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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [net/] [http/] [transfer.go] - Blame information for rev 858

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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.
 
package http
 
import (
        "bufio"
        "bytes"
        "errors"
        "fmt"
        "io"
        "io/ioutil"
        "net/textproto"
        "strconv"
        "strings"
)
 
// transferWriter inspects the fields of a user-supplied Request or Response,
// sanitizes them without changing the user object and provides methods for
// writing the respective header, body and trailer in wire format.
type transferWriter struct {
        Method           string
        Body             io.Reader
        BodyCloser       io.Closer
        ResponseToHEAD   bool
        ContentLength    int64 // -1 means unknown, 0 means exactly none
        Close            bool
        TransferEncoding []string
        Trailer          Header
}
 
func newTransferWriter(r interface{}) (t *transferWriter, err error) {
        t = &transferWriter{}
 
        // Extract relevant fields
        atLeastHTTP11 := false
        switch rr := r.(type) {
        case *Request:
                if rr.ContentLength != 0 && rr.Body == nil {
                        return nil, fmt.Errorf("http: Request.ContentLength=%d with nil Body", rr.ContentLength)
                }
                t.Method = rr.Method
                t.Body = rr.Body
                t.BodyCloser = rr.Body
                t.ContentLength = rr.ContentLength
                t.Close = rr.Close
                t.TransferEncoding = rr.TransferEncoding
                t.Trailer = rr.Trailer
                atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
                if t.Body != nil && len(t.TransferEncoding) == 0 && atLeastHTTP11 {
                        if t.ContentLength == 0 {
                                // Test to see if it's actually zero or just unset.
                                var buf [1]byte
                                n, _ := io.ReadFull(t.Body, buf[:])
                                if n == 1 {
                                        // Oh, guess there is data in this Body Reader after all.
                                        // The ContentLength field just wasn't set.
                                        // Stich the Body back together again, re-attaching our
                                        // consumed byte.
                                        t.ContentLength = -1
                                        t.Body = io.MultiReader(bytes.NewBuffer(buf[:]), t.Body)
                                } else {
                                        // Body is actually empty.
                                        t.Body = nil
                                        t.BodyCloser = nil
                                }
                        }
                        if t.ContentLength < 0 {
                                t.TransferEncoding = []string{"chunked"}
                        }
                }
        case *Response:
                t.Method = rr.Request.Method
                t.Body = rr.Body
                t.BodyCloser = rr.Body
                t.ContentLength = rr.ContentLength
                t.Close = rr.Close
                t.TransferEncoding = rr.TransferEncoding
                t.Trailer = rr.Trailer
                atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
                t.ResponseToHEAD = noBodyExpected(rr.Request.Method)
        }
 
        // Sanitize Body,ContentLength,TransferEncoding
        if t.ResponseToHEAD {
                t.Body = nil
                t.TransferEncoding = nil
                // ContentLength is expected to hold Content-Length
                if t.ContentLength < 0 {
                        return nil, ErrMissingContentLength
                }
        } else {
                if !atLeastHTTP11 || t.Body == nil {
                        t.TransferEncoding = nil
                }
                if chunked(t.TransferEncoding) {
                        t.ContentLength = -1
                } else if t.Body == nil { // no chunking, no body
                        t.ContentLength = 0
                }
        }
 
        // Sanitize Trailer
        if !chunked(t.TransferEncoding) {
                t.Trailer = nil
        }
 
        return t, nil
}
 
func noBodyExpected(requestMethod string) bool {
        return requestMethod == "HEAD"
}
 
func (t *transferWriter) shouldSendContentLength() bool {
        if chunked(t.TransferEncoding) {
                return false
        }
        if t.ContentLength > 0 {
                return true
        }
        if t.ResponseToHEAD {
                return true
        }
        // Many servers expect a Content-Length for these methods
        if t.Method == "POST" || t.Method == "PUT" {
                return true
        }
        if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {
                return true
        }
 
        return false
}
 
func (t *transferWriter) WriteHeader(w io.Writer) (err error) {
        if t.Close {
                _, err = io.WriteString(w, "Connection: close\r\n")
                if err != nil {
                        return
                }
        }
 
        // Write Content-Length and/or Transfer-Encoding whose values are a
        // function of the sanitized field triple (Body, ContentLength,
        // TransferEncoding)
        if t.shouldSendContentLength() {
                io.WriteString(w, "Content-Length: ")
                _, err = io.WriteString(w, strconv.FormatInt(t.ContentLength, 10)+"\r\n")
                if err != nil {
                        return
                }
        } else if chunked(t.TransferEncoding) {
                _, err = io.WriteString(w, "Transfer-Encoding: chunked\r\n")
                if err != nil {
                        return
                }
        }
 
        // Write Trailer header
        if t.Trailer != nil {
                // TODO: At some point, there should be a generic mechanism for
                // writing long headers, using HTTP line splitting
                io.WriteString(w, "Trailer: ")
                needComma := false
                for k := range t.Trailer {
                        k = CanonicalHeaderKey(k)
                        switch k {
                        case "Transfer-Encoding", "Trailer", "Content-Length":
                                return &badStringError{"invalid Trailer key", k}
                        }
                        if needComma {
                                io.WriteString(w, ",")
                        }
                        io.WriteString(w, k)
                        needComma = true
                }
                _, err = io.WriteString(w, "\r\n")
        }
 
        return
}
 
func (t *transferWriter) WriteBody(w io.Writer) (err error) {
        var ncopy int64
 
