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package xgb
import (
"errors"
"io"
"log"
"net"
"os"
"sync"
)
var (
// Where to log error-messages. Defaults to stderr.
// To disable logging, just set this to log.New(ioutil.Discard, "", 0)
Logger = log.New(os.Stderr, "XGB: ", log.Lshortfile)
// ExtLock is a lock used whenever new extensions are initialized.
// It should not be used. It is exported for use in the extension
// sub-packages.
ExtLock sync.Mutex
)
const (
// cookieBuffer represents the queue size of cookies existing at any
// point in time. The size of the buffer is really only important when
// there are many requests without replies made in sequence. Once the
// buffer fills, a round trip request is made to clear the buffer.
cookieBuffer = 1000
// xidBuffer represents the queue size of the xid channel.
// I don't think this value matters much, since xid generation is not
// that expensive.
xidBuffer = 5
// seqBuffer represents the queue size of the sequence number channel.
// I don't think this value matters much, since sequence number generation
// is not that expensive.
seqBuffer = 5
// reqBuffer represents the queue size of the number of requests that
// can be made until new ones block. This value seems OK.
reqBuffer = 100
// eventBuffer represents the queue size of the number of events or errors
// that can be loaded off the wire and not grabbed with WaitForEvent
// until reading an event blocks. This value should be big enough to handle
// bursts of events.
eventBuffer = 5000
)
// A Conn represents a connection to an X server.
type Conn struct {
host string
conn net.Conn
display string
DisplayNumber int
DefaultScreen int
SetupBytes []byte
setupResourceIdBase uint32
setupResourceIdMask uint32
eventChan chan eventOrError
cookieChan chan *Cookie
xidChan chan xid
seqChan chan uint16
reqChan chan *request
closing chan chan struct{}
// Extensions is a map from extension name to major opcode. It should
// not be used. It is exported for use in the extension sub-packages.
Extensions map[string]byte
}
// NewConn creates a new connection instance. It initializes locks, data
// structures, and performs the initial handshake. (The code for the handshake
// has been relegated to conn.go.)
func NewConn() (*Conn, error) {
return NewConnDisplay("")
}
// NewConnDisplay is just like NewConn, but allows a specific DISPLAY
// string to be used.
// If 'display' is empty it will be taken from os.Getenv("DISPLAY").
//
// Examples:
// NewConn(":1") -> net.Dial("unix", "", "/tmp/.X11-unix/X1")
// NewConn("/tmp/launch-12/:0") -> net.Dial("unix", "", "/tmp/launch-12/:0")
// NewConn("hostname:2.1") -> net.Dial("tcp", "", "hostname:6002")
// NewConn("tcp/hostname:1.0") -> net.Dial("tcp", "", "hostname:6001")
func NewConnDisplay(display string) (*Conn, error) {
conn := &Conn{}
// First connect. This reads authority, checks DISPLAY environment
// variable, and loads the initial Setup info.
err := conn.connect(display)
if err != nil {
return nil, err
}
return postNewConn(conn)
}
// NewConnDisplay is just like NewConn, but allows a specific net.Conn
// to be used.
func NewConnNet(netConn net.Conn) (*Conn, error) {
conn := &Conn{}
// First connect. This reads authority, checks DISPLAY environment
// variable, and loads the initial Setup info.
err := conn.connectNet(netConn)
if err != nil {
return nil, err
}
return postNewConn(conn)
}
func postNewConn(conn *Conn) (*Conn, error) {
conn.Extensions = make(map[string]byte)
conn.cookieChan = make(chan *Cookie, cookieBuffer)
conn.xidChan = make(chan xid, xidBuffer)
conn.seqChan = make(chan uint16, seqBuffer)
conn.reqChan = make(chan *request, reqBuffer)
conn.eventChan = make(chan eventOrError, eventBuffer)
conn.closing = make(chan chan struct{}, 1)
go conn.generateXIds()
go conn.generateSeqIds()
go conn.sendRequests()
go conn.readResponses()
return conn, nil
}
// Close gracefully closes the connection to the X server.
func (c *Conn) Close() {
close(c.reqChan)
}
// Event is an interface that can contain any of the events returned by the
// server. Use a type assertion switch to extract the Event structs.
type Event interface {
Bytes() []byte
String() string
}
// NewEventFun is the type of function use to construct events from raw bytes.
