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Source file src/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		"bytes"
    12		"crypto/tls"
    13		"errors"
    14		"io"
    15		"net/textproto"
    16		"net/url"
    17		"strconv"
    18		"strings"
    19	)
    20	
    21	var respExcludeHeader = map[string]bool{
    22		"Content-Length":    true,
    23		"Transfer-Encoding": true,
    24		"Trailer":           true,
    25	}
    26	
    27	// Response represents the response from an HTTP request.
    28	//
    29	type Response struct {
    30		Status     string // e.g. "200 OK"
    31		StatusCode int    // e.g. 200
    32		Proto      string // e.g. "HTTP/1.0"
    33		ProtoMajor int    // e.g. 1
    34		ProtoMinor int    // e.g. 0
    35	
    36		// Header maps header keys to values.  If the response had multiple
    37		// headers with the same key, they may be concatenated, with comma
    38		// delimiters.  (Section 4.2 of RFC 2616 requires that multiple headers
    39		// be semantically equivalent to a comma-delimited sequence.) Values
    40		// duplicated by other fields in this struct (e.g., ContentLength) are
    41		// omitted from Header.
    42		//
    43		// Keys in the map are canonicalized (see CanonicalHeaderKey).
    44		Header Header
    45	
    46		// Body represents the response body.
    47		//
    48		// The http Client and Transport guarantee that Body is always
    49		// non-nil, even on responses without a body or responses with
    50		// a zero-length body. It is the caller's responsibility to
    51		// close Body. The default HTTP client's Transport does not
    52		// attempt to reuse HTTP/1.0 or HTTP/1.1 TCP connections
    53		// ("keep-alive") unless the Body is read to completion and is
    54		// closed.
    55		//
    56		// The Body is automatically dechunked if the server replied
    57		// with a "chunked" Transfer-Encoding.
    58		Body io.ReadCloser
    59	
    60		// ContentLength records the length of the associated content.  The
    61		// value -1 indicates that the length is unknown.  Unless Request.Method
    62		// is "HEAD", values >= 0 indicate that the given number of bytes may
    63		// be read from Body.
    64		ContentLength int64
    65	
    66		// Contains transfer encodings from outer-most to inner-most. Value is
    67		// nil, means that "identity" encoding is used.
    68		TransferEncoding []string
    69	
    70		// Close records whether the header directed that the connection be
    71		// closed after reading Body.  The value is advice for clients: neither
    72		// ReadResponse nor Response.Write ever closes a connection.
    73		Close bool
    74	
    75		// Trailer maps trailer keys to values, in the same
    76		// format as the header.
    77		Trailer Header
    78	
    79		// The Request that was sent to obtain this Response.
    80		// Request's Body is nil (having already been consumed).
    81		// This is only populated for Client requests.
    82		Request *Request
    83	
    84		// TLS contains information about the TLS connection on which the
    85		// response was received. It is nil for unencrypted responses.
    86		// The pointer is shared between responses and should not be
    87		// modified.
    88		TLS *tls.ConnectionState
    89	}
    90	
    91	// Cookies parses and returns the cookies set in the Set-Cookie headers.
    92	func (r *Response) Cookies() []*Cookie {
    93		return readSetCookies(r.Header)
    94	}
    95	
    96	// ErrNoLocation is returned by Response's Location method
    97	// when no Location header is present.
    98	var ErrNoLocation = errors.New("http: no Location header in response")
    99	
   100	// Location returns the URL of the response's "Location" header,
   101	// if present.  Relative redirects are resolved relative to
   102	// the Response's Request.  ErrNoLocation is returned if no
   103	// Location header is present.
   104	func (r *Response) Location() (*url.URL, error) {
   105		lv := r.Header.Get("Location")
   106		if lv == "" {
   107			return nil, ErrNoLocation
   108		}
   109		if r.Request != nil && r.Request.URL != nil {
   110			return r.Request.URL.Parse(lv)
   111		}
   112		return url.Parse(lv)
   113	}
   114	
   115	// ReadResponse reads and returns an HTTP response from r.
   116	// The req parameter optionally specifies the Request that corresponds
   117	// to this Response. If nil, a GET request is assumed.
   118	// Clients must call resp.Body.Close when finished reading resp.Body.
   119	// After that call, clients can inspect resp.Trailer to find key/value
   120	// pairs included in the response trailer.
   121	func ReadResponse(r *bufio.Reader, req *Request) (*Response, error) {
   122		tp := textproto.NewReader(r)
   123		resp := &Response{
   124			Request: req,
   125		}
   126	
   127		// Parse the first line of the response.
   128		line, err := tp.ReadLine()
   129		if err != nil {
   130			if err == io.EOF {
   131				err = io.ErrUnexpectedEOF
   132			}
   133			return nil, err
   134		}
   135		f := strings.SplitN(line, " ", 3)
   136		if len(f) < 2 {
   137			return nil, &badStringError{"malformed HTTP response", line}
   138		}
   139		reasonPhrase := ""
   140		if len(f) > 2 {
   141			reasonPhrase = f[2]
   142		}
   143		resp.Status = f[1] + " " + reasonPhrase
   144		resp.StatusCode, err = strconv.Atoi(f[1])
   145		if err != nil {
   146			return nil, &badStringError{"malformed HTTP status code", f[1]}
   147		}
   148	
   149		resp.Proto = f[0]
   150		var ok bool
   151		if resp.ProtoMajor, resp.ProtoMinor, ok = ParseHTTPVersion(resp.Proto); !ok {
   152			return nil, &badStringError{"malformed HTTP version", resp.Proto}
   153		}
   154	
   155		// Parse the response headers.