        // Write body
        if t.Body != nil {
                if chunked(t.TransferEncoding) {
                        cw := newChunkedWriter(w)
                        _, err = io.Copy(cw, t.Body)
                        if err == nil {
                                err = cw.Close()
                        }
                } else if t.ContentLength == -1 {
                        ncopy, err = io.Copy(w, t.Body)
                } else {
                        ncopy, err = io.Copy(w, io.LimitReader(t.Body, t.ContentLength))
                        nextra, err := io.Copy(ioutil.Discard, t.Body)
                        if err != nil {
                                return err
                        }
                        ncopy += nextra
                }
                if err != nil {
                        return err
                }
                if err = t.BodyCloser.Close(); err != nil {
                        return err
                }
        }
 
        if t.ContentLength != -1 && t.ContentLength != ncopy {
                return fmt.Errorf("http: Request.ContentLength=%d with Body length %d",
                        t.ContentLength, ncopy)
        }
 
        // TODO(petar): Place trailer writer code here.
        if chunked(t.TransferEncoding) {
                // Last chunk, empty trailer
                _, err = io.WriteString(w, "\r\n")
        }
 
        return
}
 
type transferReader struct {
        // Input
        Header        Header
        StatusCode    int
        RequestMethod string
        ProtoMajor    int
        ProtoMinor    int
        // Output
        Body             io.ReadCloser
        ContentLength    int64
        TransferEncoding []string
        Close            bool
        Trailer          Header
}
 
// bodyAllowedForStatus returns whether a given response status code
// permits a body.  See RFC2616, section 4.4.
func bodyAllowedForStatus(status int) bool {
        switch {
        case status >= 100 && status <= 199:
                return false
        case status == 204:
                return false
        case status == 304:
                return false
        }
        return true
}
 
// msg is *Request or *Response.
func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
        t := &transferReader{}
 
        // Unify input
        isResponse := false
        switch rr := msg.(type) {
        case *Response:
                t.Header = rr.Header
                t.StatusCode = rr.StatusCode
                t.RequestMethod = rr.Request.Method
                t.ProtoMajor = rr.ProtoMajor
                t.ProtoMinor = rr.ProtoMinor
                t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header)
                isResponse = true
        case *Request:
                t.Header = rr.Header
                t.ProtoMajor = rr.ProtoMajor
                t.ProtoMinor = rr.ProtoMinor
                // Transfer semantics for Requests are exactly like those for
                // Responses with status code 200, responding to a GET method
                t.StatusCode = 200
                t.RequestMethod = "GET"
        default:
                panic("unexpected type")
        }
 
        // Default to HTTP/1.1
        if t.ProtoMajor == 0 && t.ProtoMinor == 0 {
                t.ProtoMajor, t.ProtoMinor = 1, 1
        }
 
        // Transfer encoding, content length
        t.TransferEncoding, err = fixTransferEncoding(t.RequestMethod, t.Header)
        if err != nil {
                return err
        }
 
        t.ContentLength, err = fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.TransferEncoding)
        if err != nil {
                return err
        }
 
        // Trailer
        t.Trailer, err = fixTrailer(t.Header, t.TransferEncoding)
        if err != nil {
                return err
        }
 
        // If there is no Content-Length or chunked Transfer-Encoding on a *Response
        // and the status is not 1xx, 204 or 304, then the body is unbounded.
        // See RFC2616, section 4.4.
        switch msg.(type) {
        case *Response:
                if t.ContentLength == -1 &&
                        !chunked(t.TransferEncoding) &&
                        bodyAllowedForStatus(t.StatusCode) {
                        // Unbounded body.
                        t.Close = true
                }
        }
 
        // Prepare body reader.  ContentLength < 0 means chunked encoding
        // or close connection when finished, since multipart is not supported yet
        switch {
        case chunked(t.TransferEncoding):
                t.Body = &body{Reader: newChunkedReader(r), hdr: msg, r: r, closing: t.Close}
        case t.ContentLength >= 0:
                // TODO: limit the Content-Length. This is an easy DoS vector.
                t.Body = &body{Reader: io.LimitReader(r, t.ContentLength), closing: t.Close}
        default:
                // t.ContentLength < 0, i.e. "Content-Length" not mentioned in header
                if t.Close {
                        // Close semantics (i.e. HTTP/1.0)
                        t.Body = &body{Reader: r, closing: t.Close}
                } else {
                        // Persistent connection (i.e. HTTP/1.1)
                        t.Body = &body{Reader: io.LimitReader(r, 0), closing: t.Close}
                }
        }
 
        // Unify output
        switch rr := msg.(type) {
        case *Request:
                rr.Body = t.Body
                rr.ContentLength = t.ContentLength
                rr.TransferEncoding = t.TransferEncoding
                rr.Close = t.Close
                rr.Trailer = t.Trailer
        case *Response:
                rr.Body = t.Body
                rr.ContentLength = t.ContentLength
                rr.TransferEncoding = t.TransferEncoding
                rr.Close = t.Close
                rr.Trailer = t.Trailer
        }
 
        return nil
}
 
// Checks whether chunked is part of the encodings stack
func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }
 
