vendor/google.golang.org/grpc/transport/http_util.go - gddo - Git at Google

 /*
  *
  * Copyright 2014 gRPC authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  */

 package transport

 import (
 	"bufio"
 	"bytes"
 	"encoding/base64"
 	"fmt"
 	"io"
 	"net"
 	"net/http"
 	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"

 	"github.com/golang/protobuf/proto"
 	"golang.org/x/net/http2"
 	"golang.org/x/net/http2/hpack"
 	spb "google.golang.org/genproto/googleapis/rpc/status"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )

 const (
 	// http2MaxFrameLen specifies the max length of a HTTP2 frame.
 	http2MaxFrameLen = 16384 // 16KB frame
 	// http://http2.github.io/http2-spec/#SettingValues
 	http2InitHeaderTableSize = 4096
 	// http2IOBufSize specifies the buffer size for sending frames.
 	http2IOBufSize = 32 * 1024
 )

 var (
 	clientPreface   = []byte(http2.ClientPreface)
 	http2ErrConvTab = map[http2.ErrCode]codes.Code{
 		http2.ErrCodeNo:                 codes.Internal,
 		http2.ErrCodeProtocol:           codes.Internal,
 		http2.ErrCodeInternal:           codes.Internal,
 		http2.ErrCodeFlowControl:        codes.ResourceExhausted,
 		http2.ErrCodeSettingsTimeout:    codes.Internal,
 		http2.ErrCodeStreamClosed:       codes.Internal,
 		http2.ErrCodeFrameSize:          codes.Internal,
 		http2.ErrCodeRefusedStream:      codes.Unavailable,
 		http2.ErrCodeCancel:             codes.Canceled,
 		http2.ErrCodeCompression:        codes.Internal,
 		http2.ErrCodeConnect:            codes.Internal,
 		http2.ErrCodeEnhanceYourCalm:    codes.ResourceExhausted,
 		http2.ErrCodeInadequateSecurity: codes.PermissionDenied,
 		http2.ErrCodeHTTP11Required:     codes.FailedPrecondition,
 	}
 	statusCodeConvTab = map[codes.Code]http2.ErrCode{
 		codes.Internal:          http2.ErrCodeInternal,
 		codes.Canceled:          http2.ErrCodeCancel,
 		codes.Unavailable:       http2.ErrCodeRefusedStream,
 		codes.ResourceExhausted: http2.ErrCodeEnhanceYourCalm,
 		codes.PermissionDenied:  http2.ErrCodeInadequateSecurity,
 	}
 	httpStatusConvTab = map[int]codes.Code{
 		// 400 Bad Request - INTERNAL.
 		http.StatusBadRequest: codes.Internal,
 		// 401 Unauthorized  - UNAUTHENTICATED.
 		http.StatusUnauthorized: codes.Unauthenticated,
 		// 403 Forbidden - PERMISSION_DENIED.
 		http.StatusForbidden: codes.PermissionDenied,
 		// 404 Not Found - UNIMPLEMENTED.
 		http.StatusNotFound: codes.Unimplemented,
 		// 429 Too Many Requests - UNAVAILABLE.
 		http.StatusTooManyRequests: codes.Unavailable,
 		// 502 Bad Gateway - UNAVAILABLE.
 		http.StatusBadGateway: codes.Unavailable,
 		// 503 Service Unavailable - UNAVAILABLE.
 		http.StatusServiceUnavailable: codes.Unavailable,
 		// 504 Gateway timeout - UNAVAILABLE.
 		http.StatusGatewayTimeout: codes.Unavailable,
 	}
 )

 // Records the states during HPACK decoding. Must be reset once the
 // decoding of the entire headers are finished.
 type decodeState struct {
 	encoding string
 	// statusGen caches the stream status received from the trailer the server
 	// sent.  Client side only.  Do not access directly.  After all trailers are
 	// parsed, use the status method to retrieve the status.
 	statusGen *status.Status
 	// rawStatusCode and rawStatusMsg are set from the raw trailer fields and are not
 	// intended for direct access outside of parsing.
 	rawStatusCode *int
 	rawStatusMsg  string
 	httpStatus    *int
 	// Server side only fields.
 	timeoutSet bool
 	timeout    time.Duration
 	method     string
 	// key-value metadata map from the peer.
 	mdata      map[string][]string
 	statsTags  []byte
 	statsTrace []byte
 }

 // isReservedHeader checks whether hdr belongs to HTTP2 headers
 // reserved by gRPC protocol. Any other headers are classified as the
 // user-specified metadata.
 func isReservedHeader(hdr string) bool {
 	if hdr != "" && hdr[0] == ':' {
 		return true
 	}
 	switch hdr {
 	case "content-type",
 		"grpc-message-type",
 		"grpc-encoding",
 		"grpc-message",
 		"grpc-status",
 		"grpc-timeout",
 		"grpc-status-details-bin",
 		"te":
 		return true
 	default:
 		return false
 	}
 }

