210 lines
6.2 KiB
Go
210 lines
6.2 KiB
Go
/*
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*
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* Copyright 2014 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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// Package metadata define the structure of the metadata supported by gRPC library.
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// Please refer to https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
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// for more information about custom-metadata.
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package metadata // import "google.golang.org/grpc/metadata"
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import (
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"context"
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"fmt"
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"strings"
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)
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// DecodeKeyValue returns k, v, nil.
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//
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// Deprecated: use k and v directly instead.
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func DecodeKeyValue(k, v string) (string, string, error) {
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return k, v, nil
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}
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// MD is a mapping from metadata keys to values. Users should use the following
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// two convenience functions New and Pairs to generate MD.
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type MD map[string][]string
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// New creates an MD from a given key-value map.
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//
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// Only the following ASCII characters are allowed in keys:
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// - digits: 0-9
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// - uppercase letters: A-Z (normalized to lower)
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// - lowercase letters: a-z
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// - special characters: -_.
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// Uppercase letters are automatically converted to lowercase.
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//
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// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
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// result in errors if set in metadata.
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func New(m map[string]string) MD {
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md := MD{}
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for k, val := range m {
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key := strings.ToLower(k)
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md[key] = append(md[key], val)
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}
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return md
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}
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// Pairs returns an MD formed by the mapping of key, value ...
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// Pairs panics if len(kv) is odd.
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//
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// Only the following ASCII characters are allowed in keys:
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// - digits: 0-9
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// - uppercase letters: A-Z (normalized to lower)
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// - lowercase letters: a-z
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// - special characters: -_.
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// Uppercase letters are automatically converted to lowercase.
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//
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// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
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// result in errors if set in metadata.
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func Pairs(kv ...string) MD {
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if len(kv)%2 == 1 {
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panic(fmt.Sprintf("metadata: Pairs got the odd number of input pairs for metadata: %d", len(kv)))
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}
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md := MD{}
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var key string
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for i, s := range kv {
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if i%2 == 0 {
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key = strings.ToLower(s)
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continue
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}
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md[key] = append(md[key], s)
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}
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return md
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}
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// Len returns the number of items in md.
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func (md MD) Len() int {
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return len(md)
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}
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// Copy returns a copy of md.
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func (md MD) Copy() MD {
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return Join(md)
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}
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// Get obtains the values for a given key.
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func (md MD) Get(k string) []string {
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k = strings.ToLower(k)
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return md[k]
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}
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// Set sets the value of a given key with a slice of values.
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func (md MD) Set(k string, vals ...string) {
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if len(vals) == 0 {
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return
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}
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k = strings.ToLower(k)
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md[k] = vals
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}
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// Append adds the values to key k, not overwriting what was already stored at that key.
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func (md MD) Append(k string, vals ...string) {
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if len(vals) == 0 {
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return
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}
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k = strings.ToLower(k)
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md[k] = append(md[k], vals...)
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}
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// Join joins any number of mds into a single MD.
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// The order of values for each key is determined by the order in which
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// the mds containing those values are presented to Join.
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func Join(mds ...MD) MD {
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out := MD{}
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for _, md := range mds {
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for k, v := range md {
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out[k] = append(out[k], v...)
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}
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}
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return out
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}
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type mdIncomingKey struct{}
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type mdOutgoingKey struct{}
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// NewIncomingContext creates a new context with incoming md attached.
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func NewIncomingContext(ctx context.Context, md MD) context.Context {
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return context.WithValue(ctx, mdIncomingKey{}, md)
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}
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// NewOutgoingContext creates a new context with outgoing md attached. If used
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// in conjunction with AppendToOutgoingContext, NewOutgoingContext will
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// overwrite any previously-appended metadata.
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func NewOutgoingContext(ctx context.Context, md MD) context.Context {
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return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md})
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}
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// AppendToOutgoingContext returns a new context with the provided kv merged
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// with any existing metadata in the context. Please refer to the
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// documentation of Pairs for a description of kv.
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func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context {
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if len(kv)%2 == 1 {
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panic(fmt.Sprintf("metadata: AppendToOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
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}
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md, _ := ctx.Value(mdOutgoingKey{}).(rawMD)
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added := make([][]string, len(md.added)+1)
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copy(added, md.added)
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added[len(added)-1] = make([]string, len(kv))
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copy(added[len(added)-1], kv)
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return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md.md, added: added})
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}
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// FromIncomingContext returns the incoming metadata in ctx if it exists. The
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// returned MD should not be modified. Writing to it may cause races.
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// Modification should be made to copies of the returned MD.
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func FromIncomingContext(ctx context.Context) (md MD, ok bool) {
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md, ok = ctx.Value(mdIncomingKey{}).(MD)
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return
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}
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// FromOutgoingContextRaw returns the un-merged, intermediary contents
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// of rawMD. Remember to perform strings.ToLower on the keys. The returned
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// MD should not be modified. Writing to it may cause races. Modification
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// should be made to copies of the returned MD.
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//
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// This is intended for gRPC-internal use ONLY.
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func FromOutgoingContextRaw(ctx context.Context) (MD, [][]string, bool) {
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raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
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if !ok {
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return nil, nil, false
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}
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return raw.md, raw.added, true
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}
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// FromOutgoingContext returns the outgoing metadata in ctx if it exists. The
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// returned MD should not be modified. Writing to it may cause races.
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// Modification should be made to copies of the returned MD.
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func FromOutgoingContext(ctx context.Context) (MD, bool) {
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raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
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if !ok {
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return nil, false
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}
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mds := make([]MD, 0, len(raw.added)+1)
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mds = append(mds, raw.md)
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for _, vv := range raw.added {
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mds = append(mds, Pairs(vv...))
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}
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return Join(mds...), ok
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}
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type rawMD struct {
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md MD
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added [][]string
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}
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