| // Copyright 2018 The Fuchsia 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 fxctx |
| |
| import ( |
| "context" |
| "encoding/json" |
| "fmt" |
| ) |
| |
| // ContextKey is used to store values in Context objects. |
| type ContextKey string |
| |
| // Set associates a JSON encodable value with a key in a Context object. |
| func Set(ctx context.Context, key ContextKey, value interface{}) (context.Context, error) { |
| data, err := json.Marshal(value) |
| if err != nil { |
| return nil, err |
| } |
| |
| return context.WithValue(ctx, key, data), nil |
| } |
| |
| // Get reads a value from a Context into `out`. Returns true iff the given key is present |
| // in the Context, even if the key cannot be read into `out`. |
| func Get(ctx context.Context, key ContextKey, out interface{}) error { |
| value := ctx.Value(key) |
| if value == nil { |
| return fmt.Errorf("not found %v", key) |
| } |
| |
| bytes, ok := value.([]byte) |
| if !ok { |
| return fmt.Errorf("expected a []byte value for %v but got %v", key, value) |
| } |
| |
| return json.Unmarshal(bytes, out) |
| } |