Source file src/pkg/net/http/request.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	// HTTP Request reading and parsing.
     6	
     7	package http
     8	
     9	import (
    10		"bufio"
    11		"bytes"
    12		"crypto/tls"
    13		"encoding/base64"
    14		"errors"
    15		"fmt"
    16		"io"
    17		"io/ioutil"
    18		"mime"
    19		"mime/multipart"
    20		"net/textproto"
    21		"net/url"
    22		"strings"
    23	)
    24	
    25	const (
    26		maxValueLength   = 4096
    27		maxHeaderLines   = 1024
    28		chunkSize        = 4 << 10  // 4 KB chunks
    29		defaultMaxMemory = 32 << 20 // 32 MB
    30	)
    31	
    32	// ErrMissingFile is returned by FormFile when the provided file field name
    33	// is either not present in the request or not a file field.
    34	var ErrMissingFile = errors.New("http: no such file")
    35	
    36	// HTTP request parsing errors.
    37	type ProtocolError struct {
    38		ErrorString string
    39	}
    40	
    41	func (err *ProtocolError) Error() string { return err.ErrorString }
    42	
    43	var (
    44		ErrHeaderTooLong        = &ProtocolError{"header too long"}
    45		ErrShortBody            = &ProtocolError{"entity body too short"}
    46		ErrNotSupported         = &ProtocolError{"feature not supported"}
    47		ErrUnexpectedTrailer    = &ProtocolError{"trailer header without chunked transfer encoding"}
    48		ErrMissingContentLength = &ProtocolError{"missing ContentLength in HEAD response"}
    49		ErrNotMultipart         = &ProtocolError{"request Content-Type isn't multipart/form-data"}
    50		ErrMissingBoundary      = &ProtocolError{"no multipart boundary param Content-Type"}
    51	)
    52	
    53	type badStringError struct {
    54		what string
    55		str  string
    56	}
    57	
    58	func (e *badStringError) Error() string { return fmt.Sprintf("%s %q", e.what, e.str) }
    59	
    60	// Headers that Request.Write handles itself and should be skipped.
    61	var reqWriteExcludeHeader = map[string]bool{
    62		"Host":              true, // not in Header map anyway
    63		"User-Agent":        true,
    64		"Content-Length":    true,
    65		"Transfer-Encoding": true,
    66		"Trailer":           true,
    67	}
    68	
    69	// A Request represents an HTTP request received by a server
    70	// or to be sent by a client.
    71	type Request struct {
    72		Method string // GET, POST, PUT, etc.
    73		URL    *url.URL
    74	
    75		// The protocol version for incoming requests.
    76		// Outgoing requests always use HTTP/1.1.
    77		Proto      string // "HTTP/1.0"
    78		ProtoMajor int    // 1
    79		ProtoMinor int    // 0
    80	
    81		// A header maps request lines to their values.
    82		// If the header says
    83		//
    84		//	accept-encoding: gzip, deflate
    85		//	Accept-Language: en-us
    86		//	Connection: keep-alive
    87		//
    88		// then
    89		//
    90		//	Header = map[string][]string{
    91		//		"Accept-Encoding": {"gzip, deflate"},
    92		//		"Accept-Language": {"en-us"},
    93		//		"Connection": {"keep-alive"},
    94		//	}
    95		//
    96		// HTTP defines that header names are case-insensitive.
    97		// The request parser implements this by canonicalizing the
    98		// name, making the first character and any characters
    99		// following a hyphen uppercase and the rest lowercase.
   100		Header Header
   101	
   102		// The message body.
   103		Body io.ReadCloser
   104	
   105		// ContentLength records the length of the associated content.
   106		// The value -1 indicates that the length is unknown.
   107		// Values >= 0 indicate that the given number of bytes may
   108		// be read from Body.
   109		// For outgoing requests, a value of 0 means unknown if Body is not nil.
   110		ContentLength int64
   111	
   112		// TransferEncoding lists the transfer encodings from outermost to
   113		// innermost. An empty list denotes the "identity" encoding.