// Checks whether the encoding is explicitly "identity".
func isIdentity(te []string) bool { return len(te) == 1 && te[0] == "identity" }
 
// Sanitize transfer encoding
func fixTransferEncoding(requestMethod string, header Header) ([]string, error) {
        raw, present := header["Transfer-Encoding"]
        if !present {
                return nil, nil
        }
 
        delete(header, "Transfer-Encoding")
 
        // Head responses have no bodies, so the transfer encoding
        // should be ignored.
        if requestMethod == "HEAD" {
                return nil, nil
        }
 
        encodings := strings.Split(raw[0], ",")
        te := make([]string, 0, len(encodings))
        // TODO: Even though we only support "identity" and "chunked"
        // encodings, the loop below is designed with foresight. One
        // invariant that must be maintained is that, if present,
        // chunked encoding must always come first.
        for _, encoding := range encodings {
                encoding = strings.ToLower(strings.TrimSpace(encoding))
                // "identity" encoding is not recored
                if encoding == "identity" {
                        break
                }
                if encoding != "chunked" {
                        return nil, &badStringError{"unsupported transfer encoding", encoding}
                }
                te = te[0 : len(te)+1]
                te[len(te)-1] = encoding
        }
        if len(te) > 1 {
                return nil, &badStringError{"too many transfer encodings", strings.Join(te, ",")}
        }
        if len(te) > 0 {
                // Chunked encoding trumps Content-Length. See RFC 2616
                // Section 4.4. Currently len(te) > 0 implies chunked
                // encoding.
                delete(header, "Content-Length")
                return te, nil
        }
 
        return nil, nil
}
 
// Determine the expected body length, using RFC 2616 Section 4.4. This
// function is not a method, because ultimately it should be shared by
// ReadResponse and ReadRequest.
func fixLength(isResponse bool, status int, requestMethod string, header Header, te []string) (int64, error) {
 
        // Logic based on response type or status
        if noBodyExpected(requestMethod) {
                return 0, nil
        }
        if status/100 == 1 {
                return 0, nil
        }
        switch status {
        case 204, 304:
                return 0, nil
        }
 
        // Logic based on Transfer-Encoding
        if chunked(te) {
                return -1, nil
        }
 
        // Logic based on Content-Length
        cl := strings.TrimSpace(header.Get("Content-Length"))
        if cl != "" {
                n, err := strconv.ParseInt(cl, 10, 64)
                if err != nil || n < 0 {
                        return -1, &badStringError{"bad Content-Length", cl}
                }
                return n, nil
        } else {
                header.Del("Content-Length")
        }
 
        if !isResponse && requestMethod == "GET" {
                // RFC 2616 doesn't explicitly permit nor forbid an
                // entity-body on a GET request so we permit one if
                // declared, but we default to 0 here (not -1 below)
                // if there's no mention of a body.
                return 0, nil
        }
 
        // Logic based on media type. The purpose of the following code is just
        // to detect whether the unsupported "multipart/byteranges" is being
        // used. A proper Content-Type parser is needed in the future.
        if strings.Contains(strings.ToLower(header.Get("Content-Type")), "multipart/byteranges") {
                return -1, ErrNotSupported
        }
 
        // Body-EOF logic based on other methods (like closing, or chunked coding)
        return -1, nil
}
 
// Determine whether to hang up after sending a request and body, or
// receiving a response and body
// 'header' is the request headers
func shouldClose(major, minor int, header Header) bool {
        if major < 1 {
                return true
        } else if major == 1 && minor == 0 {
                if !strings.Contains(strings.ToLower(header.Get("Connection")), "keep-alive") {
                        return true
                }
                return false
        } else {
                // TODO: Should split on commas, toss surrounding white space,
                // and check each field.
                if strings.ToLower(header.Get("Connection")) == "close" {
                        header.Del("Connection")
                        return true
                }
        }
        return false
}
 
// Parse the trailer header
func fixTrailer(header Header, te []string) (Header, error) {
        raw := header.Get("Trailer")
        if raw == "" {
                return nil, nil
        }
 
        header.Del("Trailer")
        trailer := make(Header)
        keys := strings.Split(raw, ",")
        for _, key := range keys {
                key = CanonicalHeaderKey(strings.TrimSpace(key))
                switch key {
                case "Transfer-Encoding", "Trailer", "Content-Length":
                        return nil, &badStringError{"bad trailer key", key}
                }
                trailer.Del(key)
        }
        if len(trailer) == 0 {
                return nil, nil
        }
        if !chunked(te) {
                // Trailer and no chunking
                return nil, ErrUnexpectedTrailer
        }
        return trailer, nil
}
 
// body turns a Reader into a ReadCloser.
// Close ensures that the body has been fully read
// and then reads the trailer if necessary.
type body struct {
        io.Reader
        hdr     interface{}   // non-nil (Response or Request) value means read trailer
        r       *bufio.Reader // underlying wire-format reader for the trailer
        closing bool          // is the connection to be closed after reading body?
        closed  bool
 
        res *response // response writer for server requests, else nil
}
 
// ErrBodyReadAfterClose is returned when reading a Request Body after
// the body has been closed. This typically happens when the body is
// read after an HTTP Handler calls WriteHeader or Write on its
// ResponseWriter.
var ErrBodyReadAfterClose = errors.New("http: invalid Read on closed request Body")
 
func (b *body) Read(p []byte) (n int, err error) {
        if b.closed {
                return 0, ErrBodyReadAfterClose
        }
        n, err = b.Reader.Read(p)
 