 // isWhitelistedPseudoHeader checks whether hdr belongs to HTTP2 pseudoheaders
 // that should be propagated into metadata visible to users.
 func isWhitelistedPseudoHeader(hdr string) bool {
 	switch hdr {
 	case ":authority":
 		return true
 	default:
 		return false
 	}
 }

 func validContentType(t string) bool {
 	e := "application/grpc"
 	if !strings.HasPrefix(t, e) {
 		return false
 	}
 	// Support variations on the content-type
 	// (e.g. "application/grpc+blah", "application/grpc;blah").
 	if len(t) > len(e) && t[len(e)] != '+' && t[len(e)] != ';' {
 		return false
 	}
 	return true
 }

 func (d *decodeState) status() *status.Status {
 	if d.statusGen == nil {
 		// No status-details were provided; generate status using code/msg.
 		d.statusGen = status.New(codes.Code(int32(*(d.rawStatusCode))), d.rawStatusMsg)
 	}
 	return d.statusGen
 }

 const binHdrSuffix = "-bin"

 func encodeBinHeader(v []byte) string {
 	return base64.RawStdEncoding.EncodeToString(v)
 }

 func decodeBinHeader(v string) ([]byte, error) {
 	if len(v)%4 == 0 {
 		// Input was padded, or padding was not necessary.
 		return base64.StdEncoding.DecodeString(v)
 	}
 	return base64.RawStdEncoding.DecodeString(v)
 }

 func encodeMetadataHeader(k, v string) string {
 	if strings.HasSuffix(k, binHdrSuffix) {
 		return encodeBinHeader(([]byte)(v))
 	}
 	return v
 }

 func decodeMetadataHeader(k, v string) (string, error) {
 	if strings.HasSuffix(k, binHdrSuffix) {
 		b, err := decodeBinHeader(v)
 		return string(b), err
 	}
 	return v, nil
 }

 func (d *decodeState) decodeResponseHeader(frame *http2.MetaHeadersFrame) error {
 	for _, hf := range frame.Fields {
 		if err := d.processHeaderField(hf); err != nil {
 			return err
 		}
 	}

 	// If grpc status exists, no need to check further.
 	if d.rawStatusCode != nil || d.statusGen != nil {
 		return nil
 	}

 	// If grpc status doesn't exist and http status doesn't exist,
 	// then it's a malformed header.
 	if d.httpStatus == nil {
 		return streamErrorf(codes.Internal, "malformed header: doesn't contain status(gRPC or HTTP)")
 	}

 	if *(d.httpStatus) != http.StatusOK {
 		code, ok := httpStatusConvTab[*(d.httpStatus)]
 		if !ok {
 			code = codes.Unknown
 		}
 		return streamErrorf(code, http.StatusText(*(d.httpStatus)))
 	}

 	// gRPC status doesn't exist and http status is OK.
 	// Set rawStatusCode to be unknown and return nil error.
 	// So that, if the stream has ended this Unknown status
 	// will be propogated to the user.
 	// Otherwise, it will be ignored. In which case, status from
 	// a later trailer, that has StreamEnded flag set, is propogated.
 	code := int(codes.Unknown)
 	d.rawStatusCode = &code
 	return nil

 }

 func (d *decodeState) addMetadata(k, v string) {
 	if d.mdata == nil {
 		d.mdata = make(map[string][]string)
 	}
 	d.mdata[k] = append(d.mdata[k], v)
 }

