Initial

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

vendor/github.com/containerd/ttrpc/metadata.go

@@ -0,0 +1,107 @@
+/*
+   Copyright The containerd 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 ttrpc
+
+import (
+	"context"
+	"strings"
+)
+
+// MD is the user type for ttrpc metadata
+type MD map[string][]string
+
+// Get returns the metadata for a given key when they exist.
+// If there is no metadata, a nil slice and false are returned.
+func (m MD) Get(key string) ([]string, bool) {
+	key = strings.ToLower(key)
+	list, ok := m[key]
+	if !ok || len(list) == 0 {
+		return nil, false
+	}
+
+	return list, true
+}
+
+// Set sets the provided values for a given key.
+// The values will overwrite any existing values.
+// If no values provided, a key will be deleted.
+func (m MD) Set(key string, values ...string) {
+	key = strings.ToLower(key)
+	if len(values) == 0 {
+		delete(m, key)
+		return
+	}
+	m[key] = values
+}
+
+// Append appends additional values to the given key.
+func (m MD) Append(key string, values ...string) {
+	key = strings.ToLower(key)
+	if len(values) == 0 {
+		return
+	}
+	current, ok := m[key]
+	if ok {
+		m.Set(key, append(current, values...)...)
+	} else {
+		m.Set(key, values...)
+	}
+}
+
+func (m MD) setRequest(r *Request) {
+	for k, values := range m {
+		for _, v := range values {
+			r.Metadata = append(r.Metadata, &KeyValue{
+				Key:   k,
+				Value: v,
+			})
+		}
+	}
+}
+
+func (m MD) fromRequest(r *Request) {
+	for _, kv := range r.Metadata {
+		m[kv.Key] = append(m[kv.Key], kv.Value)
+	}
+}
+
+type metadataKey struct{}
+
+// GetMetadata retrieves metadata from context.Context (previously attached with WithMetadata)
+func GetMetadata(ctx context.Context) (MD, bool) {
+	metadata, ok := ctx.Value(metadataKey{}).(MD)
+	return metadata, ok
+}
+
+// GetMetadataValue gets a specific metadata value by name from context.Context
+func GetMetadataValue(ctx context.Context, name string) (string, bool) {
+	metadata, ok := GetMetadata(ctx)
+	if !ok {
+		return "", false
+	}
+
+	if list, ok := metadata.Get(name); ok {
+		return list[0], true
+	}
+
+	return "", false
+}
+
+// WithMetadata attaches metadata map to a context.Context
+func WithMetadata(ctx context.Context, md MD) context.Context {
+	return context.WithValue(ctx, metadataKey{}, md)
+}