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server.go
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server.go
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// 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 2616.
package http
import (
"bufio"
"crypto/tls"
"errors"
"fmt"
"io"
"io/ioutil"
"log"
"net"
"net/url"
"os"
"path"
"runtime"
"strconv"
"strings"
"sync"
"sync/atomic"
"time"
)
// Errors introduced by the HTTP server.
var (
ErrWriteAfterFlush = errors.New("Conn.Write called after Flush")
ErrBodyNotAllowed = errors.New("http: request method or response status code does not allow body")
ErrHijacked = errors.New("Conn has been hijacked")
ErrContentLength = errors.New("Conn.Write wrote more than the declared Content-Length")
)
// Objects implementing the Handler interface can be
// registered to serve a particular path or subtree
// in the HTTP server.
//
// ServeHTTP should write reply headers and data to the ResponseWriter
// and then return. Returning signals that the request is finished
// and that the HTTP server can move on to the next request on
// the connection.
type Handler interface {
ServeHTTP(ResponseWriter, *Request)
}
// A ResponseWriter interface is used by an HTTP handler to
// construct an HTTP response.
type ResponseWriter interface {
// Header returns the header map that will be sent by WriteHeader.
// Changing the header after a call to WriteHeader (or Write) has
// no effect.
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.
Write([]byte) (int, error)
// WriteHeader sends an HTTP response header with 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.
WriteHeader(int)
}
// The Flusher interface is implemented by ResponseWriters that allow
// an HTTP handler to flush buffered data to the client.
//
// 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.
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.
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.
type CloseNotifier interface {
// CloseNotify returns a channel that receives a single value
// when the client connection has gone away.
CloseNotify() <-chan bool
}
// A conn represents the server side of an HTTP connection.
type conn struct {
remoteAddr string // network address of remote side
server *Server // the Server on which the connection arrived
rwc net.Conn // i/o connection
sr liveSwitchReader // where the LimitReader reads from; usually the rwc
lr *io.LimitedReader // io.LimitReader(sr)
buf *bufio.ReadWriter // buffered(lr,rwc), reading from bufio->limitReader->sr->rwc
tlsState *tls.ConnectionState // or nil when not using TLS
mu sync.Mutex // guards the following
clientGone bool // if client has disconnected mid-request
closeNotifyc chan bool // made lazily
hijackedv bool // connection has been hijacked by handler
}
func (c *conn) hijacked() bool {
c.mu.Lock()
defer c.mu.Unlock()
return c.hijackedv
}
func (c *conn) hijack() (rwc net.Conn, buf *bufio.ReadWriter, err error) {
c.mu.Lock()
defer c.mu.Unlock()
if c.hijackedv {
return nil, nil, ErrHijacked
}
if c.closeNotifyc != nil {
return nil, nil, errors.New("http: Hijack is incompatible with use of CloseNotifier")
}
c.hijackedv = true
rwc = c.rwc
buf = c.buf
c.rwc = nil
c.buf = nil
c.setState(rwc, StateHijacked)
return
}
func (c *conn) closeNotify() <-chan bool {
c.mu.Lock()
defer c.mu.Unlock()
if c.closeNotifyc == nil {
c.closeNotifyc = make(chan bool, 1)
if c.hijackedv {
// to obey the function signature, even though
// it'll never receive a value.
return c.closeNotifyc
}
pr, pw := io.Pipe()
readSource := c.sr.r
c.sr.Lock()
c.sr.r = pr
c.sr.Unlock()
go func() {
_, err := io.Copy(pw, readSource)
if err == nil {
err = io.EOF
}
pw.CloseWithError(err)
c.noteClientGone()
}()
}
return c.closeNotifyc
}
func (c *conn) noteClientGone() {
c.mu.Lock()
defer c.mu.Unlock()
if c.closeNotifyc != nil && !c.clientGone {
c.closeNotifyc <- true
}
c.clientGone = true
}
// A switchReader can have its Reader changed at runtime.
// It's not safe for concurrent Reads and switches.
type switchReader struct {
io.Reader
}
// A switchWriter can have its Writer changed at runtime.