 func (d *decodeState) processHeaderField(f hpack.HeaderField) error {
 	switch f.Name {
 	case "content-type":
 		if !validContentType(f.Value) {
 			return streamErrorf(codes.FailedPrecondition, "transport: received the unexpected content-type %q", f.Value)
 		}
 	case "grpc-encoding":
 		d.encoding = f.Value
 	case "grpc-status":
 		code, err := strconv.Atoi(f.Value)
 		if err != nil {
 			return streamErrorf(codes.Internal, "transport: malformed grpc-status: %v", err)
 		}
 		d.rawStatusCode = &code
 	case "grpc-message":
 		d.rawStatusMsg = decodeGrpcMessage(f.Value)
 	case "grpc-status-details-bin":
 		v, err := decodeBinHeader(f.Value)
 		if err != nil {
 			return streamErrorf(codes.Internal, "transport: malformed grpc-status-details-bin: %v", err)
 		}
 		s := &spb.Status{}
 		if err := proto.Unmarshal(v, s); err != nil {
 			return streamErrorf(codes.Internal, "transport: malformed grpc-status-details-bin: %v", err)
 		}
 		d.statusGen = status.FromProto(s)
 	case "grpc-timeout":
 		d.timeoutSet = true
 		var err error
 		if d.timeout, err = decodeTimeout(f.Value); err != nil {
 			return streamErrorf(codes.Internal, "transport: malformed time-out: %v", err)
 		}
 	case ":path":
 		d.method = f.Value
 	case ":status":
 		code, err := strconv.Atoi(f.Value)
 		if err != nil {
 			return streamErrorf(codes.Internal, "transport: malformed http-status: %v", err)
 		}
 		d.httpStatus = &code
 	case "grpc-tags-bin":
 		v, err := decodeBinHeader(f.Value)
 		if err != nil {
 			return streamErrorf(codes.Internal, "transport: malformed grpc-tags-bin: %v", err)
 		}
 		d.statsTags = v
 		d.addMetadata(f.Name, string(v))
 	case "grpc-trace-bin":
 		v, err := decodeBinHeader(f.Value)
 		if err != nil {
 			return streamErrorf(codes.Internal, "transport: malformed grpc-trace-bin: %v", err)
 		}
 		d.statsTrace = v
 		d.addMetadata(f.Name, string(v))
 	default:
 		if isReservedHeader(f.Name) && !isWhitelistedPseudoHeader(f.Name) {
 			break
 		}
 		v, err := decodeMetadataHeader(f.Name, f.Value)
 		if err != nil {
 			errorf("Failed to decode metadata header (%q, %q): %v", f.Name, f.Value, err)
 			return nil
 		}
 		d.addMetadata(f.Name, string(v))
 	}
 	return nil
 }

 type timeoutUnit uint8

 const (
 	hour        timeoutUnit = 'H'
 	minute      timeoutUnit = 'M'
 	second      timeoutUnit = 'S'
 	millisecond timeoutUnit = 'm'
 	microsecond timeoutUnit = 'u'
 	nanosecond  timeoutUnit = 'n'
 )

 func timeoutUnitToDuration(u timeoutUnit) (d time.Duration, ok bool) {
 	switch u {
 	case hour:
 		return time.Hour, true
 	case minute:
 		return time.Minute, true
 	case second:
 		return time.Second, true
 	case millisecond:
 		return time.Millisecond, true
 	case microsecond:
 		return time.Microsecond, true
 	case nanosecond:
 		return time.Nanosecond, true
 	default:
 	}
 	return
 }

 const maxTimeoutValue int64 = 100000000 - 1

 // div does integer division and round-up the result. Note that this is
 // equivalent to (d+r-1)/r but has less chance to overflow.
 func div(d, r time.Duration) int64 {
 	if m := d % r; m > 0 {
 		return int64(d/r + 1)
 	}
 	return int64(d / r)
 }

 // TODO(zhaoq): It is the simplistic and not bandwidth efficient. Improve it.
 func encodeTimeout(t time.Duration) string {
 	if t <= 0 {
 		return "0n"
 	}
 	if d := div(t, time.Nanosecond); d <= maxTimeoutValue {
 		return strconv.FormatInt(d, 10) + "n"
 	}
 	if d := div(t, time.Microsecond); d <= maxTimeoutValue {
 		return strconv.FormatInt(d, 10) + "u"
 	}
 	if d := div(t, time.Millisecond); d <= maxTimeoutValue {
 		return strconv.FormatInt(d, 10) + "m"
 	}
 	if d := div(t, time.Second); d <= maxTimeoutValue {
 		return strconv.FormatInt(d, 10) + "S"
 	}
 	if d := div(t, time.Minute); d <= maxTimeoutValue {
 		return strconv.FormatInt(d, 10) + "M"
 	}
 	// Note that maxTimeoutValue * time.Hour > MaxInt64.
 	return strconv.FormatInt(div(t, time.Hour), 10) + "H"
 }

 func decodeTimeout(s string) (time.Duration, error) {
 	size := len(s)
 	if size < 2 {
 		return 0, fmt.Errorf("transport: timeout string is too short: %q", s)
 	}
 	unit := timeoutUnit(s[size-1])
 	d, ok := timeoutUnitToDuration(unit)
 	if !ok {
 		return 0, fmt.Errorf("transport: timeout unit is not recognized: %q", s)
 	}
 	t, err := strconv.ParseInt(s[:size-1], 10, 64)
 	if err != nil {
 		return 0, err
 	}
 	return d * time.Duration(t), nil
 }

 const (
 	spaceByte   = ' '
 	tildaByte   = '~'
 	percentByte = '%'
 )

