// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// HTTP server. See RFC 7230 through 7235.

package http

import (
	
	
	
	
	
	
	
	
	
	
	
	
	urlpkg 
	
	
	
	
	
	
	
	
	

	
)

// Errors used by the HTTP server.
var (
	// ErrBodyNotAllowed is returned by ResponseWriter.Write calls
	// when the HTTP method or response code does not permit a
	// body.
	ErrBodyNotAllowed = errors.New("http: request method or response status code does not allow body")

	// ErrHijacked is returned by ResponseWriter.Write calls when
	// the underlying connection has been hijacked using the
	// Hijacker interface. A zero-byte write on a hijacked
	// connection will return ErrHijacked without any other side
	// effects.
	ErrHijacked = errors.New("http: connection has been hijacked")

	// ErrContentLength is returned by ResponseWriter.Write calls
	// when a Handler set a Content-Length response header with a
	// declared size and then attempted to write more bytes than
	// declared.
	ErrContentLength = errors.New("http: wrote more than the declared Content-Length")

	// Deprecated: ErrWriteAfterFlush is no longer returned by
	// anything in the net/http package. Callers should not
	// compare errors against this variable.
	ErrWriteAfterFlush = errors.New("unused")
)

// A Handler responds to an HTTP request.
//
// ServeHTTP should write reply headers and data to the ResponseWriter
// and then return. Returning signals that the request is finished; it
// is not valid to use the ResponseWriter or read from the
// Request.Body after or concurrently with the completion of the
// ServeHTTP call.
//
// Depending on the HTTP client software, HTTP protocol version, and
// any intermediaries between the client and the Go server, it may not
// be possible to read from the Request.Body after writing to the
// ResponseWriter. Cautious handlers should read the Request.Body
// first, and then reply.
//
// Except for reading the body, handlers should not modify the
// provided Request.
//
// If ServeHTTP panics, the server (the caller of ServeHTTP) assumes
// that the effect of the panic was isolated to the active request.
// It recovers the panic, logs a stack trace to the server error log,
// and either closes the network connection or sends an HTTP/2
// RST_STREAM, depending on the HTTP protocol. To abort a handler so
// the client sees an interrupted response but the server doesn't log
// an error, panic with the value ErrAbortHandler.
type Handler interface {
	ServeHTTP(ResponseWriter, *Request)
}

// A ResponseWriter interface is used by an HTTP handler to
// construct an HTTP response.
//
// A ResponseWriter may not be used after the Handler.ServeHTTP method
// has returned.
type ResponseWriter interface {
	// Header returns the header map that will be sent by
	// WriteHeader. The Header map also is the mechanism with which
	// Handlers can set HTTP trailers.
	//
	// Changing the header map after a call to WriteHeader (or
	// Write) has no effect unless the modified headers are
	// trailers.
	//
	// There are two ways to set Trailers. The preferred way is to
	// predeclare in the headers which trailers you will later
	// send by setting the "Trailer" header to the names of the
	// trailer keys which will come later. In this case, those
	// keys of the Header map are treated as if they were
	// trailers. See the example. The second way, for trailer
	// keys not known to the Handler until after the first Write,
	// is to prefix the Header map keys with the TrailerPrefix
	// constant value. See TrailerPrefix.
	//
	// To suppress automatic response headers (such as "Date"), set
	// their value to nil.
	Header() Header

	// Write writes the data to the connection as part of an HTTP reply.
	//
	// If WriteHeader has not yet been called, Write calls
	// WriteHeader(http.StatusOK) before writing the data. If the Header
	// does not contain a Content-Type line, Write adds a Content-Type set
	// to the result of passing the initial 512 bytes of written data to
	// DetectContentType. Additionally, if the total size of all written
	// data is under a few KB and there are no Flush calls, the
	// Content-Length header is added automatically.
	//
	// Depending on the HTTP protocol version and the client, calling
	// Write or WriteHeader may prevent future reads on the
	// Request.Body. For HTTP/1.x requests, handlers should read any
	// needed request body data before writing the response. Once the
	// headers have been flushed (due to either an explicit Flusher.Flush
	// call or writing enough data to trigger a flush), the request body
	// may be unavailable. For HTTP/2 requests, the Go HTTP server permits
	// handlers to continue to read the request body while concurrently
	// writing the response. However, such behavior may not be supported
	// by all HTTP/2 clients. Handlers should read before writing if
	// possible to maximize compatibility.
	Write([]byte) (int, error)

	// WriteHeader sends an HTTP response header with the provided
	// status code.
	//
	// If WriteHeader is not called explicitly, the first call to Write
	// will trigger an implicit WriteHeader(http.StatusOK).
	// Thus explicit calls to WriteHeader are mainly used to
	// send error codes.
	//
	// The provided code must be a valid HTTP 1xx-5xx status code.
	// Only one header may be written. Go does not currently
	// support sending user-defined 1xx informational headers,
	// with the exception of 100-continue response header that the
	// Server sends automatically when the Request.Body is read.
	WriteHeader(statusCode int)
}

// The Flusher interface is implemented by ResponseWriters that allow
// an HTTP handler to flush buffered data to the client.
//
// The default HTTP/1.x and HTTP/2 ResponseWriter implementations
// support Flusher, but ResponseWriter wrappers may not. Handlers
// should always test for this ability at runtime.
//
// Note that even for ResponseWriters that support Flush,
// if the client is connected through an HTTP proxy,
// the buffered data may not reach the client until the response
// completes.
type Flusher interface {
	// Flush sends any buffered data to the client.
	Flush()
}

// The Hijacker interface is implemented by ResponseWriters that allow
// an HTTP handler to take over the connection.
//
// The default ResponseWriter for HTTP/1.x connections supports
// Hijacker, but HTTP/2 connections intentionally do not.
// ResponseWriter wrappers may also not support Hijacker. Handlers
// should always test for this ability at runtime.
type Hijacker interface {
	// Hijack lets the caller take over the connection.
	// After a call to Hijack the HTTP server library
	// will not do anything else with the connection.
	//
	// It becomes the caller's responsibility to manage
	// and close the connection.
	//
	// The returned net.Conn may have read or write deadlines
	// already set, depending on the configuration of the
	// Server. It is the caller's responsibility to set
	// or clear those deadlines as needed.
	//
	// The returned bufio.Reader may contain unprocessed buffered
	// data from the client.
	//
	// After a call to Hijack, the original Request.Body must not
	// be used. The original Request's Context remains valid and
	// is not canceled until the Request's ServeHTTP method
	// returns.
	Hijack() (net.Conn, *bufio.ReadWriter, error)
}

// The CloseNotifier interface is implemented by ResponseWriters which
// allow detecting when the underlying connection has gone away.
//
// This mechanism can be used to cancel long operations on the server
// if the client has disconnected before the response is ready.
//
// Deprecated: the CloseNotifier interface predates Go's context package.
// New code should use Request.Context instead.
type CloseNotifier interface {
	// CloseNotify returns a channel that receives at most a
	// single value (true) when the client connection has gone
	// away.
	//
	// CloseNotify may wait to notify until Request.Body has been
	// fully read.
	//
	// After the Handler has returned, there is no guarantee
	// that the channel receives a value.
	//
	// If the protocol is HTTP/1.1 and CloseNotify is called while
	// processing an idempotent request (such a GET) while
	// HTTP/1.1 pipelining is in use, the arrival of a subsequent
	// pipelined request may cause a value to be sent on the
	// returned channel. In practice HTTP/1.1 pipelining is not
	// enabled in browsers and not seen often in the wild. If this
	// is a problem, use HTTP/2 or only use CloseNotify on methods
	// such as POST.
	CloseNotify() <-chan bool
}

var (
	// ServerContextKey is a context key. It can be used in HTTP
	// handlers with Context.Value to access the server that
	// started the handler. The associated value will be of
	// type *Server.
	ServerContextKey = &contextKey{"http-server"}

	// LocalAddrContextKey is a context key. It can be used in
	// HTTP handlers with Context.Value to access the local
	// address the connection arrived on.
	// The associated value will be of type net.Addr.
	LocalAddrContextKey = &contextKey{"local-addr"}
)

// A conn represents the server side of an HTTP connection.
type conn struct {
	// server is the server on which the connection arrived.
	// Immutable; never nil.
	server *Server

	// cancelCtx cancels the connection-level context.
	cancelCtx context.CancelFunc

	// rwc is the underlying network connection.
	// This is never wrapped by other types and is the value given out
	// to CloseNotifier callers. It is usually of type *net.TCPConn or
	// *tls.Conn.
	rwc net.Conn

	// remoteAddr is rwc.RemoteAddr().String(). It is not populated synchronously
	// inside the Listener's Accept goroutine, as some implementations block.
	// It is populated immediately inside the (*conn).serve goroutine.
	// This is the value of a Handler's (*Request).RemoteAddr.
	remoteAddr string

	// tlsState is the TLS connection state when using TLS.
	// nil means not TLS.
	tlsState *tls.ConnectionState

	// werr is set to the first write error to rwc.
	// It is set via checkConnErrorWriter{w}, where bufw writes.
	werr error

	// r is bufr's read source. It's a wrapper around rwc that provides
	// io.LimitedReader-style limiting (while reading request headers)
	// and functionality to support CloseNotifier. See *connReader docs.
	r *connReader

	// bufr reads from r.
	bufr *bufio.Reader

	// bufw writes to checkConnErrorWriter{c}, which populates werr on error.
	bufw *bufio.Writer

	// lastMethod is the method of the most recent request
	// on this connection, if any.
	lastMethod string

	curReq atomic.Value // of *response (which has a Request in it)

	curState struct{ atomic uint64 } // packed (unixtime<<8|uint8(ConnState))

	// mu guards hijackedv
	mu sync.Mutex

	// hijackedv is whether this connection has been hijacked
	// by a Handler with the Hijacker interface.
	// It is guarded by mu.
	hijackedv bool
}

func ( *conn) () bool {
	.mu.Lock()
	defer .mu.Unlock()
	return .hijackedv
}

// c.mu must be held.
func ( *conn) () ( net.Conn,  *bufio.ReadWriter,  error) {
	if .hijackedv {
		return nil, nil, ErrHijacked
	}
	.r.abortPendingRead()

	.hijackedv = true
	 = .rwc
	.SetDeadline(time.Time{})

	 = bufio.NewReadWriter(.bufr, bufio.NewWriter())
	if .r.hasByte {
		if ,  := .bufr.Peek(.bufr.Buffered() + 1);  != nil {
			return nil, nil, fmt.Errorf("unexpected Peek failure reading buffered byte: %v", )
		}
	}
	.setState(, StateHijacked, runHooks)
	return
}

// This should be >= 512 bytes for DetectContentType,
// but otherwise it's somewhat arbitrary.
const bufferBeforeChunkingSize = 2048

// chunkWriter writes to a response's conn buffer, and is the writer
// wrapped by the response.bufw buffered writer.
//
// chunkWriter also is responsible for finalizing the Header, including
// conditionally setting the Content-Type and setting a Content-Length
// in cases where the handler's final output is smaller than the buffer
// size. It also conditionally adds chunk headers, when in chunking mode.
//
// See the comment above (*response).Write for the entire write flow.
type chunkWriter struct {
	res *response

	// header is either nil or a deep clone of res.handlerHeader
	// at the time of res.writeHeader, if res.writeHeader is
	// called and extra buffering is being done to calculate
	// Content-Type and/or Content-Length.
	header Header

	// wroteHeader tells whether the header's been written to "the
	// wire" (or rather: w.conn.buf). this is unlike
	// (*response).wroteHeader, which tells only whether it was
	// logically written.
	wroteHeader bool

	// set by the writeHeader method:
	chunking bool // using chunked transfer encoding for reply body
}

var (
	crlf       = []byte("\r\n")
	colonSpace = []byte(": ")
)

func ( *chunkWriter) ( []byte) ( int,  error) {
	if !.wroteHeader {
		.writeHeader()
	}
	if .res.req.Method == "HEAD" {
		// Eat writes.
		return len(), nil
	}
	if .chunking {
		_,  = fmt.Fprintf(.res.conn.bufw, "%x\r\n", len())
		if  != nil {
			.res.conn.rwc.Close()
			return
		}
	}
	,  = .res.conn.bufw.Write()
	if .chunking &&  == nil {
		_,  = .res.conn.bufw.Write(crlf)
	}
	if  != nil {
		.res.conn.rwc.Close()
	}
	return
}

func ( *chunkWriter) () {
	if !.wroteHeader {
		.writeHeader(nil)
	}
	.res.conn.bufw.Flush()
}

func ( *chunkWriter) () {
	if !.wroteHeader {
		.writeHeader(nil)
	}
	if .chunking {
		 := .res.conn.bufw // conn's bufio writer
		// zero chunk to mark EOF
		.WriteString("0\r\n")
		if  := .res.finalTrailers();  != nil {
			.Write() // the writer handles noting errors
		}
		// final blank line after the trailers (whether
		// present or not)
		.WriteString("\r\n")
	}
}

// A response represents the server side of an HTTP response.
type response struct {
	conn             *conn
	req              *Request // request for this response
	reqBody          io.ReadCloser
	cancelCtx        context.CancelFunc // when ServeHTTP exits
	wroteHeader      bool               // reply header has been (logically) written
	wroteContinue    bool               // 100 Continue response was written
	wants10KeepAlive bool               // HTTP/1.0 w/ Connection "keep-alive"
	wantsClose       bool               // HTTP request has Connection "close"