        // Read the final trailer once we hit EOF.
        if err == io.EOF && b.hdr != nil {
                if e := b.readTrailer(); e != nil {
                        err = e
                }
                b.hdr = nil
        }
        return n, err
}
 
var (
        singleCRLF = []byte("\r\n")
        doubleCRLF = []byte("\r\n\r\n")
)
 
func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
        for peekSize := 4; ; peekSize++ {
                // This loop stops when Peek returns an error,
                // which it does when r's buffer has been filled.
                buf, err := r.Peek(peekSize)
                if bytes.HasSuffix(buf, doubleCRLF) {
                        return true
                }
                if err != nil {
                        break
                }
        }
        return false
}
 
func (b *body) readTrailer() error {
        // The common case, since nobody uses trailers.
        buf, _ := b.r.Peek(2)
        if bytes.Equal(buf, singleCRLF) {
                b.r.ReadByte()
                b.r.ReadByte()
                return nil
        }
 
        // Make sure there's a header terminator coming up, to prevent
        // a DoS with an unbounded size Trailer.  It's not easy to
        // slip in a LimitReader here, as textproto.NewReader requires
        // a concrete *bufio.Reader.  Also, we can't get all the way
        // back up to our conn's LimitedReader that *might* be backing
        // this bufio.Reader.  Instead, a hack: we iteratively Peek up
        // to the bufio.Reader's max size, looking for a double CRLF.
        // This limits the trailer to the underlying buffer size, typically 4kB.
        if !seeUpcomingDoubleCRLF(b.r) {
                return errors.New("http: suspiciously long trailer after chunked body")
        }
 
        hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
        if err != nil {
                return err
        }
        switch rr := b.hdr.(type) {
        case *Request:
                rr.Trailer = Header(hdr)
        case *Response:
                rr.Trailer = Header(hdr)
        }
        return nil
}
 
func (b *body) Close() error {
        if b.closed {
                return nil
        }
        defer func() {
                b.closed = true
        }()
        if b.hdr == nil && b.closing {
                // no trailer and closing the connection next.
                // no point in reading to EOF.
                return nil
        }
 
        // In a server request, don't continue reading from the client
        // if we've already hit the maximum body size set by the
        // handler. If this is set, that also means the TCP connection
        // is about to be closed, so getting to the next HTTP request
        // in the stream is not necessary.
        if b.res != nil && b.res.requestBodyLimitHit {
                return nil
        }
 
        // Fully consume the body, which will also lead to us reading
        // the trailer headers after the body, if present.
        if _, err := io.Copy(ioutil.Discard, b); err != nil {
                return err
        }
        return nil
}

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Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [net/] [http/] [transfer.go] - Blame information for rev 858