// It's not safe for concurrent Writes and switches.
type switchWriter struct {
io.Writer
}
// A liveSwitchReader is a switchReader that's safe for concurrent
// reads and switches, if its mutex is held.
type liveSwitchReader struct {
sync.Mutex
r io.Reader
}
func (sr *liveSwitchReader) Read(p []byte) (n int, err error) {
sr.Lock()
r := sr.r
sr.Unlock()
return r.Read(p)
}
// 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 (cw *chunkWriter) Write(p []byte) (n int, err error) {
if !cw.wroteHeader {
cw.writeHeader(p)
}
if cw.res.req.Method == "HEAD" {
// Eat writes.
return len(p), nil
}
if cw.chunking {
_, err = fmt.Fprintf(cw.res.conn.buf, "%x\r\n", len(p))
if err != nil {
cw.res.conn.rwc.Close()
return
}
}
n, err = cw.res.conn.buf.Write(p)
if cw.chunking && err == nil {
_, err = cw.res.conn.buf.Write(crlf)
}
if err != nil {
cw.res.conn.rwc.Close()
}
return
}
func (cw *chunkWriter) flush() {
if !cw.wroteHeader {
cw.writeHeader(nil)
}
cw.res.conn.buf.Flush()
}
func (cw *chunkWriter) close() {
if !cw.wroteHeader {
cw.writeHeader(nil)
}
if cw.chunking {
// zero EOF chunk, trailer key/value pairs (currently
// unsupported in Go's server), followed by a blank
// line.
cw.res.conn.buf.WriteString("0\r\n\r\n")
}
}
// A response represents the server side of an HTTP response.
type response struct {
conn *conn
req *Request // request for this response
wroteHeader bool // reply header has been (logically) written
wroteContinue bool // 100 Continue response was written
w *bufio.Writer // buffers output in chunks to chunkWriter
cw chunkWriter
sw *switchWriter // of the bufio.Writer, for return to putBufioWriter
// 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
handlerDone bool // set true when the handler exits
// Buffers for Date and Content-Length
dateBuf [len(TimeFormat)]byte
clenBuf [10]byte
}
// requestTooLarge is called by maxBytesReader when too much input has
// been read from the client.
func (w *response) requestTooLarge() {
w.closeAfterReply = true
w.requestBodyLimitHit = true
if !w.wroteHeader {
w.Header().Set("Connection", "close")
}
}
// needsSniff reports whether a Content-Type still needs to be sniffed.
func (w *response) needsSniff() bool {
_, haveType := w.handlerHeader["Content-Type"]
return !w.cw.wroteHeader && !haveType && w.written < sniffLen
}
// writerOnly hides an io.Writer value's optional ReadFrom method
// from io.Copy.
type writerOnly struct {
io.Writer
}
func srcIsRegularFile(src io.Reader) (isRegular bool, err error) {
switch v := src.(type) {
case *os.File:
fi, err := v.Stat()
if err != nil {
return false, err
}
return fi.Mode().IsRegular(), nil
case *io.LimitedReader:
return srcIsRegularFile(v.R)
default:
return
}
}
// ReadFrom is here to optimize copying from an *os.File regular file
// to a *net.TCPConn with sendfile.
func (w *response) ReadFrom(src io.Reader) (n int64, err error) {
// Our underlying w.conn.rwc is usually a *TCPConn (with its
// own ReadFrom method). If not, or if our src isn't a regular
// file, just fall back to the normal copy method.
rf, ok := w.conn.rwc.(io.ReaderFrom)
regFile, err := srcIsRegularFile(src)
if err != nil {
return 0, err
}
if !ok || !regFile {
return io.Copy(writerOnly{w}, src)
}
// sendfile path:
if !w.wroteHeader {
w.WriteHeader(StatusOK)
}
if w.needsSniff() {
n0, err := io.Copy(writerOnly{w}, io.LimitReader(src, sniffLen))
n += n0
if err != nil {
return n, err
}
}
w.w.Flush() // get rid of any previous writes
w.cw.flush() // make sure Header is written; flush data to rwc
// Now that cw has been flushed, its chunking field is guaranteed initialized.
if !w.cw.chunking && w.bodyAllowed() {
n0, err := rf.ReadFrom(src)
n += n0
w.written += n0
return n, err
}
n0, err := io.Copy(writerOnly{w}, src)
n += n0
return n, err
}
// noLimit is an effective infinite upper bound for io.LimitedReader
const noLimit int64 = (1 << 63) - 1
// debugServerConnections controls whether all server connections are wrapped
// with a verbose logging wrapper.
const debugServerConnections = false
// Create new connection from rwc.
