| // Copyright 2019 The Go 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 event |
| |
| import ( |
| "context" |
| "sync/atomic" |
| "time" |
| "unsafe" |
| ) |
| |
| // Exporter is a function that handles events. |
| // It may return a modified context and event. |
| type Exporter func(context.Context, Event, TagMap) context.Context |
| |
| var ( |
| exporter unsafe.Pointer |
| ) |
| |
| // SetExporter sets the global exporter function that handles all events. |
| // The exporter is called synchronously from the event call site, so it should |
| // return quickly so as not to hold up user code. |
| func SetExporter(e Exporter) { |
| p := unsafe.Pointer(&e) |
| if e == nil { |
| // &e is always valid, and so p is always valid, but for the early abort |
| // of ProcessEvent to be efficient it needs to make the nil check on the |
| // pointer without having to dereference it, so we make the nil function |
| // also a nil pointer |
| p = nil |
| } |
| atomic.StorePointer(&exporter, p) |
| } |
| |
| // dispatch is called to deliver an event to the supplied exporter. |
| // it will fill in the time and generate the basic tag source. |
| func dispatch(ctx context.Context, ev Event) context.Context { |
| // get the global exporter and abort early if there is not one |
| exporterPtr := (*Exporter)(atomic.LoadPointer(&exporter)) |
| if exporterPtr == nil { |
| return ctx |
| } |
| // add the current time to the event |
| ev.At = time.Now() |
| // hand the event off to the current exporter |
| return (*exporterPtr)(ctx, ev, ev.Map()) |
| } |