   114		// TransferEncoding can usually be ignored; chunked encoding is
   115		// automatically added and removed as necessary when sending and
   116		// receiving requests.
   117		TransferEncoding []string
   118	
   119		// Close indicates whether to close the connection after
   120		// replying to this request.
   121		Close bool
   122	
   123		// The host on which the URL is sought.
   124		// Per RFC 2616, this is either the value of the Host: header
   125		// or the host name given in the URL itself.
   126		Host string
   127	
   128		// Form contains the parsed form data, including both the URL
   129		// field's query parameters and the POST or PUT form data.
   130		// This field is only available after ParseForm is called.
   131		// The HTTP client ignores Form and uses Body instead.
   132		Form url.Values
   133	
   134		// MultipartForm is the parsed multipart form, including file uploads.
   135		// This field is only available after ParseMultipartForm is called.
   136		// The HTTP client ignores MultipartForm and uses Body instead.
   137		MultipartForm *multipart.Form
   138	
   139		// Trailer maps trailer keys to values.  Like for Header, if the
   140		// response has multiple trailer lines with the same key, they will be
   141		// concatenated, delimited by commas.
   142		// For server requests, Trailer is only populated after Body has been
   143		// closed or fully consumed.
   144		// Trailer support is only partially complete.
   145		Trailer Header
   146	
   147		// RemoteAddr allows HTTP servers and other software to record
   148		// the network address that sent the request, usually for
   149		// logging. This field is not filled in by ReadRequest and
   150		// has no defined format. The HTTP server in this package
   151		// sets RemoteAddr to an "IP:port" address before invoking a
   152		// handler.
   153		// This field is ignored by the HTTP client.
   154		RemoteAddr string
   155	
   156		// RequestURI is the unmodified Request-URI of the
   157		// Request-Line (RFC 2616, Section 5.1) as sent by the client
   158		// to a server. Usually the URL field should be used instead.
   159		// It is an error to set this field in an HTTP client request.
   160		RequestURI string
   161	
   162		// TLS allows HTTP servers and other software to record
   163		// information about the TLS connection on which the request
   164		// was received. This field is not filled in by ReadRequest.
   165		// The HTTP server in this package sets the field for
   166		// TLS-enabled connections before invoking a handler;
   167		// otherwise it leaves the field nil.
   168		// This field is ignored by the HTTP client.
   169		TLS *tls.ConnectionState
   170	}
   171	
   172	// ProtoAtLeast returns whether the HTTP protocol used
   173	// in the request is at least major.minor.
   174	func (r *Request) ProtoAtLeast(major, minor int) bool {
   175		return r.ProtoMajor > major ||
   176			r.ProtoMajor == major && r.ProtoMinor >= minor
   177	}
   178	
   179	// UserAgent returns the client's User-Agent, if sent in the request.
   180	func (r *Request) UserAgent() string {
   181		return r.Header.Get("User-Agent")
   182	}
   183	
   184	// Cookies parses and returns the HTTP cookies sent with the request.
   185	func (r *Request) Cookies() []*Cookie {
   186		return readCookies(r.Header, "")
   187	}
   188	
   189	var ErrNoCookie = errors.New("http: named cookie not present")
   190	
   191	// Cookie returns the named cookie provided in the request or
   192	// ErrNoCookie if not found.
   193	func (r *Request) Cookie(name string) (*Cookie, error) {
   194		for _, c := range readCookies(r.Header, name) {
   195			return c, nil
   196		}
   197		return nil, ErrNoCookie
   198	}
   199	
   200	// AddCookie adds a cookie to the request.  Per RFC 6265 section 5.4,
   201	// AddCookie does not attach more than one Cookie header field.  That
   202	// means all cookies, if any, are written into the same line,
   203	// separated by semicolon.