	// canWriteContinue is a boolean value accessed as an atomic int32
	// that says whether or not a 100 Continue header can be written
	// to the connection.
	// writeContinueMu must be held while writing the header.
	// These two fields together synchronize the body reader
	// (the expectContinueReader, which wants to write 100 Continue)
	// against the main writer.
	canWriteContinue atomicBool
	writeContinueMu  sync.Mutex

	w  *bufio.Writer // buffers output in chunks to chunkWriter
	cw chunkWriter

	// handlerHeader is the Header that Handlers get access to,
	// which may be retained and mutated even after WriteHeader.
	// handlerHeader is copied into cw.header at WriteHeader
	// time, and privately mutated thereafter.
	handlerHeader Header
	calledHeader  bool // handler accessed handlerHeader via Header

	written       int64 // number of bytes written in body
	contentLength int64 // explicitly-declared Content-Length; or -1
	status        int   // status code passed to WriteHeader

	// close connection after this reply.  set on request and
	// updated after response from handler if there's a
	// "Connection: keep-alive" response header and a
	// Content-Length.
	closeAfterReply bool

	// requestBodyLimitHit is set by requestTooLarge when
	// maxBytesReader hits its max size. It is checked in
	// WriteHeader, to make sure we don't consume the
	// remaining request body to try to advance to the next HTTP
	// request. Instead, when this is set, we stop reading
	// subsequent requests on this connection and stop reading
	// input from it.
	requestBodyLimitHit bool

	// trailers are the headers to be sent after the handler
	// finishes writing the body. This field is initialized from
	// the Trailer response header when the response header is
	// written.
	trailers []string

	handlerDone atomicBool // set true when the handler exits

	// Buffers for Date, Content-Length, and status code
	dateBuf   [len(TimeFormat)]byte
	clenBuf   [10]byte
	statusBuf [3]byte

	// closeNotifyCh is the channel returned by CloseNotify.
	// TODO(bradfitz): this is currently (for Go 1.8) always
	// non-nil. Make this lazily-created again as it used to be?
	closeNotifyCh  chan bool
	didCloseNotify int32 // atomic (only 0->1 winner should send)
}

// TrailerPrefix is a magic prefix for ResponseWriter.Header map keys
// that, if present, signals that the map entry is actually for
// the response trailers, and not the response headers. The prefix
// is stripped after the ServeHTTP call finishes and the values are
// sent in the trailers.
//
// This mechanism is intended only for trailers that are not known
// prior to the headers being written. If the set of trailers is fixed
// or known before the header is written, the normal Go trailers mechanism
// is preferred:
//    https://golang.org/pkg/net/http/#ResponseWriter
//    https://golang.org/pkg/net/http/#example_ResponseWriter_trailers
const TrailerPrefix = "Trailer:"

// finalTrailers is called after the Handler exits and returns a non-nil
// value if the Handler set any trailers.
func ( *response) () Header {
	var  Header
	for ,  := range .handlerHeader {
		if strings.HasPrefix(, TrailerPrefix) {
			if  == nil {
				 = make(Header)
			}
			[strings.TrimPrefix(, TrailerPrefix)] = 
		}
	}
	for ,  := range .trailers {
		if  == nil {
			 = make(Header)
		}
		for ,  := range .handlerHeader[] {
			.Add(, )
		}
	}
	return 
}

type atomicBool int32

func ( *atomicBool) () bool { return atomic.LoadInt32((*int32)()) != 0 }
func ( *atomicBool) ()    { atomic.StoreInt32((*int32)(), 1) }
func ( *atomicBool) ()   { atomic.StoreInt32((*int32)(), 0) }

// declareTrailer is called for each Trailer header when the
// response header is written. It notes that a header will need to be
// written in the trailers at the end of the response.
func ( *response) ( string) {
	 = CanonicalHeaderKey()
	if !httpguts.ValidTrailerHeader() {
		// Forbidden by RFC 7230, section 4.1.2
		return
	}
	.trailers = append(.trailers, )
}

// requestTooLarge is called by maxBytesReader when too much input has
// been read from the client.
func ( *response) () {
	.closeAfterReply = true
	.requestBodyLimitHit = true
	if !.wroteHeader {
		.Header().Set("Connection", "close")
	}
}

// needsSniff reports whether a Content-Type still needs to be sniffed.
func ( *response) () bool {
	,  := .handlerHeader["Content-Type"]
	return !.cw.wroteHeader && ! && .written < sniffLen
}

// writerOnly hides an io.Writer value's optional ReadFrom method
// from io.Copy.
type writerOnly struct {
	io.Writer
}

// ReadFrom is here to optimize copying from an *os.File regular file
// to a *net.TCPConn with sendfile, or from a supported src type such
// as a *net.TCPConn on Linux with splice.
func ( *response) ( io.Reader) ( int64,  error) {
	 := copyBufPool.Get().(*[]byte)
	 := *
	defer copyBufPool.Put()

	// Our underlying w.conn.rwc is usually a *TCPConn (with its
	// own ReadFrom method). If not, just fall back to the normal
	// copy method.
	,  := .conn.rwc.(io.ReaderFrom)
	if ! {
		return io.CopyBuffer(writerOnly{}, , )
	}

	// sendfile path:

	// Do not start actually writing response until src is readable.
	// If body length is <= sniffLen, sendfile/splice path will do
	// little anyway. This small read also satisfies sniffing the
	// body in case Content-Type is missing.
	,  := .Read([:sniffLen])
	 := errors.Is(, io.EOF)
	 += int64()

	if  > 0 {
		// Write the small amount read normally.
		,  := .Write([:])
		if  != nil {
			 = 
		} else if  !=  {
			 = io.ErrShortWrite
		}
	}
	if  == nil &&  != nil && ! {
		 = 
	}

	// Do not send StatusOK in the error case where nothing has been written.
	if  == nil && !.wroteHeader {
		.WriteHeader(StatusOK) // nr == 0, no error (or EOF)
	}

	if  != nil ||  {
		return , 
	}

	.w.Flush()  // get rid of any previous writes
	.cw.flush() // make sure Header is written; flush data to rwc

	// Now that cw has been flushed, its chunking field is guaranteed initialized.
	if !.cw.chunking && .bodyAllowed() {
		,  := .ReadFrom()
		 += 
		.written += 
		return , 
	}

	,  := io.Copy(writerOnly{}, )
	 += 
	return , 
}

// debugServerConnections controls whether all server connections are wrapped
// with a verbose logging wrapper.
const debugServerConnections = false

// Create new connection from rwc.
func ( *Server) ( net.Conn) *conn {
	 := &conn{
		server: ,
		rwc:    ,
	}
	if debugServerConnections {
		.rwc = newLoggingConn("server", .rwc)
	}
	return 
}

type readResult struct {
	_   incomparable
	n   int
	err error
	b   byte // byte read, if n == 1
}

// connReader is the io.Reader wrapper used by *conn. It combines a
// selectively-activated io.LimitedReader (to bound request header
// read sizes) with support for selectively keeping an io.Reader.Read
// call blocked in a background goroutine to wait for activity and
// trigger a CloseNotifier channel.
type connReader struct {
	conn *conn

	mu      sync.Mutex // guards following
	hasByte bool
	byteBuf [1]byte
	cond    *sync.Cond
	inRead  bool
	aborted bool  // set true before conn.rwc deadline is set to past
	remain  int64 // bytes remaining
}

func ( *connReader) () {
	.mu.Lock()
	if .cond == nil {
		.cond = sync.NewCond(&.mu)
	}
}

func ( *connReader) () { .mu.Unlock() }

func ( *connReader) () {
	.lock()
	defer .unlock()
	if .inRead {
		panic("invalid concurrent Body.Read call")
	}
	if .hasByte {
		return
	}
	.inRead = true
	.conn.rwc.SetReadDeadline(time.Time{})
	go .backgroundRead()
}

func ( *connReader) () {
	,  := .conn.rwc.Read(.byteBuf[:])
	.lock()
	if  == 1 {
		.hasByte = true
		// We were past the end of the previous request's body already
		// (since we wouldn't be in a background read otherwise), so
		// this is a pipelined HTTP request. Prior to Go 1.11 we used to
		// send on the CloseNotify channel and cancel the context here,
		// but the behavior was documented as only "may", and we only
		// did that because that's how CloseNotify accidentally behaved
		// in very early Go releases prior to context support. Once we
		// added context support, people used a Handler's
		// Request.Context() and passed it along. Having that context
		// cancel on pipelined HTTP requests caused problems.
		// Fortunately, almost nothing uses HTTP/1.x pipelining.
		// Unfortunately, apt-get does, or sometimes does.
		// New Go 1.11 behavior: don't fire CloseNotify or cancel
		// contexts on pipelined requests. Shouldn't affect people, but
		// fixes cases like Issue 23921. This does mean that a client
		// closing their TCP connection after sending a pipelined
		// request won't cancel the context, but we'll catch that on any
		// write failure (in checkConnErrorWriter.Write).
		// If the server never writes, yes, there are still contrived
		// server & client behaviors where this fails to ever cancel the
		// context, but that's kinda why HTTP/1.x pipelining died
		// anyway.
	}
	if ,  := .(net.Error);  && .aborted && .Timeout() {
		// Ignore this error. It's the expected error from
		// another goroutine calling abortPendingRead.
	} else if  != nil {
		.handleReadError()
	}
	.aborted = false
	.inRead = false
	.unlock()
	.cond.Broadcast()
}

func ( *connReader) () {
	.lock()
	defer .unlock()
	if !.inRead {
		return
	}
	.aborted = true
	.conn.rwc.SetReadDeadline(aLongTimeAgo)
	for .inRead {
		.cond.Wait()
	}
	.conn.rwc.SetReadDeadline(time.Time{})
}

func ( *connReader) ( int64) { .remain =  }
func ( *connReader) ()     { .remain = maxInt64 }
func ( *connReader) () bool        { return .remain <= 0 }

// handleReadError is called whenever a Read from the client returns a
// non-nil error.
//
// The provided non-nil err is almost always io.EOF or a "use of
// closed network connection". In any case, the error is not
// particularly interesting, except perhaps for debugging during
// development. Any error means the connection is dead and we should
// down its context.
//
// It may be called from multiple goroutines.
func ( *connReader) ( error) {
	.conn.cancelCtx()
	.closeNotify()
}

// may be called from multiple goroutines.
func ( *connReader) () {
	,  := .conn.curReq.Load().(*response)
	if  != nil && atomic.CompareAndSwapInt32(&.didCloseNotify, 0, 1) {
		.closeNotifyCh <- true
	}
}

func ( *connReader) ( []byte) ( int,  error) {
	.lock()
	if .inRead {
		.unlock()
		if .conn.hijacked() {
			panic("invalid Body.Read call. After hijacked, the original Request must not be used")
		}
		panic("invalid concurrent Body.Read call")
	}
	if .hitReadLimit() {
		.unlock()
		return 0, io.EOF
	}
	if len() == 0 {
		.unlock()
		return 0, nil
	}
	if int64(len()) > .remain {
		 = [:.remain]
	}
	if .hasByte {
		[0] = .byteBuf[0]
		.hasByte = false
		.unlock()
		return 1, nil
	}
	.inRead = true
	.unlock()
	,  = .conn.rwc.Read()

	.lock()
	.inRead = false
	if  != nil {
		.handleReadError()
	}
	.remain -= int64()
	.unlock()

	.cond.Broadcast()
	return , 
}

var (
	bufioReaderPool   sync.Pool
	bufioWriter2kPool sync.Pool
	bufioWriter4kPool sync.Pool
)

var copyBufPool = sync.Pool{
	New: func() interface{} {
		 := make([]byte, 32*1024)
		return &
	},
}

func bufioWriterPool( int) *sync.Pool {
	switch  {
	case 2 << 10:
		return &bufioWriter2kPool
	case 4 << 10:
		return &bufioWriter4kPool
	}
	return nil
}

func newBufioReader( io.Reader) *bufio.Reader {
	if  := bufioReaderPool.Get();  != nil {
		 := .(*bufio.Reader)
		.Reset()
		return 
	}
	// Note: if this reader size is ever changed, update
	// TestHandlerBodyClose's assumptions.
	return bufio.NewReader()
}

func putBufioReader( *bufio.Reader) {
	.Reset(nil)
	bufioReaderPool.Put()
}

func newBufioWriterSize( io.Writer,  int) *bufio.Writer {
	 := bufioWriterPool()
	if  != nil {
		if  := .Get();  != nil {
			 := .(*bufio.Writer)
			.Reset()
			return 
		}
	}
	return bufio.NewWriterSize(, )
}

func putBufioWriter( *bufio.Writer) {
	.Reset(nil)
	if  := bufioWriterPool(.Available());  != nil {
		.Put()
	}
}

// DefaultMaxHeaderBytes is the maximum permitted size of the headers
// in an HTTP request.
// This can be overridden by setting Server.MaxHeaderBytes.
const DefaultMaxHeaderBytes = 1 << 20 // 1 MB

func ( *Server) () int {
	if .MaxHeaderBytes > 0 {
		return .MaxHeaderBytes
	}
	return DefaultMaxHeaderBytes
}

func ( *Server) () int64 {
	return int64(.maxHeaderBytes()) + 4096 // bufio slop
}