 // encodeGrpcMessage is used to encode status code in header field
 // "grpc-message".
 // It checks to see if each individual byte in msg is an
 // allowable byte, and then either percent encoding or passing it through.
 // When percent encoding, the byte is converted into hexadecimal notation
 // with a '%' prepended.
 func encodeGrpcMessage(msg string) string {
 	if msg == "" {
 		return ""
 	}
 	lenMsg := len(msg)
 	for i := 0; i < lenMsg; i++ {
 		c := msg[i]
 		if !(c >= spaceByte && c < tildaByte && c != percentByte) {
 			return encodeGrpcMessageUnchecked(msg)
 		}
 	}
 	return msg
 }

 func encodeGrpcMessageUnchecked(msg string) string {
 	var buf bytes.Buffer
 	lenMsg := len(msg)
 	for i := 0; i < lenMsg; i++ {
 		c := msg[i]
 		if c >= spaceByte && c < tildaByte && c != percentByte {
 			buf.WriteByte(c)
 		} else {
 			buf.WriteString(fmt.Sprintf("%%%02X", c))
 		}
 	}
 	return buf.String()
 }

 // decodeGrpcMessage decodes the msg encoded by encodeGrpcMessage.
 func decodeGrpcMessage(msg string) string {
 	if msg == "" {
 		return ""
 	}
 	lenMsg := len(msg)
 	for i := 0; i < lenMsg; i++ {
 		if msg[i] == percentByte && i+2 < lenMsg {
 			return decodeGrpcMessageUnchecked(msg)
 		}
 	}
 	return msg
 }

 func decodeGrpcMessageUnchecked(msg string) string {
 	var buf bytes.Buffer
 	lenMsg := len(msg)
 	for i := 0; i < lenMsg; i++ {
 		c := msg[i]
 		if c == percentByte && i+2 < lenMsg {
 			parsed, err := strconv.ParseUint(msg[i+1:i+3], 16, 8)
 			if err != nil {
 				buf.WriteByte(c)
 			} else {
 				buf.WriteByte(byte(parsed))
 				i += 2
 			}
 		} else {
 			buf.WriteByte(c)
 		}
 	}
 	return buf.String()
 }

 type framer struct {
 	numWriters int32
 	reader     io.Reader
 	writer     *bufio.Writer
 	fr         *http2.Framer
 }

 func newFramer(conn net.Conn) *framer {
 	f := &framer{
 		reader: bufio.NewReaderSize(conn, http2IOBufSize),
 		writer: bufio.NewWriterSize(conn, http2IOBufSize),
 	}
 	f.fr = http2.NewFramer(f.writer, f.reader)
 	// Opt-in to Frame reuse API on framer to reduce garbage.
 	// Frames aren't safe to read from after a subsequent call to ReadFrame.
 	f.fr.SetReuseFrames()
 	f.fr.ReadMetaHeaders = hpack.NewDecoder(http2InitHeaderTableSize, nil)
 	return f
 }

 func (f *framer) adjustNumWriters(i int32) int32 {
 	return atomic.AddInt32(&f.numWriters, i)
 }

 // The following writeXXX functions can only be called when the caller gets
 // unblocked from writableChan channel (i.e., owns the privilege to write).

 func (f *framer) writeContinuation(forceFlush bool, streamID uint32, endHeaders bool, headerBlockFragment []byte) error {
 	if err := f.fr.WriteContinuation(streamID, endHeaders, headerBlockFragment); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writeData(forceFlush bool, streamID uint32, endStream bool, data []byte) error {
 	if err := f.fr.WriteData(streamID, endStream, data); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writeGoAway(forceFlush bool, maxStreamID uint32, code http2.ErrCode, debugData []byte) error {
 	if err := f.fr.WriteGoAway(maxStreamID, code, debugData); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writeHeaders(forceFlush bool, p http2.HeadersFrameParam) error {
 	if err := f.fr.WriteHeaders(p); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writePing(forceFlush, ack bool, data [8]byte) error {
 	if err := f.fr.WritePing(ack, data); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writePriority(forceFlush bool, streamID uint32, p http2.PriorityParam) error {
 	if err := f.fr.WritePriority(streamID, p); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writePushPromise(forceFlush bool, p http2.PushPromiseParam) error {
 	if err := f.fr.WritePushPromise(p); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writeRSTStream(forceFlush bool, streamID uint32, code http2.ErrCode) error {
 	if err := f.fr.WriteRSTStream(streamID, code); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writeSettings(forceFlush bool, settings ...http2.Setting) error {
 	if err := f.fr.WriteSettings(settings...); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writeSettingsAck(forceFlush bool) error {
 	if err := f.fr.WriteSettingsAck(); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) writeWindowUpdate(forceFlush bool, streamID, incr uint32) error {
 	if err := f.fr.WriteWindowUpdate(streamID, incr); err != nil {
 		return err
 	}
 	if forceFlush {
 		return f.writer.Flush()
 	}
 	return nil
 }

