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