golang/xenlight: Add error constants and standard handling

Create error type Errorxl for throwing proper xenlight
errors.

Update Ctx functions to throw Errorxl errors.

Signed-off-by: Ronald Rojas <ronladred@gmail.com>
Reviewed-by:  George Dunlap <george.dunlap@citrix.com>
Acked-by: Ian Jackson <ian.jackson@citrix.com>

tools/golang/xenlight/xenlight.go

@@ -36,9 +36,83 @@ import (
 	"unsafe"
 )
 
+/*
+ * Errors
+ */
+
+type Error int
+
+const (
+	ErrorNonspecific                  = Error(-C.ERROR_NONSPECIFIC)
+	ErrorVersion                      = Error(-C.ERROR_VERSION)
+	ErrorFail                         = Error(-C.ERROR_FAIL)
+	ErrorNi                           = Error(-C.ERROR_NI)
+	ErrorNomem                        = Error(-C.ERROR_NOMEM)
+	ErrorInval                        = Error(-C.ERROR_INVAL)
+	ErrorBadfail                      = Error(-C.ERROR_BADFAIL)
+	ErrorGuestTimedout                = Error(-C.ERROR_GUEST_TIMEDOUT)
+	ErrorTimedout                     = Error(-C.ERROR_TIMEDOUT)
+	ErrorNoparavirt                   = Error(-C.ERROR_NOPARAVIRT)
+	ErrorNotReady                     = Error(-C.ERROR_NOT_READY)
+	ErrorOseventRegFail               = Error(-C.ERROR_OSEVENT_REG_FAIL)
+	ErrorBufferfull                   = Error(-C.ERROR_BUFFERFULL)
+	ErrorUnknownChild                 = Error(-C.ERROR_UNKNOWN_CHILD)
+	ErrorLockFail                     = Error(-C.ERROR_LOCK_FAIL)
+	ErrorJsonConfigEmpty              = Error(-C.ERROR_JSON_CONFIG_EMPTY)
+	ErrorDeviceExists                 = Error(-C.ERROR_DEVICE_EXISTS)
+	ErrorCheckpointDevopsDoesNotMatch = Error(-C.ERROR_CHECKPOINT_DEVOPS_DOES_NOT_MATCH)
+	ErrorCheckpointDeviceNotSupported = Error(-C.ERROR_CHECKPOINT_DEVICE_NOT_SUPPORTED)
+	ErrorVnumaConfigInvalid           = Error(-C.ERROR_VNUMA_CONFIG_INVALID)
+	ErrorDomainNotfound               = Error(-C.ERROR_DOMAIN_NOTFOUND)
+	ErrorAborted                      = Error(-C.ERROR_ABORTED)
+	ErrorNotfound                     = Error(-C.ERROR_NOTFOUND)
+	ErrorDomainDestroyed              = Error(-C.ERROR_DOMAIN_DESTROYED)
+	ErrorFeatureRemoved               = Error(-C.ERROR_FEATURE_REMOVED)
+)
+
+var errors = [...]string{
+	ErrorNonspecific:                  "Non-specific error",
+	ErrorVersion:                      "Wrong version",
+	ErrorFail:                         "Failed",
+	ErrorNi:                           "Not Implemented",
+	ErrorNomem:                        "No memory",
+	ErrorInval:                        "Invalid argument",
+	ErrorBadfail:                      "Bad Fail",
+	ErrorGuestTimedout:                "Guest timed out",
+	ErrorTimedout:                     "Timed out",
+	ErrorNoparavirt:                   "No Paravirtualization",
+	ErrorNotReady:                     "Not ready",
+	ErrorOseventRegFail:               "OS event registration failed",
+	ErrorBufferfull:                   "Buffer full",
+	ErrorUnknownChild:                 "Unknown child",
+	ErrorLockFail:                     "Lock failed",
+	ErrorJsonConfigEmpty:              "JSON config empty",
+	ErrorDeviceExists:                 "Device exists",
+	ErrorCheckpointDevopsDoesNotMatch: "Checkpoint devops does not match",
+	ErrorCheckpointDeviceNotSupported: "Checkpoint device not supported",
+	ErrorVnumaConfigInvalid:           "VNUMA config invalid",
+	ErrorDomainNotfound:               "Domain not found",
+	ErrorAborted:                      "Aborted",
+	ErrorNotfound:                     "Not found",
+	ErrorDomainDestroyed:              "Domain destroyed",
+	ErrorFeatureRemoved:               "Feature removed",
+}
+
+func (e Error) Error() string {
+	if 0 < int(e) && int(e) < len(errors) {
+		s := errors[e]
+		if s != "" {
+			return s
+		}
+	}
+	return fmt.Sprintf("libxl error: %d", -e)
+
+}
+
 /*
  * Types: Builtins
  */
+
 type Context struct {
 	ctx    *C.libxl_ctx
 	logger *C.xentoollog_logger_stdiostream
@@ -68,7 +142,7 @@ func (Ctx *Context) Open() (err error) {
 		0, unsafe.Pointer(Ctx.logger))
 
 	if ret != 0 {
-		err = fmt.Errorf("Error: %d", -ret)
+		err = Error(-ret)
 	}
 	return
 }
@@ -78,7 +152,7 @@ func (Ctx *Context) Close() (err error) {
 	Ctx.ctx = nil
 
 	if ret != 0 {
-		err = fmt.Errorf("Error: %d", -ret)
+		err = Error(-ret)
 	}
 	C.xtl_logger_destroy(unsafe.Pointer(Ctx.logger))
 	return