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一起看一下golang的HTTP包怎么write Request信息
先看一下看golang http Request的struct，不解释，慢慢看（HTTP权威指南，RFC文档）
type Request struct {
// Method specifies the HTTP method (GET, POST, PUT, etc.).
// For client requests an empty string means GET.
Method string
// URL specifies either the URI being requested (for server
// requests) or the URL to access (for client requests).
//
// For server requests the URL is parsed from the URI
// supplied on the Request-Line as stored in RequestURI. For
// most requests, fields other than Path and RawQuery will be
// empty. (See RFC 2616, Section 5.1.2)
//
// For client requests, the URL‘s Host specifies the server to
// connect to, while the Request‘s Host field optionally
// specifies the Host header value to send in the HTTP
// request.
URL *url.URL
// The protocol version for incoming requests.
// Client requests always use HTTP/1.1.
Proto string // "HTTP/1.0"
ProtoMajor int // 1
ProtoMinor int // 0
// A header maps request lines to their values.
// If the header says
//
// accept-encoding: gzip, deflate
// Accept-Language: en-us
// Connection: keep-alive
//
// then
//
// Header = map[string][]string{
// "Accept-Encoding": {"gzip, deflate"},
// "Accept-Language": {"en-us"},
// "Connection": {"keep-alive"},
// }
//
// HTTP defines that header names are case-insensitive.
// The request parser implements this by canonicalizing the
// name, making the first character and any characters
// following a hyphen uppercase and the rest lowercase.
//
// For client requests certain headers are automatically
// added and may override values in Header.
//
// See the documentation for the Request.Write method.
Header Header
// Body is the request‘s body.
//
// For client requests a nil body means the request has no
// body, such as a GET request. The HTTP Client‘s Transport
// is responsible for calling the Close method.
//
// For server requests the Request Body is always non-nil
// but will return EOF immediately when no body is present.
// The Server will close the request body. The ServeHTTP
// Handler does not need to.
Body io.ReadCloser
// ContentLength records the length of the associated content.
// The value -1 indicates that the length is unknown.
// Values >= 0 indicate that the given number of bytes may
// be read from Body.
// For client requests, a value of 0 means unknown if Body is not nil.
ContentLength int64
// TransferEncoding lists the transfer encodings from outermost to
// innermost. An empty list denotes the "identity" encoding.
// TransferEncoding can usually be ignored; chunked encoding is
// automatically added and removed as necessary when sending and
// receiving requests.
TransferEncoding []string
// Close indicates whether to close the connection after
// replying to this request (for servers) or after sending
// the request (for clients).
Close bool
// For server requests Host specifies the host on which the
// URL is sought. Per RFC 2616, this is either the value of
// the "Host" header or the host name given in the URL itself.
// It may be of the form "host:port".
//
// For client requests Host optionally overrides the Host
// header to send. If empty, the Request.Write method uses
// the value of URL.Host.
Host string
// Form contains the parsed form data, including both the URL
// field‘s query parameters and the POST or PUT form data.
// This field is only available after ParseForm is called.
// The HTTP client ignores Form and uses Body instead.
Form url.Values
// PostForm contains the parsed form data from POST or PUT
// body parameters.
// This field is only available after ParseForm is called.
// The HTTP client ignores PostForm and uses Body instead.
PostForm url.Values
// MultipartForm is the parsed multipart form, including file uploads.
// This field is only available after ParseMultipartForm is called.
// The HTTP client ignores MultipartForm and uses Body instead.
MultipartForm *multipart.Form
// Trailer specifies additional headers that are sent after the request
// body.
//
// For server requests the Trailer map initially contains only the
// trailer keys, with nil values. (The client declares which trailers it
// will later send.) While the handler is reading from Body, it must
// not reference Trailer. After reading from Body returns EOF, Trailer
// can be read again and will contain non-nil values, if they were sent
// by the client.
//
// For client requests Trailer must be initialized to a map containing
// the trailer keys to later send. The values may be nil or their final
// values. The ContentLength must be 0 or -1, to send a chunked request.
// After the HTTP request is sent the map values can be updated while
// the request body is read. Once the body returns EOF, the caller must
// not mutate Trailer.
//
// Few HTTP clients, servers, or proxies support HTTP trailers.
Trailer Header
// RemoteAddr allows HTTP servers and other software to record
// the network address that sent the request, usually for
// logging. This field is not filled in by ReadRequest and
// has no defined format. The HTTP server in this package
// sets RemoteAddr to an "IP:port" address before invoking a
// handler.
// This field is ignored by the HTTP client.
RemoteAddr string
// RequestURI is the unmodified Request-URI of the
// Request-Line (RFC 2616, Section 5.1) as sent by the client
// to a server. Usually the URL field should be used instead.
// It is an error to set this field in an HTTP client request.
RequestURI string
// TLS allows HTTP servers and other software to record
// information about the TLS connection on which the request
// was received. This field is not filled in by ReadRequest.