func (srv *Server) newConn(rwc net.Conn) (c *conn, err error) {
c = new(conn)
c.remoteAddr = rwc.RemoteAddr().String()
c.server = srv
c.rwc = rwc
if debugServerConnections {
c.rwc = newLoggingConn("server", c.rwc)
}
c.sr = liveSwitchReader{r: c.rwc}
c.lr = io.LimitReader(&c.sr, noLimit).(*io.LimitedReader)
br := newBufioReader(c.lr)
bw := newBufioWriterSize(c.rwc, 4<<10)
c.buf = bufio.NewReadWriter(br, bw)
return c, nil
}
var (
bufioReaderPool sync.Pool
bufioWriter2kPool sync.Pool
bufioWriter4kPool sync.Pool
)
func bufioWriterPool(size int) *sync.Pool {
switch size {
case 2 << 10:
return &bufioWriter2kPool
case 4 << 10:
return &bufioWriter4kPool
}
return nil
}
func newBufioReader(r io.Reader) *bufio.Reader {
if v := bufioReaderPool.Get(); v != nil {
br := v.(*bufio.Reader)
br.Reset(r)
return br
}
return bufio.NewReader(r)
}
func putBufioReader(br *bufio.Reader) {
br.Reset(nil)
bufioReaderPool.Put(br)
}
func newBufioWriterSize(w io.Writer, size int) *bufio.Writer {
pool := bufioWriterPool(size)
if pool != nil {
if v := pool.Get(); v != nil {
bw := v.(*bufio.Writer)
bw.Reset(w)
return bw
}
}
return bufio.NewWriterSize(w, size)
}
func putBufioWriter(bw *bufio.Writer) {
bw.Reset(nil)
if pool := bufioWriterPool(bw.Available()); pool != nil {
pool.Put(bw)
}
}
// 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 (srv *Server) maxHeaderBytes() int {
if srv.MaxHeaderBytes > 0 {
return srv.MaxHeaderBytes
}
return DefaultMaxHeaderBytes
}
func (srv *Server) initialLimitedReaderSize() int64 {
return int64(srv.maxHeaderBytes()) + 4096 // bufio slop
}
// wrapper around io.ReaderCloser which on first read, sends an
// HTTP/1.1 100 Continue header
type expectContinueReader struct {
resp *response
readCloser io.ReadCloser
closed bool
}
func (ecr *expectContinueReader) Read(p []byte) (n int, err error) {
if ecr.closed {
return 0, ErrBodyReadAfterClose
}
if !ecr.resp.wroteContinue && !ecr.resp.conn.hijacked() {
ecr.resp.wroteContinue = true
ecr.resp.conn.buf.WriteString("HTTP/1.1 100 Continue\r\n\r\n")
ecr.resp.conn.buf.Flush()
}
return ecr.readCloser.Read(p)
}
func (ecr *expectContinueReader) Close() error {
ecr.closed = true
return ecr.readCloser.Close()
}
// TimeFormat is the time format to use with
// time.Parse and time.Time.Format when parsing
// or generating times in HTTP headers.
// It is like time.RFC1123 but hard codes GMT as the time zone.
const TimeFormat = "Mon, 02 Jan 2006 15:04:05 GMT"
// appendTime is a non-allocating version of []byte(t.UTC().Format(TimeFormat))
func appendTime(b []byte, t time.Time) []byte {
const days = "SunMonTueWedThuFriSat"
const months = "JanFebMarAprMayJunJulAugSepOctNovDec"
t = t.UTC()
yy, mm, dd := t.Date()
hh, mn, ss := t.Clock()
day := days[3*t.Weekday():]
mon := months[3*(mm-1):]
return append(b,
day[0], day[1], day[2], ',', ' ',
byte('0'+dd/10), byte('0'+dd%10), ' ',
mon[0], mon[1], mon[2], ' ',
byte('0'+yy/1000), byte('0'+(yy/100)%10), byte('0'+(yy/10)%10), byte('0'+yy%10), ' ',
byte('0'+hh/10), byte('0'+hh%10), ':',
byte('0'+mn/10), byte('0'+mn%10), ':',
byte('0'+ss/10), byte('0'+ss%10), ' ',
'G', 'M', 'T')
}
var errTooLarge = errors.New("http: request too large")
// Read next request from connection.
