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/*
*
* Copyright 2014 gRPC 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 metadata define the structure of the metadata supported by gRPC library.
// Please refer to https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
// for more information about custom-metadata.
package metadata // import "google.golang.org/grpc/metadata"
import (
"context"
"fmt"
"strings"
)
// DecodeKeyValue returns k, v, nil.
//
// Deprecated: use k and v directly instead.
func DecodeKeyValue(k, v string) (string, string, error) {
return k, v, nil
}
// MD is a mapping from metadata keys to values. Users should use the following
// two convenience functions New and Pairs to generate MD.
type MD map[string][]string
// New creates an MD from a given key-value map.
//
// Only the following ASCII characters are allowed in keys:
// - digits: 0-9
// - uppercase letters: A-Z (normalized to lower)
// - lowercase letters: a-z
// - special characters: -_.
// Uppercase letters are automatically converted to lowercase.
//
// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
// result in errors if set in metadata.
func New(m map[string]string) MD {
md := MD{}
for k, val := range m {
key := strings.ToLower(k)
md[key] = append(md[key], val)
}
return md
}
// Pairs returns an MD formed by the mapping of key, value ...
// Pairs panics if len(kv) is odd.
//
// Only the following ASCII characters are allowed in keys:
// - digits: 0-9
// - uppercase letters: A-Z (normalized to lower)
// - lowercase letters: a-z
// - special characters: -_.
// Uppercase letters are automatically converted to lowercase.
//
// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
// result in errors if set in metadata.
func Pairs(kv ...string) MD {
if len(kv)%2 == 1 {
panic(fmt.Sprintf("metadata: Pairs got the odd number of input pairs for metadata: %d", len(kv)))
}
md := MD{}
var key string
for i, s := range kv {
if i%2 == 0 {
key = strings.ToLower(s)
continue
}
md[key] = append(md[key], s)
}
return md
}
// Len returns the number of items in md.
func (md MD) Len() int {
return len(md)
}
// Copy returns a copy of md.
func (md MD) Copy() MD {
return Join(md)
}
// Get obtains the values for a given key.
func (md MD) Get(k string) []string {
k = strings.ToLower(k)
return md[k]
}
// Set sets the value of a given key with a slice of values.
func (md MD) Set(k string, vals ...string) {
if len(vals) == 0 {
return
}
k = strings.ToLower(k)
md[k] = vals
}
// Append adds the values to key k, not overwriting what was already stored at that key.
func (md MD) Append(k string, vals ...string) {
if len(vals) == 0 {
return
}
k = strings.ToLower(k)
md[k] = append(md[k], vals...)
}
// Join joins any number of mds into a single MD.
// The order of values for each key is determined by the order in which
// the mds containing those values are presented to Join.
func Join(mds ...MD) MD {
out := MD{}
for _, md := range mds {
for k, v := range md {
out[k] = append(out[k], v...)
}
}
return out
}
type mdIncomingKey struct{}
type mdOutgoingKey struct{}
// NewIncomingContext creates a new context with incoming md attached.
func NewIncomingContext(ctx context.Context, md MD) context.Context {
return context.WithValue(ctx, mdIncomingKey{}, md)
}
// NewOutgoingContext creates a new context with outgoing md attached. If used
// in conjunction with AppendToOutgoingContext, NewOutgoingContext will
// overwrite any previously-appended metadata.
func NewOutgoingContext(ctx context.Context, md MD) context.Context {
return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md})
}
// AppendToOutgoingContext returns a new context with the provided kv merged
// with any existing metadata in the context. Please refer to the
// documentation of Pairs for a description of kv.
func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context {
if len(kv)%2 == 1 {
panic(fmt.Sprintf("metadata: AppendToOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
}
md, _ := ctx.Value(mdOutgoingKey{}).(rawMD)
added := make([][]string, len(md.added)+1)
copy(added, md.added)
added[len(added)-1] = make([]string, len(kv))
copy(added[len(added)-1], kv)
return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md.md, added: added})
}
// FromIncomingContext returns the incoming metadata in ctx if it exists. The
// returned MD should not be modified. Writing to it may cause races.
// Modification should be made to copies of the returned MD.
func FromIncomingContext(ctx context.Context) (md MD, ok bool) {
md, ok = ctx.Value(mdIncomingKey{}).(MD)
return
}
// FromOutgoingContextRaw returns the un-merged, intermediary contents
// of rawMD. Remember to perform strings.ToLower on the keys. The returned
// MD should not be modified. Writing to it may cause races. Modification
// should be made to copies of the returned MD.
//
// This is intended for gRPC-internal use ONLY.
func FromOutgoingContextRaw(ctx context.Context) (MD, [][]string, bool) {
raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
if !ok {
return nil, nil, false
}
return raw.md, raw.added, true
}
// FromOutgoingContext returns the outgoing metadata in ctx if it exists. The
// returned MD should not be modified. Writing to it may cause races.
// Modification should be made to copies of the returned MD.
func FromOutgoingContext(ctx context.Context) (MD, bool) {
raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
if !ok {
return nil, false
}
mds := make([]MD, 0, len(raw.added)+1)
mds = append(mds, raw.md)
for _, vv := range raw.added {
mds = append(mds, Pairs(vv...))
}
return Join(mds...), ok
}
type rawMD struct {
md MD
added [][]string
}
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