// wrapper around io.ReadCloser which on first read, sends an
// HTTP/1.1 100 Continue header
type expectContinueReader struct {
	resp       *response
	readCloser io.ReadCloser
	closed     atomicBool
	sawEOF     atomicBool
}

func ( *expectContinueReader) ( []byte) ( int,  error) {
	if .closed.isSet() {
		return 0, ErrBodyReadAfterClose
	}
	 := .resp
	if !.wroteContinue && .canWriteContinue.isSet() && !.conn.hijacked() {
		.wroteContinue = true
		.writeContinueMu.Lock()
		if .canWriteContinue.isSet() {
			.conn.bufw.WriteString("HTTP/1.1 100 Continue\r\n\r\n")
			.conn.bufw.Flush()
			.canWriteContinue.setFalse()
		}
		.writeContinueMu.Unlock()
	}
	,  = .readCloser.Read()
	if  == io.EOF {
		.sawEOF.setTrue()
	}
	return
}

func ( *expectContinueReader) () error {
	.closed.setTrue()
	return .readCloser.Close()
}

// TimeFormat is the time format to use when generating times in HTTP
// headers. It is like time.RFC1123 but hard-codes GMT as the time
// zone. The time being formatted must be in UTC for Format to
// generate the correct format.
//
// For parsing this time format, see ParseTime.
const TimeFormat = "Mon, 02 Jan 2006 15:04:05 GMT"

// appendTime is a non-allocating version of []byte(t.UTC().Format(TimeFormat))
func appendTime( []byte,  time.Time) []byte {
	const  = "SunMonTueWedThuFriSat"
	const  = "JanFebMarAprMayJunJulAugSepOctNovDec"

	 = .UTC()
	, ,  := .Date()
	, ,  := .Clock()
	 := [3*.Weekday():]
	 := [3*(-1):]

	return append(,
		[0], [1], [2], ',', ' ',
		byte('0'+/10), byte('0'+%10), ' ',
		[0], [1], [2], ' ',
		byte('0'+/1000), byte('0'+(/100)%10), byte('0'+(/10)%10), byte('0'+%10), ' ',
		byte('0'+/10), byte('0'+%10), ':',
		byte('0'+/10), byte('0'+%10), ':',
		byte('0'+/10), byte('0'+%10), ' ',
		'G', 'M', 'T')
}

var errTooLarge = errors.New("http: request too large")

// Read next request from connection.
func ( *conn) ( context.Context) ( *response,  error) {
	if .hijacked() {
		return nil, ErrHijacked
	}

	var (
		 time.Time // or zero if none
		      time.Time // or zero if none
	)
	 := time.Now()
	if  := .server.readHeaderTimeout();  != 0 {
		 = .Add()
	}
	if  := .server.ReadTimeout;  != 0 {
		 = .Add()
	}
	.rwc.SetReadDeadline()
	if  := .server.WriteTimeout;  != 0 {
		defer func() {
			.rwc.SetWriteDeadline(time.Now().Add())
		}()
	}

	.r.setReadLimit(.server.initialReadLimitSize())
	if .lastMethod == "POST" {
		// RFC 7230 section 3 tolerance for old buggy clients.
		,  := .bufr.Peek(4) // ReadRequest will get err below
		.bufr.Discard(numLeadingCRorLF())
	}
	,  := readRequest(.bufr, keepHostHeader)
	if  != nil {
		if .r.hitReadLimit() {
			return nil, errTooLarge
		}
		return nil, 
	}

	if !http1ServerSupportsRequest() {
		return nil, statusError{StatusHTTPVersionNotSupported, "unsupported protocol version"}
	}

	.lastMethod = .Method
	.r.setInfiniteReadLimit()

	,  := .Header["Host"]
	 := .isH2Upgrade()
	if .ProtoAtLeast(1, 1) && (! || len() == 0) && ! && .Method != "CONNECT" {
		return nil, badRequestError("missing required Host header")
	}
	if len() > 1 {
		return nil, badRequestError("too many Host headers")
	}
	if len() == 1 && !httpguts.ValidHostHeader([0]) {
		return nil, badRequestError("malformed Host header")
	}
	for ,  := range .Header {
		if !httpguts.ValidHeaderFieldName() {
			return nil, badRequestError("invalid header name")
		}
		for ,  := range  {
			if !httpguts.ValidHeaderFieldValue() {
				return nil, badRequestError("invalid header value")
			}
		}
	}
	delete(.Header, "Host")

	,  := context.WithCancel()
	.ctx = 
	.RemoteAddr = .remoteAddr
	.TLS = .tlsState
	if ,  := .Body.(*body);  {
		.doEarlyClose = true
	}

	// Adjust the read deadline if necessary.
	if !.Equal() {
		.rwc.SetReadDeadline()
	}

	 = &response{
		conn:          ,
		cancelCtx:     ,
		req:           ,
		reqBody:       .Body,
		handlerHeader: make(Header),
		contentLength: -1,
		closeNotifyCh: make(chan bool, 1),

		// We populate these ahead of time so we're not
		// reading from req.Header after their Handler starts
		// and maybe mutates it (Issue 14940)
		wants10KeepAlive: .wantsHttp10KeepAlive(),
		wantsClose:       .wantsClose(),
	}
	if  {
		.closeAfterReply = true
	}
	.cw.res = 
	.w = newBufioWriterSize(&.cw, bufferBeforeChunkingSize)
	return , nil
}

// http1ServerSupportsRequest reports whether Go's HTTP/1.x server
// supports the given request.
func http1ServerSupportsRequest( *Request) bool {
	if .ProtoMajor == 1 {
		return true
	}
	// Accept "PRI * HTTP/2.0" upgrade requests, so Handlers can
	// wire up their own HTTP/2 upgrades.
	if .ProtoMajor == 2 && .ProtoMinor == 0 &&
		.Method == "PRI" && .RequestURI == "*" {
		return true
	}
	// Reject HTTP/0.x, and all other HTTP/2+ requests (which
	// aren't encoded in ASCII anyway).
	return false
}

func ( *response) () Header {
	if .cw.header == nil && .wroteHeader && !.cw.wroteHeader {
		// Accessing the header between logically writing it
		// and physically writing it means we need to allocate
		// a clone to snapshot the logically written state.
		.cw.header = .handlerHeader.Clone()
	}
	.calledHeader = true
	return .handlerHeader
}

// maxPostHandlerReadBytes is the max number of Request.Body bytes not
// consumed by a handler that the server will read from the client
// in order to keep a connection alive. If there are more bytes than
// this then the server to be paranoid instead sends a "Connection:
// close" response.
//
// This number is approximately what a typical machine's TCP buffer
// size is anyway.  (if we have the bytes on the machine, we might as
// well read them)
const maxPostHandlerReadBytes = 256 << 10

func checkWriteHeaderCode( int) {
	// Issue 22880: require valid WriteHeader status codes.
	// For now we only enforce that it's three digits.
	// In the future we might block things over 599 (600 and above aren't defined
	// at https://httpwg.org/specs/rfc7231.html#status.codes)
	// and we might block under 200 (once we have more mature 1xx support).
	// But for now any three digits.
	//
	// We used to send "HTTP/1.1 000 0" on the wire in responses but there's
	// no equivalent bogus thing we can realistically send in HTTP/2,
	// so we'll consistently panic instead and help people find their bugs
	// early. (We can't return an error from WriteHeader even if we wanted to.)
	if  < 100 ||  > 999 {
		panic(fmt.Sprintf("invalid WriteHeader code %v", ))
	}
}

// relevantCaller searches the call stack for the first function outside of net/http.
// The purpose of this function is to provide more helpful error messages.
func relevantCaller() runtime.Frame {
	 := make([]uintptr, 16)
	 := runtime.Callers(1, )
	 := runtime.CallersFrames([:])
	var  runtime.Frame
	for {
		,  := .Next()
		if !strings.HasPrefix(.Function, "net/http.") {
			return 
		}
		if ! {
			break
		}
	}
	return 
}

func ( *response) ( int) {
	if .conn.hijacked() {
		 := relevantCaller()
		.conn.server.logf("http: response.WriteHeader on hijacked connection from %s (%s:%d)", .Function, path.Base(.File), .Line)
		return
	}
	if .wroteHeader {
		 := relevantCaller()
		.conn.server.logf("http: superfluous response.WriteHeader call from %s (%s:%d)", .Function, path.Base(.File), .Line)
		return
	}
	checkWriteHeaderCode()
	.wroteHeader = true
	.status = 

	if .calledHeader && .cw.header == nil {
		.cw.header = .handlerHeader.Clone()
	}

	if  := .handlerHeader.get("Content-Length");  != "" {
		,  := strconv.ParseInt(, 10, 64)
		if  == nil &&  >= 0 {
			.contentLength = 
		} else {
			.conn.server.logf("http: invalid Content-Length of %q", )
			.handlerHeader.Del("Content-Length")
		}
	}
}

// extraHeader is the set of headers sometimes added by chunkWriter.writeHeader.
// This type is used to avoid extra allocations from cloning and/or populating
// the response Header map and all its 1-element slices.
type extraHeader struct {
	contentType      string
	connection       string
	transferEncoding string
	date             []byte // written if not nil
	contentLength    []byte // written if not nil
}

// Sorted the same as extraHeader.Write's loop.
var extraHeaderKeys = [][]byte{
	[]byte("Content-Type"),
	[]byte("Connection"),
	[]byte("Transfer-Encoding"),
}

var (
	headerContentLength = []byte("Content-Length: ")
	headerDate          = []byte("Date: ")
)

// Write writes the headers described in h to w.
//
// This method has a value receiver, despite the somewhat large size
// of h, because it prevents an allocation. The escape analysis isn't
// smart enough to realize this function doesn't mutate h.
func ( extraHeader) ( *bufio.Writer) {
	if .date != nil {
		.Write(headerDate)
		.Write(.date)
		.Write(crlf)
	}
	if .contentLength != nil {
		.Write(headerContentLength)
		.Write(.contentLength)
		.Write(crlf)
	}
	for ,  := range []string{.contentType, .connection, .transferEncoding} {
		if  != "" {
			.Write(extraHeaderKeys[])
			.Write(colonSpace)
			.WriteString()
			.Write(crlf)
		}
	}
}

// writeHeader finalizes the header sent to the client and writes it
// to cw.res.conn.bufw.
//
// p is not written by writeHeader, but is the first chunk of the body
// that will be written. It is sniffed for a Content-Type if none is
// set explicitly. It's also used to set the Content-Length, if the
// total body size was small and the handler has already finished
// running.
func ( *chunkWriter) ( []byte) {
	if .wroteHeader {
		return
	}
	.wroteHeader = true

	 := .res
	 := .conn.server.doKeepAlives()
	 := .req.Method == "HEAD"

	// header is written out to w.conn.buf below. Depending on the
	// state of the handler, we either own the map or not. If we
	// don't own it, the exclude map is created lazily for
	// WriteSubset to remove headers. The setHeader struct holds
	// headers we need to add.
	 := .header
	 :=  != nil
	if ! {
		 = .handlerHeader
	}
	var  map[string]bool
	 := func( string) {
		if  {
			.Del()
			return
		}
		if ,  := []; ! {
			return
		}
		if  == nil {
			 = make(map[string]bool)
		}
		[] = true
	}
	var  extraHeader

	// Don't write out the fake "Trailer:foo" keys. See TrailerPrefix.
	 := false
	for  := range .header {
		if strings.HasPrefix(, TrailerPrefix) {
			if  == nil {
				 = make(map[string]bool)
			}
			[] = true
			 = true
		}
	}
	for ,  := range .header["Trailer"] {
		 = true
		foreachHeaderElement(, .res.declareTrailer)
	}

	 := .get("Transfer-Encoding")
	 :=  != ""

	// If the handler is done but never sent a Content-Length
	// response header and this is our first (and last) write, set
	// it, even to zero. This helps HTTP/1.0 clients keep their
	// "keep-alive" connections alive.
	// Exceptions: 304/204/1xx responses never get Content-Length, and if
	// it was a HEAD request, we don't know the difference between
	// 0 actual bytes and 0 bytes because the handler noticed it
	// was a HEAD request and chose not to write anything. So for
	// HEAD, the handler should either write the Content-Length or
	// write non-zero bytes. If it's actually 0 bytes and the
	// handler never looked at the Request.Method, we just don't
	// send a Content-Length header.
	// Further, we don't send an automatic Content-Length if they
	// set a Transfer-Encoding, because they're generally incompatible.
	if .handlerDone.isSet() && ! && ! && bodyAllowedForStatus(.status) && .get("Content-Length") == "" && (! || len() > 0) {
		.contentLength = int64(len())
		.contentLength = strconv.AppendInt(.res.clenBuf[:0], int64(len()), 10)
	}

	// If this was an HTTP/1.0 request with keep-alive and we sent a
	// Content-Length back, we can make this a keep-alive response ...
	if .wants10KeepAlive &&  {
		 := .get("Content-Length") != ""
		if  && .get("Connection") == "keep-alive" {
			.closeAfterReply = false
		}
	}

