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package runtime
import (
"errors"
"fmt"
"io"
"net/http"
"net/textproto"
"context"
"github.com/golang/protobuf/proto"
"github.com/grpc-ecosystem/grpc-gateway/internal"
"google.golang.org/grpc/grpclog"
)
var errEmptyResponse = errors.New("empty response")
// ForwardResponseStream forwards the stream from gRPC server to REST client.
func ForwardResponseStream(ctx context.Context, mux *ServeMux, marshaler Marshaler, w http.ResponseWriter, req *http.Request, recv func() (proto.Message, error), opts ...func(context.Context, http.ResponseWriter, proto.Message) error) {
f, ok := w.(http.Flusher)
if !ok {
grpclog.Infof("Flush not supported in %T", w)
http.Error(w, "unexpected type of web server", http.StatusInternalServerError)
return
}
md, ok := ServerMetadataFromContext(ctx)
if !ok {
grpclog.Infof("Failed to extract ServerMetadata from context")
http.Error(w, "unexpected error", http.StatusInternalServerError)
return
}
handleForwardResponseServerMetadata(w, mux, md)
w.Header().Set("Transfer-Encoding", "chunked")
w.Header().Set("Content-Type", marshaler.ContentType())
if err := handleForwardResponseOptions(ctx, w, nil, opts); err != nil {
HTTPError(ctx, mux, marshaler, w, req, err)
return
}
var delimiter []byte
if d, ok := marshaler.(Delimited); ok {
delimiter = d.Delimiter()
} else {
delimiter = []byte("\n")
}
var wroteHeader bool
for {
resp, err := recv()
if err == io.EOF {
return
}
if err != nil {
handleForwardResponseStreamError(ctx, wroteHeader, marshaler, w, req, mux, err)
return
}
if err := handleForwardResponseOptions(ctx, w, resp, opts); err != nil {
handleForwardResponseStreamError(ctx, wroteHeader, marshaler, w, req, mux, err)
return
}
buf, err := marshaler.Marshal(streamChunk(ctx, resp, mux.streamErrorHandler))
if err != nil {
grpclog.Infof("Failed to marshal response chunk: %v", err)
handleForwardResponseStreamError(ctx, wroteHeader, marshaler, w, req, mux, err)
return
}
if _, err = w.Write(buf); err != nil {
grpclog.Infof("Failed to send response chunk: %v", err)
return
}
wroteHeader = true
if _, err = w.Write(delimiter); err != nil {
grpclog.Infof("Failed to send delimiter chunk: %v", err)
return
}
f.Flush()
}
}
func handleForwardResponseServerMetadata(w http.ResponseWriter, mux *ServeMux, md ServerMetadata) {
for k, vs := range md.HeaderMD {
if h, ok := mux.outgoingHeaderMatcher(k); ok {
for _, v := range vs {
w.Header().Add(h, v)
}
}
}
}
func handleForwardResponseTrailerHeader(w http.ResponseWriter, md ServerMetadata) {
for k := range md.TrailerMD {
tKey := textproto.CanonicalMIMEHeaderKey(fmt.Sprintf("%s%s", MetadataTrailerPrefix, k))
w.Header().Add("Trailer", tKey)
}
}
func handleForwardResponseTrailer(w http.ResponseWriter, md ServerMetadata) {
for k, vs := range md.TrailerMD {
tKey := fmt.Sprintf("%s%s", MetadataTrailerPrefix, k)
for _, v := range vs {
w.Header().Add(tKey, v)
}
}
}
// responseBody interface contains method for getting field for marshaling to the response body
// this method is generated for response struct from the value of `response_body` in the `google.api.HttpRule`
type responseBody interface {
XXX_ResponseBody() interface{}
}
// ForwardResponseMessage forwards the message "resp" from gRPC server to REST client.
func ForwardResponseMessage(ctx context.Context, mux *ServeMux, marshaler Marshaler, w http.ResponseWriter, req *http.Request, resp proto.Message, opts ...func(context.Context, http.ResponseWriter, proto.Message) error) {
md, ok := ServerMetadataFromContext(ctx)
if !ok {
grpclog.Infof("Failed to extract ServerMetadata from context")
}
handleForwardResponseServerMetadata(w, mux, md)
handleForwardResponseTrailerHeader(w, md)
contentType := marshaler.ContentType()
// Check marshaler on run time in order to keep backwards compatability
// An interface param needs to be added to the ContentType() function on
// the Marshal interface to be able to remove this check
if httpBodyMarshaler, ok := marshaler.(*HTTPBodyMarshaler); ok {
contentType = httpBodyMarshaler.ContentTypeFromMessage(resp)
}
w.Header().Set("Content-Type", contentType)
if err := handleForwardResponseOptions(ctx, w, resp, opts); err != nil {
HTTPError(ctx, mux, marshaler, w, req, err)
return
}
var buf []byte
var err error
if rb, ok := resp.(responseBody); ok {
buf, err = marshaler.Marshal(rb.XXX_ResponseBody())
} else {
buf, err = marshaler.Marshal(resp)
}
if err != nil {
grpclog.Infof("Marshal error: %v", err)
HTTPError(ctx, mux, marshaler, w, req, err)
return
}
if _, err = w.Write(buf); err != nil {
grpclog.Infof("Failed to write response: %v", err)
}
handleForwardResponseTrailer(w, md)
}
func handleForwardResponseOptions(ctx context.Context, w http.ResponseWriter, resp proto.Message, opts []func(context.Context, http.ResponseWriter, proto.Message) error) error {
if len(opts) == 0 {
return nil
}
for _, opt := range opts {
if err := opt(ctx, w, resp); err != nil {
grpclog.Infof("Error handling ForwardResponseOptions: %v", err)
return err
}
}
return nil
}
func handleForwardResponseStreamError(ctx context.Context, wroteHeader bool, marshaler Marshaler, w http.ResponseWriter, req *http.Request, mux *ServeMux, err error) {
serr := streamError(ctx, mux.streamErrorHandler, err)
if !wroteHeader {
w.WriteHeader(int(serr.HttpCode))
}
buf, merr := marshaler.Marshal(errorChunk(serr))
if merr != nil {
grpclog.Infof("Failed to marshal an error: %v", merr)
return
}
if _, werr := w.Write(buf); werr != nil {
grpclog.Infof("Failed to notify error to client: %v", werr)
return
}
}
// streamChunk returns a chunk in a response stream for the given result. The
// given errHandler is used to render an error chunk if result is nil.
func streamChunk(ctx context.Context, result proto.Message, errHandler StreamErrorHandlerFunc) map[string]proto.Message {
if result == nil {
return errorChunk(streamError(ctx, errHandler, errEmptyResponse))
}
return map[string]proto.Message{"result": result}
}
// streamError returns the payload for the final message in a response stream
// that represents the given err.
func streamError(ctx context.Context, errHandler StreamErrorHandlerFunc, err error) *StreamError {
serr := errHandler(ctx, err)
if serr != nil {
return serr
}
// TODO: log about misbehaving stream error handler?
return DefaultHTTPStreamErrorHandler(ctx, err)
}
func errorChunk(err *StreamError) map[string]proto.Message {
return map[string]proto.Message{"error": (*internal.StreamError)(err)}
}
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