// It should not be used. It is exported for use in the extension sub-packages.
type NewEventFun func(buf []byte) Event
// NewEventFuncs is a map from event numbers to functions that create
// the corresponding event. It should not be used. It is exported for use
// in the extension sub-packages.
var NewEventFuncs = make(map[int]NewEventFun)
// NewExtEventFuncs is a temporary map that stores event constructor functions
// for each extension. When an extension is initialized, each event for that
// extension is added to the 'NewEventFuncs' map. It should not be used. It is
// exported for use in the extension sub-packages.
var NewExtEventFuncs = make(map[string]map[int]NewEventFun)
// Error is an interface that can contain any of the errors returned by
// the server. Use a type assertion switch to extract the Error structs.
type Error interface {
SequenceId() uint16
BadId() uint32
Error() string
}
// NewErrorFun is the type of function use to construct errors from raw bytes.
// It should not be used. It is exported for use in the extension sub-packages.
type NewErrorFun func(buf []byte) Error
// NewErrorFuncs is a map from error numbers to functions that create
// the corresponding error. It should not be used. It is exported for use in
// the extension sub-packages.
var NewErrorFuncs = make(map[int]NewErrorFun)
// NewExtErrorFuncs is a temporary map that stores error constructor functions
// for each extension. When an extension is initialized, each error for that
// extension is added to the 'NewErrorFuncs' map. It should not be used. It is
// exported for use in the extension sub-packages.
var NewExtErrorFuncs = make(map[string]map[int]NewErrorFun)
// eventOrError corresponds to values that can be either an event or an
// error.
type eventOrError interface{}
// NewId generates a new unused ID for use with requests like CreateWindow.
// If no new ids can be generated, the id returned is 0 and error is non-nil.
// This shouldn't be used directly, and is exported for use in the extension
// sub-packages.
// If you need identifiers, use the appropriate constructor.
// e.g., For a window id, use xproto.NewWindowId. For
// a new pixmap id, use xproto.NewPixmapId. And so on.
func (c *Conn) NewId() (uint32, error) {
xid := <-c.xidChan
if xid.err != nil {
return 0, xid.err
}
return xid.id, nil
}
// xid encapsulates a resource identifier being sent over the Conn.xidChan
// channel. If no new resource id can be generated, id is set to 0 and a
// non-nil error is set in xid.err.
type xid struct {
id uint32
err error
}
// generateXids sends new Ids down the channel for NewId to use.
// generateXids should be run in its own goroutine.
// This needs to be updated to use the XC Misc extension once we run out of
// new ids.
// Thanks to libxcb/src/xcb_xid.c. This code is greatly inspired by it.
func (conn *Conn) generateXIds() {
defer close(conn.xidChan)
// This requires some explanation. From the horse's mouth:
// "The resource-id-mask contains a single contiguous set of bits (at least
// 18). The client allocates resource IDs for types WINDOW, PIXMAP,
// CURSOR, FONT, GCONTEXT, and COLORMAP by choosing a value with only some
// subset of these bits set and ORing it with resource-id-base. Only values
// constructed in this way can be used to name newly created resources over
// this connection."
// So for example (using 8 bit integers), the mask might look like:
// 00111000
// So that valid values would be 00101000, 00110000, 00001000, and so on.
// Thus, the idea is to increment it by the place of the last least
// significant '1'. In this case, that value would be 00001000. To get
// that value, we can AND the original mask with its two's complement:
// 00111000 & 11001000 = 00001000.
// And we use that value to increment the last resource id to get a new one.
// (And then, of course, we OR it with resource-id-base.)
inc := conn.setupResourceIdMask & -conn.setupResourceIdMask
max := conn.setupResourceIdMask
last := uint32(0)
for {
// TODO: Use the XC Misc extension to look for released ids.
if last > 0 && last >= max-inc+1 {
conn.xidChan <- xid{
id: 0,
err: errors.New("There are no more available resource" +
"identifiers."),
}
}
last += inc
conn.xidChan <- xid{
id: last | conn.setupResourceIdBase,
err: nil,
}
}
}
// newSeqId fetches the next sequence id from the Conn.seqChan channel.
func (c *Conn) newSequenceId() uint16 {
return <-c.seqChan
}
// generateSeqIds returns new sequence ids. It is meant to be run in its
// own goroutine.
// A sequence id is generated for *every* request. It's the identifier used
// to match up replies with requests.
// Since sequence ids can only be 16 bit integers we start over at zero when it
// comes time to wrap.
