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// Copyright 2009 The XGB 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 xgb
import (
"bufio"
"errors"
"io"
"os"
)
// readAuthority reads the X authority file for the DISPLAY.
// If hostname == "" or hostname == "localhost",
// then use the system's hostname (as returned by os.Hostname) instead.
func readAuthority(hostname, display string) (
name string, data []byte, 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
if len(hostname) == 0 || hostname == "localhost" {
hostname, err = os.Hostname()
if err != nil {
return "", nil, err
}
}
fname := os.Getenv("XAUTHORITY")
if len(fname) == 0 {
home := os.Getenv("HOME")
if len(home) == 0 {
err = errors.New("Xauthority not found: $XAUTHORITY, $HOME not set")
return "", nil, err
}
fname = home + "/.Xauthority"
}
r, err := os.Open(fname)
if err != nil {
return "", nil, err
}
defer r.Close()
br := bufio.NewReader(r)
for {
family, err := getU16BE(br, b[0:2])
if err != nil {
return "", nil, err
}
addr, err := getString(br, b[0:])
if err != nil {
return "", nil, err
}
disp, err := getString(br, b[0:])
if err != nil {
return "", nil, err
}
name0, err := getString(br, b[0:])
if err != nil {
return "", nil, err
}
data0, err := getBytes(br, b[0:])
if err != nil {
return "", nil, err
}
if family == familyLocal && addr == hostname && disp == display {
return name0, data0, nil
}
}
panic("unreachable")
}
func getU16BE(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
}
func getBytes(r io.Reader, b []byte) ([]byte, error) {
n, err := getU16BE(r, b)
if err != nil {
return nil, err
}
if int(n) > len(b) {
return nil, errors.New("bytes too long for buffer")
}
_, err = io.ReadFull(r, b[0:n])
if err != nil {
return nil, err
}
return b[0:n], nil
}
func getString(r io.Reader, b []byte) (string, error) {
b, err := getBytes(r, b)
if err != nil {
return "", err
}
return string(b), nil
}
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