Uses time.Duration for ReadTimeout now

- Replaced uint32 with time.Duration for consistency
- Updated README describing ReadTimeout is Total Timeout
- Merged duplicated logic to a common function posixTimeoutValues
- Set ReadIntervalTimeout on Windows to 0

README.md

@@ -60,16 +60,18 @@ func main() {
 
 NonBlocking Mode
 ----------------
-By default goserial reads in blocking mode. Which means Read() will
+By default goserial reads in blocking mode. Which means `Read()` will
 block until at least one byte is returned. If that's not what you want,
-specify a ReadTimeout in milliseconds and the Read() will timeout
-returning 0 bytes if no bytes are read.
+specify a positive ReadTimeout and the Read() will timeout returning 0
+bytes if no bytes are read.
+Please note that this is the total timeout the read operation will wait
+and not the interval timeout between two bytes.
 
 ```go
-	c := &serial.Config{Name: "COM45", Baud: 115200, ReadTimeout: 1000}
+	c := &serial.Config{Name: "COM45", Baud: 115200, ReadTimeout: time.Second * 5}
 
 	// In this mode, you will want to suppress error for read
-	// as 0 bytes returns EOF error on Linux / POSIX
+	// as 0 bytes return EOF error on Linux / POSIX
 	n, _ = s.Read(buf)
 ```
 

serial.go

@@ -55,7 +55,10 @@ Example usage:
 */
 package serial
 
-import "io"
+import (
+	"io"
+	"time"
+)
 
 // Config contains the information needed to open a serial port.
 //
@@ -65,16 +68,17 @@ import "io"
 //
 // For example:
 //
-//    c0 := &serial.Config{Name: "COM45", Baud: 115200, ReadTimeout: 1000}
+//    c0 := &serial.Config{Name: "COM45", Baud: 115200, ReadTimeout: time.Millisecond * 500}
 // or
 //    c1 := new(serial.Config)
 //    c1.Name = "/dev/tty.usbserial"
 //    c1.Baud = 115200
-//    c1.ReadTimeout = 1000
+//    c1.ReadTimeout = time.Millisecond * 500
 //
 type Config struct {
-	Name string
-	Baud int
+	Name        string
+	Baud        int
+	ReadTimeout time.Duration // Total timeout
 
 	// Size     int // 0 get translated to 8
 	// Parity   SomeNewTypeToGetCorrectDefaultOf_None
@@ -85,14 +89,38 @@ type Config struct {
 	// XONFlowControl bool
 
 	// CRLFTranslate bool
-	ReadTimeout uint32
 }
 
 // OpenPort opens a serial port with the specified configuration
 func OpenPort(c *Config) (io.ReadWriteCloser, error) {
 	return openPort(c.Name, c.Baud, c.ReadTimeout)
 }
 
+// Converts the timeout values for Linux / POSIX systems
+func posixTimeoutValues(readTimeout time.Duration) (vmin uint8, vtime uint8) {
+	const MAXUINT8 = 1<<8 - 1 // 255
+	// set blocking / non-blocking read
+	var minBytesToRead uint8 = 1
+	var readTimeoutInDeci uint8 = 0
+	if readTimeout > 0 {
+		// EOF on zero read
+		minBytesToRead = 0
+		timeoutMs := uint32(readTimeout.Nanoseconds() / 1e6)
+		// capping the timeout
+		if timeoutMs < 100 {
+			// min possible timeout 1 Deciseconds (0.1s)
+			readTimeoutInDeci = 1
+		} else if timeoutMs > (MAXUINT8 * 100) {
+			// max possible timeout is 255 Deciseconds (25.5s)
+			readTimeoutInDeci = MAXUINT8
+		} else {
+			// convert milliseconds to deciseconds as expected by VTIME
+			readTimeoutInDeci = uint8(timeoutMs / 100)
+		}
+	}
+	return minBytesToRead, readTimeoutInDeci
+}
+
 // func Flush()
 
 // func SendBreak()

serial_linux.go

@@ -6,10 +6,11 @@ import (
 	"io"
 	"os"
 	"syscall"
+	"time"
 	"unsafe"
 )
 