// N.B. As long as the cookie buffer is less than 2^16, there are no limitations
// on the number (or kind) of requests made in sequence.
func (c *Conn) generateSeqIds() {
defer close(c.seqChan)
seqid := uint16(1)
for {
c.seqChan <- seqid
if seqid == uint16((1<<16)-1) {
seqid = 0
} else {
seqid++
}
}
}
// request encapsulates a buffer of raw bytes (containing the request data)
// and a cookie, which when combined represents a single request.
// The cookie is used to match up the reply/error.
type request struct {
buf []byte
cookie *Cookie
// seq is closed when the request (cookie) has been sequenced by the Conn.
seq chan struct{}
}
// NewRequest takes the bytes and a cookie of a particular request, constructs
// a request type, and sends it over the Conn.reqChan channel.
// Note that the sequence number is added to the cookie after it is sent
// over the request channel, but before it is sent to X.
//
// Note that you may safely use NewRequest to send arbitrary byte requests
// to X. The resulting cookie can be used just like any normal cookie and
// abides by the same rules, except that for replies, you'll get back the
// raw byte data. This may be useful for performance critical sections where
// every allocation counts, since all X requests in XGB allocate a new byte
// slice. In contrast, NewRequest allocates one small request struct and
// nothing else. (Except when the cookie buffer is full and has to be flushed.)
//
// If you're using NewRequest manually, you'll need to use NewCookie to create
// a new cookie.
//
// In all likelihood, you should be able to copy and paste with some minor
// edits the generated code for the request you want to issue.
func (c *Conn) NewRequest(buf []byte, cookie *Cookie) {
seq := make(chan struct{})
c.reqChan <- &request{buf: buf, cookie: cookie, seq: seq}
<-seq
}
// sendRequests is run as a single goroutine that takes requests and writes
// the bytes to the wire and adds the cookie to the cookie queue.
// It is meant to be run as its own goroutine.
func (c *Conn) sendRequests() {
defer close(c.cookieChan)
for req := range c.reqChan {
// ho there! if the cookie channel is nearly full, force a round
// trip to clear out the cookie buffer.
// Note that we circumvent the request channel, because we're *in*
// the request channel.
if len(c.cookieChan) == cookieBuffer-1 {
if err := c.noop(); err != nil {
// Shut everything down.
break
}
}
req.cookie.Sequence = c.newSequenceId()
close(req.seq)
c.cookieChan <- req.cookie
c.writeBuffer(req.buf)
}
response := make(chan struct{})
c.closing <- response
c.noop() // Flush the response reading goroutine, ignore error.
<-response
c.conn.Close()
}
// noop circumvents the usual request sending goroutines and forces a round
// trip request manually.
func (c *Conn) noop() error {
cookie := c.NewCookie(true, true)
cookie.Sequence = c.newSequenceId()
c.cookieChan <- cookie
if err := c.writeBuffer(c.getInputFocusRequest()); err != nil {
return err
}
cookie.Reply() // wait for the buffer to clear
return nil
}
// writeBuffer is a convenience function for writing a byte slice to the wire.
func (c *Conn) writeBuffer(buf []byte) error {
if _, err := c.conn.Write(buf); err != nil {
Logger.Printf("A write error is unrecoverable: %s", err)
return err
} else {
return nil
}
}
// readResponses is a goroutine that reads events, errors and
// replies off the wire.
// When an event is read, it is always added to the event channel.
// When an error is read, if it corresponds to an existing checked cookie,
// it is sent to that cookie's error channel. Otherwise it is added to the
// event channel.
// When a reply is read, it is added to the corresponding cookie's reply
// channel. (It is an error if no such cookie exists in this case.)
// Finally, cookies that came "before" this reply are always cleaned up.
func (c *Conn) readResponses() {
defer close(c.eventChan)
var (
err Error
seq uint16
replyBytes []byte
)
for {
select {
case respond := <-c.closing:
respond <- struct{}{}
return
default:
}
buf := make([]byte, 32)
err, seq = nil, 0
if _, err := io.ReadFull(c.conn, buf); err != nil {
Logger.Printf("A read error is unrecoverable: %s", err)
c.eventChan <- err
c.Close()
continue
}
switch buf[0] {
case 0: // This is an error
// Use the constructor function for this error (that is auto
// generated) by looking it up by the error number.