func (c *conn) readRequest() (w *response, err error) {
if c.hijacked() {
return nil, ErrHijacked
}
if d := c.server.ReadTimeout; d != 0 {
c.rwc.SetReadDeadline(time.Now().Add(d))
}
if d := c.server.WriteTimeout; d != 0 {
defer func() {
c.rwc.SetWriteDeadline(time.Now().Add(d))
}()
}
c.lr.N = c.server.initialLimitedReaderSize()
var req *Request
if req, err = ReadRequest(c.buf.Reader); err != nil {
if c.lr.N == 0 {
return nil, errTooLarge
}
return nil, err
}
c.lr.N = noLimit
req.RemoteAddr = c.remoteAddr
req.TLS = c.tlsState
w = &response{
conn: c,
req: req,
handlerHeader: make(Header),
contentLength: -1,
}
w.cw.res = w
w.w = newBufioWriterSize(&w.cw, bufferBeforeChunkingSize)
return w, nil
}
func (w *response) Header() Header {
if w.cw.header == nil && w.wroteHeader && !w.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.
w.cw.header = w.handlerHeader.clone()
}
w.calledHeader = true
return w.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 (w *response) WriteHeader(code int) {
if w.conn.hijacked() {
w.conn.server.logf("http: response.WriteHeader on hijacked connection")
return
}
if w.wroteHeader {
w.conn.server.logf("http: multiple response.WriteHeader calls")
return
}
w.wroteHeader = true
w.status = code
if w.calledHeader && w.cw.header == nil {
w.cw.header = w.handlerHeader.clone()
}
if cl := w.handlerHeader.get("Content-Length"); cl != "" {
v, err := strconv.ParseInt(cl, 10, 64)
if err == nil && v >= 0 {
w.contentLength = v
} else {
w.conn.server.logf("http: invalid Content-Length of %q", cl)
w.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 (h extraHeader) Write(w *bufio.Writer) {
if h.date != nil {
w.Write(headerDate)
w.Write(h.date)
w.Write(crlf)
}
if h.contentLength != nil {
w.Write(headerContentLength)
w.Write(h.contentLength)
w.Write(crlf)
}
for i, v := range []string{h.contentType, h.connection, h.transferEncoding} {
if v != "" {
w.Write(extraHeaderKeys[i])
w.Write(colonSpace)
w.WriteString(v)
w.Write(crlf)
}
}
}
// writeHeader finalizes the header sent to the client and writes it
// to cw.res.conn.buf.
//
// 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 (cw *chunkWriter) writeHeader(p []byte) {
if cw.wroteHeader {
return
}
cw.wroteHeader = true
w := cw.res
keepAlivesEnabled := w.conn.server.doKeepAlives()
isHEAD := w.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 := cw.header
owned := header != nil
if !owned {
header = w.handlerHeader
}
var excludeHeader map[string]bool
delHeader := func(key string) {
if owned {
header.Del(key)
return
}
if _, ok := header[key]; !ok {
return
}
if excludeHeader == nil {
excludeHeader = make(map[string]bool)
}
excludeHeader[key] = true
}
var setHeader extraHeader
// 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.
if w.handlerDone && bodyAllowedForStatus(w.status) && header.get("Content-Length") == "" && (!isHEAD || len(p) > 0) {
w.contentLength = int64(len(p))
setHeader.contentLength = strconv.AppendInt(cw.res.clenBuf[:0], int64(len(p)), 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 w.req.wantsHttp10KeepAlive() && keepAlivesEnabled {
sentLength := header.get("Content-Length") != ""
if sentLength && header.get("Connection") == "keep-alive" {
w.closeAfterReply = false
}
}
// Check for a explicit (and valid) Content-Length header.
hasCL := w.contentLength != -1
if w.req.wantsHttp10KeepAlive() && (isHEAD || hasCL) {
_, connectionHeaderSet := header["Connection"]
if !connectionHeaderSet {
setHeader.connection = "keep-alive"
}
} else if !w.req.ProtoAtLeast(1, 1) || w.req.wantsClose() {
w.closeAfterReply = true
}
if header.get("Connection") == "close" || !keepAlivesEnabled {
w.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.
if w.req.ContentLength != 0 && !w.closeAfterReply {
ecr, isExpecter := w.req.Body.(*expectContinueReader)
if !isExpecter || ecr.resp.wroteContinue {
n, _ := io.CopyN(ioutil.Discard, w.req.Body, maxPostHandlerReadBytes+1)
if n >= maxPostHandlerReadBytes {
w.requestTooLarge()
delHeader("Connection")
setHeader.connection = "close"
} else {
w.req.Body.Close()
}
}
}
code := w.status
if bodyAllowedForStatus(code) {
// If no content type, apply sniffing algorithm to body.
