blob: adebc38f8ea12f6faf391bb59679221d7d78686e [file] [log] [blame]
/*
*
* Copyright 2014, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
// Package metadata define the structure of the metadata supported by gRPC library.
package metadata // import "google.golang.org/grpc/metadata"
import (
"encoding/base64"
"fmt"
"strings"
"golang.org/x/net/context"
)
const (
binHdrSuffix = "-bin"
)
// grpc-http2 requires ASCII header key and value (more detail can be found in
// "Requests" subsection in go/grpc-http2).
func isASCII(s string) bool {
for _, c := range s {
if c > 127 {
return false
}
}
return true
}
// encodeKeyValue encodes key and value qualified for transmission via gRPC.
// Transmitting binary headers violates HTTP/2 spec.
// TODO(zhaoq): Maybe check if k is ASCII also.
func encodeKeyValue(k, v string) (string, string) {
if isASCII(v) {
return k, v
}
key := strings.ToLower(k + binHdrSuffix)
val := base64.StdEncoding.EncodeToString([]byte(v))
return key, string(val)
}
// DecodeKeyValue returns the original key and value corresponding to the
// encoded data in k, v.
func DecodeKeyValue(k, v string) (string, string, error) {
if !strings.HasSuffix(k, binHdrSuffix) {
return k, v, nil
}
key := k[:len(k)-len(binHdrSuffix)]
val, err := base64.StdEncoding.DecodeString(v)
if err != nil {
return "", "", err
}
return key, string(val), 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 a MD from given key-value map.
func New(m map[string]string) MD {
md := MD{}
for k, v := range m {
key, val := encodeKeyValue(k, v)
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.
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 k string
for i, s := range kv {
if i%2 == 0 {
k = s
continue
}
key, val := encodeKeyValue(k, s)
md[key] = append(md[key], val)
}
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 {
out := MD{}
for k, v := range md {
for _, i := range v {
out[k] = append(out[k], i)
}
}
return out
}
type mdKey struct{}
// NewContext creates a new context with md attached.
func NewContext(ctx context.Context, md MD) context.Context {
return context.WithValue(ctx, mdKey{}, md)
}
// FromContext returns the MD in ctx if it exists.
func FromContext(ctx context.Context) (md MD, ok bool) {
md, ok = ctx.Value(mdKey{}).(MD)
return
}