	// Check for an explicit (and valid) Content-Length header.
	 := .contentLength != -1

	if .wants10KeepAlive && ( ||  || !bodyAllowedForStatus(.status)) {
		,  := ["Connection"]
		if ! {
			.connection = "keep-alive"
		}
	} else if !.req.ProtoAtLeast(1, 1) || .wantsClose {
		.closeAfterReply = true
	}

	if .get("Connection") == "close" || ! {
		.closeAfterReply = true
	}

	// If the client wanted a 100-continue but we never sent it to
	// them (or, more strictly: we never finished reading their
	// request body), don't reuse this connection because it's now
	// in an unknown state: we might be sending this response at
	// the same time the client is now sending its request body
	// after a timeout.  (Some HTTP clients send Expect:
	// 100-continue but knowing that some servers don't support
	// it, the clients set a timer and send the body later anyway)
	// If we haven't seen EOF, we can't skip over the unread body
	// because we don't know if the next bytes on the wire will be
	// the body-following-the-timer or the subsequent request.
	// See Issue 11549.
	if ,  := .req.Body.(*expectContinueReader);  && !.sawEOF.isSet() {
		.closeAfterReply = true
	}

	// Per RFC 2616, we should consume the request body before
	// replying, if the handler hasn't already done so. But we
	// don't want to do an unbounded amount of reading here for
	// DoS reasons, so we only try up to a threshold.
	// TODO(bradfitz): where does RFC 2616 say that? See Issue 15527
	// about HTTP/1.x Handlers concurrently reading and writing, like
	// HTTP/2 handlers can do. Maybe this code should be relaxed?
	if .req.ContentLength != 0 && !.closeAfterReply {
		var ,  bool

		switch bdy := .req.Body.(type) {
		case *expectContinueReader:
			if .resp.wroteContinue {
				 = true
			}
		case *body:
			.mu.Lock()
			switch {
			case .closed:
				if !.sawEOF {
					// Body was closed in handler with non-EOF error.
					.closeAfterReply = true
				}
			case .unreadDataSizeLocked() >= maxPostHandlerReadBytes:
				 = true
			default:
				 = true
			}
			.mu.Unlock()
		default:
			 = true
		}

		if  {
			,  := io.CopyN(io.Discard, .reqBody, maxPostHandlerReadBytes+1)
			switch  {
			case nil:
				// There must be even more data left over.
				 = true
			case ErrBodyReadAfterClose:
				// Body was already consumed and closed.
			case io.EOF:
				// The remaining body was just consumed, close it.
				 = .reqBody.Close()
				if  != nil {
					.closeAfterReply = true
				}
			default:
				// Some other kind of error occurred, like a read timeout, or
				// corrupt chunked encoding. In any case, whatever remains
				// on the wire must not be parsed as another HTTP request.
				.closeAfterReply = true
			}
		}

		if  {
			.requestTooLarge()
			("Connection")
			.connection = "close"
		}
	}

	 := .status
	if bodyAllowedForStatus() {
		// If no content type, apply sniffing algorithm to body.
		,  := ["Content-Type"]

		// If the Content-Encoding was set and is non-blank,
		// we shouldn't sniff the body. See Issue 31753.
		 := .Get("Content-Encoding")
		 := len() > 0
		if ! && ! && ! && len() > 0 {
			.contentType = DetectContentType()
		}
	} else {
		for ,  := range suppressedHeaders() {
			()
		}
	}

	if !.has("Date") {
		.date = appendTime(.res.dateBuf[:0], time.Now())
	}

	if  &&  &&  != "identity" {
		// TODO: return an error if WriteHeader gets a return parameter
		// For now just ignore the Content-Length.
		.conn.server.logf("http: WriteHeader called with both Transfer-Encoding of %q and a Content-Length of %d",
			, .contentLength)
		("Content-Length")
		 = false
	}

	if .req.Method == "HEAD" || !bodyAllowedForStatus() {
		// do nothing
	} else if  == StatusNoContent {
		("Transfer-Encoding")
	} else if  {
		("Transfer-Encoding")
	} else if .req.ProtoAtLeast(1, 1) {
		// HTTP/1.1 or greater: Transfer-Encoding has been set to identity, and no
		// content-length has been provided. The connection must be closed after the
		// reply is written, and no chunking is to be done. This is the setup
		// recommended in the Server-Sent Events candidate recommendation 11,
		// section 8.
		if  &&  == "identity" {
			.chunking = false
			.closeAfterReply = true
		} else {
			// HTTP/1.1 or greater: use chunked transfer encoding
			// to avoid closing the connection at EOF.
			.chunking = true
			.transferEncoding = "chunked"
			if  &&  == "chunked" {
				// We will send the chunked Transfer-Encoding header later.
				("Transfer-Encoding")
			}
		}
	} else {
		// HTTP version < 1.1: cannot do chunked transfer
		// encoding and we don't know the Content-Length so
		// signal EOF by closing connection.
		.closeAfterReply = true
		("Transfer-Encoding") // in case already set
	}

	// Cannot use Content-Length with non-identity Transfer-Encoding.
	if .chunking {
		("Content-Length")
	}
	if !.req.ProtoAtLeast(1, 0) {
		return
	}

	// Only override the Connection header if it is not a successful
	// protocol switch response and if KeepAlives are not enabled.
	// See https://golang.org/issue/36381.
	 := .closeAfterReply &&
		(! || !hasToken(.header.get("Connection"), "close")) &&
		!isProtocolSwitchResponse(.status, )
	if  {
		("Connection")
		if .req.ProtoAtLeast(1, 1) {
			.connection = "close"
		}
	}

	writeStatusLine(.conn.bufw, .req.ProtoAtLeast(1, 1), , .statusBuf[:])
	.header.WriteSubset(.conn.bufw, )
	.Write(.conn.bufw)
	.conn.bufw.Write(crlf)
}

// foreachHeaderElement splits v according to the "#rule" construction
// in RFC 7230 section 7 and calls fn for each non-empty element.
func foreachHeaderElement( string,  func(string)) {
	 = textproto.TrimString()
	if  == "" {
		return
	}
	if !strings.Contains(, ",") {
		()
		return
	}
	for ,  := range strings.Split(, ",") {
		if  = textproto.TrimString();  != "" {
			()
		}
	}
}

// writeStatusLine writes an HTTP/1.x Status-Line (RFC 7230 Section 3.1.2)
// to bw. is11 is whether the HTTP request is HTTP/1.1. false means HTTP/1.0.
// code is the response status code.
// scratch is an optional scratch buffer. If it has at least capacity 3, it's used.
func writeStatusLine( *bufio.Writer,  bool,  int,  []byte) {
	if  {
		.WriteString("HTTP/1.1 ")
	} else {
		.WriteString("HTTP/1.0 ")
	}
	if ,  := statusText[];  {
		.Write(strconv.AppendInt([:0], int64(), 10))
		.WriteByte(' ')
		.WriteString()
		.WriteString("\r\n")
	} else {
		// don't worry about performance
		fmt.Fprintf(, "%03d status code %d\r\n", , )
	}
}

// bodyAllowed reports whether a Write is allowed for this response type.
// It's illegal to call this before the header has been flushed.
func ( *response) () bool {
	if !.wroteHeader {
		panic("")
	}
	return bodyAllowedForStatus(.status)
}

// The Life Of A Write is like this:
//
// Handler starts. No header has been sent. The handler can either
// write a header, or just start writing. Writing before sending a header
// sends an implicitly empty 200 OK header.
//
// If the handler didn't declare a Content-Length up front, we either
// go into chunking mode or, if the handler finishes running before
// the chunking buffer size, we compute a Content-Length and send that
// in the header instead.
//
// Likewise, if the handler didn't set a Content-Type, we sniff that
// from the initial chunk of output.
//
// The Writers are wired together like:
//
// 1. *response (the ResponseWriter) ->
// 2. (*response).w, a *bufio.Writer of bufferBeforeChunkingSize bytes
// 3. chunkWriter.Writer (whose writeHeader finalizes Content-Length/Type)
//    and which writes the chunk headers, if needed.
// 4. conn.buf, a bufio.Writer of default (4kB) bytes, writing to ->
// 5. checkConnErrorWriter{c}, which notes any non-nil error on Write
//    and populates c.werr with it if so. but otherwise writes to:
// 6. the rwc, the net.Conn.
//
// TODO(bradfitz): short-circuit some of the buffering when the
// initial header contains both a Content-Type and Content-Length.
// Also short-circuit in (1) when the header's been sent and not in
// chunking mode, writing directly to (4) instead, if (2) has no
// buffered data. More generally, we could short-circuit from (1) to
// (3) even in chunking mode if the write size from (1) is over some
// threshold and nothing is in (2).  The answer might be mostly making
// bufferBeforeChunkingSize smaller and having bufio's fast-paths deal
// with this instead.
func ( *response) ( []byte) ( int,  error) {
	return .write(len(), , "")
}

func ( *response) ( string) ( int,  error) {
	return .write(len(), nil, )
}

// either dataB or dataS is non-zero.
func ( *response) ( int,  []byte,  string) ( int,  error) {
	if .conn.hijacked() {
		if  > 0 {
			 := relevantCaller()
			.conn.server.logf("http: response.Write on hijacked connection from %s (%s:%d)", .Function, path.Base(.File), .Line)
		}
		return 0, ErrHijacked
	}

	if .canWriteContinue.isSet() {
		// Body reader wants to write 100 Continue but hasn't yet.
		// Tell it not to. The store must be done while holding the lock
		// because the lock makes sure that there is not an active write
		// this very moment.
		.writeContinueMu.Lock()
		.canWriteContinue.setFalse()
		.writeContinueMu.Unlock()
	}

	if !.wroteHeader {
		.WriteHeader(StatusOK)
	}
	if  == 0 {
		return 0, nil
	}
	if !.bodyAllowed() {
		return 0, ErrBodyNotAllowed
	}

	.written += int64() // ignoring errors, for errorKludge
	if .contentLength != -1 && .written > .contentLength {
		return 0, ErrContentLength
	}
	if  != nil {
		return .w.Write()
	} else {
		return .w.WriteString()
	}
}

func ( *response) () {
	.handlerDone.setTrue()

	if !.wroteHeader {
		.WriteHeader(StatusOK)
	}

	.w.Flush()
	putBufioWriter(.w)
	.cw.close()
	.conn.bufw.Flush()

	.conn.r.abortPendingRead()

	// Close the body (regardless of w.closeAfterReply) so we can
	// re-use its bufio.Reader later safely.
	.reqBody.Close()

	if .req.MultipartForm != nil {
		.req.MultipartForm.RemoveAll()
	}
}

// shouldReuseConnection reports whether the underlying TCP connection can be reused.
// It must only be called after the handler is done executing.
func ( *response) () bool {
	if .closeAfterReply {
		// The request or something set while executing the
		// handler indicated we shouldn't reuse this
		// connection.
		return false
	}

	if .req.Method != "HEAD" && .contentLength != -1 && .bodyAllowed() && .contentLength != .written {
		// Did not write enough. Avoid getting out of sync.
		return false
	}

	// There was some error writing to the underlying connection
	// during the request, so don't re-use this conn.
	if .conn.werr != nil {
		return false
	}

	if .closedRequestBodyEarly() {
		return false
	}

	return true
}

func ( *response) () bool {
	,  := .req.Body.(*body)
	return  && .didEarlyClose()
}

func ( *response) () {
	if !.wroteHeader {
		.WriteHeader(StatusOK)
	}
	.w.Flush()
	.cw.flush()
}

func ( *conn) () {
	if .bufr != nil {
		// Steal the bufio.Reader (~4KB worth of memory) and its associated
		// reader for a future connection.
		putBufioReader(.bufr)
		.bufr = nil
	}

	if .bufw != nil {
		.bufw.Flush()
		// Steal the bufio.Writer (~4KB worth of memory) and its associated
		// writer for a future connection.
		putBufioWriter(.bufw)
		.bufw = nil
	}
}

// Close the connection.
func ( *conn) () {
	.finalFlush()
	.rwc.Close()
}

// rstAvoidanceDelay is the amount of time we sleep after closing the
// write side of a TCP connection before closing the entire socket.
// By sleeping, we increase the chances that the client sees our FIN
// and processes its final data before they process the subsequent RST
// from closing a connection with known unread data.
// This RST seems to occur mostly on BSD systems. (And Windows?)
// This timeout is somewhat arbitrary (~latency around the planet).
const rstAvoidanceDelay = 500 * time.Millisecond

type closeWriter interface {
	CloseWrite() error
}

var _ closeWriter = (*net.TCPConn)(nil)

// closeWrite flushes any outstanding data and sends a FIN packet (if
// client is connected via TCP), signalling that we're done. We then
// pause for a bit, hoping the client processes it before any
// subsequent RST.
//
// See https://golang.org/issue/3595
func ( *conn) () {
	.finalFlush()
	if ,  := .rwc.(closeWriter);  {
		.CloseWrite()
	}
	time.Sleep(rstAvoidanceDelay)
}

// validNextProto reports whether the proto is a valid ALPN protocol name.
// Everything is valid except the empty string and built-in protocol types,
// so that those can't be overridden with alternate implementations.
func validNextProto( string) bool {
	switch  {
	case "", "http/1.1", "http/1.0":
		return false
	}
	return true
}

const (
	runHooks  = true
	skipHooks = false
)

func ( *conn) ( net.Conn,  ConnState,  bool) {
	 := .server
	switch  {
	case StateNew:
		.trackConn(, true)
	case StateHijacked, StateClosed:
		.trackConn(, false)
	}
	if  > 0xff ||  < 0 {
		panic("internal error")
	}
	 := uint64(time.Now().Unix()<<8) | uint64()
	atomic.StoreUint64(&.curState.atomic, )
	if ! {
		return
	}
	if  := .ConnState;  != nil {
		(, )
	}
}

func ( *conn) () ( ConnState,  int64) {
	 := atomic.LoadUint64(&.curState.atomic)
	return ConnState( & 0xff), int64( >> 8)
}