_, haveType := header["Content-Type"]
if !haveType {
setHeader.contentType = DetectContentType(p)
}
} else {
for _, k := range suppressedHeaders(code) {
delHeader(k)
}
}
if _, ok := header["Date"]; !ok {
setHeader.date = appendTime(cw.res.dateBuf[:0], time.Now())
}
te := header.get("Transfer-Encoding")
hasTE := te != ""
if hasCL && hasTE && te != "identity" {
// TODO: return an error if WriteHeader gets a return parameter
// For now just ignore the Content-Length.
w.conn.server.logf("http: WriteHeader called with both Transfer-Encoding of %q and a Content-Length of %d",
te, w.contentLength)
delHeader("Content-Length")
hasCL = false
}
if w.req.Method == "HEAD" || !bodyAllowedForStatus(code) {
// do nothing
} else if code == StatusNoContent {
delHeader("Transfer-Encoding")
} else if hasCL {
delHeader("Transfer-Encoding")
} else if w.req.ProtoAtLeast(1, 1) {
// HTTP/1.1 or greater: use chunked transfer encoding
// to avoid closing the connection at EOF.
// TODO: this blows away any custom or stacked Transfer-Encoding they
// might have set. Deal with that as need arises once we have a valid
// use case.
cw.chunking = true
setHeader.transferEncoding = "chunked"
} else {
// HTTP version < 1.1: cannot do chunked transfer
// encoding and we don't know the Content-Length so
// signal EOF by closing connection.
w.closeAfterReply = true
delHeader("Transfer-Encoding") // in case already set
}
// Cannot use Content-Length with non-identity Transfer-Encoding.
if cw.chunking {
delHeader("Content-Length")
}
if !w.req.ProtoAtLeast(1, 0) {
return
}
if w.closeAfterReply && (!keepAlivesEnabled || !hasToken(cw.header.get("Connection"), "close")) {
delHeader("Connection")
if w.req.ProtoAtLeast(1, 1) {
setHeader.connection = "close"
}
}
w.conn.buf.WriteString(statusLine(w.req, code))
cw.header.WriteSubset(w.conn.buf, excludeHeader)
setHeader.Write(w.conn.buf.Writer)
w.conn.buf.Write(crlf)
}
// statusLines is a cache of Status-Line strings, keyed by code (for
// HTTP/1.1) or negative code (for HTTP/1.0). This is faster than a
// map keyed by struct of two fields. This map's max size is bounded
// by 2*len(statusText), two protocol types for each known official
// status code in the statusText map.
var (
statusMu sync.RWMutex
statusLines = make(map[int]string)
)
// statusLine returns a response Status-Line (RFC 2616 Section 6.1)
// for the given request and response status code.
func statusLine(req *Request, code int) string {
// Fast path:
key := code
proto11 := req.ProtoAtLeast(1, 1)
if !proto11 {
key = -key
}
statusMu.RLock()
line, ok := statusLines[key]
statusMu.RUnlock()
if ok {
return line
}
// Slow path:
proto := "HTTP/1.0"
if proto11 {
proto = "HTTP/1.1"
}
codestring := strconv.Itoa(code)
text, ok := statusText[code]
if !ok {
text = "status code " + codestring
}
line = proto + " " + codestring + " " + text + "\r\n"
if ok {
statusMu.Lock()
defer statusMu.Unlock()
statusLines[key] = line
}
return line
}
// bodyAllowed returns true if a Write is allowed for this response type.
// It's illegal to call this before the header has been flushed.
func (w *response) bodyAllowed() bool {
if !w.wroteHeader {
panic("")
}
return bodyAllowedForStatus(w.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
// 5. 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 (w *response) Write(data []byte) (n int, err error) {
return w.write(len(data), data, "")
}
func (w *response) WriteString(data string) (n int, err error) {
return w.write(len(data), nil, data)
}
// either dataB or dataS is non-zero.
func (w *response) write(lenData int, dataB []byte, dataS string) (n int, err error) {
if w.conn.hijacked() {
w.conn.server.logf("http: response.Write on hijacked connection")
return 0, ErrHijacked
}
if !w.wroteHeader {
w.WriteHeader(StatusOK)
}
if lenData == 0 {
return 0, nil
}
if !w.bodyAllowed() {
return 0, ErrBodyNotAllowed
}
w.written += int64(lenData) // ignoring errors, for errorKludge
if w.contentLength != -1 && w.written > w.contentLength {
return 0, ErrContentLength
}
if dataB != nil {
return w.w.Write(dataB)
} else {
return w.w.WriteString(dataS)
}
}
func (w *response) finishRequest() {
w.handlerDone = true
if !w.wroteHeader {
w.WriteHeader(StatusOK)
}
w.w.Flush()