Line No.	Rev	Author	Line
1	747	jeremybenn	`// 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			`package http`
6
7			`import (`
8			`"bufio"`
9			`"bytes"`
10			`"errors"`
11			`"fmt"`
12			`"io"`
13			`"io/ioutil"`
14			`"net/textproto"`
15			`"strconv"`
16			`"strings"`
17			`)`
18
19			`// transferWriter inspects the fields of a user-supplied Request or Response,`
20			`// sanitizes them without changing the user object and provides methods for`
21			`// writing the respective header, body and trailer in wire format.`
22			`type transferWriter struct {`
23			`Method string`
24			`Body io.Reader`
25			`BodyCloser io.Closer`
26			`ResponseToHEAD bool`
27			`ContentLength int64 // -1 means unknown, 0 means exactly none`
28			`Close bool`
29			`TransferEncoding []string`
30			`Trailer Header`
31			`}`
32
33			`func newTransferWriter(r interface{}) (t *transferWriter, err error) {`
34			`t = &transferWriter{}`
35
36			`// Extract relevant fields`
37			`atLeastHTTP11 := false`
38			`switch rr := r.(type) {`
39			`case *Request:`
40			`if rr.ContentLength != 0 && rr.Body == nil {`
41			`return nil, fmt.Errorf("http: Request.ContentLength=%d with nil Body", rr.ContentLength)`
42			`}`
43			`t.Method = rr.Method`
44			`t.Body = rr.Body`
45			`t.BodyCloser = rr.Body`
46			`t.ContentLength = rr.ContentLength`
47			`t.Close = rr.Close`
48			`t.TransferEncoding = rr.TransferEncoding`
49			`t.Trailer = rr.Trailer`
50			`atLeastHTTP11 = rr.ProtoAtLeast(1, 1)`
51			`if t.Body != nil && len(t.TransferEncoding) == 0 && atLeastHTTP11 {`
52			`if t.ContentLength == 0 {`
53			`// Test to see if it's actually zero or just unset.`
54			`var buf [1]byte`
55			`n, _ := io.ReadFull(t.Body, buf[:])`
56			`if n == 1 {`
57			`// Oh, guess there is data in this Body Reader after all.`
58			`// The ContentLength field just wasn't set.`
59			`// Stich the Body back together again, re-attaching our`
60			`// consumed byte.`
61			`t.ContentLength = -1`
62			`t.Body = io.MultiReader(bytes.NewBuffer(buf[:]), t.Body)`
63			`} else {`
64			`// Body is actually empty.`
65			`t.Body = nil`
66			`t.BodyCloser = nil`
67			`}`
68			`}`
69			`if t.ContentLength < 0 {`
70			`t.TransferEncoding = []string{"chunked"}`
71			`}`
72			`}`
73			`case *Response:`
74			`t.Method = rr.Request.Method`
75			`t.Body = rr.Body`
76			`t.BodyCloser = rr.Body`
77			`t.ContentLength = rr.ContentLength`
78			`t.Close = rr.Close`
79			`t.TransferEncoding = rr.TransferEncoding`
80			`t.Trailer = rr.Trailer`
81			`atLeastHTTP11 = rr.ProtoAtLeast(1, 1)`
82			`t.ResponseToHEAD = noBodyExpected(rr.Request.Method)`
83			`}`
84
85			`// Sanitize Body,ContentLength,TransferEncoding`
86			`if t.ResponseToHEAD {`
87			`t.Body = nil`
88			`t.TransferEncoding = nil`
89			`// ContentLength is expected to hold Content-Length`
90			`if t.ContentLength < 0 {`
91			`return nil, ErrMissingContentLength`
92			`}`
93			`} else {`
94			`if !atLeastHTTP11 \|\| t.Body == nil {`
95			`t.TransferEncoding = nil`
96			`}`
97			`if chunked(t.TransferEncoding) {`
98			`t.ContentLength = -1`
99			`} else if t.Body == nil { // no chunking, no body`
100			`t.ContentLength = 0`
101			`}`
102			`}`
103
104			`// Sanitize Trailer`
105			`if !chunked(t.TransferEncoding) {`
106			`t.Trailer = nil`
107			`}`
108
109			`return t, nil`
110			`}`
111
112			`func noBodyExpected(requestMethod string) bool {`
113			`return requestMethod == "HEAD"`
114			`}`
115
116			`func (t *transferWriter) shouldSendContentLength() bool {`
117			`if chunked(t.TransferEncoding) {`
118			`return false`
119			`}`
120			`if t.ContentLength > 0 {`
121			`return true`
122			`}`
123			`if t.ResponseToHEAD {`
124			`return true`
125			`}`
126			`// Many servers expect a Content-Length for these methods`
127			`if t.Method == "POST" \|\| t.Method == "PUT" {`
128			`return true`
129			`}`
130			`if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {`
131			`return true`
132			`}`
133
134			`return false`
135			`}`
136
137			`func (t *transferWriter) WriteHeader(w io.Writer) (err error) {`
138			`if t.Close {`
139			`_, err = io.WriteString(w, "Connection: close\r\n")`
140			`if err != nil {`
141			`return`
142			`}`
143			`}`
144
145			`// Write Content-Length and/or Transfer-Encoding whose values are a`
146			`// function of the sanitized field triple (Body, ContentLength,`
147			`// TransferEncoding)`
148			`if t.shouldSendContentLength() {`
149			`io.WriteString(w, "Content-Length: ")`
150			`_, err = io.WriteString(w, strconv.FormatInt(t.ContentLength, 10)+"\r\n")`
151			`if err != nil {`
152			`return`
153			`}`
154			`} else if chunked(t.TransferEncoding) {`
155			`_, err = io.WriteString(w, "Transfer-Encoding: chunked\r\n")`
156			`if err != nil {`
157			`return`
158			`}`
159			`}`
160
161			`// Write Trailer header`
162			`if t.Trailer != nil {`
163			`// TODO: At some point, there should be a generic mechanism for`
164			`// writing long headers, using HTTP line splitting`
165			`io.WriteString(w, "Trailer: ")`
166			`needComma := false`
167			`for k := range t.Trailer {`
