [PATCH 1/2] Remove unnecessary code, originally for checking
 disconnects

The old code is no more needed when using overlapped I/O,
getOverlappedEvent() returns all required error codes.

Calling getCommState()/setCommState() every second in some
applications contributes to other downstream issues. For examples:

https://github.com/bugst/go-serial/issues/60#issuecomment-625749122
https://github.com/arduino/arduino-ide/issues/375
---
 serial_windows.go | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/serial_windows.go b/serial_windows.go
index 4b652b5..96b021c 100644
--- a/serial_windows.go
+++ b/serial_windows.go
@@ -114,17 +114,6 @@ func (port *windowsPort) Read(p []byte) (int, error) {
 				return 0, nil
 			}
 		}
-
-		// At the moment it seems that the only reliable way to check if
-		// a serial port is alive in Windows is to check if the SetCommState
-		// function fails.
-
-		params := &dcb{}
-		getCommState(port.handle, params)
-		if err := setCommState(port.handle, params); err != nil {
-			port.Close()
-			return 0, err
-		}
 	}
 }
 

From 5d3a516f129c780bbacec69cdb4caf06de49a1b7 Mon Sep 17 00:00:00 2001
From: Cristian Maglie <c.maglie@bug.st>
Date: Thu, 24 Nov 2022 17:14:03 +0100
Subject: [PATCH 2/2] Removed port-alive-check loop on Windows implementation

---
 serial_windows.go | 81 +++++++++++++++++++----------------------------
 1 file changed, 33 insertions(+), 48 deletions(-)

diff --git a/serial_windows.go b/serial_windows.go
index 96b021c..1a3db7a 100644
--- a/serial_windows.go
+++ b/serial_windows.go
@@ -24,9 +24,8 @@ import (
 )
 
 type windowsPort struct {
-	mu                sync.Mutex
-	handle            syscall.Handle
-	readTimeoutCycles int64
+	mu     sync.Mutex
+	handle syscall.Handle
 }
 
 func nativeGetPortsList() ([]string, error) {
@@ -83,38 +82,26 @@ func (port *windowsPort) Read(p []byte) (int, error) {
 	}
 	defer syscall.CloseHandle(ev.HEvent)
 
-	cycles := int64(0)
-	for {
-		err := syscall.ReadFile(port.handle, p, &readed, ev)
-		if err == syscall.ERROR_IO_PENDING {
-			err = getOverlappedResult(port.handle, ev, &readed, true)
-		}
-		switch err {
-		case nil:
-			// operation completed successfully
-		case syscall.ERROR_OPERATION_ABORTED:
-			// port may have been closed
-			return int(readed), &PortError{code: PortClosed, causedBy: err}
-		default:
-			// error happened
-			return int(readed), err
-		}
-
-		if readed > 0 {
-			return int(readed), nil
-		}
-		if err := resetEvent(ev.HEvent); err != nil {
-			return 0, err
-		}
-
-		if port.readTimeoutCycles != -1 {
-			cycles++
-			if cycles == port.readTimeoutCycles {
-				// Timeout
-				return 0, nil
-			}
-		}
+	err = syscall.ReadFile(port.handle, p, &readed, ev)
+	if err == syscall.ERROR_IO_PENDING {
+		err = getOverlappedResult(port.handle, ev, &readed, true)
 	}
+	switch err {
+	case nil:
+		// operation completed successfully
+	case syscall.ERROR_OPERATION_ABORTED:
+		// port may have been closed
+		return int(readed), &PortError{code: PortClosed, causedBy: err}
+	default:
+		// error happened
+		return int(readed), err
+	}
+	if readed > 0 {
+		return int(readed), nil
+	}
+
+	// Timeout
+	return 0, nil
 }
 
 func (port *windowsPort) Write(p []byte) (int, error) {
@@ -372,26 +359,24 @@ func (port *windowsPort) GetModemStatusBits() (*ModemStatusBits, error) {
 }
 
 func (port *windowsPort) SetReadTimeout(timeout time.Duration) error {
-	var cycles, cycleDuration int64
-	if timeout == NoTimeout {
-		cycles = -1
-		cycleDuration = 1000
-	} else {
-		cycles = timeout.Milliseconds()/1000 + 1
-		cycleDuration = timeout.Milliseconds() / cycles
-	}
-
-	err := setCommTimeouts(port.handle, &commTimeouts{
+	commTimeouts := &commTimeouts{
 		ReadIntervalTimeout:         0xFFFFFFFF,
 		ReadTotalTimeoutMultiplier:  0xFFFFFFFF,
-		ReadTotalTimeoutConstant:    uint32(cycleDuration),
+		ReadTotalTimeoutConstant:    0xFFFFFFFE,
 		WriteTotalTimeoutConstant:   0,
 		WriteTotalTimeoutMultiplier: 0,
-	})
-	if err != nil {
+	}
+	if timeout != NoTimeout {
+		ms := timeout.Milliseconds()
+		if ms > 0xFFFFFFFE || ms < 0 {
+			return &PortError{code: InvalidTimeoutValue}
+		}
+		commTimeouts.ReadTotalTimeoutConstant = uint32(ms)
+	}
+
+	if err := setCommTimeouts(port.handle, commTimeouts); err != nil {
 		return &PortError{code: InvalidTimeoutValue, causedBy: err}
 	}
-	port.readTimeoutCycles = cycles
 
 	return nil
 }