From 3351cd50e044ef9fb7a3bced9067345b31396459 Mon Sep 17 00:00:00 2001
From: Cristian Maglie <c.maglie@bug.st>
Date: Sun, 14 Dec 2014 18:38:44 +0100
Subject: [PATCH] Added SetDataBits function (linux only for now)

---
 serial.go           |  6 ++++++
 serial_linux.go     | 21 +++++++++++++++++++++
 test/serial_test.go |  3 +++
 3 files changed, 30 insertions(+)

diff --git a/serial.go b/serial.go
index 6c933a0..e205b53 100644
--- a/serial.go
+++ b/serial.go
@@ -20,6 +20,9 @@ type SerialPort interface {
 
 	// Set port parity
 	SetParity(parity Parity) error
+
+	// Set data bits
+	SetDataBits(bits int) error
 }
 
 type Parity int
@@ -44,6 +47,7 @@ const (
 	ERROR_INVALID_SERIAL_PORT
 	ERROR_PERMISSION_DENIED
 	ERROR_INVALID_PORT_SPEED
+	ERROR_INVALID_PORT_DATA_BITS
 	ERROR_ENUMERATING_PORTS
 	ERROR_OTHER
 )
@@ -60,6 +64,8 @@ func (e SerialPortError) Error() string {
 		return "Permission denied"
 	case ERROR_INVALID_PORT_SPEED:
 		return "Invalid port speed"
+	case ERROR_INVALID_PORT_DATA_BITS:
+		return "Invalid port data bits"
 	case ERROR_ENUMERATING_PORTS:
 		return "Could not enumerate serial ports"
 	}
diff --git a/serial_linux.go b/serial_linux.go
index 264a7eb..55da7a5 100644
--- a/serial_linux.go
+++ b/serial_linux.go
@@ -245,6 +245,27 @@ func (port *linuxSerialPort) SetParity(parity Parity) error {
 	return setTermSettings(port.Handle, settings)
 }
 
+var databitsMap = map[int]C.tcflag_t{
+	5: C.CS5,
+	6: C.CS6,
+	7: C.CS7,
+	8: C.CS8,
+}
+
+func (port *linuxSerialPort) SetDataBits(bits int) error {
+	databits, ok := databitsMap[bits]
+	if !ok {
+		return &SerialPortError{code: ERROR_INVALID_PORT_DATA_BITS}
+	}
+	settings, err := getTermSettings(port.Handle)
+	if err != nil {
+		return err
+	}
+	settings.c_cflag &= ^C.tcflag_t(syscall.CSIZE)
+	settings.c_cflag |= databits
+	return setTermSettings(port.Handle, settings)
+}
+
 func OpenPort(portName string, exclusive bool) (SerialPort, error) {
 	handle, err := syscall.Open(portName, syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_NDELAY, 0)
 	if err != nil {
diff --git a/test/serial_test.go b/test/serial_test.go
index 15d29d4..eb5a97c 100644
--- a/test/serial_test.go
+++ b/test/serial_test.go
@@ -33,6 +33,9 @@ func ExampleCommunication() {
 	if err := port.SetParity(serial.PARITY_NONE); err != nil {
 		log.Fatal(err)
 	}
+	if err := port.SetDataBits(8); err != nil {
+		log.Fatal(err)
+	}
 
 	n, err := port.Write([]byte("10,20,30\n\r"))
 	if err != nil {