Source file src/pkg/net/http/response.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 Response reading and parsing.
     6	
     7	package http
     8	
     9	import (
    10		"bufio"
    11		"errors"
    12		"io"
    13		"net/textproto"
    14		"net/url"
    15		"strconv"
    16		"strings"
    17	)
    18	
    19	var respExcludeHeader = map[string]bool{
    20		"Content-Length":    true,
    21		"Transfer-Encoding": true,
    22		"Trailer":           true,
    23	}
    24	
    25	// Response represents the response from an HTTP request.
    26	//
    27	type Response struct {
    28		Status     string // e.g. "200 OK"
    29		StatusCode int    // e.g. 200
    30		Proto      string // e.g. "HTTP/1.0"
    31		ProtoMajor int    // e.g. 1
    32		ProtoMinor int    // e.g. 0
    33	
    34		// Header maps header keys to values.  If the response had multiple
    35		// headers with the same key, they will be concatenated, with comma
    36		// delimiters.  (Section 4.2 of RFC 2616 requires that multiple headers
    37		// be semantically equivalent to a comma-delimited sequence.) Values
    38		// duplicated by other fields in this struct (e.g., ContentLength) are
    39		// omitted from Header.
    40		//
    41		// Keys in the map are canonicalized (see CanonicalHeaderKey).
    42		Header Header
    43	
    44		// Body represents the response body.
    45		//
    46		// The http Client and Transport guarantee that Body is always
    47		// non-nil, even on responses without a body or responses with
    48		// a zero-lengthed body.
    49		Body io.ReadCloser
    50	
    51		// ContentLength records the length of the associated content.  The
    52		// value -1 indicates that the length is unknown.  Unless RequestMethod
    53		// is "HEAD", values >= 0 indicate that the given number of bytes may
    54		// be read from Body.
    55		ContentLength int64
    56	
    57		// Contains transfer encodings from outer-most to inner-most. Value is
    58		// nil, means that "identity" encoding is used.
    59		TransferEncoding []string
    60	
    61		// Close records whether the header directed that the connection be
    62		// closed after reading Body.  The value is advice for clients: neither
    63		// ReadResponse nor Response.Write ever closes a connection.
    64		Close bool
    65	
    66		// Trailer maps trailer keys to values, in the same
    67		// format as the header.
    68		Trailer Header
    69	
    70		// The Request that was sent to obtain this Response.
    71		// Request's Body is nil (having already been consumed).
    72		// This is only populated for Client requests.
    73		Request *Request
    74	}
    75	
    76	// Cookies parses and returns the cookies set in the Set-Cookie headers.
    77	func (r *Response) Cookies() []*Cookie {
    78		return readSetCookies(r.Header)
    79	}
    80	
    81	var ErrNoLocation = errors.New("http: no Location header in response")
    82	
    83	// Location returns the URL of the response's "Location" header,
    84	// if present.  Relative redirects are resolved relative to
    85	// the Response's Request.  ErrNoLocation is returned if no
    86	// Location header is present.
    87	func (r *Response) Location() (*url.URL, error) {
    88		lv := r.Header.Get("Location")
    89		if lv == "" {
    90			return nil, ErrNoLocation
    91		}
    92		if r.Request != nil && r.Request.URL != nil {
    93			return r.Request.URL.Parse(lv)
    94		}
    95		return url.Parse(lv)
    96	}
    97	
    98	// ReadResponse reads and returns an HTTP response from r.  The
    99	// req parameter specifies the Request that corresponds to
   100	// this Response.  Clients must call resp.Body.Close when finished
   101	// reading resp.Body.  After that call, clients can inspect
   102	// resp.Trailer to find key/value pairs included in the response
   103	// trailer.
   104	func ReadResponse(r *bufio.Reader, req *Request) (resp *Response, err error) {
   105	
   106		tp := textproto.NewReader(r)
   107		resp = new(Response)
   108	
   109		resp.Request = req
   110		resp.Request.Method = strings.ToUpper(resp.Request.Method)
   111	
   112		// Parse the first line of the response.