newErrFun, ok := NewErrorFuncs[int(buf[1])]
if !ok {
Logger.Printf("BUG: Could not find error constructor function "+
"for error with number %d.", buf[1])
continue
}
err = newErrFun(buf)
seq = err.SequenceId()
// This error is either sent to the event channel or a specific
// cookie's error channel below.
case 1: // This is a reply
seq = Get16(buf[2:])
// check to see if this reply has more bytes to be read
size := Get32(buf[4:])
if size > 0 {
byteCount := 32 + size*4
biggerBuf := make([]byte, byteCount)
copy(biggerBuf[:32], buf)
if _, err := io.ReadFull(c.conn, biggerBuf[32:]); err != nil {
Logger.Printf("A read error is unrecoverable: %s", err)
c.eventChan <- err
c.Close()
continue
}
replyBytes = biggerBuf
} else {
replyBytes = buf
}
// This reply is sent to its corresponding cookie below.
default: // This is an event
// Use the constructor function for this event (like for errors,
// and is also auto generated) by looking it up by the event number.
// Note that we AND the event number with 127 so that we ignore
// the most significant bit (which is set when it was sent from
// a SendEvent request).
evNum := int(buf[0] & 127)
newEventFun, ok := NewEventFuncs[evNum]
if !ok {
Logger.Printf("BUG: Could not find event construct function "+
"for event with number %d.", evNum)
continue
}
c.eventChan <- newEventFun(buf)
continue
}
// At this point, we have a sequence number and we're either
// processing an error or a reply, which are both responses to
// requests. So all we have to do is find the cookie corresponding
// to this error/reply, and send the appropriate data to it.
// In doing so, we make sure that any cookies that came before it
// are marked as successful if they are void and checked.
// If there's a cookie that requires a reply that is before this
// reply, then something is wrong.
for cookie := range c.cookieChan {
// This is the cookie we're looking for. Process and break.
if cookie.Sequence == seq {
if err != nil { // this is an error to a request
// synchronous processing
if cookie.errorChan != nil {
cookie.errorChan <- err
} else { // asynchronous processing
c.eventChan <- err
// if this is an unchecked reply, ping the cookie too
if cookie.pingChan != nil {
cookie.pingChan <- true
}
}
} else { // this is a reply
if cookie.replyChan == nil {
Logger.Printf("Reply with sequence id %d does not "+
"have a cookie with a valid reply channel.", seq)
continue
} else {
cookie.replyChan <- replyBytes
}
}
break
}
switch {
// Checked requests with replies
case cookie.replyChan != nil && cookie.errorChan != nil:
Logger.Printf("Found cookie with sequence id %d that is "+
"expecting a reply but will never get it. Currently "+
"on sequence number %d", cookie.Sequence, seq)
// Unchecked requests with replies
case cookie.replyChan != nil && cookie.pingChan != nil:
Logger.Printf("Found cookie with sequence id %d that is "+
"expecting a reply (and not an error) but will never "+
"get it. Currently on sequence number %d",
cookie.Sequence, seq)
// Checked requests without replies
case cookie.pingChan != nil && cookie.errorChan != nil:
cookie.pingChan <- true
// Unchecked requests without replies don't have any channels,
// so we can't do anything with them except let them pass by.
}
}
}
}
// processEventOrError takes an eventOrError, type switches on it,
// and returns it in Go idiomatic style.
func processEventOrError(everr eventOrError) (Event, Error) {
switch ee := everr.(type) {
case Event:
return ee, nil
case Error:
return nil, ee
default:
Logger.Printf("Invalid event/error type: %T", everr)
return nil, nil
}
}
// WaitForEvent returns the next event from the server.
// It will block until an event is available.
// WaitForEvent returns either an Event or an Error. (Returning both
// is a bug.) Note than an Error here is an X error and not an XGB error. That
// is, X errors are sometimes completely expected (and you may want to ignore
// them in some cases).
//
// If both the event and error are nil, then the connection has been closed.
func (c *Conn) WaitForEvent() (Event, Error) {
return processEventOrError(<-c.eventChan)
}
// PollForEvent returns the next event from the server if one is available in
// the internal queue without blocking. Note that unlike WaitForEvent, both
// Event and Error could be nil. Indeed, they are both nil when the event queue
// is empty.
func (c *Conn) PollForEvent() (Event, Error) {
select {
case everr := <-c.eventChan:
return processEventOrError(everr)
default:
return nil, nil
}
}
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