   204	func (r *Request) AddCookie(c *Cookie) {
   205		s := fmt.Sprintf("%s=%s", sanitizeName(c.Name), sanitizeValue(c.Value))
   206		if c := r.Header.Get("Cookie"); c != "" {
   207			r.Header.Set("Cookie", c+"; "+s)
   208		} else {
   209			r.Header.Set("Cookie", s)
   210		}
   211	}
   212	
   213	// Referer returns the referring URL, if sent in the request.
   214	//
   215	// Referer is misspelled as in the request itself, a mistake from the
   216	// earliest days of HTTP.  This value can also be fetched from the
   217	// Header map as Header["Referer"]; the benefit of making it available
   218	// as a method is that the compiler can diagnose programs that use the
   219	// alternate (correct English) spelling req.Referrer() but cannot
   220	// diagnose programs that use Header["Referrer"].
   221	func (r *Request) Referer() string {
   222		return r.Header.Get("Referer")
   223	}
   224	
   225	// multipartByReader is a sentinel value.
   226	// Its presence in Request.MultipartForm indicates that parsing of the request
   227	// body has been handed off to a MultipartReader instead of ParseMultipartFrom.
   228	var multipartByReader = &multipart.Form{
   229		Value: make(map[string][]string),
   230		File:  make(map[string][]*multipart.FileHeader),
   231	}
   232	
   233	// MultipartReader returns a MIME multipart reader if this is a
   234	// multipart/form-data POST request, else returns nil and an error.
   235	// Use this function instead of ParseMultipartForm to
   236	// process the request body as a stream.
   237	func (r *Request) MultipartReader() (*multipart.Reader, error) {
   238		if r.MultipartForm == multipartByReader {
   239			return nil, errors.New("http: MultipartReader called twice")
   240		}
   241		if r.MultipartForm != nil {
   242			return nil, errors.New("http: multipart handled by ParseMultipartForm")
   243		}
   244		r.MultipartForm = multipartByReader
   245		return r.multipartReader()
   246	}
   247	
   248	func (r *Request) multipartReader() (*multipart.Reader, error) {
   249		v := r.Header.Get("Content-Type")
   250		if v == "" {
   251			return nil, ErrNotMultipart
   252		}
   253		d, params, err := mime.ParseMediaType(v)
   254		if err != nil || d != "multipart/form-data" {
   255			return nil, ErrNotMultipart
   256		}
   257		boundary, ok := params["boundary"]
   258		if !ok {
   259			return nil, ErrMissingBoundary
   260		}
   261		return multipart.NewReader(r.Body, boundary), nil
   262	}
   263	
   264	// Return value if nonempty, def otherwise.
   265	func valueOrDefault(value, def string) string {
   266		if value != "" {
   267			return value
   268		}
   269		return def
   270	}
   271	
   272	const defaultUserAgent = "Go http package"
   273	
   274	// Write writes an HTTP/1.1 request -- header and body -- in wire format.
   275	// This method consults the following fields of the request:
   276	//	Host
   277	//	URL
   278	//	Method (defaults to "GET")
   279	//	Header
   280	//	ContentLength
   281	//	TransferEncoding
   282	//	Body
   283	//
   284	// If Body is present, Content-Length is <= 0 and TransferEncoding
   285	// hasn't been set to "identity", Write adds "Transfer-Encoding:
   286	// chunked" to the header. Body is closed after it is sent.
   287	func (r *Request) Write(w io.Writer) error {
   288		return r.write(w, false, nil)
   289	}
   290	
   291	// WriteProxy is like Write but writes the request in the form
   292	// expected by an HTTP proxy.  In particular, WriteProxy writes the
   293	// initial Request-URI line of the request with an absolute URI, per
   294	// section 5.1.2 of RFC 2616, including the scheme and host.
   295	// In either case, WriteProxy also writes a Host header, using
   296	// either r.Host or r.URL.Host.