   113		line, err := tp.ReadLine()
   114		if err != nil {
   115			if err == io.EOF {
   116				err = io.ErrUnexpectedEOF
   117			}
   118			return nil, err
   119		}
   120		f := strings.SplitN(line, " ", 3)
   121		if len(f) < 2 {
   122			return nil, &badStringError{"malformed HTTP response", line}
   123		}
   124		reasonPhrase := ""
   125		if len(f) > 2 {
   126			reasonPhrase = f[2]
   127		}
   128		resp.Status = f[1] + " " + reasonPhrase
   129		resp.StatusCode, err = strconv.Atoi(f[1])
   130		if err != nil {
   131			return nil, &badStringError{"malformed HTTP status code", f[1]}
   132		}
   133	
   134		resp.Proto = f[0]
   135		var ok bool
   136		if resp.ProtoMajor, resp.ProtoMinor, ok = ParseHTTPVersion(resp.Proto); !ok {
   137			return nil, &badStringError{"malformed HTTP version", resp.Proto}
   138		}
   139	
   140		// Parse the response headers.
   141		mimeHeader, err := tp.ReadMIMEHeader()
   142		if err != nil {
   143			return nil, err
   144		}
   145		resp.Header = Header(mimeHeader)
   146	
   147		fixPragmaCacheControl(resp.Header)
   148	
   149		err = readTransfer(resp, r)
   150		if err != nil {
   151			return nil, err
   152		}
   153	
   154		return resp, nil
   155	}
   156	
   157	// RFC2616: Should treat
   158	//	Pragma: no-cache
   159	// like
   160	//	Cache-Control: no-cache
   161	func fixPragmaCacheControl(header Header) {
   162		if hp, ok := header["Pragma"]; ok && len(hp) > 0 && hp[0] == "no-cache" {
   163			if _, presentcc := header["Cache-Control"]; !presentcc {
   164				header["Cache-Control"] = []string{"no-cache"}
   165			}
   166		}
   167	}
   168	
   169	// ProtoAtLeast returns whether the HTTP protocol used
   170	// in the response is at least major.minor.
   171	func (r *Response) ProtoAtLeast(major, minor int) bool {
   172		return r.ProtoMajor > major ||
   173			r.ProtoMajor == major && r.ProtoMinor >= minor
   174	}
   175	
   176	// Writes the response (header, body and trailer) in wire format. This method
   177	// consults the following fields of the response:
   178	//
   179	//  StatusCode
   180	//  ProtoMajor
   181	//  ProtoMinor
   182	//  RequestMethod
   183	//  TransferEncoding
   184	//  Trailer
   185	//  Body
   186	//  ContentLength
   187	//  Header, values for non-canonical keys will have unpredictable behavior
   188	//
   189	func (r *Response) Write(w io.Writer) error {
   190	
   191		// RequestMethod should be upper-case
   192		if r.Request != nil {
   193			r.Request.Method = strings.ToUpper(r.Request.Method)
   194		}
   195	
   196		// Status line
   197		text := r.Status
   198		if text == "" {
   199			var ok bool
   200			text, ok = statusText[r.StatusCode]
   201			if !ok {
   202				text = "status code " + strconv.Itoa(r.StatusCode)
   203			}
   204		}
   205		io.WriteString(w, "HTTP/"+strconv.Itoa(r.ProtoMajor)+".")
   206		io.WriteString(w, strconv.Itoa(r.ProtoMinor)+" ")
   207		io.WriteString(w, strconv.Itoa(r.StatusCode)+" "+text+"\r\n")
   208	
   209		// Process Body,ContentLength,Close,Trailer
   210		tw, err := newTransferWriter(r)
   211		if err != nil {
   212			return err
   213		}
   214		err = tw.WriteHeader(w)
   215		if err != nil {
   216			return err
   217		}
   218	
   219		// Rest of header
   220		err = r.Header.WriteSubset(w, respExcludeHeader)
   221		if err != nil {
   222			return err
   223		}
   224	
   225		// End-of-header
   226		io.WriteString(w, "\r\n")
   227	
   228		// Write body and trailer
   229		err = tw.WriteBody(w)
   230		if err != nil {
   231			return err
   232		}
   233	
   234		// Success
   235		return nil
   236	}