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// Copyright 2016 Michal Witkowski. All Rights Reserved.
// See LICENSE for licensing terms.
package metautils
import (
"strings"
"golang.org/x/net/context"
"google.golang.org/grpc/metadata"
)
// NiceMD is a convenience wrapper definiting extra functions on the metadata.
type NiceMD metadata.MD
// ExtractIncoming extracts an inbound metadata from the server-side context.
//
// This function always returns a NiceMD wrapper of the metadata.MD, in case the context doesn't have metadata it returns
// a new empty NiceMD.
func ExtractIncoming(ctx context.Context) NiceMD {
md, ok := metadata.FromIncomingContext(ctx)
if !ok {
return NiceMD(metadata.Pairs())
}
return NiceMD(md)
}
// ExtractOutgoing extracts an outbound metadata from the client-side context.
//
// This function always returns a NiceMD wrapper of the metadata.MD, in case the context doesn't have metadata it returns
// a new empty NiceMD.
func ExtractOutgoing(ctx context.Context) NiceMD {
md, ok := metadata.FromOutgoingContext(ctx)
if !ok {
return NiceMD(metadata.Pairs())
}
return NiceMD(md)
}
// Clone performs a *deep* copy of the metadata.MD.
//
// You can specify the lower-case copiedKeys to only copy certain whitelisted keys. If no keys are explicitly whitelisted
// all keys get copied.
func (m NiceMD) Clone(copiedKeys ...string) NiceMD {
newMd := NiceMD(metadata.Pairs())
for k, vv := range m {
found := false
if len(copiedKeys) == 0 {
found = true
} else {
for _, allowedKey := range copiedKeys {
if strings.ToLower(allowedKey) == strings.ToLower(k) {
found = true
break
}
}
}
if !found {
continue
}
newMd[k] = make([]string, len(vv))
copy(newMd[k], vv)
}
return NiceMD(newMd)
}
// ToOutgoing sets the given NiceMD as a client-side context for dispatching.
func (m NiceMD) ToOutgoing(ctx context.Context) context.Context {
return metadata.NewOutgoingContext(ctx, metadata.MD(m))
}
// ToIncoming sets the given NiceMD as a server-side context for dispatching.
//
// This is mostly useful in ServerInterceptors..
func (m NiceMD) ToIncoming(ctx context.Context) context.Context {
return metadata.NewIncomingContext(ctx, metadata.MD(m))
}
// Get retrieves a single value from the metadata.
//
// It works analogously to http.Header.Get, returning the first value if there are many set. If the value is not set,
// an empty string is returned.
//
// The function is binary-key safe.
func (m NiceMD) Get(key string) string {
k, _ := encodeKeyValue(key, "")
vv, ok := m[k]
if !ok {
return ""
}
return vv[0]
}
// Del retrieves a single value from the metadata.
//
// It works analogously to http.Header.Del, deleting all values if they exist.
//
// The function is binary-key safe.
func (m NiceMD) Del(key string) NiceMD {
k, _ := encodeKeyValue(key, "")
delete(m, k)
return m
}
// Set sets the given value in a metadata.
//
// It works analogously to http.Header.Set, overwriting all previous metadata values.
//
// The function is binary-key safe.
func (m NiceMD) Set(key string, value string) NiceMD {
k, v := encodeKeyValue(key, value)
m[k] = []string{v}
return m
}
// Add retrieves a single value from the metadata.
//
// It works analogously to http.Header.Add, as it appends to any existing values associated with key.
//
// The function is binary-key safe.
func (m NiceMD) Add(key string, value string) NiceMD {
k, v := encodeKeyValue(key, value)
m[k] = append(m[k], v)
return m
}
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