168			`k = CanonicalHeaderKey(k)`
169			`switch k {`
170			`case "Transfer-Encoding", "Trailer", "Content-Length":`
171			`return &badStringError{"invalid Trailer key", k}`
172			`}`
173			`if needComma {`
174			`io.WriteString(w, ",")`
175			`}`
176			`io.WriteString(w, k)`
177			`needComma = true`
178			`}`
179			`_, err = io.WriteString(w, "\r\n")`
180			`}`
181
182			`return`
183			`}`
184
185			`func (t *transferWriter) WriteBody(w io.Writer) (err error) {`
186			`var ncopy int64`
187
188			`// Write body`
189			`if t.Body != nil {`
190			`if chunked(t.TransferEncoding) {`
191			`cw := newChunkedWriter(w)`
192			`_, err = io.Copy(cw, t.Body)`
193			`if err == nil {`
194			`err = cw.Close()`
195			`}`
196			`} else if t.ContentLength == -1 {`
197			`ncopy, err = io.Copy(w, t.Body)`
198			`} else {`
199			`ncopy, err = io.Copy(w, io.LimitReader(t.Body, t.ContentLength))`
200			`nextra, err := io.Copy(ioutil.Discard, t.Body)`
201			`if err != nil {`
202			`return err`
203			`}`
204			`ncopy += nextra`
205			`}`
206			`if err != nil {`
207			`return err`
208			`}`
209			`if err = t.BodyCloser.Close(); err != nil {`
210			`return err`
211			`}`
212			`}`
213
214			`if t.ContentLength != -1 && t.ContentLength != ncopy {`
215			`return fmt.Errorf("http: Request.ContentLength=%d with Body length %d",`
216			`t.ContentLength, ncopy)`
217			`}`
218
219			`// TODO(petar): Place trailer writer code here.`
220			`if chunked(t.TransferEncoding) {`
221			`// Last chunk, empty trailer`
222			`_, err = io.WriteString(w, "\r\n")`
223			`}`
224
225			`return`
226			`}`
227
228			`type transferReader struct {`
229			`// Input`
230			`Header Header`
231			`StatusCode int`
232			`RequestMethod string`
233			`ProtoMajor int`
234			`ProtoMinor int`
235			`// Output`
236			`Body io.ReadCloser`
237			`ContentLength int64`
238			`TransferEncoding []string`
239			`Close bool`
240			`Trailer Header`
241			`}`
242
243			`// bodyAllowedForStatus returns whether a given response status code`
244			`// permits a body. See RFC2616, section 4.4.`
245			`func bodyAllowedForStatus(status int) bool {`
246			`switch {`
247			`case status >= 100 && status <= 199:`
248			`return false`
249			`case status == 204:`
250			`return false`
251			`case status == 304:`
252			`return false`
253			`}`
254			`return true`
255			`}`
256
257			`// msg is Request or Response.`
258			`func readTransfer(msg interface{}, r *bufio.Reader) (err error) {`
259			`t := &transferReader{}`
260
261			`// Unify input`
262			`isResponse := false`
263			`switch rr := msg.(type) {`
264			`case *Response:`
265			`t.Header = rr.Header`
266			`t.StatusCode = rr.StatusCode`
267			`t.RequestMethod = rr.Request.Method`
268			`t.ProtoMajor = rr.ProtoMajor`
269			`t.ProtoMinor = rr.ProtoMinor`
270			`t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header)`
271			`isResponse = true`
272			`case *Request:`
273			`t.Header = rr.Header`
274			`t.ProtoMajor = rr.ProtoMajor`
275			`t.ProtoMinor = rr.ProtoMinor`
276			`// Transfer semantics for Requests are exactly like those for`
277			`// Responses with status code 200, responding to a GET method`
278			`t.StatusCode = 200`
279			`t.RequestMethod = "GET"`
280			`default:`
281			`panic("unexpected type")`
282			`}`
283
284			`// Default to HTTP/1.1`
285			`if t.ProtoMajor == 0 && t.ProtoMinor == 0 {`
286			`t.ProtoMajor, t.ProtoMinor = 1, 1`
287			`}`
288
289			`// Transfer encoding, content length`
290			`t.TransferEncoding, err = fixTransferEncoding(t.RequestMethod, t.Header)`
291			`if err != nil {`
292			`return err`
293			`}`
294
295			`t.ContentLength, err = fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.TransferEncoding)`
296			`if err != nil {`
297			`return err`
298			`}`
299
300			`// Trailer`
301			`t.Trailer, err = fixTrailer(t.Header, t.TransferEncoding)`
302			`if err != nil {`
303			`return err`
304			`}`
305
306			`// If there is no Content-Length or chunked Transfer-Encoding on a *Response`
307			`// and the status is not 1xx, 204 or 304, then the body is unbounded.`
308			`// See RFC2616, section 4.4.`
309			`switch msg.(type) {`
310			`case *Response:`
311			`if t.ContentLength == -1 &&`
312			`!chunked(t.TransferEncoding) &&`
313			`bodyAllowedForStatus(t.StatusCode) {`
314			`// Unbounded body.`
315			`t.Close = true`
316			`}`
317			`}`
318
319			`// Prepare body reader. ContentLength < 0 means chunked encoding`
320			`// or close connection when finished, since multipart is not supported yet`
321			`switch {`
322			`case chunked(t.TransferEncoding):`
323			`t.Body = &body{Reader: newChunkedReader(r), hdr: msg, r: r, closing: t.Close}`
324			`case t.ContentLength >= 0:`
325			`// TODO: limit the Content-Length. This is an easy DoS vector.`
326			`t.Body = &body{Reader: io.LimitReader(r, t.ContentLength), closing: t.Close}`
327			`default:`
328			`// t.ContentLength < 0, i.e. "Content-Length" not mentioned in header`
329			`if t.Close {`
330			`// Close semantics (i.e. HTTP/1.0)`
331			`t.Body = &body{Reader: r, closing: t.Close}`