   297	func (r *Request) WriteProxy(w io.Writer) error {
   298		return r.write(w, true, nil)
   299	}
   300	
   301	// extraHeaders may be nil
   302	func (req *Request) write(w io.Writer, usingProxy bool, extraHeaders Header) error {
   303		host := req.Host
   304		if host == "" {
   305			if req.URL == nil {
   306				return errors.New("http: Request.Write on Request with no Host or URL set")
   307			}
   308			host = req.URL.Host
   309		}
   310	
   311		ruri := req.URL.RequestURI()
   312		if usingProxy && req.URL.Scheme != "" && req.URL.Opaque == "" {
   313			ruri = req.URL.Scheme + "://" + host + ruri
   314		} else if req.Method == "CONNECT" && req.URL.Path == "" {
   315			// CONNECT requests normally give just the host and port, not a full URL.
   316			ruri = host
   317		}
   318		// TODO(bradfitz): escape at least newlines in ruri?
   319	
   320		bw := bufio.NewWriter(w)
   321		fmt.Fprintf(bw, "%s %s HTTP/1.1\r\n", valueOrDefault(req.Method, "GET"), ruri)
   322	
   323		// Header lines
   324		fmt.Fprintf(bw, "Host: %s\r\n", host)
   325	
   326		// Use the defaultUserAgent unless the Header contains one, which
   327		// may be blank to not send the header.
   328		userAgent := defaultUserAgent
   329		if req.Header != nil {
   330			if ua := req.Header["User-Agent"]; len(ua) > 0 {
   331				userAgent = ua[0]
   332			}
   333		}
   334		if userAgent != "" {
   335			fmt.Fprintf(bw, "User-Agent: %s\r\n", userAgent)
   336		}
   337	
   338		// Process Body,ContentLength,Close,Trailer
   339		tw, err := newTransferWriter(req)
   340		if err != nil {
   341			return err
   342		}
   343		err = tw.WriteHeader(bw)
   344		if err != nil {
   345			return err
   346		}
   347	
   348		// TODO: split long values?  (If so, should share code with Conn.Write)
   349		err = req.Header.WriteSubset(bw, reqWriteExcludeHeader)
   350		if err != nil {
   351			return err
   352		}
   353	
   354		if extraHeaders != nil {
   355			err = extraHeaders.Write(bw)
   356			if err != nil {
   357				return err
   358			}
   359		}
   360	
   361		io.WriteString(bw, "\r\n")
   362	
   363		// Write body and trailer
   364		err = tw.WriteBody(bw)
   365		if err != nil {
   366			return err
   367		}
   368	
   369		return bw.Flush()
   370	}
   371	
   372	// Convert decimal at s[i:len(s)] to integer,
   373	// returning value, string position where the digits stopped,
   374	// and whether there was a valid number (digits, not too big).
   375	func atoi(s string, i int) (n, i1 int, ok bool) {
   376		const Big = 1000000
   377		if i >= len(s) || s[i] < '0' || s[i] > '9' {
   378			return 0, 0, false
   379		}
   380		n = 0
   381		for ; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
   382			n = n*10 + int(s[i]-'0')
   383			if n > Big {
   384				return 0, 0, false
   385			}
   386		}
   387		return n, i, true
   388	}
   389	
   390	// ParseHTTPVersion parses a HTTP version string.
   391	// "HTTP/1.0" returns (1, 0, true).
   392	func ParseHTTPVersion(vers string) (major, minor int, ok bool) {
   393		if len(vers) < 5 || vers[0:5] != "HTTP/" {
   394			return 0, 0, false
   395		}
   396		major, i, ok := atoi(vers, 5)
   397		if !ok || i >= len(vers) || vers[i] != '.' {
   398			return 0, 0, false
   399		}
   400		minor, i, ok = atoi(vers, i+1)
   401		if !ok || i != len(vers) {
   402			return 0, 0, false
   403		}
   404		return major, minor, true
   405	}
   406	
   407	// NewRequest returns a new Request given a method, URL, and optional body.
