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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package x11
import (
"bufio"
"errors"
"io"
"os"
)
// readU16BE reads a big-endian uint16 from r, using b as a scratch buffer.
func readU16BE(r io.Reader, b []byte) (uint16, error) {
_, err := io.ReadFull(r, b[0:2])
if err != nil {
return 0, err
}
return uint16(b[0])<<8 + uint16(b[1]), nil
}
// readStr reads a length-prefixed string from r, using b as a scratch buffer.
func readStr(r io.Reader, b []byte) (string, error) {
n, err := readU16BE(r, b)
if err != nil {
return "", err
}
if int(n) > len(b) {
return "", errors.New("Xauthority entry too long for buffer")
}
_, err = io.ReadFull(r, b[0:n])
if err != nil {
return "", err
}
return string(b[0:n]), nil
}
// readAuth reads the X authority file and returns the name/data pair for the display.
// displayStr is the "12" out of a $DISPLAY like ":12.0".
func readAuth(displayStr string) (name, data string, err error) {
// b is a scratch buffer to use and should be at least 256 bytes long
// (i.e. it should be able to hold a hostname).
var b [256]byte
// As per /usr/include/X11/Xauth.h.
const familyLocal = 256
fn := os.Getenv("XAUTHORITY")
if fn == "" {
home := os.Getenv("HOME")
if home == "" {
err = errors.New("Xauthority not found: $XAUTHORITY, $HOME not set")
return
}
fn = home + "/.Xauthority"
}
r, err := os.Open(fn)
if err != nil {
return
}
defer r.Close()
br := bufio.NewReader(r)
hostname, err := os.Hostname()
if err != nil {
return
}
for {
var family uint16
var addr, disp, name0, data0 string
family, err = readU16BE(br, b[0:2])
if err != nil {
return
}
addr, err = readStr(br, b[0:])
if err != nil {
return
}
disp, err = readStr(br, b[0:])
if err != nil {
return
}
name0, err = readStr(br, b[0:])
if err != nil {
return
}
data0, err = readStr(br, b[0:])
if err != nil {
return
}
if family == familyLocal && addr == hostname && disp == displayStr {
return name0, data0, nil
}
}
panic("unreachable")
}
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