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package grpc
import (
"context"
"encoding/base64"
"strings"
"google.golang.org/grpc/metadata"
)
const (
binHdrSuffix = "-bin"
)
// ClientRequestFunc may take information from context and use it to construct
// metadata headers to be transported to the server. ClientRequestFuncs are
// executed after creating the request but prior to sending the gRPC request to
// the server.
type ClientRequestFunc func(context.Context, *metadata.MD) context.Context
// ServerRequestFunc may take information from the received metadata header and
// use it to place items in the request scoped context. ServerRequestFuncs are
// executed prior to invoking the endpoint.
type ServerRequestFunc func(context.Context, metadata.MD) context.Context
// ServerResponseFunc may take information from a request context and use it to
// manipulate the gRPC response metadata headers and trailers. ResponseFuncs are
// only executed in servers, after invoking the endpoint but prior to writing a
// response.
type ServerResponseFunc func(ctx context.Context, header *metadata.MD, trailer *metadata.MD) context.Context
// ClientResponseFunc may take information from a gRPC metadata header and/or
// trailer and make the responses available for consumption. ClientResponseFuncs
// are only executed in clients, after a request has been made, but prior to it
// being decoded.
type ClientResponseFunc func(ctx context.Context, header metadata.MD, trailer metadata.MD) context.Context
// SetRequestHeader returns a ClientRequestFunc that sets the specified metadata
// key-value pair.
func SetRequestHeader(key, val string) ClientRequestFunc {
return func(ctx context.Context, md *metadata.MD) context.Context {
key, val := EncodeKeyValue(key, val)
(*md)[key] = append((*md)[key], val)
return ctx
}
}
// SetResponseHeader returns a ResponseFunc that sets the specified metadata
// key-value pair.
func SetResponseHeader(key, val string) ServerResponseFunc {
return func(ctx context.Context, md *metadata.MD, _ *metadata.MD) context.Context {
key, val := EncodeKeyValue(key, val)
(*md)[key] = append((*md)[key], val)
return ctx
}
}
// SetResponseTrailer returns a ResponseFunc that sets the specified metadata
// key-value pair.
func SetResponseTrailer(key, val string) ServerResponseFunc {
return func(ctx context.Context, _ *metadata.MD, md *metadata.MD) context.Context {
key, val := EncodeKeyValue(key, val)
(*md)[key] = append((*md)[key], val)
return ctx
}
}
// EncodeKeyValue sanitizes a key-value pair for use in gRPC metadata headers.
func EncodeKeyValue(key, val string) (string, string) {
key = strings.ToLower(key)
if strings.HasSuffix(key, binHdrSuffix) {
val = base64.StdEncoding.EncodeToString([]byte(val))
}
return key, val
}
type contextKey int
const (
ContextKeyRequestMethod contextKey = iota
)
|