-func openPort(name string, baud int, readTimeout uint32) (rwc io.ReadWriteCloser, err error) {
+func openPort(name string, baud int, readTimeout time.Duration) (rwc io.ReadWriteCloser, err error) {
 
 	var bauds = map[int]uint32{
 		50:      syscall.B50,
@@ -62,26 +63,11 @@ func openPort(name string, baud int, readTimeout uint32) (rwc io.ReadWriteCloser
 	}()
 
 	fd := f.Fd()
-	// set blocking / non-blocking read
-	var minBytesToRead uint8 = 1
-	if readTimeout > 0 {
-		// EOF on zero read
-		minBytesToRead = 0
-		// capping the timeout
-		if readTimeout < 100 {
-			// min possible timeout
-			readTimeout = 100
-		} else if readTimeout > 25500 {
-			// max possible timeout
-			readTimeout = 25500
-		}
-		// convert milliseconds to deciseconds as expected by VTIME
-		readTimeout = readTimeout / 100
-	}
+	vmin, vtime := posixTimeoutValues(readTimeout)
 	t := syscall.Termios{
 		Iflag:  syscall.IGNPAR,
 		Cflag:  syscall.CS8 | syscall.CREAD | syscall.CLOCAL | rate,
-		Cc:     [32]uint8{syscall.VMIN: minBytesToRead, syscall.VTIME: uint8(readTimeout)},
+		Cc:     [32]uint8{syscall.VMIN: vmin, syscall.VTIME: vtime},
 		Ispeed: rate,
 		Ospeed: rate,
 	}

serial_posix.go

@@ -14,10 +14,11 @@ import (
 	"io"
 	"os"
 	"syscall"
+	"time"
 	//"unsafe"
 )
 
-func openPort(name string, baud int, readTimeout uint32) (rwc io.ReadWriteCloser, err error) {
+func openPort(name string, baud int, readTimeout time.Duration) (rwc io.ReadWriteCloser, err error) {
 	f, err := os.OpenFile(name, syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_NONBLOCK, 0666)
 	if err != nil {
 		return
@@ -83,23 +84,9 @@ func openPort(name string, baud int, readTimeout uint32) (rwc io.ReadWriteCloser
 	*	http://man7.org/linux/man-pages/man3/termios.3.html
 	* - Supports blocking read and read with timeout operations
 	 */
-	var minBytesToRead uint8 = 1
-	if readTimeout > 0 {
-		// EOF on zero read
-		minBytesToRead = 0
-		// capping the timeout
-		if readTimeout < 100 {
-			// min possible timeout
-			readTimeout = 100
-		} else if readTimeout > 25500 {
-			// max possible timeout
-			readTimeout = 25500
-		}
-		// convert milliseconds to deciseconds as expected by VTIME
-		readTimeout = readTimeout / 100
-	}
-	st.c_cc[C.VMIN] = C.cc_t(minBytesToRead)
-	st.c_cc[C.VTIME] = C.cc_t(readTimeout)
+	vmin, vtime := posixTimeoutValues(readTimeout)
+	st.c_cc[C.VMIN] = C.cc_t(vmin)
+	st.c_cc[C.VTIME] = C.cc_t(vtime)
 
 	_, err = C.tcsetattr(fd, C.TCSANOW, &st)
 	if err != nil {

serial_windows.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"sync"
 	"syscall"
+	"time"
 	"unsafe"
 )
 
@@ -37,7 +38,7 @@ type structTimeouts struct {
 	WriteTotalTimeoutConstant   uint32
 }
 
-func openPort(name string, baud int, readTimeout uint32) (rwc io.ReadWriteCloser, err error) {
+func openPort(name string, baud int, readTimeout time.Duration) (rwc io.ReadWriteCloser, err error) {
 	if len(name) > 0 && name[0] != '\\' {
 		name = "\\\\.\\" + name
 	}
@@ -178,14 +179,16 @@ func setCommState(h syscall.Handle, baud int) error {
 	return nil
 }
 
-func setCommTimeouts(h syscall.Handle, readTimeout uint32) error {
+func setCommTimeouts(h syscall.Handle, readTimeout time.Duration) error {
 	var timeouts structTimeouts
 	const MAXDWORD = 1<<32 - 1
-	if readTimeout > 0 {
+	timeoutMs := uint32(readTimeout.Nanoseconds() / 1e6)
+
+	if timeoutMs > 0 {
 		// non-blocking read
-		timeouts.ReadIntervalTimeout = 1000
+		timeouts.ReadIntervalTimeout = 0
 		timeouts.ReadTotalTimeoutMultiplier = 0
-		timeouts.ReadTotalTimeoutConstant = readTimeout
+		timeouts.ReadTotalTimeoutConstant = timeoutMs
 	} else {
 		// blocking read
 		timeouts.ReadIntervalTimeout = MAXDWORD