// The HTTP server in this package sets the field for
// TLS-enabled connections before invoking a handler;
// otherwise it leaves the field nil.
// This field is ignored by the HTTP client.
TLS *tls.ConnectionState
}
再来具体分析一下http request write的具体执行流程
func (req *Request) write(w io.Writer, usingProxy bool, extraHeaders Header) error {
host := req.Host
if host == "" {
if req.URL == nil {
return errors.New("http: Request.Write on Request with no Host or URL set")
}
host = req.URL.Host
}
ruri := req.URL.RequestURI()
//代理模式的时候ruri需要加上协议名http/https等
if usingProxy && req.URL.Scheme != "" && req.URL.Opaque == "" {
ruri = req.URL.Scheme + "://" + host + ruri
} else if req.Method == "CONNECT" && req.URL.Path == "" {
// CONNECT requests normally give just the host and port, not a full URL.
ruri = host
}
// TODO(bradfitz): escape at least newlines in ruri?
// Wrap the writer in a bufio Writer if it‘s not already buffered.
// Don‘t always call NewWriter, as that forces a bytes.Buffer
// and other small bufio Writers to have a minimum 4k buffer
// size.
//创建一个Writer,往里面写内容
var bw *bufio.Writer
if _, ok := w.(io.ByteWriter); !ok {
bw = bufio.NewWriter(w)
w = bw
}
//写http最开始数据
_, err := fmt.Fprintf(w, "%s %s HTTP/1.1\r\n", valueOrDefault(req.Method, "GET"), ruri)
if err != nil {
return err
}
// Header lines 写Host内容
_, err = fmt.Fprintf(w, "Host: %s\r\n", host)
if err != nil {
return err
}
// Use the defaultUserAgent unless the Header contains one, which
// may be blank to not send the header.
//这东西的数据如下：
/* const defaultUserAgent = "Go 1.1 package http" */
userAgent := defaultUserAgent
if req.Header != nil {
if ua := req.Header["User-Agent"]; len(ua) > 0 {
userAgent = ua[0]
}
}
if userAgent != "" {
_, err = fmt.Fprintf(w, "User-Agent: %s\r\n", userAgent)
if err != nil {
return err
}
}
// Process Body,ContentLength,Close,Trailer
//封装的transferWriter结构
tw, err := newTransferWriter(req)
if err != nil {
return err
}
err = tw.WriteHeader(w)
if err != nil {
return err
}
err = req.Header.WriteSubset(w, reqWriteExcludeHeader)
if err != nil {
return err
}
if extraHeaders != nil {
err = extraHeaders.Write(w)
if err != nil {
return err
}
}
_, err = io.WriteString(w, "\r\n")
if err != nil {
return err
}
// Write body and trailer
err = tw.WriteBody(w)
if err != nil {
return err
}
if bw != nil {
return bw.Flush()
}
return nil
}
再来看看transferWriter结构相关的操作：
//主要用于写HTTP的Body,ContentLength,Close,Trailer
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
}
创建transferWriter的过程：
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, rerr := io.ReadFull(t.Body, buf[:])
if rerr != nil && rerr != io.EOF {
t.ContentLength = -1
t.Body = &errorReader{rerr}
} else 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.NewReader(buf[:]), t.Body)
} else {
// Body is actually empty.
t.Body = nil
t.BodyCloser = nil
}
}
if t.ContentLength < 0 {
t.TransferEncoding = []string{"chunked"}
}
}
case *Response:
if rr.Request != nil {
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(t.Method)
}
// Sanitize Body,ContentLength,TransferEncoding
if t.ResponseToHEAD {
t.Body = nil
if chunked(t.TransferEncoding) {
t.ContentLength = -1
}
} 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
}
最后再看看WriteBody的操作：
func (t *transferWriter) WriteBody(w io.Writer) error {
var err error
var ncopy int64
// Write body 写body的操作在这里
if t.Body != nil {
if chunked(t.TransferEncoding) {
cw := internal.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))
if err != nil {
return err
}
var nextra int64
nextra, err = io.Copy(ioutil.Discard, t.Body)
ncopy += nextra
}
if err != nil {
return err
}
if err = t.BodyCloser.Close(); err != nil {
return err
}
}
if !t.ResponseToHEAD && t.ContentLength != -1 && t.ContentLength != ncopy {
return fmt.Errorf("http: ContentLength=%d with Body length %d",
t.ContentLength, ncopy)
}
// TODO(petar): Place trailer writer code here.
if chunked(t.TransferEncoding) {
// Write Trailer header
if t.Trailer != nil {
if err := t.Trailer.Write(w); err != nil {
return err
}
}
// Last chunk, empty trailer
_, err = io.WriteString(w, "\r\n")
}
return err
}
自己实现HTTP服务器可以借鉴一下此处代码
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原文地址：http://my.oschina.net/yang1992/blog/530816
