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		//
    50		// The Body is automatically dechunked if the server replied
    51		// with a "chunked" Transfer-Encoding.
    52		Body io.ReadCloser
    53	
    54		// ContentLength records the length of the associated content.  The
    55		// value -1 indicates that the length is unknown.  Unless Request.Method
    56		// is "HEAD", values >= 0 indicate that the given number of bytes may
    57		// be read from Body.
    58		ContentLength int64
    59	
    60		// Contains transfer encodings from outer-most to inner-most. Value is
    61		// nil, means that "identity" encoding is used.
    62		TransferEncoding []string
    63	
    64		// Close records whether the header directed that the connection be
    65		// closed after reading Body.  The value is advice for clients: neither
    66		// ReadResponse nor Response.Write ever closes a connection.
    67		Close bool
    68	
    69		// Trailer maps trailer keys to values, in the same
    70		// format as the header.
    71		Trailer Header
    72	
    73		// The Request that was sent to obtain this Response.
    74		// Request's Body is nil (having already been consumed).
    75		// This is only populated for Client requests.
    76		Request *Request
    77	}
    78	
    79	// Cookies parses and returns the cookies set in the Set-Cookie headers.
    80	func (r *Response) Cookies() []*Cookie {
    81		return readSetCookies(r.Header)
    82	}
    83	
    84	var ErrNoLocation = errors.New("http: no Location header in response")
    85	
    86	// Location returns the URL of the response's "Location" header,
    87	// if present.  Relative redirects are resolved relative to
    88	// the Response's Request.  ErrNoLocation is returned if no
    89	// Location header is present.
    90	func (r *Response) Location() (*url.URL, error) {
    91		lv := r.Header.Get("Location")
    92		if lv == "" {
    93			return nil, ErrNoLocation
    94		}
    95		if r.Request != nil && r.Request.URL != nil {
    96			return r.Request.URL.Parse(lv)
    97		}
    98		return url.Parse(lv)
    99	}
   100	
   101	// ReadResponse reads and returns an HTTP response from r.  The
   102	// req parameter specifies the Request that corresponds to
   103	// this Response.  Clients must call resp.Body.Close when finished
   104	// reading resp.Body.  After that call, clients can inspect
   105	// resp.Trailer to find key/value pairs included in the response
   106	// trailer.
   107	func ReadResponse(r *bufio.Reader, req *Request) (resp *Response, err error) {
   108	
   109		tp := textproto.NewReader(r)
   110		resp = new(Response)
   111	
   112		resp.Request = req
   113	
   114		// Parse the first line of the response.
   115		line, err := tp.ReadLine()
   116		if err != nil {
   117			if err == io.EOF {
   118				err = io.ErrUnexpectedEOF
   119			}
   120			return nil, err
   121		}
   122		f := strings.SplitN(line, " ", 3)
   123		if len(f) < 2 {
   124			return nil, &badStringError{"malformed HTTP response", line}
   125		}
   126		reasonPhrase := ""
   127		if len(f) > 2 {
   128			reasonPhrase = f[2]
   129		}
   130		resp.Status = f[1] + " " + reasonPhrase
   131		resp.StatusCode, err = strconv.Atoi(f[1])
   132		if err != nil {
   133			return nil, &badStringError{"malformed HTTP status code", f[1]}
   134		}
   135	
   136		resp.Proto = f[0]
   137		var ok bool
   138		if resp.ProtoMajor, resp.ProtoMinor, ok = ParseHTTPVersion(resp.Proto); !ok {
   139			return nil, &badStringError{"malformed HTTP version", resp.Proto}
   140		}
   141	
   142		// Parse the response headers.
   143		mimeHeader, err := tp.ReadMIMEHeader()
   144		if err != nil {
   145			return nil, err
   146		}
   147		resp.Header = Header(mimeHeader)
   148	
   149		fixPragmaCacheControl(resp.Header)
   150	
   151		err = readTransfer(resp, r)
   152		if err != nil {
   153			return nil, err
   154		}
   155	
   156		return resp, nil
   157	}
   158	
   159	// RFC2616: Should treat
   160	//	Pragma: no-cache
   161	// like
   162	//	Cache-Control: no-cache
   163	func fixPragmaCacheControl(header Header) {
   164		if hp, ok := header["Pragma"]; ok && len(hp) > 0 && hp[0] == "no-cache" {
   165			if _, presentcc := header["Cache-Control"]; !presentcc {
   166				header["Cache-Control"] = []string{"no-cache"}
   167			}
   168		}
   169	}
   170	
   171	// ProtoAtLeast returns whether the HTTP protocol used
   172	// in the response is at least major.minor.
   173	func (r *Response) ProtoAtLeast(major, minor int) bool {
   174		return r.ProtoMajor > major ||
   175			r.ProtoMajor == major && r.ProtoMinor >= minor
   176	}
   177	
   178	// Writes the response (header, body and trailer) in wire format. This method
   179	// consults the following fields of the response:
   180	//
   181	//  StatusCode
   182	//  ProtoMajor
   183	//  ProtoMinor
   184	//  Request.Method
   185	//  TransferEncoding
   186	//  Trailer
   187	//  Body
   188	//  ContentLength
   189	//  Header, values for non-canonical keys will have unpredictable behavior
   190	//
   191	func (r *Response) Write(w io.Writer) error {
   192	
   193		// Status line
   194		text := r.Status
   195		if text == "" {
   196			var ok bool
   197			text, ok = statusText[r.StatusCode]
   198			if !ok {
   199				text = "status code " + strconv.Itoa(r.StatusCode)
   200			}
   201		}
   202		protoMajor, protoMinor := strconv.Itoa(r.ProtoMajor), strconv.Itoa(r.ProtoMinor)
   203		statusCode := strconv.Itoa(r.StatusCode) + " "
   204		text = strings.TrimPrefix(text, statusCode)
   205		io.WriteString(w, "HTTP/"+protoMajor+"."+protoMinor+" "+statusCode+text+"\r\n")
   206	
   207		// Process Body,ContentLength,Close,Trailer
   208		tw, err := newTransferWriter(r)
   209		if err != nil {
   210			return err
   211		}
   212		err = tw.WriteHeader(w)
   213		if err != nil {
   214			return err
   215		}
   216	
   217		// Rest of header
   218		err = r.Header.WriteSubset(w, respExcludeHeader)
   219		if err != nil {
   220			return err
   221		}
   222	
   223		// End-of-header
   224		io.WriteString(w, "\r\n")
   225	
   226		// Write body and trailer
   227		err = tw.WriteBody(w)
   228		if err != nil {
   229			return err
   230		}
   231	
   232		// Success
   233		return nil
   234	}

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