// badRequestError is a literal string (used by in the server in HTML,
// unescaped) to tell the user why their request was bad. It should
// be plain text without user info or other embedded errors.
func badRequestError( string) error { return statusError{StatusBadRequest, } }

// statusError is an error used to respond to a request with an HTTP status.
// The text should be plain text without user info or other embedded errors.
type statusError struct {
	code int
	text string
}

func ( statusError) () string { return StatusText(.code) + ": " + .text }

// ErrAbortHandler is a sentinel panic value to abort a handler.
// While any panic from ServeHTTP aborts the response to the client,
// panicking with ErrAbortHandler also suppresses logging of a stack
// trace to the server's error log.
var ErrAbortHandler = errors.New("net/http: abort Handler")

// isCommonNetReadError reports whether err is a common error
// encountered during reading a request off the network when the
// client has gone away or had its read fail somehow. This is used to
// determine which logs are interesting enough to log about.
func isCommonNetReadError( error) bool {
	if  == io.EOF {
		return true
	}
	if ,  := .(net.Error);  && .Timeout() {
		return true
	}
	if ,  := .(*net.OpError);  && .Op == "read" {
		return true
	}
	return false
}

// Serve a new connection.
func ( *conn) ( context.Context) {
	.remoteAddr = .rwc.RemoteAddr().String()
	 = context.WithValue(, LocalAddrContextKey, .rwc.LocalAddr())
	defer func() {
		if  := recover();  != nil &&  != ErrAbortHandler {
			const  = 64 << 10
			 := make([]byte, )
			 = [:runtime.Stack(, false)]
			.server.logf("http: panic serving %v: %v\n%s", .remoteAddr, , )
		}
		if !.hijacked() {
			.close()
			.setState(.rwc, StateClosed, runHooks)
		}
	}()

	if ,  := .rwc.(*tls.Conn);  {
		if  := .server.ReadTimeout;  != 0 {
			.rwc.SetReadDeadline(time.Now().Add())
		}
		if  := .server.WriteTimeout;  != 0 {
			.rwc.SetWriteDeadline(time.Now().Add())
		}
		if  := .Handshake();  != nil {
			// If the handshake failed due to the client not speaking
			// TLS, assume they're speaking plaintext HTTP and write a
			// 400 response on the TLS conn's underlying net.Conn.
			if ,  := .(tls.RecordHeaderError);  && .Conn != nil && tlsRecordHeaderLooksLikeHTTP(.RecordHeader) {
				io.WriteString(.Conn, "HTTP/1.0 400 Bad Request\r\n\r\nClient sent an HTTP request to an HTTPS server.\n")
				.Conn.Close()
				return
			}
			.server.logf("http: TLS handshake error from %s: %v", .rwc.RemoteAddr(), )
			return
		}
		.tlsState = new(tls.ConnectionState)
		*.tlsState = .ConnectionState()
		if  := .tlsState.NegotiatedProtocol; validNextProto() {
			if  := .server.TLSNextProto[];  != nil {
				 := initALPNRequest{, , serverHandler{.server}}
				// Mark freshly created HTTP/2 as active and prevent any server state hooks
				// from being run on these connections. This prevents closeIdleConns from
				// closing such connections. See issue https://golang.org/issue/39776.
				.setState(.rwc, StateActive, skipHooks)
				(.server, , )
			}
			return
		}
	}

	// HTTP/1.x from here on.

	,  := context.WithCancel()
	.cancelCtx = 
	defer ()

	.r = &connReader{conn: }
	.bufr = newBufioReader(.r)
	.bufw = newBufioWriterSize(checkConnErrorWriter{}, 4<<10)

	for {
		,  := .readRequest()
		if .r.remain != .server.initialReadLimitSize() {
			// If we read any bytes off the wire, we're active.
			.setState(.rwc, StateActive, runHooks)
		}
		if  != nil {
			const  = "\r\nContent-Type: text/plain; charset=utf-8\r\nConnection: close\r\n\r\n"

			switch {
			case  == errTooLarge:
				// Their HTTP client may or may not be
				// able to read this if we're
				// responding to them and hanging up
				// while they're still writing their
				// request. Undefined behavior.
				const  = "431 Request Header Fields Too Large"
				fmt.Fprintf(.rwc, "HTTP/1.1 "+++)
				.closeWriteAndWait()
				return

			case isUnsupportedTEError():
				// Respond as per RFC 7230 Section 3.3.1 which says,
				//      A server that receives a request message with a
				//      transfer coding it does not understand SHOULD
				//      respond with 501 (Unimplemented).
				 := StatusNotImplemented

				// We purposefully aren't echoing back the transfer-encoding's value,
				// so as to mitigate the risk of cross side scripting by an attacker.
				fmt.Fprintf(.rwc, "HTTP/1.1 %d %s%sUnsupported transfer encoding", , StatusText(), )
				return

			case isCommonNetReadError():
				return // don't reply

			default:
				if ,  := .(statusError);  {
					fmt.Fprintf(.rwc, "HTTP/1.1 %d %s: %s%s%d %s: %s", .code, StatusText(.code), .text, , .code, StatusText(.code), .text)
					return
				}
				 := "400 Bad Request"
				fmt.Fprintf(.rwc, "HTTP/1.1 "+++)
				return
			}
		}

		// Expect 100 Continue support
		 := .req
		if .expectsContinue() {
			if .ProtoAtLeast(1, 1) && .ContentLength != 0 {
				// Wrap the Body reader with one that replies on the connection
				.Body = &expectContinueReader{readCloser: .Body, resp: }
				.canWriteContinue.setTrue()
			}
		} else if .Header.get("Expect") != "" {
			.sendExpectationFailed()
			return
		}

		.curReq.Store()

		if requestBodyRemains(.Body) {
			registerOnHitEOF(.Body, .conn.r.startBackgroundRead)
		} else {
			.conn.r.startBackgroundRead()
		}

		// HTTP cannot have multiple simultaneous active requests.[*]
		// Until the server replies to this request, it can't read another,
		// so we might as well run the handler in this goroutine.
		// [*] Not strictly true: HTTP pipelining. We could let them all process
		// in parallel even if their responses need to be serialized.
		// But we're not going to implement HTTP pipelining because it
		// was never deployed in the wild and the answer is HTTP/2.
		serverHandler{.server}.ServeHTTP(, .req)
		.cancelCtx()
		if .hijacked() {
			return
		}
		.finishRequest()
		if !.shouldReuseConnection() {
			if .requestBodyLimitHit || .closedRequestBodyEarly() {
				.closeWriteAndWait()
			}
			return
		}
		.setState(.rwc, StateIdle, runHooks)
		.curReq.Store((*response)(nil))

		if !.conn.server.doKeepAlives() {
			// We're in shutdown mode. We might've replied
			// to the user without "Connection: close" and
			// they might think they can send another
			// request, but such is life with HTTP/1.1.
			return
		}

		if  := .server.idleTimeout();  != 0 {
			.rwc.SetReadDeadline(time.Now().Add())
			if ,  := .bufr.Peek(4);  != nil {
				return
			}
		}
		.rwc.SetReadDeadline(time.Time{})
	}
}

func ( *response) () {
	// TODO(bradfitz): let ServeHTTP handlers handle
	// requests with non-standard expectation[s]? Seems
	// theoretical at best, and doesn't fit into the
	// current ServeHTTP model anyway. We'd need to
	// make the ResponseWriter an optional
	// "ExpectReplier" interface or something.
	//
	// For now we'll just obey RFC 7231 5.1.1 which says
	// "A server that receives an Expect field-value other
	// than 100-continue MAY respond with a 417 (Expectation
	// Failed) status code to indicate that the unexpected
	// expectation cannot be met."
	.Header().Set("Connection", "close")
	.WriteHeader(StatusExpectationFailed)
	.finishRequest()
}

// Hijack implements the Hijacker.Hijack method. Our response is both a ResponseWriter
// and a Hijacker.
func ( *response) () ( net.Conn,  *bufio.ReadWriter,  error) {
	if .handlerDone.isSet() {
		panic("net/http: Hijack called after ServeHTTP finished")
	}
	if .wroteHeader {
		.cw.flush()
	}

	 := .conn
	.mu.Lock()
	defer .mu.Unlock()

	// Release the bufioWriter that writes to the chunk writer, it is not
	// used after a connection has been hijacked.
	, ,  = .hijackLocked()
	if  == nil {
		putBufioWriter(.w)
		.w = nil
	}
	return , , 
}

func ( *response) () <-chan bool {
	if .handlerDone.isSet() {
		panic("net/http: CloseNotify called after ServeHTTP finished")
	}
	return .closeNotifyCh
}

func registerOnHitEOF( io.ReadCloser,  func()) {
	switch v := .(type) {
	case *expectContinueReader:
		(.readCloser, )
	case *body:
		.registerOnHitEOF()
	default:
		panic("unexpected type " + fmt.Sprintf("%T", ))
	}
}

// requestBodyRemains reports whether future calls to Read
// on rc might yield more data.
func requestBodyRemains( io.ReadCloser) bool {
	if  == NoBody {
		return false
	}
	switch v := .(type) {
	case *expectContinueReader:
		return (.readCloser)
	case *body:
		return .bodyRemains()
	default:
		panic("unexpected type " + fmt.Sprintf("%T", ))
	}
}

// The HandlerFunc type is an adapter to allow the use of
// ordinary functions as HTTP handlers. If f is a function
// with the appropriate signature, HandlerFunc(f) is a
// Handler that calls f.
type HandlerFunc func(ResponseWriter, *Request)

// ServeHTTP calls f(w, r).
func ( HandlerFunc) ( ResponseWriter,  *Request) {
	(, )
}

// Helper handlers

// Error replies to the request with the specified error message and HTTP code.
// It does not otherwise end the request; the caller should ensure no further
// writes are done to w.
// The error message should be plain text.
func ( ResponseWriter,  string,  int) {
	.Header().Set("Content-Type", "text/plain; charset=utf-8")
	.Header().Set("X-Content-Type-Options", "nosniff")
	.WriteHeader()
	fmt.Fprintln(, )
}

// NotFound replies to the request with an HTTP 404 not found error.
func ( ResponseWriter,  *Request) { Error(, "404 page not found", StatusNotFound) }

// NotFoundHandler returns a simple request handler
// that replies to each request with a ``404 page not found'' reply.
func () Handler { return HandlerFunc(NotFound) }

// StripPrefix returns a handler that serves HTTP requests by removing the
// given prefix from the request URL's Path (and RawPath if set) and invoking
// the handler h. StripPrefix handles a request for a path that doesn't begin
// with prefix by replying with an HTTP 404 not found error. The prefix must
// match exactly: if the prefix in the request contains escaped characters
// the reply is also an HTTP 404 not found error.
func ( string,  Handler) Handler {
	if  == "" {
		return 
	}
	return HandlerFunc(func( ResponseWriter,  *Request) {
		 := strings.TrimPrefix(.URL.Path, )
		 := strings.TrimPrefix(.URL.RawPath, )
		if len() < len(.URL.Path) && (.URL.RawPath == "" || len() < len(.URL.RawPath)) {
			 := new(Request)
			* = *
			.URL = new(url.URL)
			*.URL = *.URL
			.URL.Path = 
			.URL.RawPath = 
			.ServeHTTP(, )
		} else {
			NotFound(, )
		}
	})
}

// Redirect replies to the request with a redirect to url,
// which may be a path relative to the request path.
//
// The provided code should be in the 3xx range and is usually
// StatusMovedPermanently, StatusFound or StatusSeeOther.
//
// If the Content-Type header has not been set, Redirect sets it
// to "text/html; charset=utf-8" and writes a small HTML body.
// Setting the Content-Type header to any value, including nil,
// disables that behavior.
func ( ResponseWriter,  *Request,  string,  int) {
	if ,  := urlpkg.Parse();  == nil {
		// If url was relative, make its path absolute by
		// combining with request path.
		// The client would probably do this for us,
		// but doing it ourselves is more reliable.
		// See RFC 7231, section 7.1.2
		if .Scheme == "" && .Host == "" {
			 := .URL.Path
			if  == "" { // should not happen, but avoid a crash if it does
				 = "/"
			}

			// no leading http://server
			if  == "" || [0] != '/' {
				// make relative path absolute
				,  := path.Split()
				 =  + 
			}

			var  string
			if  := strings.Index(, "?");  != -1 {
				,  = [:], [:]
			}

			// clean up but preserve trailing slash
			 := strings.HasSuffix(, "/")
			 = path.Clean()
			if  && !strings.HasSuffix(, "/") {
				 += "/"
			}
			 += 
		}
	}

	 := .Header()

	// RFC 7231 notes that a short HTML body is usually included in
	// the response because older user agents may not understand 301/307.
	// Do it only if the request didn't already have a Content-Type header.
	,  := ["Content-Type"]

	.Set("Location", hexEscapeNonASCII())
	if ! && (.Method == "GET" || .Method == "HEAD") {
		.Set("Content-Type", "text/html; charset=utf-8")
	}
	.WriteHeader()

	// Shouldn't send the body for POST or HEAD; that leaves GET.
	if ! && .Method == "GET" {
		 := "<a href=\"" + htmlEscape() + "\">" + statusText[] + "</a>.\n"
		fmt.Fprintln(, )
	}
}

var htmlReplacer = strings.NewReplacer(
	"&", "&amp;",
	"<", "&lt;",
	">", "&gt;",
	// "&#34;" is shorter than "&quot;".
	`"`, "&#34;",
	// "&#39;" is shorter than "&apos;" and apos was not in HTML until HTML5.
	"'", "&#39;",
)

func htmlEscape( string) string {
	return htmlReplacer.Replace()
}

// Redirect to a fixed URL
type redirectHandler struct {
	url  string
	code int
}

func ( *redirectHandler) ( ResponseWriter,  *Request) {
	Redirect(, , .url, .code)
}