   156		mimeHeader, err := tp.ReadMIMEHeader()
   157		if err != nil {
   158			if err == io.EOF {
   159				err = io.ErrUnexpectedEOF
   160			}
   161			return nil, err
   162		}
   163		resp.Header = Header(mimeHeader)
   164	
   165		fixPragmaCacheControl(resp.Header)
   166	
   167		err = readTransfer(resp, r)
   168		if err != nil {
   169			return nil, err
   170		}
   171	
   172		return resp, nil
   173	}
   174	
   175	// RFC2616: Should treat
   176	//	Pragma: no-cache
   177	// like
   178	//	Cache-Control: no-cache
   179	func fixPragmaCacheControl(header Header) {
   180		if hp, ok := header["Pragma"]; ok && len(hp) > 0 && hp[0] == "no-cache" {
   181			if _, presentcc := header["Cache-Control"]; !presentcc {
   182				header["Cache-Control"] = []string{"no-cache"}
   183			}
   184		}
   185	}
   186	
   187	// ProtoAtLeast reports whether the HTTP protocol used
   188	// in the response is at least major.minor.
   189	func (r *Response) ProtoAtLeast(major, minor int) bool {
   190		return r.ProtoMajor > major ||
   191			r.ProtoMajor == major && r.ProtoMinor >= minor
   192	}
   193	
   194	// Write writes r to w in the HTTP/1.n server response format,
   195	// including the status line, headers, body, and optional trailer.
   196	//
   197	// This method consults the following fields of the response r:
   198	//
   199	//  StatusCode
   200	//  ProtoMajor
   201	//  ProtoMinor
   202	//  Request.Method
   203	//  TransferEncoding
   204	//  Trailer
   205	//  Body
   206	//  ContentLength
   207	//  Header, values for non-canonical keys will have unpredictable behavior
   208	//
   209	// The Response Body is closed after it is sent.
   210	func (r *Response) Write(w io.Writer) error {
   211		// Status line
   212		text := r.Status
   213		if text == "" {
   214			var ok bool
   215			text, ok = statusText[r.StatusCode]
   216			if !ok {
   217				text = "status code " + strconv.Itoa(r.StatusCode)
   218			}
   219		}
   220		protoMajor, protoMinor := strconv.Itoa(r.ProtoMajor), strconv.Itoa(r.ProtoMinor)
   221		statusCode := strconv.Itoa(r.StatusCode) + " "
   222		text = strings.TrimPrefix(text, statusCode)
   223		if _, err := io.WriteString(w, "HTTP/"+protoMajor+"."+protoMinor+" "+statusCode+text+"\r\n"); err != nil {
   224			return err
   225		}
   226	
   227		// Clone it, so we can modify r1 as needed.
   228		r1 := new(Response)
   229		*r1 = *r
   230		if r1.ContentLength == 0 && r1.Body != nil {
   231			// Is it actually 0 length? Or just unknown?
   232			var buf [1]byte
   233			n, err := r1.Body.Read(buf[:])
   234			if err != nil && err != io.EOF {
   235				return err
   236			}
   237			if n == 0 {
   238				// Reset it to a known zero reader, in case underlying one
   239				// is unhappy being read repeatedly.
   240				r1.Body = eofReader
   241			} else {
   242				r1.ContentLength = -1
   243				r1.Body = struct {
   244					io.Reader
   245					io.Closer
   246				}{
   247					io.MultiReader(bytes.NewReader(buf[:1]), r.Body),
   248					r.Body,
   249				}
   250			}
   251		}
   252		// If we're sending a non-chunked HTTP/1.1 response without a
   253		// content-length, the only way to do that is the old HTTP/1.0
   254		// way, by noting the EOF with a connection close, so we need
   255		// to set Close.
   256		if r1.ContentLength == -1 && !r1.Close && r1.ProtoAtLeast(1, 1) && !chunked(r1.TransferEncoding) {
   257			r1.Close = true
   258		}
   259	
   260		// Process Body,ContentLength,Close,Trailer
   261		tw, err := newTransferWriter(r1)
   262		if err != nil {
   263			return err
   264		}
   265		err = tw.WriteHeader(w)
   266		if err != nil {
   267			return err
   268		}
   269	
   270		// Rest of header
   271		err = r.Header.WriteSubset(w, respExcludeHeader)
   272		if err != nil {
   273			return err
   274		}
   275	
   276		// contentLengthAlreadySent may have been already sent for
   277		// POST/PUT requests, even if zero length. See Issue 8180.
   278		contentLengthAlreadySent := tw.shouldSendContentLength()
   279		if r1.ContentLength == 0 && !chunked(r1.TransferEncoding) && !contentLengthAlreadySent {
   280			if _, err := io.WriteString(w, "Content-Length: 0\r\n"); err != nil {
   281				return err
   282			}
   283		}
   284	
   285		// End-of-header
   286		if _, err := io.WriteString(w, "\r\n"); err != nil {
   287			return err
   288		}
   289	
   290		// Write body and trailer
   291		err = tw.WriteBody(w)
   292		if err != nil {
   293			return err
   294		}
   295	
   296		// Success
   297		return nil
   298	}
   299	

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