 func (f *framer) flushWrite() error {
 	return f.writer.Flush()
 }

 func (f *framer) readFrame() (http2.Frame, error) {
 	return f.fr.ReadFrame()
 }

 func (f *framer) errorDetail() error {
 	return f.fr.ErrorDetail()
 }
	/*
	*
	* Copyright 2014 gRPC authors.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*
	*/

	package transport

	import (
	"bufio"
	"bytes"
	"encoding/base64"
	"fmt"
	"io"
	"net"
	"net/http"
	"strconv"
	"strings"
	"sync/atomic"
	"time"

	"github.com/golang/protobuf/proto"
	"golang.org/x/net/http2"
	"golang.org/x/net/http2/hpack"
	spb "google.golang.org/genproto/googleapis/rpc/status"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
	)

	const (
	// http2MaxFrameLen specifies the max length of a HTTP2 frame.
	http2MaxFrameLen = 16384 // 16KB frame
	// http://http2.github.io/http2-spec/#SettingValues
	http2InitHeaderTableSize = 4096
	// http2IOBufSize specifies the buffer size for sending frames.
	http2IOBufSize = 32 * 1024
	)

	var (
	clientPreface = []byte(http2.ClientPreface)
	http2ErrConvTab = map[http2.ErrCode]codes.Code{
	http2.ErrCodeNo: codes.Internal,
	http2.ErrCodeProtocol: codes.Internal,
	http2.ErrCodeInternal: codes.Internal,
	http2.ErrCodeFlowControl: codes.ResourceExhausted,
	http2.ErrCodeSettingsTimeout: codes.Internal,
	http2.ErrCodeStreamClosed: codes.Internal,
	http2.ErrCodeFrameSize: codes.Internal,
	http2.ErrCodeRefusedStream: codes.Unavailable,
	http2.ErrCodeCancel: codes.Canceled,
	http2.ErrCodeCompression: codes.Internal,
	http2.ErrCodeConnect: codes.Internal,
	http2.ErrCodeEnhanceYourCalm: codes.ResourceExhausted,
	http2.ErrCodeInadequateSecurity: codes.PermissionDenied,
	http2.ErrCodeHTTP11Required: codes.FailedPrecondition,
	}
	statusCodeConvTab = map[codes.Code]http2.ErrCode{
	codes.Internal: http2.ErrCodeInternal,
	codes.Canceled: http2.ErrCodeCancel,
	codes.Unavailable: http2.ErrCodeRefusedStream,
	codes.ResourceExhausted: http2.ErrCodeEnhanceYourCalm,
	codes.PermissionDenied: http2.ErrCodeInadequateSecurity,
	}
	httpStatusConvTab = map[int]codes.Code{
	// 400 Bad Request - INTERNAL.
	http.StatusBadRequest: codes.Internal,
	// 401 Unauthorized - UNAUTHENTICATED.
	http.StatusUnauthorized: codes.Unauthenticated,
	// 403 Forbidden - PERMISSION_DENIED.
	http.StatusForbidden: codes.PermissionDenied,
	// 404 Not Found - UNIMPLEMENTED.
	http.StatusNotFound: codes.Unimplemented,
	// 429 Too Many Requests - UNAVAILABLE.
	http.StatusTooManyRequests: codes.Unavailable,
	// 502 Bad Gateway - UNAVAILABLE.
	http.StatusBadGateway: codes.Unavailable,
	// 503 Service Unavailable - UNAVAILABLE.
	http.StatusServiceUnavailable: codes.Unavailable,
	// 504 Gateway timeout - UNAVAILABLE.
	http.StatusGatewayTimeout: codes.Unavailable,
	}
	)

	// Records the states during HPACK decoding. Must be reset once the
	// decoding of the entire headers are finished.
	type decodeState struct {
	encoding string
	// statusGen caches the stream status received from the trailer the server
	// sent. Client side only. Do not access directly. After all trailers are
	// parsed, use the status method to retrieve the status.
	statusGen *status.Status
	// rawStatusCode and rawStatusMsg are set from the raw trailer fields and are not
	// intended for direct access outside of parsing.
	rawStatusCode *int
	rawStatusMsg string
	httpStatus *int
	// Server side only fields.
	timeoutSet bool
	timeout time.Duration
	method string
	// key-value metadata map from the peer.
	mdata map[string][]string
	statsTags []byte
	statsTrace []byte
	}

