Personal warehouse management system
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package ql
import (
"errors"
"image"
"io"
"os"
"path/filepath"
"syscall"
"time"
"unsafe"
)
// #include <linux/ioctl.h>
import "C"
// -----------------------------------------------------------------------------
func _IOC(dir, typ, nr, size int) uintptr {
return (uintptr(dir) << C._IOC_DIRSHIFT) |
(uintptr(typ) << C._IOC_TYPESHIFT) |
(uintptr(nr) << C._IOC_NRSHIFT) |
(uintptr(size) << C._IOC_SIZESHIFT)
}
const (
iocnrGetDeviceID = 1
)
// lpiocGetDeviceID reads the IEEE-1284 Device ID string of a printer.
func lpiocGetDeviceID(fd uintptr) ([]byte, error) {
var buf [1024]byte
if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd,
_IOC(C._IOC_READ, 'P', iocnrGetDeviceID, len(buf)),
uintptr(unsafe.Pointer(&buf))); err != 0 {
return nil, err
}
// In theory it might get trimmed along the way.
length := int(buf[0])<<8 | int(buf[1])
if 2+length > len(buf) {
return buf[2:], errors.New("the device ID string got trimmed")
}
return buf[2 : 2+length], nil
}
// -----------------------------------------------------------------------------
type Printer struct {
File *os.File
Manufacturer string
Model string
LastStatus *Status
MediaInfo *MediaInfo
// StatusNotify is called whenever we receive a status packet.
StatusNotify func(*Status)
}
// Open finds and initializes the first USB printer found supporting
// the appropriate protocol. Returns nil if no printer could be found.
func Open() (*Printer, error) {
// Linux usblp module, located in /drivers/usb/class/usblp.c
paths, err := filepath.Glob("/dev/usb/lp[0-9]*")
if err != nil {
return nil, err
}
for _, candidate := range paths {
f, err := os.OpenFile(candidate, os.O_RDWR, 0)
if err != nil {
continue
}
// Filter out obvious non-printers.
deviceID, err := lpiocGetDeviceID(f.Fd())
if err != nil {
f.Close()
continue
}
parsedID := parseIEEE1284DeviceID(deviceID)
// Filter out printers that wouldn't understand the protocol.
if !compatible(parsedID) {
f.Close()
continue
}
return &Printer{
File: f,
Manufacturer: parsedID.FindFirst("MANUFACTURER", "MFG"),
Model: parsedID.FindFirst("MODEL", "MDL"),
}, nil
}
return nil, nil
}
// Initialize initializes the printer for further operations.
func (p *Printer) Initialize() error {
// Clear the print buffer.
invalidate := make([]byte, 400)
if _, err := p.File.Write(invalidate); err != nil {
return err
}
// Initialize.
if _, err := p.File.WriteString("\x1b\x40"); err != nil {
return err
}
// Flush any former responses in the printer's queue.
//
// I haven't checked if this is the kernel driver or the printer doing
// the buffering that causes data to be returned at this point.
var dummy [32]byte
for {
if _, err := p.File.Read(dummy[:]); err == io.EOF {
break
}
}
return nil
}
var errTimeout = errors.New("timeout")
var errInvalidRead = errors.New("invalid read")
func (p *Printer) updateStatus(status Status) {
p.LastStatus = &status
if p.StatusNotify != nil {
p.StatusNotify(p.LastStatus)
}
}
// pollStatusBytes waits for the printer to send a status packet and returns
// it as raw data.
func (p *Printer) pollStatusBytes(
timeout time.Duration) (*Status, error) {
start, buf := time.Now(), [32]byte{}
for {
if n, err := p.File.Read(buf[:]); err == io.EOF {
time.Sleep(10 * time.Millisecond)
} else if err != nil {
return nil, err
} else if n < 32 {
return nil, errInvalidRead
} else {
p.updateStatus(Status(buf))
return p.LastStatus, nil
}
if time.Now().Sub(start) > timeout {
return nil, errTimeout
}
}
}
// Request new status information from the printer. The printer
// must be in an appropriate mode, i.e. on-line and not currently printing.
func (p *Printer) UpdateStatus() error {
// Request status information.
if _, err := p.File.WriteString("\x1b\x69\x53"); err != nil {
return err
}
// Retrieve status information.
if _, err := p.pollStatusBytes(time.Second); err != nil {
p.LastStatus = nil
return err
}
return nil
}
var errErrorOccurred = errors.New("error occurred")
var errUnexpectedStatus = errors.New("unexpected status")
var errUnknownMedia = errors.New("unknown media")
func (p *Printer) Print(image image.Image, rb bool) error {
data := makePrintData(p.LastStatus, image, rb)
if data == nil {
return errUnknownMedia
}
if _, err := p.File.Write(data); err != nil {
return err
}
// See diagrams: we may receive an error status instead of the transition
// to the printing state. Or even after it.
//
// Not sure how exactly cooling behaves and I don't want to test it.
for {
status, err := p.pollStatusBytes(10 * time.Second)
if err != nil {
return err
}
switch status.Type() {
case StatusTypePhaseChange:
// Nothing to do.
case StatusTypePrintingCompleted:
return nil
case StatusTypeErrorOccurred:
return errErrorOccurred
default:
return errUnexpectedStatus
}
}
}
// Close closes the underlying file.
func (p *Printer) Close() error {
return p.File.Close()
}