   408	func NewRequest(method, urlStr string, body io.Reader) (*Request, error) {
   409		u, err := url.Parse(urlStr)
   410		if err != nil {
   411			return nil, err
   412		}
   413		rc, ok := body.(io.ReadCloser)
   414		if !ok && body != nil {
   415			rc = ioutil.NopCloser(body)
   416		}
   417		req := &Request{
   418			Method:     method,
   419			URL:        u,
   420			Proto:      "HTTP/1.1",
   421			ProtoMajor: 1,
   422			ProtoMinor: 1,
   423			Header:     make(Header),
   424			Body:       rc,
   425			Host:       u.Host,
   426		}
   427		if body != nil {
   428			switch v := body.(type) {
   429			case *strings.Reader:
   430				req.ContentLength = int64(v.Len())
   431			case *bytes.Buffer:
   432				req.ContentLength = int64(v.Len())
   433			}
   434		}
   435	
   436		return req, nil
   437	}
   438	
   439	// SetBasicAuth sets the request's Authorization header to use HTTP
   440	// Basic Authentication with the provided username and password.
   441	//
   442	// With HTTP Basic Authentication the provided username and password
   443	// are not encrypted.
   444	func (r *Request) SetBasicAuth(username, password string) {
   445		s := username + ":" + password
   446		r.Header.Set("Authorization", "Basic "+base64.StdEncoding.EncodeToString([]byte(s)))
   447	}
   448	
   449	// ReadRequest reads and parses a request from b.
   450	func ReadRequest(b *bufio.Reader) (req *Request, err error) {
   451	
   452		tp := textproto.NewReader(b)
   453		req = new(Request)
   454	
   455		// First line: GET /index.html HTTP/1.0
   456		var s string
   457		if s, err = tp.ReadLine(); err != nil {
   458			return nil, err
   459		}
   460		defer func() {
   461			if err == io.EOF {
   462				err = io.ErrUnexpectedEOF
   463			}
   464		}()
   465	
   466		var f []string
   467		if f = strings.SplitN(s, " ", 3); len(f) < 3 {
   468			return nil, &badStringError{"malformed HTTP request", s}
   469		}
   470		req.Method, req.RequestURI, req.Proto = f[0], f[1], f[2]
   471		rawurl := req.RequestURI
   472		var ok bool
   473		if req.ProtoMajor, req.ProtoMinor, ok = ParseHTTPVersion(req.Proto); !ok {
   474			return nil, &badStringError{"malformed HTTP version", req.Proto}
   475		}
   476	
   477		// CONNECT requests are used two different ways, and neither uses a full URL:
   478		// The standard use is to tunnel HTTPS through an HTTP proxy.
   479		// It looks like "CONNECT www.google.com:443 HTTP/1.1", and the parameter is
   480		// just the authority section of a URL. This information should go in req.URL.Host.
   481		//
   482		// The net/rpc package also uses CONNECT, but there the parameter is a path
   483		// that starts with a slash. It can be parsed with the regular URL parser,
   484		// and the path will end up in req.URL.Path, where it needs to be in order for
   485		// RPC to work.
   486		justAuthority := req.Method == "CONNECT" && !strings.HasPrefix(rawurl, "/")
   487		if justAuthority {
   488			rawurl = "http://" + rawurl
   489		}
   490	
   491		if req.URL, err = url.ParseRequestURI(rawurl); err != nil {
   492			return nil, err
   493		}
   494	
   495		if justAuthority {
   496			// Strip the bogus "http://" back off.
   497			req.URL.Scheme = ""
   498		}
   499	
   500		// Subsequent lines: Key: value.
   501		mimeHeader, err := tp.ReadMIMEHeader()
   502		if err != nil {
   503			return nil, err
   504		}
   505		req.Header = Header(mimeHeader)
   506	
   507		// RFC2616: Must treat
   508		//	GET /index.html HTTP/1.1
   509		//	Host: www.google.com
   510		// and
   511		//	GET http://www.google.com/index.html HTTP/1.1
   512		//	Host: doesntmatter
   513		// the same.  In the second case, any Host line is ignored.
