| // Copyright 2016 The LUCI Authors. |
| // |
| // 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 clock |
| |
| import "context" |
| |
| var clockTagKey = "clock-tag" |
| |
| // Tag returns a derivative Context with the supplied Tag appended to it. |
| // |
| // Tag chains can be used by timers to identify themselves. |
| func Tag(ctx context.Context, v string) context.Context { |
| return context.WithValue(ctx, &clockTagKey, append(Tags(ctx), v)) |
| } |
| |
| // Tags returns a copy of the set of tags in the current Context. |
| func Tags(ctx context.Context) []string { |
| if tags, ok := ctx.Value(&clockTagKey).([]string); ok && len(tags) > 0 { |
| tclone := make([]string, len(tags)) |
| copy(tclone, tags) |
| return tclone |
| } |
| return nil |
| } |