	// isReservedHeader checks whether hdr belongs to HTTP2 headers
	// reserved by gRPC protocol. Any other headers are classified as the
	// user-specified metadata.
	func isReservedHeader(hdr string) bool {
	if hdr != "" && hdr[0] == ':' {
	return true
	}
	switch hdr {
	case "content-type",
	"grpc-message-type",
	"grpc-encoding",
	"grpc-message",
	"grpc-status",
	"grpc-timeout",
	"grpc-status-details-bin",
	"te":
	return true
	default:
	return false
	}
	}

	// isWhitelistedPseudoHeader checks whether hdr belongs to HTTP2 pseudoheaders
	// that should be propagated into metadata visible to users.
	func isWhitelistedPseudoHeader(hdr string) bool {
	switch hdr {
	case ":authority":
	return true
	default:
	return false
	}
	}

	func validContentType(t string) bool {
	e := "application/grpc"
	if !strings.HasPrefix(t, e) {
	return false
	}
	// Support variations on the content-type
	// (e.g. "application/grpc+blah", "application/grpc;blah").
	if len(t) > len(e) && t[len(e)] != '+' && t[len(e)] != ';' {
	return false
	}
	return true
	}

	func (d decodeState) status() status.Status {
	if d.statusGen == nil {
	// No status-details were provided; generate status using code/msg.
	d.statusGen = status.New(codes.Code(int32(*(d.rawStatusCode))), d.rawStatusMsg)
	}
	return d.statusGen
	}

	const binHdrSuffix = "-bin"

	func encodeBinHeader(v []byte) string {
	return base64.RawStdEncoding.EncodeToString(v)
	}

	func decodeBinHeader(v string) ([]byte, error) {
	if len(v)%4 == 0 {
	// Input was padded, or padding was not necessary.
	return base64.StdEncoding.DecodeString(v)
	}
	return base64.RawStdEncoding.DecodeString(v)
	}

	func encodeMetadataHeader(k, v string) string {
	if strings.HasSuffix(k, binHdrSuffix) {
	return encodeBinHeader(([]byte)(v))
	}
	return v
	}

	func decodeMetadataHeader(k, v string) (string, error) {
	if strings.HasSuffix(k, binHdrSuffix) {
	b, err := decodeBinHeader(v)
	return string(b), err
	}
	return v, nil
	}

	func (d decodeState) decodeResponseHeader(frame http2.MetaHeadersFrame) error {
	for _, hf := range frame.Fields {
	if err := d.processHeaderField(hf); err != nil {
	return err
	}
	}

	// If grpc status exists, no need to check further.
	if d.rawStatusCode != nil \|\| d.statusGen != nil {
	return nil
	}

	// If grpc status doesn't exist and http status doesn't exist,
	// then it's a malformed header.
	if d.httpStatus == nil {
	return streamErrorf(codes.Internal, "malformed header: doesn't contain status(gRPC or HTTP)")
	}

	if *(d.httpStatus) != http.StatusOK {
	code, ok := httpStatusConvTab[*(d.httpStatus)]
	if !ok {
	code = codes.Unknown
	}
	return streamErrorf(code, http.StatusText(*(d.httpStatus)))
	}

	// gRPC status doesn't exist and http status is OK.
	// Set rawStatusCode to be unknown and return nil error.
	// So that, if the stream has ended this Unknown status
	// will be propogated to the user.
	// Otherwise, it will be ignored. In which case, status from
	// a later trailer, that has StreamEnded flag set, is propogated.
	code := int(codes.Unknown)
	d.rawStatusCode = &code
	return nil

	}

	func (d *decodeState) addMetadata(k, v string) {
	if d.mdata == nil {
	d.mdata = make(map[string][]string)
	}
	d.mdata[k] = append(d.mdata[k], v)
	}