   514		req.Host = req.URL.Host
   515		if req.Host == "" {
   516			req.Host = req.Header.Get("Host")
   517		}
   518		req.Header.Del("Host")
   519	
   520		fixPragmaCacheControl(req.Header)
   521	
   522		// TODO: Parse specific header values:
   523		//	Accept
   524		//	Accept-Encoding
   525		//	Accept-Language
   526		//	Authorization
   527		//	Cache-Control
   528		//	Connection
   529		//	Date
   530		//	Expect
   531		//	From
   532		//	If-Match
   533		//	If-Modified-Since
   534		//	If-None-Match
   535		//	If-Range
   536		//	If-Unmodified-Since
   537		//	Max-Forwards
   538		//	Proxy-Authorization
   539		//	Referer [sic]
   540		//	TE (transfer-codings)
   541		//	Trailer
   542		//	Transfer-Encoding
   543		//	Upgrade
   544		//	User-Agent
   545		//	Via
   546		//	Warning
   547	
   548		err = readTransfer(req, b)
   549		if err != nil {
   550			return nil, err
   551		}
   552	
   553		return req, nil
   554	}
   555	
   556	// MaxBytesReader is similar to io.LimitReader but is intended for
   557	// limiting the size of incoming request bodies. In contrast to
   558	// io.LimitReader, MaxBytesReader's result is a ReadCloser, returns a
   559	// non-EOF error for a Read beyond the limit, and Closes the
   560	// underlying reader when its Close method is called.
   561	//
   562	// MaxBytesReader prevents clients from accidentally or maliciously
   563	// sending a large request and wasting server resources.
   564	func MaxBytesReader(w ResponseWriter, r io.ReadCloser, n int64) io.ReadCloser {
   565		return &maxBytesReader{w: w, r: r, n: n}
   566	}
   567	
   568	type maxBytesReader struct {
   569		w       ResponseWriter
   570		r       io.ReadCloser // underlying reader
   571		n       int64         // max bytes remaining
   572		stopped bool
   573	}
   574	
   575	func (l *maxBytesReader) Read(p []byte) (n int, err error) {
   576		if l.n <= 0 {
   577			if !l.stopped {
   578				l.stopped = true
   579				if res, ok := l.w.(*response); ok {
   580					res.requestTooLarge()
   581				}
   582			}
   583			return 0, errors.New("http: request body too large")
   584		}
   585		if int64(len(p)) > l.n {
   586			p = p[:l.n]
   587		}
   588		n, err = l.r.Read(p)
   589		l.n -= int64(n)
   590		return
   591	}
   592	
   593	func (l *maxBytesReader) Close() error {
   594		return l.r.Close()
   595	}
   596	
   597	// ParseForm parses the raw query from the URL.
   598	//
   599	// For POST or PUT requests, it also parses the request body as a form.
   600	// If the request Body's size has not already been limited by MaxBytesReader,
   601	// the size is capped at 10MB.
   602	//
   603	// ParseMultipartForm calls ParseForm automatically.
   604	// It is idempotent.
   605	func (r *Request) ParseForm() (err error) {
   606		if r.Form != nil {
   607			return
   608		}
   609		if r.URL != nil {
   610			r.Form, err = url.ParseQuery(r.URL.RawQuery)
   611		}
   612		if r.Method == "POST" || r.Method == "PUT" {
   613			if r.Body == nil {
   614				return errors.New("missing form body")
   615			}
   616			ct := r.Header.Get("Content-Type")
   617			ct, _, err = mime.ParseMediaType(ct)
   618			switch {
   619			case ct == "application/x-www-form-urlencoded":
   620				var reader io.Reader = r.Body
   621				maxFormSize := int64(1<<63 - 1)
   622				if _, ok := r.Body.(*maxBytesReader); !ok {
   623					maxFormSize = int64(10 << 20) // 10 MB is a lot of text.