332			`} else {`
333			`// Persistent connection (i.e. HTTP/1.1)`
334			`t.Body = &body{Reader: io.LimitReader(r, 0), closing: t.Close}`
335			`}`
336			`}`
337
338			`// Unify output`
339			`switch rr := msg.(type) {`
340			`case *Request:`
341			`rr.Body = t.Body`
342			`rr.ContentLength = t.ContentLength`
343			`rr.TransferEncoding = t.TransferEncoding`
344			`rr.Close = t.Close`
345			`rr.Trailer = t.Trailer`
346			`case *Response:`
347			`rr.Body = t.Body`
348			`rr.ContentLength = t.ContentLength`
349			`rr.TransferEncoding = t.TransferEncoding`
350			`rr.Close = t.Close`
351			`rr.Trailer = t.Trailer`
352			`}`
353
354			`return nil`
355			`}`
356
357			`// Checks whether chunked is part of the encodings stack`
358			`func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }`
359
360			`// Checks whether the encoding is explicitly "identity".`
361			`func isIdentity(te []string) bool { return len(te) == 1 && te[0] == "identity" }`
362
363			`// Sanitize transfer encoding`
364			`func fixTransferEncoding(requestMethod string, header Header) ([]string, error) {`
365			`raw, present := header["Transfer-Encoding"]`
366			`if !present {`
367			`return nil, nil`
368			`}`
369
370			`delete(header, "Transfer-Encoding")`
371
372			`// Head responses have no bodies, so the transfer encoding`
373			`// should be ignored.`
374			`if requestMethod == "HEAD" {`
375			`return nil, nil`
376			`}`
377
378			`encodings := strings.Split(raw[0], ",")`
379			`te := make([]string, 0, len(encodings))`
380			`// TODO: Even though we only support "identity" and "chunked"`
381			`// encodings, the loop below is designed with foresight. One`
382			`// invariant that must be maintained is that, if present,`
383			`// chunked encoding must always come first.`
384			`for _, encoding := range encodings {`
385			`encoding = strings.ToLower(strings.TrimSpace(encoding))`
386			`// "identity" encoding is not recored`
387			`if encoding == "identity" {`
388			`break`
389			`}`
390			`if encoding != "chunked" {`
391			`return nil, &badStringError{"unsupported transfer encoding", encoding}`
392			`}`
393			`te = te[0 : len(te)+1]`
394			`te[len(te)-1] = encoding`
395			`}`
396			`if len(te) > 1 {`
397			`return nil, &badStringError{"too many transfer encodings", strings.Join(te, ",")}`
398			`}`
399			`if len(te) > 0 {`
400			`// Chunked encoding trumps Content-Length. See RFC 2616`
401			`// Section 4.4. Currently len(te) > 0 implies chunked`
402			`// encoding.`
403			`delete(header, "Content-Length")`
404			`return te, nil`
405			`}`
406
407			`return nil, nil`
408			`}`
409
410			`// Determine the expected body length, using RFC 2616 Section 4.4. This`
411			`// function is not a method, because ultimately it should be shared by`
412			`// ReadResponse and ReadRequest.`
413			`func fixLength(isResponse bool, status int, requestMethod string, header Header, te []string) (int64, error) {`
414
415			`// Logic based on response type or status`
416			`if noBodyExpected(requestMethod) {`
417			`return 0, nil`
418			`}`
419			`if status/100 == 1 {`
420			`return 0, nil`
421			`}`
422			`switch status {`
423			`case 204, 304:`
424			`return 0, nil`
425			`}`
426
427			`// Logic based on Transfer-Encoding`
428			`if chunked(te) {`
429			`return -1, nil`
430			`}`
431
432			`// Logic based on Content-Length`
433			`cl := strings.TrimSpace(header.Get("Content-Length"))`
434			`if cl != "" {`
435			`n, err := strconv.ParseInt(cl, 10, 64)`
436			`if err != nil \|\| n < 0 {`
437			`return -1, &badStringError{"bad Content-Length", cl}`
438			`}`
439			`return n, nil`
440			`} else {`
441			`header.Del("Content-Length")`
442			`}`
443
444			`if !isResponse && requestMethod == "GET" {`
445			`// RFC 2616 doesn't explicitly permit nor forbid an`
446			`// entity-body on a GET request so we permit one if`
447			`// declared, but we default to 0 here (not -1 below)`
448			`// if there's no mention of a body.`
449			`return 0, nil`
450			`}`
451
452			`// Logic based on media type. The purpose of the following code is just`
453			`// to detect whether the unsupported "multipart/byteranges" is being`
454			`// used. A proper Content-Type parser is needed in the future.`
455			`if strings.Contains(strings.ToLower(header.Get("Content-Type")), "multipart/byteranges") {`
456			`return -1, ErrNotSupported`
457			`}`
458
459			`// Body-EOF logic based on other methods (like closing, or chunked coding)`
460			`return -1, nil`
461			`}`
462
463			`// Determine whether to hang up after sending a request and body, or`
464			`// receiving a response and body`
465			`// 'header' is the request headers`
466			`func shouldClose(major, minor int, header Header) bool {`
467			`if major < 1 {`
468			`return true`
469			`} else if major == 1 && minor == 0 {`
470			`if !strings.Contains(strings.ToLower(header.Get("Connection")), "keep-alive") {`
471			`return true`
472			`}`
473			`return false`
474			`} else {`
475			`// TODO: Should split on commas, toss surrounding white space,`
476			`// and check each field.`