// RedirectHandler returns a request handler that redirects
// each request it receives to the given url using the given
// status code.
//
// The provided code should be in the 3xx range and is usually
// StatusMovedPermanently, StatusFound or StatusSeeOther.
func ( string,  int) Handler {
	return &redirectHandler{, }
}

// ServeMux is an HTTP request multiplexer.
// It matches the URL of each incoming request against a list of registered
// patterns and calls the handler for the pattern that
// most closely matches the URL.
//
// Patterns name fixed, rooted paths, like "/favicon.ico",
// or rooted subtrees, like "/images/" (note the trailing slash).
// Longer patterns take precedence over shorter ones, so that
// if there are handlers registered for both "/images/"
// and "/images/thumbnails/", the latter handler will be
// called for paths beginning "/images/thumbnails/" and the
// former will receive requests for any other paths in the
// "/images/" subtree.
//
// Note that since a pattern ending in a slash names a rooted subtree,
// the pattern "/" matches all paths not matched by other registered
// patterns, not just the URL with Path == "/".
//
// If a subtree has been registered and a request is received naming the
// subtree root without its trailing slash, ServeMux redirects that
// request to the subtree root (adding the trailing slash). This behavior can
// be overridden with a separate registration for the path without
// the trailing slash. For example, registering "/images/" causes ServeMux
// to redirect a request for "/images" to "/images/", unless "/images" has
// been registered separately.
//
// Patterns may optionally begin with a host name, restricting matches to
// URLs on that host only. Host-specific patterns take precedence over
// general patterns, so that a handler might register for the two patterns
// "/codesearch" and "codesearch.google.com/" without also taking over
// requests for "http://www.google.com/".
//
// ServeMux also takes care of sanitizing the URL request path and the Host
// header, stripping the port number and redirecting any request containing . or
// .. elements or repeated slashes to an equivalent, cleaner URL.
type ServeMux struct {
	mu    sync.RWMutex
	m     map[string]muxEntry
	es    []muxEntry // slice of entries sorted from longest to shortest.
	hosts bool       // whether any patterns contain hostnames
}

type muxEntry struct {
	h       Handler
	pattern string
}

// NewServeMux allocates and returns a new ServeMux.
func () *ServeMux { return new(ServeMux) }

// DefaultServeMux is the default ServeMux used by Serve.
var DefaultServeMux = &defaultServeMux

var defaultServeMux ServeMux

// cleanPath returns the canonical path for p, eliminating . and .. elements.
func cleanPath( string) string {
	if  == "" {
		return "/"
	}
	if [0] != '/' {
		 = "/" + 
	}
	 := path.Clean()
	// path.Clean removes trailing slash except for root;
	// put the trailing slash back if necessary.
	if [len()-1] == '/' &&  != "/" {
		// Fast path for common case of p being the string we want:
		if len() == len()+1 && strings.HasPrefix(, ) {
			 = 
		} else {
			 += "/"
		}
	}
	return 
}

// stripHostPort returns h without any trailing ":<port>".
func stripHostPort( string) string {
	// If no port on host, return unchanged
	if strings.IndexByte(, ':') == -1 {
		return 
	}
	, ,  := net.SplitHostPort()
	if  != nil {
		return  // on error, return unchanged
	}
	return 
}

// Find a handler on a handler map given a path string.
// Most-specific (longest) pattern wins.
func ( *ServeMux) ( string) ( Handler,  string) {
	// Check for exact match first.
	,  := .m[]
	if  {
		return .h, .pattern
	}

	// Check for longest valid match.  mux.es contains all patterns
	// that end in / sorted from longest to shortest.
	for ,  := range .es {
		if strings.HasPrefix(, .pattern) {
			return .h, .pattern
		}
	}
	return nil, ""
}

// redirectToPathSlash determines if the given path needs appending "/" to it.
// This occurs when a handler for path + "/" was already registered, but
// not for path itself. If the path needs appending to, it creates a new
// URL, setting the path to u.Path + "/" and returning true to indicate so.
func ( *ServeMux) (,  string,  *url.URL) (*url.URL, bool) {
	.mu.RLock()
	 := .shouldRedirectRLocked(, )
	.mu.RUnlock()
	if ! {
		return , false
	}
	 =  + "/"
	 = &url.URL{Path: , RawQuery: .RawQuery}
	return , true
}

// shouldRedirectRLocked reports whether the given path and host should be redirected to
// path+"/". This should happen if a handler is registered for path+"/" but
// not path -- see comments at ServeMux.
func ( *ServeMux) (,  string) bool {
	 := []string{,  + }

	for ,  := range  {
		if ,  := .m[];  {
			return false
		}
	}

	 := len()
	if  == 0 {
		return false
	}
	for ,  := range  {
		if ,  := .m[+"/"];  {
			return [-1] != '/'
		}
	}

	return false
}

// Handler returns the handler to use for the given request,
// consulting r.Method, r.Host, and r.URL.Path. It always returns
// a non-nil handler. If the path is not in its canonical form, the
// handler will be an internally-generated handler that redirects
// to the canonical path. If the host contains a port, it is ignored
// when matching handlers.
//
// The path and host are used unchanged for CONNECT requests.
//
// Handler also returns the registered pattern that matches the
// request or, in the case of internally-generated redirects,
// the pattern that will match after following the redirect.
//
// If there is no registered handler that applies to the request,
// Handler returns a ``page not found'' handler and an empty pattern.
func ( *ServeMux) ( *Request) ( Handler,  string) {

	// CONNECT requests are not canonicalized.
	if .Method == "CONNECT" {
		// If r.URL.Path is /tree and its handler is not registered,
		// the /tree -> /tree/ redirect applies to CONNECT requests
		// but the path canonicalization does not.
		if ,  := .redirectToPathSlash(.URL.Host, .URL.Path, .URL);  {
			return RedirectHandler(.String(), StatusMovedPermanently), .Path
		}

		return .handler(.Host, .URL.Path)
	}

	// All other requests have any port stripped and path cleaned
	// before passing to mux.handler.
	 := stripHostPort(.Host)
	 := cleanPath(.URL.Path)

	// If the given path is /tree and its handler is not registered,
	// redirect for /tree/.
	if ,  := .redirectToPathSlash(, , .URL);  {
		return RedirectHandler(.String(), StatusMovedPermanently), .Path
	}

	if  != .URL.Path {
		_,  = .handler(, )
		 := *.URL
		.Path = 
		return RedirectHandler(.String(), StatusMovedPermanently), 
	}

	return .handler(, .URL.Path)
}

// handler is the main implementation of Handler.
// The path is known to be in canonical form, except for CONNECT methods.
func ( *ServeMux) (,  string) ( Handler,  string) {
	.mu.RLock()
	defer .mu.RUnlock()

	// Host-specific pattern takes precedence over generic ones
	if .hosts {
		,  = .match( + )
	}
	if  == nil {
		,  = .match()
	}
	if  == nil {
		,  = NotFoundHandler(), ""
	}
	return
}

// ServeHTTP dispatches the request to the handler whose
// pattern most closely matches the request URL.
func ( *ServeMux) ( ResponseWriter,  *Request) {
	if .RequestURI == "*" {
		if .ProtoAtLeast(1, 1) {
			.Header().Set("Connection", "close")
		}
		.WriteHeader(StatusBadRequest)
		return
	}
	,  := .Handler()
	.ServeHTTP(, )
}

// Handle registers the handler for the given pattern.
// If a handler already exists for pattern, Handle panics.
func ( *ServeMux) ( string,  Handler) {
	.mu.Lock()
	defer .mu.Unlock()

	if  == "" {
		panic("http: invalid pattern")
	}
	if  == nil {
		panic("http: nil handler")
	}
	if ,  := .m[];  {
		panic("http: multiple registrations for " + )
	}

	if .m == nil {
		.m = make(map[string]muxEntry)
	}
	 := muxEntry{h: , pattern: }
	.m[] = 
	if [len()-1] == '/' {
		.es = appendSorted(.es, )
	}

	if [0] != '/' {
		.hosts = true
	}
}

func appendSorted( []muxEntry,  muxEntry) []muxEntry {
	 := len()
	 := sort.Search(, func( int) bool {
		return len([].pattern) < len(.pattern)
	})
	if  ==  {
		return append(, )
	}
	// we now know that i points at where we want to insert
	 = append(, muxEntry{}) // try to grow the slice in place, any entry works.
	copy([+1:], [:])      // Move shorter entries down
	[] = 
	return 
}

// HandleFunc registers the handler function for the given pattern.
func ( *ServeMux) ( string,  func(ResponseWriter, *Request)) {
	if  == nil {
		panic("http: nil handler")
	}
	.Handle(, HandlerFunc())
}

// Handle registers the handler for the given pattern
// in the DefaultServeMux.
// The documentation for ServeMux explains how patterns are matched.
func ( string,  Handler) { DefaultServeMux.Handle(, ) }

// HandleFunc registers the handler function for the given pattern
// in the DefaultServeMux.
// The documentation for ServeMux explains how patterns are matched.
func ( string,  func(ResponseWriter, *Request)) {
	DefaultServeMux.HandleFunc(, )
}

// Serve accepts incoming HTTP connections on the listener l,
// creating a new service goroutine for each. The service goroutines
// read requests and then call handler to reply to them.
//
// The handler is typically nil, in which case the DefaultServeMux is used.
//
// HTTP/2 support is only enabled if the Listener returns *tls.Conn
// connections and they were configured with "h2" in the TLS
// Config.NextProtos.
//
// Serve always returns a non-nil error.
func ( net.Listener,  Handler) error {
	 := &Server{Handler: }
	return .Serve()
}

// ServeTLS accepts incoming HTTPS connections on the listener l,
// creating a new service goroutine for each. The service goroutines
// read requests and then call handler to reply to them.
//
// The handler is typically nil, in which case the DefaultServeMux is used.
//
// Additionally, files containing a certificate and matching private key
// for the server must be provided. If the certificate is signed by a
// certificate authority, the certFile should be the concatenation
// of the server's certificate, any intermediates, and the CA's certificate.
//
// ServeTLS always returns a non-nil error.
func ( net.Listener,  Handler, ,  string) error {
	 := &Server{Handler: }
	return .ServeTLS(, , )
}

// A Server defines parameters for running an HTTP server.
// The zero value for Server is a valid configuration.
type Server struct {
	// Addr optionally specifies the TCP address for the server to listen on,
	// in the form "host:port". If empty, ":http" (port 80) is used.
	// The service names are defined in RFC 6335 and assigned by IANA.
	// See net.Dial for details of the address format.
	Addr string

	Handler Handler // handler to invoke, http.DefaultServeMux if nil

	// TLSConfig optionally provides a TLS configuration for use
	// by ServeTLS and ListenAndServeTLS. Note that this value is
	// cloned by ServeTLS and ListenAndServeTLS, so it's not
	// possible to modify the configuration with methods like
	// tls.Config.SetSessionTicketKeys. To use
	// SetSessionTicketKeys, use Server.Serve with a TLS Listener
	// instead.
	TLSConfig *tls.Config

	// ReadTimeout is the maximum duration for reading the entire
	// request, including the body.
	//
	// Because ReadTimeout does not let Handlers make per-request
	// decisions on each request body's acceptable deadline or
	// upload rate, most users will prefer to use
	// ReadHeaderTimeout. It is valid to use them both.
	ReadTimeout time.Duration

	// ReadHeaderTimeout is the amount of time allowed to read
	// request headers. The connection's read deadline is reset
	// after reading the headers and the Handler can decide what
	// is considered too slow for the body. If ReadHeaderTimeout
	// is zero, the value of ReadTimeout is used. If both are
	// zero, there is no timeout.
	ReadHeaderTimeout time.Duration

	// WriteTimeout is the maximum duration before timing out
	// writes of the response. It is reset whenever a new
	// request's header is read. Like ReadTimeout, it does not
	// let Handlers make decisions on a per-request basis.
	WriteTimeout time.Duration

	// IdleTimeout is the maximum amount of time to wait for the
	// next request when keep-alives are enabled. If IdleTimeout
	// is zero, the value of ReadTimeout is used. If both are
	// zero, there is no timeout.
	IdleTimeout time.Duration

	// MaxHeaderBytes controls the maximum number of bytes the
	// server will read parsing the request header's keys and
	// values, including the request line. It does not limit the
	// size of the request body.
	// If zero, DefaultMaxHeaderBytes is used.
	MaxHeaderBytes int

	// TLSNextProto optionally specifies a function to take over
	// ownership of the provided TLS connection when an ALPN
	// protocol upgrade has occurred. The map key is the protocol
	// name negotiated. The Handler argument should be used to
	// handle HTTP requests and will initialize the Request's TLS
	// and RemoteAddr if not already set. The connection is
	// automatically closed when the function returns.
	// If TLSNextProto is not nil, HTTP/2 support is not enabled
	// automatically.
	TLSNextProto map[string]func(*Server, *tls.Conn, Handler)

	// ConnState specifies an optional callback function that is
	// called when a client connection changes state. See the
	// ConnState type and associated constants for details.
	ConnState func(net.Conn, ConnState)

