x11: wrap libxcb ChangeHosts request

Even though many pure Go libxcb implementations exist, it is at least as complex and unreadable as libxcb, if not more. Since well known libraries like SDL, qt and gtk uses libxcb, and they somehow understand how to use it, I can only assume these people have read enough code to make sure it's correct enough. Call it wishful thinking. I don't care anymore.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

acl.go

@@ -1,6 +1,5 @@
 package main
 
-import "C"
 import (
 	"errors"
 	"fmt"

x11.go

@@ -0,0 +1,72 @@
+package main
+
+import "C"
+import (
+	"errors"
+	"unsafe"
+)
+
+//#include <stdlib.h>
+//#include <xcb/xcb.h>
+//#cgo linux LDFLAGS: -lxcb
+import "C"
+
+const (
+	xcbHostModeInsert = C.XCB_HOST_MODE_INSERT
+	xcbHostModeDelete = C.XCB_HOST_MODE_DELETE
+
+	xcbFamilyInternet          = C.XCB_FAMILY_INTERNET
+	xcbFamilyDecnet            = C.XCB_FAMILY_DECNET
+	xcbFamilyChaos             = C.XCB_FAMILY_CHAOS
+	xcbFamilyServerInterpreted = C.XCB_FAMILY_SERVER_INTERPRETED
+	xcbFamilyInternet6         = C.XCB_FAMILY_INTERNET_6
+)
+
+func changeHosts(mode, family C.uint8_t, address string) error {
+	var c *C.xcb_connection_t
+	c = C.xcb_connect(nil, nil)
+	defer C.xcb_disconnect(c)
+
+	if err := xcbHandleConnectionError(c); err != nil {
+		return err
+	}
+
+	addr := C.CString(address)
+	cookie := C.xcb_change_hosts_checked(c, mode, family, C.ushort(len(address)), (*C.uchar)(unsafe.Pointer(addr)))
+	C.free(unsafe.Pointer(addr))
+
+	if err := xcbHandleConnectionError(c); err != nil {
+		return err
+	}
+
+	e := C.xcb_request_check(c, cookie)
+	if e != nil {
+		defer C.free(unsafe.Pointer(e))
+		return errors.New("xcb_change_hosts() failed")
+	}
+
+	return nil
+}
+
+func xcbHandleConnectionError(c *C.xcb_connection_t) error {
+	if errno := C.xcb_connection_has_error(c); errno != 0 {
+		switch errno {
+		case C.XCB_CONN_ERROR:
+			return errors.New("connection error")
+		case C.XCB_CONN_CLOSED_EXT_NOTSUPPORTED:
+			return errors.New("extension not supported")
+		case C.XCB_CONN_CLOSED_MEM_INSUFFICIENT:
+			return errors.New("memory not available")
+		case C.XCB_CONN_CLOSED_REQ_LEN_EXCEED:
+			return errors.New("request length exceeded")
+		case C.XCB_CONN_CLOSED_PARSE_ERR:
+			return errors.New("invalid display string")
+		case C.XCB_CONN_CLOSED_INVALID_SCREEN:
+			return errors.New("server has no screen matching display")
+		default:
+			return errors.New("generic X11 failure")
+		}
+	} else {
+		return nil
+	}
+}