// +build windows
package serial
import (
"fmt"
"os"
"sync"
"syscall"
"time"
"unsafe"
)
type Port struct {
f *os.File
fd syscall.Handle
rl sync.Mutex
wl sync.Mutex
ro *syscall.Overlapped
wo *syscall.Overlapped
}
type structDCB struct {
DCBlength, BaudRate uint32
flags [4]byte
wReserved, XonLim, XoffLim uint16
ByteSize, Parity, StopBits byte
XonChar, XoffChar, ErrorChar, EofChar, EvtChar byte
wReserved1 uint16
}
type structTimeouts struct {
ReadIntervalTimeout uint32
ReadTotalTimeoutMultiplier uint32
ReadTotalTimeoutConstant uint32
WriteTotalTimeoutMultiplier uint32
WriteTotalTimeoutConstant uint32
}
func openPort(name string, baud int, readTimeout time.Duration) (p *Port, err error) {
if len(name) > 0 && name[0] != '\\' {
name = "\\\\.\\" + name
}
h, err := syscall.CreateFile(syscall.StringToUTF16Ptr(name),
syscall.GENERIC_READ|syscall.GENERIC_WRITE,
0,
nil,
syscall.OPEN_EXISTING,
syscall.FILE_ATTRIBUTE_NORMAL|syscall.FILE_FLAG_OVERLAPPED,
0)
if err != nil {
return nil, err
}
f := os.NewFile(uintptr(h), name)
defer func() {
if err != nil {
f.Close()
}
}()
if err = setCommState(h, baud); err != nil {
return
}
if err = setupComm(h, 64, 64); err != nil {
return
}
if err = setCommTimeouts(h, readTimeout); err != nil {
return
}
if err = setCommMask(h); err != nil {
return
}
ro, err := newOverlapped()
if err != nil {
return
}
wo, err := newOverlapped()
if err != nil {
return
}
port := new(Port)
port.f = f
port.fd = h
port.ro = ro
port.wo = wo
return port, nil
}
func (p *Port) Close() error {
return p.f.Close()
}
func (p *Port) Write(buf []byte) (int, error) {
p.wl.Lock()
defer p.wl.Unlock()
if err := resetEvent(p.wo.HEvent); err != nil {
return 0, err
}
var n uint32
err := syscall.WriteFile(p.fd, buf, &n, p.wo)
if err != nil && err != syscall.ERROR_IO_PENDING {
return int(n), err
}
return getOverlappedResult(p.fd, p.wo)
}
func (p *Port) Read(buf []byte) (int, error) {
if p == nil || p.f == nil {
return 0, fmt.Errorf("Invalid port on read %v %v", p, p.f)
}
p.rl.Lock()
defer p.rl.Unlock()
if err := resetEvent(p.ro.HEvent); err != nil {
return 0, err
}
var done uint32
err := syscall.ReadFile(p.fd, buf, &done, p.ro)
if err != nil && err != syscall.ERROR_IO_PENDING {
return int(done), err
}
return getOverlappedResult(p.fd, p.ro)
}
// Discards data written to the port but not transmitted,
// or data received but not read
func (p *Port) Flush() error {
return purgeComm(p.fd)
}
var (
nSetCommState,
nSetCommTimeouts,
nSetCommMask,
nSetupComm,
nGetOverlappedResult,
nCreateEvent,
nResetEvent,
nPurgeComm,
nFlushFileBuffers uintptr
)
func init() {
k32, err := syscall.LoadLibrary("kernel32.dll")
if err != nil {
panic("LoadLibrary " + err.Error())
}
defer syscall.FreeLibrary(k32)
nSetCommState = getProcAddr(k32, "SetCommState")
nSetCommTimeouts = getProcAddr(k32, "SetCommTimeouts")
nSetCommMask = getProcAddr(k32, "SetCommMask")
nSetupComm = getProcAddr(k32, "SetupComm")
nGetOverlappedResult = getProcAddr(k32, "GetOverlappedResult")
nCreateEvent = getProcAddr(k32, "CreateEventW")
nResetEvent = getProcAddr(k32, "ResetEvent")
nPurgeComm = getProcAddr(k32, "PurgeComm")
nFlushFileBuffers = getProcAddr(k32, "FlushFileBuffers")
}