	// ErrorLog specifies an optional logger for errors accepting
	// connections, unexpected behavior from handlers, and
	// underlying FileSystem errors.
	// If nil, logging is done via the log package's standard logger.
	ErrorLog *log.Logger

	// BaseContext optionally specifies a function that returns
	// the base context for incoming requests on this server.
	// The provided Listener is the specific Listener that's
	// about to start accepting requests.
	// If BaseContext is nil, the default is context.Background().
	// If non-nil, it must return a non-nil context.
	BaseContext func(net.Listener) context.Context

	// ConnContext optionally specifies a function that modifies
	// the context used for a new connection c. The provided ctx
	// is derived from the base context and has a ServerContextKey
	// value.
	ConnContext func(ctx context.Context, c net.Conn) context.Context

	inShutdown atomicBool // true when when server is in shutdown

	disableKeepAlives int32     // accessed atomically.
	nextProtoOnce     sync.Once // guards setupHTTP2_* init
	nextProtoErr      error     // result of http2.ConfigureServer if used

	mu         sync.Mutex
	listeners  map[*net.Listener]struct{}
	activeConn map[*conn]struct{}
	doneChan   chan struct{}
	onShutdown []func()
}

func ( *Server) () <-chan struct{} {
	.mu.Lock()
	defer .mu.Unlock()
	return .getDoneChanLocked()
}

func ( *Server) () chan struct{} {
	if .doneChan == nil {
		.doneChan = make(chan struct{})
	}
	return .doneChan
}

func ( *Server) () {
	 := .getDoneChanLocked()
	select {
	case <-:
		// Already closed. Don't close again.
	default:
		// Safe to close here. We're the only closer, guarded
		// by s.mu.
		close()
	}
}

// Close immediately closes all active net.Listeners and any
// connections in state StateNew, StateActive, or StateIdle. For a
// graceful shutdown, use Shutdown.
//
// Close does not attempt to close (and does not even know about)
// any hijacked connections, such as WebSockets.
//
// Close returns any error returned from closing the Server's
// underlying Listener(s).
func ( *Server) () error {
	.inShutdown.setTrue()
	.mu.Lock()
	defer .mu.Unlock()
	.closeDoneChanLocked()
	 := .closeListenersLocked()
	for  := range .activeConn {
		.rwc.Close()
		delete(.activeConn, )
	}
	return 
}

// shutdownPollIntervalMax is the max polling interval when checking
// quiescence during Server.Shutdown. Polling starts with a small
// interval and backs off to the max.
// Ideally we could find a solution that doesn't involve polling,
// but which also doesn't have a high runtime cost (and doesn't
// involve any contentious mutexes), but that is left as an
// exercise for the reader.
const shutdownPollIntervalMax = 500 * time.Millisecond

// Shutdown gracefully shuts down the server without interrupting any
// active connections. Shutdown works by first closing all open
// listeners, then closing all idle connections, and then waiting
// indefinitely for connections to return to idle and then shut down.
// If the provided context expires before the shutdown is complete,
// Shutdown returns the context's error, otherwise it returns any
// error returned from closing the Server's underlying Listener(s).
//
// When Shutdown is called, Serve, ListenAndServe, and
// ListenAndServeTLS immediately return ErrServerClosed. Make sure the
// program doesn't exit and waits instead for Shutdown to return.
//
// Shutdown does not attempt to close nor wait for hijacked
// connections such as WebSockets. The caller of Shutdown should
// separately notify such long-lived connections of shutdown and wait
// for them to close, if desired. See RegisterOnShutdown for a way to
// register shutdown notification functions.
//
// Once Shutdown has been called on a server, it may not be reused;
// future calls to methods such as Serve will return ErrServerClosed.
func ( *Server) ( context.Context) error {
	.inShutdown.setTrue()

	.mu.Lock()
	 := .closeListenersLocked()
	.closeDoneChanLocked()
	for ,  := range .onShutdown {
		go ()
	}
	.mu.Unlock()

	 := time.Millisecond
	 := func() time.Duration {
		// Add 10% jitter.
		 :=  + time.Duration(rand.Intn(int(/10)))
		// Double and clamp for next time.
		 *= 2
		if  > shutdownPollIntervalMax {
			 = shutdownPollIntervalMax
		}
		return 
	}

	 := time.NewTimer(())
	defer .Stop()
	for {
		if .closeIdleConns() && .numListeners() == 0 {
			return 
		}
		select {
		case <-.Done():
			return .Err()
		case <-.C:
			.Reset(())
		}
	}
}

// RegisterOnShutdown registers a function to call on Shutdown.
// This can be used to gracefully shutdown connections that have
// undergone ALPN protocol upgrade or that have been hijacked.
// This function should start protocol-specific graceful shutdown,
// but should not wait for shutdown to complete.
func ( *Server) ( func()) {
	.mu.Lock()
	.onShutdown = append(.onShutdown, )
	.mu.Unlock()
}

func ( *Server) () int {
	.mu.Lock()
	defer .mu.Unlock()
	return len(.listeners)
}

// closeIdleConns closes all idle connections and reports whether the
// server is quiescent.
func ( *Server) () bool {
	.mu.Lock()
	defer .mu.Unlock()
	 := true
	for  := range .activeConn {
		,  := .getState()
		// Issue 22682: treat StateNew connections as if
		// they're idle if we haven't read the first request's
		// header in over 5 seconds.
		if  == StateNew &&  < time.Now().Unix()-5 {
			 = StateIdle
		}
		if  != StateIdle ||  == 0 {
			// Assume unixSec == 0 means it's a very new
			// connection, without state set yet.
			 = false
			continue
		}
		.rwc.Close()
		delete(.activeConn, )
	}
	return 
}

func ( *Server) () error {
	var  error
	for  := range .listeners {
		if  := (*).Close();  != nil &&  == nil {
			 = 
		}
	}
	return 
}

// A ConnState represents the state of a client connection to a server.
// It's used by the optional Server.ConnState hook.
type ConnState int

const (
	// StateNew represents a new connection that is expected to
	// send a request immediately. Connections begin at this
	// state and then transition to either StateActive or
	// StateClosed.
	StateNew ConnState = iota

	// StateActive represents a connection that has read 1 or more
	// bytes of a request. The Server.ConnState hook for
	// StateActive fires before the request has entered a handler
	// and doesn't fire again until the request has been
	// handled. After the request is handled, the state
	// transitions to StateClosed, StateHijacked, or StateIdle.
	// For HTTP/2, StateActive fires on the transition from zero
	// to one active request, and only transitions away once all
	// active requests are complete. That means that ConnState
	// cannot be used to do per-request work; ConnState only notes
	// the overall state of the connection.
	StateActive

	// StateIdle represents a connection that has finished
	// handling a request and is in the keep-alive state, waiting
	// for a new request. Connections transition from StateIdle
	// to either StateActive or StateClosed.
	StateIdle

	// StateHijacked represents a hijacked connection.
	// This is a terminal state. It does not transition to StateClosed.
	StateHijacked

	// StateClosed represents a closed connection.
	// This is a terminal state. Hijacked connections do not
	// transition to StateClosed.
	StateClosed
)

var stateName = map[ConnState]string{
	StateNew:      "new",
	StateActive:   "active",
	StateIdle:     "idle",
	StateHijacked: "hijacked",
	StateClosed:   "closed",
}

func ( ConnState) () string {
	return stateName[]
}

// serverHandler delegates to either the server's Handler or
// DefaultServeMux and also handles "OPTIONS *" requests.
type serverHandler struct {
	srv *Server
}

func ( serverHandler) ( ResponseWriter,  *Request) {
	 := .srv.Handler
	if  == nil {
		 = DefaultServeMux
	}
	if .RequestURI == "*" && .Method == "OPTIONS" {
		 = globalOptionsHandler{}
	}
	.ServeHTTP(, )
}

// ListenAndServe listens on the TCP network address srv.Addr and then
// calls Serve to handle requests on incoming connections.
// Accepted connections are configured to enable TCP keep-alives.
//
// If srv.Addr is blank, ":http" is used.
//
// ListenAndServe always returns a non-nil error. After Shutdown or Close,
// the returned error is ErrServerClosed.
func ( *Server) () error {
	if .shuttingDown() {
		return ErrServerClosed
	}
	 := .Addr
	if  == "" {
		 = ":http"
	}
	,  := net.Listen("tcp", )
	if  != nil {
		return 
	}
	return .Serve()
}

var testHookServerServe func(*Server, net.Listener) // used if non-nil

// shouldDoServeHTTP2 reports whether Server.Serve should configure
// automatic HTTP/2. (which sets up the srv.TLSNextProto map)
func ( *Server) () bool {
	if .TLSConfig == nil {
		// Compatibility with Go 1.6:
		// If there's no TLSConfig, it's possible that the user just
		// didn't set it on the http.Server, but did pass it to
		// tls.NewListener and passed that listener to Serve.
		// So we should configure HTTP/2 (to set up srv.TLSNextProto)
		// in case the listener returns an "h2" *tls.Conn.
		return true
	}
	// The user specified a TLSConfig on their http.Server.
	// In this, case, only configure HTTP/2 if their tls.Config
	// explicitly mentions "h2". Otherwise http2.ConfigureServer
	// would modify the tls.Config to add it, but they probably already
	// passed this tls.Config to tls.NewListener. And if they did,
	// it's too late anyway to fix it. It would only be potentially racy.
	// See Issue 15908.
	return strSliceContains(.TLSConfig.NextProtos, http2NextProtoTLS)
}

// ErrServerClosed is returned by the Server's Serve, ServeTLS, ListenAndServe,
// and ListenAndServeTLS methods after a call to Shutdown or Close.
var ErrServerClosed = errors.New("http: Server closed")

// Serve accepts incoming connections on the Listener l, creating a
// new service goroutine for each. The service goroutines read requests and
// then call srv.Handler to reply to them.
//
// HTTP/2 support is only enabled if the Listener returns *tls.Conn
// connections and they were configured with "h2" in the TLS
// Config.NextProtos.
//
// Serve always returns a non-nil error and closes l.
// After Shutdown or Close, the returned error is ErrServerClosed.
func ( *Server) ( net.Listener) error {
	if  := testHookServerServe;  != nil {
		(, ) // call hook with unwrapped listener
	}

	 := 
	 = &onceCloseListener{Listener: }
	defer .Close()

	if  := .setupHTTP2_Serve();  != nil {
		return 
	}

	if !.trackListener(&, true) {
		return ErrServerClosed
	}
	defer .trackListener(&, false)

	 := context.Background()
	if .BaseContext != nil {
		 = .BaseContext()
		if  == nil {
			panic("BaseContext returned a nil context")
		}
	}

	var  time.Duration // how long to sleep on accept failure

	 := context.WithValue(, ServerContextKey, )
	for {
		,  := .Accept()
		if  != nil {
			select {
			case <-.getDoneChan():
				return ErrServerClosed
			default:
			}
			if ,  := .(net.Error);  && .Temporary() {
				if  == 0 {
					 = 5 * time.Millisecond
				} else {
					 *= 2
				}
				if  := 1 * time.Second;  >  {
					 = 
				}
				.logf("http: Accept error: %v; retrying in %v", , )
				time.Sleep()
				continue
			}
			return 
		}
		 := 
		if  := .ConnContext;  != nil {
			 = (, )
			if  == nil {
				panic("ConnContext returned nil")
			}
		}
		 = 0
		 := .newConn()
		.setState(.rwc, StateNew, runHooks) // before Serve can return
		go .serve()
	}
}

// ServeTLS accepts incoming connections on the Listener l, creating a
// new service goroutine for each. The service goroutines perform TLS
// setup and then read requests, calling srv.Handler to reply to them.
//
// Files containing a certificate and matching private key for the
// server must be provided if neither the Server's
// TLSConfig.Certificates nor TLSConfig.GetCertificate are populated.
// If the certificate is signed by a certificate authority, the
// certFile should be the concatenation of the server's certificate,
// any intermediates, and the CA's certificate.
//
// ServeTLS always returns a non-nil error. After Shutdown or Close, the
// returned error is ErrServerClosed.
func ( *Server) ( net.Listener, ,  string) error {
	// Setup HTTP/2 before srv.Serve, to initialize srv.TLSConfig
	// before we clone it and create the TLS Listener.
	if  := .setupHTTP2_ServeTLS();  != nil {
		return 
	}

	 := cloneTLSConfig(.TLSConfig)
	if !strSliceContains(.NextProtos, "http/1.1") {
		.NextProtos = append(.NextProtos, "http/1.1")
	}

	 := len(.Certificates) > 0 || .GetCertificate != nil
	if ! ||  != "" ||  != "" {
		var  error
		.Certificates = make([]tls.Certificate, 1)
		.Certificates[0],  = tls.LoadX509KeyPair(, )
		if  != nil {
			return 
		}
	}

