2 files changed, 146 insertions, 0 deletions
diff --git a/system/internal/xcb/c.go b/system/internal/xcb/c.go
new file mode 100644
index 00000000..f2703f94
--- /dev/null
+++ b/system/internal/xcb/c.go
@@ -0,0 +1,124 @@
+package xcb
+
+import (
+	"runtime"
+	"unsafe"
+)
+
+/*
+#cgo linux pkg-config: --static xcb
+
+#include <stdlib.h>
+#include <xcb/xcb.h>
+
+static int _go_xcb_change_hosts_checked(xcb_connection_t *c, uint8_t mode, uint8_t family, uint16_t address_len, const uint8_t *address) {
+	xcb_void_cookie_t cookie = xcb_change_hosts_checked(c, mode, family, address_len, address);
+	free((void *)address);
+
+	int errno = xcb_connection_has_error(c);
+	if (errno != 0)
+		return errno;
+
+	xcb_generic_error_t *e = xcb_request_check(c, cookie);
+	if (e != NULL) {
+		// don't want to deal with xcb errors
+		free((void *)e);
+		return -1;
+	}
+
+	return 0;
+}
+*/
+import "C"
+
+const (
+	HostModeInsert = C.XCB_HOST_MODE_INSERT
+	HostModeDelete = C.XCB_HOST_MODE_DELETE
+
+	FamilyInternet          = C.XCB_FAMILY_INTERNET
+	FamilyDecnet            = C.XCB_FAMILY_DECNET
+	FamilyChaos             = C.XCB_FAMILY_CHAOS
+	FamilyServerInterpreted = C.XCB_FAMILY_SERVER_INTERPRETED
+	FamilyInternet6         = C.XCB_FAMILY_INTERNET_6
+)
+
+type (
+	HostMode = C.xcb_host_mode_t
+	Family   = C.xcb_family_t
+)
+
+func (conn *connection) changeHostsChecked(mode HostMode, family Family, address string) error {
+	errno := C._go_xcb_change_hosts_checked(
+		conn.c,
+		C.uint8_t(mode),
+		C.uint8_t(family),
+		C.uint16_t(len(address)),
+		(*C.uint8_t)(unsafe.Pointer(C.CString(address))),
+	)
+	switch errno {
+	case 0:
+		return nil
+	case -1:
+		return ErrChangeHosts
+	default:
+		return &ConnectionError{errno}
+	}
+}
+
+type connection struct{ c *C.xcb_connection_t }
+
+func connect() (*connection, error) {
+	conn := newConnection(C.xcb_connect(nil, nil))
+	return conn, conn.hasError()
+}
+
+func newConnection(c *C.xcb_connection_t) *connection {
+	conn := &connection{c}
+	runtime.SetFinalizer(conn, (*connection).disconnect)
+	return conn
+}
+
+const (
+	ConnError                 = C.XCB_CONN_ERROR
+	ConnClosedExtNotSupported = C.XCB_CONN_CLOSED_EXT_NOTSUPPORTED
+	ConnClosedMemInsufficient = C.XCB_CONN_CLOSED_MEM_INSUFFICIENT
+	ConnClosedReqLenExceed    = C.XCB_CONN_CLOSED_REQ_LEN_EXCEED
+	ConnClosedParseErr        = C.XCB_CONN_CLOSED_PARSE_ERR
+	ConnClosedInvalidScreen   = C.XCB_CONN_CLOSED_INVALID_SCREEN
+)
+
+type ConnectionError struct{ errno C.int }
+
+func (ce *ConnectionError) Error() string {
+	switch ce.errno {
+	case ConnError:
+		return "connection error"
+	case ConnClosedExtNotSupported:
+		return "extension not supported"
+	case ConnClosedMemInsufficient:
+		return "memory not available"
+	case ConnClosedReqLenExceed:
+		return "request length exceeded"
+	case ConnClosedParseErr:
+		return "invalid display string"
+	case ConnClosedInvalidScreen:
+		return "server has no screen matching display"
+	default:
+		return "generic X11 failure"
+	}
+}
+
+func (conn *connection) hasError() error {
+	errno := C.xcb_connection_has_error(conn.c)
+	if errno == 0 {
+		return nil
+	}
+	return &ConnectionError{errno}
+}
+
+func (conn *connection) disconnect() {
+	C.xcb_disconnect(conn.c)
+
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(conn, nil)
+}
diff --git a/system/internal/xcb/export.go b/system/internal/xcb/export.go
new file mode 100644
index 00000000..1ed9997f
--- /dev/null
+++ b/system/internal/xcb/export.go
@@ -0,0 +1,22 @@
+// Package xcb implements X11 ChangeHosts via libxcb.
+package xcb
+
+import (
+	"errors"
+)
+
+var ErrChangeHosts = errors.New("xcb_change_hosts() failed")
+
+func ChangeHosts(mode HostMode, family Family, address string) error {
+	var conn *connection
+
+	if c, err := connect(); err != nil {
+		c.disconnect()
+		return err
+	} else {
+		defer c.disconnect()
+		conn = c
+	}
+
+	return conn.changeHostsChecked(mode, family, address)
+}