func getProcAddr(lib syscall.Handle, name string) uintptr {
addr, err := syscall.GetProcAddress(lib, name)
if err != nil {
panic(name + " " + err.Error())
}
return addr
}
func setCommState(h syscall.Handle, baud int) error {
var params structDCB
params.DCBlength = uint32(unsafe.Sizeof(params))
params.flags[0] = 0x01 // fBinary
params.flags[0] |= 0x10 // Assert DSR
params.BaudRate = uint32(baud)
params.ByteSize = 8
r, _, err := syscall.Syscall(nSetCommState, 2, uintptr(h), uintptr(unsafe.Pointer(¶ms)), 0)
if r == 0 {
return err
}
return nil
}
func setCommTimeouts(h syscall.Handle, readTimeout time.Duration) error {
var timeouts structTimeouts
const MAXDWORD = 1<<32 - 1
// blocking read by default
var timeoutMs int64 = MAXDWORD - 1
if readTimeout > 0 {
// non-blocking read
timeoutMs = readTimeout.Nanoseconds() / 1e6
if timeoutMs < 1 {
timeoutMs = 1
} else if timeoutMs > MAXDWORD-1 {
timeoutMs = MAXDWORD - 1
}
}
/* From http://msdn.microsoft.com/en-us/library/aa363190(v=VS.85).aspx
For blocking I/O see below:
Remarks:
If an application sets ReadIntervalTimeout and
ReadTotalTimeoutMultiplier to MAXDWORD and sets
ReadTotalTimeoutConstant to a value greater than zero and
less than MAXDWORD, one of the following occurs when the
ReadFile function is called:
If there are any bytes in the input buffer, ReadFile returns
immediately with the bytes in the buffer.
If there are no bytes in the input buffer, ReadFile waits
until a byte arrives and then returns immediately.
If no bytes arrive within the time specified by
ReadTotalTimeoutConstant, ReadFile times out.
*/
timeouts.ReadIntervalTimeout = MAXDWORD
timeouts.ReadTotalTimeoutMultiplier = MAXDWORD
timeouts.ReadTotalTimeoutConstant = uint32(timeoutMs)
r, _, err := syscall.Syscall(nSetCommTimeouts, 2, uintptr(h), uintptr(unsafe.Pointer(&timeouts)), 0)
if r == 0 {
return err
}
return nil
}
func setupComm(h syscall.Handle, in, out int) error {
r, _, err := syscall.Syscall(nSetupComm, 3, uintptr(h), uintptr(in), uintptr(out))
if r == 0 {
return err
}
return nil
}
func setCommMask(h syscall.Handle) error {
const EV_RXCHAR = 0x0001
r, _, err := syscall.Syscall(nSetCommMask, 2, uintptr(h), EV_RXCHAR, 0)
if r == 0 {
return err
}
return nil
}
func resetEvent(h syscall.Handle) error {
r, _, err := syscall.Syscall(nResetEvent, 1, uintptr(h), 0, 0)
if r == 0 {
return err
}
return nil
}
func purgeComm(h syscall.Handle) error {
const PURGE_TXABORT = 0x0001
const PURGE_RXABORT = 0x0002
const PURGE_TXCLEAR = 0x0004
const PURGE_RXCLEAR = 0x0008
r, _, err := syscall.Syscall(nPurgeComm, 2, uintptr(h),
PURGE_TXABORT|PURGE_RXABORT|PURGE_TXCLEAR|PURGE_RXCLEAR, 0)
if r == 0 {
return err
}
return nil
}
func newOverlapped() (*syscall.Overlapped, error) {
var overlapped syscall.Overlapped
r, _, err := syscall.Syscall6(nCreateEvent, 4, 0, 1, 0, 0, 0, 0)
if r == 0 {
return nil, err
}
overlapped.HEvent = syscall.Handle(r)
return &overlapped, nil
}
func getOverlappedResult(h syscall.Handle, overlapped *syscall.Overlapped) (int, error) {
var n int
r, _, err := syscall.Syscall6(nGetOverlappedResult, 4,
uintptr(h),
uintptr(unsafe.Pointer(overlapped)),
uintptr(unsafe.Pointer(&n)), 1, 0, 0)
if r == 0 {
return n, err
}
return n, nil
}