	 := tls.NewListener(, )
	return .Serve()
}

// trackListener adds or removes a net.Listener to the set of tracked
// listeners.
//
// We store a pointer to interface in the map set, in case the
// net.Listener is not comparable. This is safe because we only call
// trackListener via Serve and can track+defer untrack the same
// pointer to local variable there. We never need to compare a
// Listener from another caller.
//
// It reports whether the server is still up (not Shutdown or Closed).
func ( *Server) ( *net.Listener,  bool) bool {
	.mu.Lock()
	defer .mu.Unlock()
	if .listeners == nil {
		.listeners = make(map[*net.Listener]struct{})
	}
	if  {
		if .shuttingDown() {
			return false
		}
		.listeners[] = struct{}{}
	} else {
		delete(.listeners, )
	}
	return true
}

func ( *Server) ( *conn,  bool) {
	.mu.Lock()
	defer .mu.Unlock()
	if .activeConn == nil {
		.activeConn = make(map[*conn]struct{})
	}
	if  {
		.activeConn[] = struct{}{}
	} else {
		delete(.activeConn, )
	}
}

func ( *Server) () time.Duration {
	if .IdleTimeout != 0 {
		return .IdleTimeout
	}
	return .ReadTimeout
}

func ( *Server) () time.Duration {
	if .ReadHeaderTimeout != 0 {
		return .ReadHeaderTimeout
	}
	return .ReadTimeout
}

func ( *Server) () bool {
	return atomic.LoadInt32(&.disableKeepAlives) == 0 && !.shuttingDown()
}

func ( *Server) () bool {
	return .inShutdown.isSet()
}

// SetKeepAlivesEnabled controls whether HTTP keep-alives are enabled.
// By default, keep-alives are always enabled. Only very
// resource-constrained environments or servers in the process of
// shutting down should disable them.
func ( *Server) ( bool) {
	if  {
		atomic.StoreInt32(&.disableKeepAlives, 0)
		return
	}
	atomic.StoreInt32(&.disableKeepAlives, 1)

	// Close idle HTTP/1 conns:
	.closeIdleConns()

	// TODO: Issue 26303: close HTTP/2 conns as soon as they become idle.
}

func ( *Server) ( string,  ...interface{}) {
	if .ErrorLog != nil {
		.ErrorLog.Printf(, ...)
	} else {
		log.Printf(, ...)
	}
}

// logf prints to the ErrorLog of the *Server associated with request r
// via ServerContextKey. If there's no associated server, or if ErrorLog
// is nil, logging is done via the log package's standard logger.
func logf( *Request,  string,  ...interface{}) {
	,  := .Context().Value(ServerContextKey).(*Server)
	if  != nil && .ErrorLog != nil {
		.ErrorLog.Printf(, ...)
	} else {
		log.Printf(, ...)
	}
}

// ListenAndServe listens on the TCP network address addr and then calls
// Serve with handler to handle requests on incoming connections.
// Accepted connections are configured to enable TCP keep-alives.
//
// The handler is typically nil, in which case the DefaultServeMux is used.
//
// ListenAndServe always returns a non-nil error.
func ( string,  Handler) error {
	 := &Server{Addr: , Handler: }
	return .ListenAndServe()
}

// ListenAndServeTLS acts identically to ListenAndServe, except that it
// expects HTTPS connections. Additionally, files containing a certificate and
// matching private key for the server must be provided. If the certificate
// is signed by a certificate authority, the certFile should be the concatenation
// of the server's certificate, any intermediates, and the CA's certificate.
func (, ,  string,  Handler) error {
	 := &Server{Addr: , Handler: }
	return .ListenAndServeTLS(, )
}

// ListenAndServeTLS listens on the TCP network address srv.Addr and
// then calls ServeTLS to handle requests on incoming TLS connections.
// Accepted connections are configured to enable TCP keep-alives.
//
// Filenames containing a certificate and matching private key for the
// server must be provided if neither the Server's TLSConfig.Certificates
// nor TLSConfig.GetCertificate are populated. If the certificate is
// signed by a certificate authority, the certFile should be the
// concatenation of the server's certificate, any intermediates, and
// the CA's certificate.
//
// If srv.Addr is blank, ":https" is used.
//
// ListenAndServeTLS always returns a non-nil error. After Shutdown or
// Close, the returned error is ErrServerClosed.
func ( *Server) (,  string) error {
	if .shuttingDown() {
		return ErrServerClosed
	}
	 := .Addr
	if  == "" {
		 = ":https"
	}

	,  := net.Listen("tcp", )
	if  != nil {
		return 
	}

	defer .Close()

	return .ServeTLS(, , )
}

// setupHTTP2_ServeTLS conditionally configures HTTP/2 on
// srv and reports whether there was an error setting it up. If it is
// not configured for policy reasons, nil is returned.
func ( *Server) () error {
	.nextProtoOnce.Do(.onceSetNextProtoDefaults)
	return .nextProtoErr
}

// setupHTTP2_Serve is called from (*Server).Serve and conditionally
// configures HTTP/2 on srv using a more conservative policy than
// setupHTTP2_ServeTLS because Serve is called after tls.Listen,
// and may be called concurrently. See shouldConfigureHTTP2ForServe.
//
// The tests named TestTransportAutomaticHTTP2* and
// TestConcurrentServerServe in server_test.go demonstrate some
// of the supported use cases and motivations.
func ( *Server) () error {
	.nextProtoOnce.Do(.onceSetNextProtoDefaults_Serve)
	return .nextProtoErr
}

func ( *Server) () {
	if .shouldConfigureHTTP2ForServe() {
		.onceSetNextProtoDefaults()
	}
}

// onceSetNextProtoDefaults configures HTTP/2, if the user hasn't
// configured otherwise. (by setting srv.TLSNextProto non-nil)
// It must only be called via srv.nextProtoOnce (use srv.setupHTTP2_*).
func ( *Server) () {
	if omitBundledHTTP2 || strings.Contains(os.Getenv("GODEBUG"), "http2server=0") {
		return
	}
	// Enable HTTP/2 by default if the user hasn't otherwise
	// configured their TLSNextProto map.
	if .TLSNextProto == nil {
		 := &http2Server{
			NewWriteScheduler: func() http2WriteScheduler { return http2NewPriorityWriteScheduler(nil) },
		}
		.nextProtoErr = http2ConfigureServer(, )
	}
}

// TimeoutHandler returns a Handler that runs h with the given time limit.
//
// The new Handler calls h.ServeHTTP to handle each request, but if a
// call runs for longer than its time limit, the handler responds with
// a 503 Service Unavailable error and the given message in its body.
// (If msg is empty, a suitable default message will be sent.)
// After such a timeout, writes by h to its ResponseWriter will return
// ErrHandlerTimeout.
//
// TimeoutHandler supports the Pusher interface but does not support
// the Hijacker or Flusher interfaces.
func ( Handler,  time.Duration,  string) Handler {
	return &timeoutHandler{
		handler: ,
		body:    ,
		dt:      ,
	}
}

// ErrHandlerTimeout is returned on ResponseWriter Write calls
// in handlers which have timed out.
var ErrHandlerTimeout = errors.New("http: Handler timeout")

type timeoutHandler struct {
	handler Handler
	body    string
	dt      time.Duration

	// When set, no context will be created and this context will
	// be used instead.
	testContext context.Context
}

func ( *timeoutHandler) () string {
	if .body != "" {
		return .body
	}
	return "<html><head><title>Timeout</title></head><body><h1>Timeout</h1></body></html>"
}

func ( *timeoutHandler) ( ResponseWriter,  *Request) {
	 := .testContext
	if  == nil {
		var  context.CancelFunc
		,  = context.WithTimeout(.Context(), .dt)
		defer ()
	}
	 = .WithContext()
	 := make(chan struct{})
	 := &timeoutWriter{
		w:   ,
		h:   make(Header),
		req: ,
	}
	 := make(chan interface{}, 1)
	go func() {
		defer func() {
			if  := recover();  != nil {
				 <- 
			}
		}()
		.handler.ServeHTTP(, )
		close()
	}()
	select {
	case  := <-:
		panic()
	case <-:
		.mu.Lock()
		defer .mu.Unlock()
		 := .Header()
		for ,  := range .h {
			[] = 
		}
		if !.wroteHeader {
			.code = StatusOK
		}
		.WriteHeader(.code)
		.Write(.wbuf.Bytes())
	case <-.Done():
		.mu.Lock()
		defer .mu.Unlock()
		.WriteHeader(StatusServiceUnavailable)
		io.WriteString(, .errorBody())
		.timedOut = true
	}
}

type timeoutWriter struct {
	w    ResponseWriter
	h    Header
	wbuf bytes.Buffer
	req  *Request

	mu          sync.Mutex
	timedOut    bool
	wroteHeader bool
	code        int
}

var _ Pusher = (*timeoutWriter)(nil)

// Push implements the Pusher interface.
func ( *timeoutWriter) ( string,  *PushOptions) error {
	if ,  := .w.(Pusher);  {
		return .Push(, )
	}
	return ErrNotSupported
}

func ( *timeoutWriter) () Header { return .h }

func ( *timeoutWriter) ( []byte) (int, error) {
	.mu.Lock()
	defer .mu.Unlock()
	if .timedOut {
		return 0, ErrHandlerTimeout
	}
	if !.wroteHeader {
		.writeHeaderLocked(StatusOK)
	}
	return .wbuf.Write()
}

func ( *timeoutWriter) ( int) {
	checkWriteHeaderCode()

	switch {
	case .timedOut:
		return
	case .wroteHeader:
		if .req != nil {
			 := relevantCaller()
			logf(.req, "http: superfluous response.WriteHeader call from %s (%s:%d)", .Function, path.Base(.File), .Line)
		}
	default:
		.wroteHeader = true
		.code = 
	}
}

func ( *timeoutWriter) ( int) {
	.mu.Lock()
	defer .mu.Unlock()
	.writeHeaderLocked()
}

// onceCloseListener wraps a net.Listener, protecting it from
// multiple Close calls.
type onceCloseListener struct {
	net.Listener
	once     sync.Once
	closeErr error
}

func ( *onceCloseListener) () error {
	.once.Do(.close)
	return .closeErr
}

func ( *onceCloseListener) () { .closeErr = .Listener.Close() }

// globalOptionsHandler responds to "OPTIONS *" requests.
type globalOptionsHandler struct{}

func (globalOptionsHandler) ( ResponseWriter,  *Request) {
	.Header().Set("Content-Length", "0")
	if .ContentLength != 0 {
		// Read up to 4KB of OPTIONS body (as mentioned in the
		// spec as being reserved for future use), but anything
		// over that is considered a waste of server resources
		// (or an attack) and we abort and close the connection,
		// courtesy of MaxBytesReader's EOF behavior.
		 := MaxBytesReader(, .Body, 4<<10)
		io.Copy(io.Discard, )
	}
}

// initALPNRequest is an HTTP handler that initializes certain
// uninitialized fields in its *Request. Such partially-initialized
// Requests come from ALPN protocol handlers.
type initALPNRequest struct {
	ctx context.Context
	c   *tls.Conn
	h   serverHandler
}

// BaseContext is an exported but unadvertised http.Handler method
// recognized by x/net/http2 to pass down a context; the TLSNextProto
// API predates context support so we shoehorn through the only
// interface we have available.
func ( initALPNRequest) () context.Context { return .ctx }

func ( initALPNRequest) ( ResponseWriter,  *Request) {
	if .TLS == nil {
		.TLS = &tls.ConnectionState{}
		*.TLS = .c.ConnectionState()
	}
	if .Body == nil {
		.Body = NoBody
	}
	if .RemoteAddr == "" {
		.RemoteAddr = .c.RemoteAddr().String()
	}
	.h.ServeHTTP(, )
}

// loggingConn is used for debugging.
type loggingConn struct {
	name string
	net.Conn
}

var (
	uniqNameMu   sync.Mutex
	uniqNameNext = make(map[string]int)
)

func newLoggingConn( string,  net.Conn) net.Conn {
	uniqNameMu.Lock()
	defer uniqNameMu.Unlock()
	uniqNameNext[]++
	return &loggingConn{
		name: fmt.Sprintf("%s-%d", , uniqNameNext[]),
		Conn: ,
	}
}

func ( *loggingConn) ( []byte) ( int,  error) {
	log.Printf("%s.Write(%d) = ....", .name, len())
	,  = .Conn.Write()
	log.Printf("%s.Write(%d) = %d, %v", .name, len(), , )
	return
}

func ( *loggingConn) ( []byte) ( int,  error) {
	log.Printf("%s.Read(%d) = ....", .name, len())
	,  = .Conn.Read()
	log.Printf("%s.Read(%d) = %d, %v", .name, len(), , )
	return
}

func ( *loggingConn) () ( error) {
	log.Printf("%s.Close() = ...", .name)
	 = .Conn.Close()
	log.Printf("%s.Close() = %v", .name, )
	return
}

// checkConnErrorWriter writes to c.rwc and records any write errors to c.werr.
// It only contains one field (and a pointer field at that), so it
// fits in an interface value without an extra allocation.
type checkConnErrorWriter struct {
	c *conn
}

func ( checkConnErrorWriter) ( []byte) ( int,  error) {
	,  = .c.rwc.Write()
	if  != nil && .c.werr == nil {
		.c.werr = 
		.c.cancelCtx()
	}
	return
}

func numLeadingCRorLF( []byte) ( int) {
	for ,  := range  {
		if  == '\r' ||  == '\n' {
			++
			continue
		}
		break
	}
	return

}

func strSliceContains( []string,  string) bool {
	for ,  := range  {
		if  ==  {
			return true
		}
	}
	return false
}

// tlsRecordHeaderLooksLikeHTTP reports whether a TLS record header
// looks like it might've been a misdirected plaintext HTTP request.
func tlsRecordHeaderLooksLikeHTTP( [5]byte) bool {
	switch string([:]) {
	case "GET /", "HEAD ", "POST ", "PUT /", "OPTIO":
		return true
	}
	return false
}