   624					reader = io.LimitReader(r.Body, maxFormSize+1)
   625				}
   626				b, e := ioutil.ReadAll(reader)
   627				if e != nil {
   628					if err == nil {
   629						err = e
   630					}
   631					break
   632				}
   633				if int64(len(b)) > maxFormSize {
   634					return errors.New("http: POST too large")
   635				}
   636				var newValues url.Values
   637				newValues, e = url.ParseQuery(string(b))
   638				if err == nil {
   639					err = e
   640				}
   641				if r.Form == nil {
   642					r.Form = make(url.Values)
   643				}
   644				// Copy values into r.Form. TODO: make this smoother.
   645				for k, vs := range newValues {
   646					for _, value := range vs {
   647						r.Form.Add(k, value)
   648					}
   649				}
   650			case ct == "multipart/form-data":
   651				// handled by ParseMultipartForm (which is calling us, or should be)
   652				// TODO(bradfitz): there are too many possible
   653				// orders to call too many functions here.
   654				// Clean this up and write more tests.
   655				// request_test.go contains the start of this,
   656				// in TestRequestMultipartCallOrder.
   657			}
   658		}
   659		return err
   660	}
   661	
   662	// ParseMultipartForm parses a request body as multipart/form-data.
   663	// The whole request body is parsed and up to a total of maxMemory bytes of
   664	// its file parts are stored in memory, with the remainder stored on
   665	// disk in temporary files.
   666	// ParseMultipartForm calls ParseForm if necessary.
   667	// After one call to ParseMultipartForm, subsequent calls have no effect.
   668	func (r *Request) ParseMultipartForm(maxMemory int64) error {
   669		if r.MultipartForm == multipartByReader {
   670			return errors.New("http: multipart handled by MultipartReader")
   671		}
   672		if r.Form == nil {
   673			err := r.ParseForm()
   674			if err != nil {
   675				return err
   676			}
   677		}
   678		if r.MultipartForm != nil {
   679			return nil
   680		}
   681	
   682		mr, err := r.multipartReader()
   683		if err == ErrNotMultipart {
   684			return nil
   685		} else if err != nil {
   686			return err
   687		}
   688	
   689		f, err := mr.ReadForm(maxMemory)
   690		if err != nil {
   691			return err
   692		}
   693		for k, v := range f.Value {
   694			r.Form[k] = append(r.Form[k], v...)
   695		}
   696		r.MultipartForm = f
   697	
   698		return nil
   699	}
   700	
   701	// FormValue returns the first value for the named component of the query.
   702	// FormValue calls ParseMultipartForm and ParseForm if necessary.
   703	func (r *Request) FormValue(key string) string {
   704		if r.Form == nil {
   705			r.ParseMultipartForm(defaultMaxMemory)
   706		}
   707		if vs := r.Form[key]; len(vs) > 0 {
   708			return vs[0]
   709		}
   710		return ""
   711	}
   712	
   713	// FormFile returns the first file for the provided form key.
   714	// FormFile calls ParseMultipartForm and ParseForm if necessary.
   715	func (r *Request) FormFile(key string) (multipart.File, *multipart.FileHeader, error) {
   716		if r.MultipartForm == multipartByReader {
   717			return nil, nil, errors.New("http: multipart handled by MultipartReader")
   718		}
   719		if r.MultipartForm == nil {
   720			err := r.ParseMultipartForm(defaultMaxMemory)
   721			if err != nil {
   722				return nil, nil, err
   723			}
   724		}
   725		if r.MultipartForm != nil && r.MultipartForm.File != nil {
   726			if fhs := r.MultipartForm.File[key]; len(fhs) > 0 {
   727				f, err := fhs[0].Open()
   728				return f, fhs[0], err
   729			}
   730		}
   731		return nil, nil, ErrMissingFile
   732	}
   733	
   734	func (r *Request) expectsContinue() bool {
   735		return strings.ToLower(r.Header.Get("Expect")) == "100-continue"
   736	}
   737	
   738	func (r *Request) wantsHttp10KeepAlive() bool {
   739		if r.ProtoMajor != 1 || r.ProtoMinor != 0 {
   740			return false
   741		}
   742		return strings.Contains(strings.ToLower(r.Header.Get("Connection")), "keep-alive")
   743	}