Instana tracer implementation

vendor/github.com/looplab/fsm/event.go

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+// Copyright (c) 2013 - Max Persson <max@looplab.se>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fsm
+
+// Event is the info that get passed as a reference in the callbacks.
+type Event struct {
+	// FSM is a reference to the current FSM.
+	FSM *FSM
+
+	// Event is the event name.
+	Event string
+
+	// Src is the state before the transition.
+	Src string
+
+	// Dst is the state after the transition.
+	Dst string
+
+	// Err is an optional error that can be returned from a callback.
+	Err error
+
+	// Args is a optinal list of arguments passed to the callback.
+	Args []interface{}
+
+	// canceled is an internal flag set if the transition is canceled.
+	canceled bool
+
+	// async is an internal flag set if the transition should be asynchronous
+	async bool
+}
+
+// Cancel can be called in before_<EVENT> or leave_<STATE> to cancel the
+// current transition before it happens. It takes an opitonal error, which will
+// overwrite e.Err if set before.
+func (e *Event) Cancel(err ...error) {
+	e.canceled = true
+
+	if len(err) > 0 {
+		e.Err = err[0]
+	}
+}
+
+// Async can be called in leave_<STATE> to do an asynchronous state transition.
+//
+// The current state transition will be on hold in the old state until a final
+// call to Transition is made. This will comlete the transition and possibly
+// call the other callbacks.
+func (e *Event) Async() {
+	e.async = true
+}