	func (d *decodeState) processHeaderField(f hpack.HeaderField) error {
	switch f.Name {
	case "content-type":
	if !validContentType(f.Value) {
	return streamErrorf(codes.FailedPrecondition, "transport: received the unexpected content-type %q", f.Value)
	}
	case "grpc-encoding":
	d.encoding = f.Value
	case "grpc-status":
	code, err := strconv.Atoi(f.Value)
	if err != nil {
	return streamErrorf(codes.Internal, "transport: malformed grpc-status: %v", err)
	}
	d.rawStatusCode = &code
	case "grpc-message":
	d.rawStatusMsg = decodeGrpcMessage(f.Value)
	case "grpc-status-details-bin":
	v, err := decodeBinHeader(f.Value)
	if err != nil {
	return streamErrorf(codes.Internal, "transport: malformed grpc-status-details-bin: %v", err)
	}
	s := &spb.Status{}
	if err := proto.Unmarshal(v, s); err != nil {
	return streamErrorf(codes.Internal, "transport: malformed grpc-status-details-bin: %v", err)
	}
	d.statusGen = status.FromProto(s)
	case "grpc-timeout":
	d.timeoutSet = true
	var err error
	if d.timeout, err = decodeTimeout(f.Value); err != nil {
	return streamErrorf(codes.Internal, "transport: malformed time-out: %v", err)
	}
	case ":path":
	d.method = f.Value
	case ":status":
	code, err := strconv.Atoi(f.Value)
	if err != nil {
	return streamErrorf(codes.Internal, "transport: malformed http-status: %v", err)
	}
	d.httpStatus = &code
	case "grpc-tags-bin":
	v, err := decodeBinHeader(f.Value)
	if err != nil {
	return streamErrorf(codes.Internal, "transport: malformed grpc-tags-bin: %v", err)
	}
	d.statsTags = v
	d.addMetadata(f.Name, string(v))
	case "grpc-trace-bin":
	v, err := decodeBinHeader(f.Value)
	if err != nil {
	return streamErrorf(codes.Internal, "transport: malformed grpc-trace-bin: %v", err)
	}
	d.statsTrace = v
	d.addMetadata(f.Name, string(v))
	default:
	if isReservedHeader(f.Name) && !isWhitelistedPseudoHeader(f.Name) {
	break
	}
	v, err := decodeMetadataHeader(f.Name, f.Value)
	if err != nil {
	errorf("Failed to decode metadata header (%q, %q): %v", f.Name, f.Value, err)
	return nil
	}
	d.addMetadata(f.Name, string(v))
	}
	return nil
	}

	type timeoutUnit uint8

	const (
	hour timeoutUnit = 'H'
	minute timeoutUnit = 'M'
	second timeoutUnit = 'S'
	millisecond timeoutUnit = 'm'
	microsecond timeoutUnit = 'u'
	nanosecond timeoutUnit = 'n'
	)

	func timeoutUnitToDuration(u timeoutUnit) (d time.Duration, ok bool) {
	switch u {
	case hour:
	return time.Hour, true
	case minute:
	return time.Minute, true
	case second:
	return time.Second, true
	case millisecond:
	return time.Millisecond, true
	case microsecond:
	return time.Microsecond, true
	case nanosecond:
	return time.Nanosecond, true
	default:
	}
	return
	}

	const maxTimeoutValue int64 = 100000000 - 1

	// div does integer division and round-up the result. Note that this is
	// equivalent to (d+r-1)/r but has less chance to overflow.
	func div(d, r time.Duration) int64 {
	if m := d % r; m > 0 {
	return int64(d/r + 1)
	}
	return int64(d / r)
	}

	// TODO(zhaoq): It is the simplistic and not bandwidth efficient. Improve it.
	func encodeTimeout(t time.Duration) string {
	if t <= 0 {
	return "0n"
	}
	if d := div(t, time.Nanosecond); d <= maxTimeoutValue {
	return strconv.FormatInt(d, 10) + "n"
	}
	if d := div(t, time.Microsecond); d <= maxTimeoutValue {
	return strconv.FormatInt(d, 10) + "u"
	}
	if d := div(t, time.Millisecond); d <= maxTimeoutValue {
	return strconv.FormatInt(d, 10) + "m"
	}
	if d := div(t, time.Second); d <= maxTimeoutValue {
	return strconv.FormatInt(d, 10) + "S"
	}
	if d := div(t, time.Minute); d <= maxTimeoutValue {
	return strconv.FormatInt(d, 10) + "M"
	}
	// Note that maxTimeoutValue * time.Hour > MaxInt64.
	return strconv.FormatInt(div(t, time.Hour), 10) + "H"
	}

	func decodeTimeout(s string) (time.Duration, error) {
	size := len(s)
	if size < 2 {
	return 0, fmt.Errorf("transport: timeout string is too short: %q", s)
	}
	unit := timeoutUnit(s[size-1])
	d, ok := timeoutUnitToDuration(unit)
	if !ok {
	return 0, fmt.Errorf("transport: timeout unit is not recognized: %q", s)
	}
	t, err := strconv.ParseInt(s[:size-1], 10, 64)
	if err != nil {
	return 0, err
	}
	return d * time.Duration(t), nil
	}

	const (
	spaceByte = ' '
	tildaByte = '~'
	percentByte = '%'
	)