477			`if strings.ToLower(header.Get("Connection")) == "close" {`
478			`header.Del("Connection")`
479			`return true`
480			`}`
481			`}`
482			`return false`
483			`}`
484
485			`// Parse the trailer header`
486			`func fixTrailer(header Header, te []string) (Header, error) {`
487			`raw := header.Get("Trailer")`
488			`if raw == "" {`
489			`return nil, nil`
490			`}`
491
492			`header.Del("Trailer")`
493			`trailer := make(Header)`
494			`keys := strings.Split(raw, ",")`
495			`for _, key := range keys {`
496			`key = CanonicalHeaderKey(strings.TrimSpace(key))`
497			`switch key {`
498			`case "Transfer-Encoding", "Trailer", "Content-Length":`
499			`return nil, &badStringError{"bad trailer key", key}`
500			`}`
501			`trailer.Del(key)`
502			`}`
503			`if len(trailer) == 0 {`
504			`return nil, nil`
505			`}`
506			`if !chunked(te) {`
507			`// Trailer and no chunking`
508			`return nil, ErrUnexpectedTrailer`
509			`}`
510			`return trailer, nil`
511			`}`
512
513			`// body turns a Reader into a ReadCloser.`
514			`// Close ensures that the body has been fully read`
515			`// and then reads the trailer if necessary.`
516			`type body struct {`
517			`io.Reader`
518			`hdr interface{} // non-nil (Response or Request) value means read trailer`
519			`r *bufio.Reader // underlying wire-format reader for the trailer`
520			`closing bool // is the connection to be closed after reading body?`
521			`closed bool`
522
523			`res *response // response writer for server requests, else nil`
524			`}`
525
526			`// ErrBodyReadAfterClose is returned when reading a Request Body after`
527			`// the body has been closed. This typically happens when the body is`
528			`// read after an HTTP Handler calls WriteHeader or Write on its`
529			`// ResponseWriter.`
530			`var ErrBodyReadAfterClose = errors.New("http: invalid Read on closed request Body")`
531
532			`func (b *body) Read(p []byte) (n int, err error) {`
533			`if b.closed {`
534			`return 0, ErrBodyReadAfterClose`
535			`}`
536			`n, err = b.Reader.Read(p)`
537
538			`// Read the final trailer once we hit EOF.`
539			`if err == io.EOF && b.hdr != nil {`
540			`if e := b.readTrailer(); e != nil {`
541			`err = e`
542			`}`
543			`b.hdr = nil`
544			`}`
545			`return n, err`
546			`}`
547
548			`var (`
549			`singleCRLF = []byte("\r\n")`
550			`doubleCRLF = []byte("\r\n\r\n")`
551			`)`
552
553			`func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {`
554			`for peekSize := 4; ; peekSize++ {`
555			`// This loop stops when Peek returns an error,`
556			`// which it does when r's buffer has been filled.`
557			`buf, err := r.Peek(peekSize)`
558			`if bytes.HasSuffix(buf, doubleCRLF) {`
559			`return true`
560			`}`
561			`if err != nil {`
562			`break`
563			`}`
564			`}`
565			`return false`
566			`}`
567
568			`func (b *body) readTrailer() error {`
569			`// The common case, since nobody uses trailers.`
570			`buf, _ := b.r.Peek(2)`
571			`if bytes.Equal(buf, singleCRLF) {`
572			`b.r.ReadByte()`
573			`b.r.ReadByte()`
574			`return nil`
575			`}`
576
577			`// Make sure there's a header terminator coming up, to prevent`
578			`// a DoS with an unbounded size Trailer. It's not easy to`
579			`// slip in a LimitReader here, as textproto.NewReader requires`
580			`// a concrete *bufio.Reader. Also, we can't get all the way`
581			`// back up to our conn's LimitedReader that might be backing`
582			`// this bufio.Reader. Instead, a hack: we iteratively Peek up`
583			`// to the bufio.Reader's max size, looking for a double CRLF.`
584			`// This limits the trailer to the underlying buffer size, typically 4kB.`
585			`if !seeUpcomingDoubleCRLF(b.r) {`
586			`return errors.New("http: suspiciously long trailer after chunked body")`
587			`}`
588
589			`hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()`
590			`if err != nil {`
591			`return err`
592			`}`
593			`switch rr := b.hdr.(type) {`
594			`case *Request:`
595			`rr.Trailer = Header(hdr)`
596			`case *Response:`
597			`rr.Trailer = Header(hdr)`
598			`}`
599			`return nil`
600			`}`
601
602			`func (b *body) Close() error {`
603			`if b.closed {`
604			`return nil`
605			`}`
606			`defer func() {`
607			`b.closed = true`
608			`}()`
609			`if b.hdr == nil && b.closing {`
610			`// no trailer and closing the connection next.`
611			`// no point in reading to EOF.`
612			`return nil`
613			`}`
614
615			`// In a server request, don't continue reading from the client`
616			`// if we've already hit the maximum body size set by the`
617			`// handler. If this is set, that also means the TCP connection`
618			`// is about to be closed, so getting to the next HTTP request`
619			`// in the stream is not necessary.`
620			`if b.res != nil && b.res.requestBodyLimitHit {`
621			`return nil`
622			`}`
623
624			`// Fully consume the body, which will also lead to us reading`
625			`// the trailer headers after the body, if present.`
626			`if _, err := io.Copy(ioutil.Discard, b); err != nil {`
627			`return err`
628			`}`
629			`return nil`
630			`}`