	// encodeGrpcMessage is used to encode status code in header field
	// "grpc-message".
	// It checks to see if each individual byte in msg is an
	// allowable byte, and then either percent encoding or passing it through.
	// When percent encoding, the byte is converted into hexadecimal notation
	// with a '%' prepended.
	func encodeGrpcMessage(msg string) string {
	if msg == "" {
	return ""
	}
	lenMsg := len(msg)
	for i := 0; i < lenMsg; i++ {
	c := msg[i]
	if !(c >= spaceByte && c < tildaByte && c != percentByte) {
	return encodeGrpcMessageUnchecked(msg)
	}
	}
	return msg
	}

	func encodeGrpcMessageUnchecked(msg string) string {
	var buf bytes.Buffer
	lenMsg := len(msg)
	for i := 0; i < lenMsg; i++ {
	c := msg[i]
	if c >= spaceByte && c < tildaByte && c != percentByte {
	buf.WriteByte(c)
	} else {
	buf.WriteString(fmt.Sprintf("%%%02X", c))
	}
	}
	return buf.String()
	}

	// decodeGrpcMessage decodes the msg encoded by encodeGrpcMessage.
	func decodeGrpcMessage(msg string) string {
	if msg == "" {
	return ""
	}
	lenMsg := len(msg)
	for i := 0; i < lenMsg; i++ {
	if msg[i] == percentByte && i+2 < lenMsg {
	return decodeGrpcMessageUnchecked(msg)
	}
	}
	return msg
	}

	func decodeGrpcMessageUnchecked(msg string) string {
	var buf bytes.Buffer
	lenMsg := len(msg)
	for i := 0; i < lenMsg; i++ {
	c := msg[i]
	if c == percentByte && i+2 < lenMsg {
	parsed, err := strconv.ParseUint(msg[i+1:i+3], 16, 8)
	if err != nil {
	buf.WriteByte(c)
	} else {
	buf.WriteByte(byte(parsed))
	i += 2
	}
	} else {
	buf.WriteByte(c)
	}
	}
	return buf.String()
	}

	type framer struct {
	numWriters int32
	reader io.Reader
	writer *bufio.Writer
	fr *http2.Framer
	}

	func newFramer(conn net.Conn) *framer {
	f := &framer{
	reader: bufio.NewReaderSize(conn, http2IOBufSize),
	writer: bufio.NewWriterSize(conn, http2IOBufSize),
	}
	f.fr = http2.NewFramer(f.writer, f.reader)
	// Opt-in to Frame reuse API on framer to reduce garbage.
	// Frames aren't safe to read from after a subsequent call to ReadFrame.
	f.fr.SetReuseFrames()
	f.fr.ReadMetaHeaders = hpack.NewDecoder(http2InitHeaderTableSize, nil)
	return f
	}

	func (f *framer) adjustNumWriters(i int32) int32 {
	return atomic.AddInt32(&f.numWriters, i)
	}

	// The following writeXXX functions can only be called when the caller gets
	// unblocked from writableChan channel (i.e., owns the privilege to write).

	func (f *framer) writeContinuation(forceFlush bool, streamID uint32, endHeaders bool, headerBlockFragment []byte) error {
	if err := f.fr.WriteContinuation(streamID, endHeaders, headerBlockFragment); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writeData(forceFlush bool, streamID uint32, endStream bool, data []byte) error {
	if err := f.fr.WriteData(streamID, endStream, data); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writeGoAway(forceFlush bool, maxStreamID uint32, code http2.ErrCode, debugData []byte) error {
	if err := f.fr.WriteGoAway(maxStreamID, code, debugData); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writeHeaders(forceFlush bool, p http2.HeadersFrameParam) error {
	if err := f.fr.WriteHeaders(p); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writePing(forceFlush, ack bool, data [8]byte) error {
	if err := f.fr.WritePing(ack, data); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writePriority(forceFlush bool, streamID uint32, p http2.PriorityParam) error {
	if err := f.fr.WritePriority(streamID, p); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writePushPromise(forceFlush bool, p http2.PushPromiseParam) error {
	if err := f.fr.WritePushPromise(p); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writeRSTStream(forceFlush bool, streamID uint32, code http2.ErrCode) error {
	if err := f.fr.WriteRSTStream(streamID, code); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writeSettings(forceFlush bool, settings ...http2.Setting) error {
	if err := f.fr.WriteSettings(settings...); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writeSettingsAck(forceFlush bool) error {
	if err := f.fr.WriteSettingsAck(); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) writeWindowUpdate(forceFlush bool, streamID, incr uint32) error {
	if err := f.fr.WriteWindowUpdate(streamID, incr); err != nil {
	return err
	}
	if forceFlush {
	return f.writer.Flush()
	}
	return nil
	}

	func (f *framer) flushWrite() error {
	return f.writer.Flush()
	}

	func (f *framer) readFrame() (http2.Frame, error) {
	return f.fr.ReadFrame()
	}

	func (f *framer) errorDetail() error {
	return f.fr.ErrorDetail()
	}