// 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.

// HTTP client. See RFC 7230 through 7235.
//
// This is the high-level Client interface.
// The low-level implementation is in transport.go.

package http

import (
	
	
	
	
	
	
	
	
	
	
	
	
	
)

// A Client is an HTTP client. Its zero value (DefaultClient) is a
// usable client that uses DefaultTransport.
//
// The Client's Transport typically has internal state (cached TCP
// connections), so Clients should be reused instead of created as
// needed. Clients are safe for concurrent use by multiple goroutines.
//
// A Client is higher-level than a RoundTripper (such as Transport)
// and additionally handles HTTP details such as cookies and
// redirects.
//
// When following redirects, the Client will forward all headers set on the
// initial Request except:
//
// • when forwarding sensitive headers like "Authorization",
// "WWW-Authenticate", and "Cookie" to untrusted targets.
// These headers will be ignored when following a redirect to a domain
// that is not a subdomain match or exact match of the initial domain.
// For example, a redirect from "foo.com" to either "foo.com" or "sub.foo.com"
// will forward the sensitive headers, but a redirect to "bar.com" will not.
//
// • when forwarding the "Cookie" header with a non-nil cookie Jar.
// Since each redirect may mutate the state of the cookie jar,
// a redirect may possibly alter a cookie set in the initial request.
// When forwarding the "Cookie" header, any mutated cookies will be omitted,
// with the expectation that the Jar will insert those mutated cookies
// with the updated values (assuming the origin matches).
// If Jar is nil, the initial cookies are forwarded without change.
//
type Client struct {
	// Transport specifies the mechanism by which individual
	// HTTP requests are made.
	// If nil, DefaultTransport is used.
	Transport RoundTripper

	// CheckRedirect specifies the policy for handling redirects.
	// If CheckRedirect is not nil, the client calls it before
	// following an HTTP redirect. The arguments req and via are
	// the upcoming request and the requests made already, oldest
	// first. If CheckRedirect returns an error, the Client's Get
	// method returns both the previous Response (with its Body
	// closed) and CheckRedirect's error (wrapped in a url.Error)
	// instead of issuing the Request req.
	// As a special case, if CheckRedirect returns ErrUseLastResponse,
	// then the most recent response is returned with its body
	// unclosed, along with a nil error.
	//
	// If CheckRedirect is nil, the Client uses its default policy,
	// which is to stop after 10 consecutive requests.
	CheckRedirect func(req *Request, via []*Request) error

	// Jar specifies the cookie jar.
	//
	// The Jar is used to insert relevant cookies into every
	// outbound Request and is updated with the cookie values
	// of every inbound Response. The Jar is consulted for every
	// redirect that the Client follows.
	//
	// If Jar is nil, cookies are only sent if they are explicitly
	// set on the Request.
	Jar CookieJar

	// Timeout specifies a time limit for requests made by this
	// Client. The timeout includes connection time, any
	// redirects, and reading the response body. The timer remains
	// running after Get, Head, Post, or Do return and will
	// interrupt reading of the Response.Body.
	//
	// A Timeout of zero means no timeout.
	//
	// The Client cancels requests to the underlying Transport
	// as if the Request's Context ended.
	//
	// For compatibility, the Client will also use the deprecated
	// CancelRequest method on Transport if found. New
	// RoundTripper implementations should use the Request's Context
	// for cancellation instead of implementing CancelRequest.
	Timeout time.Duration
}

// DefaultClient is the default Client and is used by Get, Head, and Post.
var DefaultClient = &Client{}

// RoundTripper is an interface representing the ability to execute a
// single HTTP transaction, obtaining the Response for a given Request.
//
// A RoundTripper must be safe for concurrent use by multiple
// goroutines.
type RoundTripper interface {
	// RoundTrip executes a single HTTP transaction, returning
	// a Response for the provided Request.
	//
	// RoundTrip should not attempt to interpret the response. In
	// particular, RoundTrip must return err == nil if it obtained
	// a response, regardless of the response's HTTP status code.
	// A non-nil err should be reserved for failure to obtain a
	// response. Similarly, RoundTrip should not attempt to
	// handle higher-level protocol details such as redirects,
	// authentication, or cookies.
	//
	// RoundTrip should not modify the request, except for
	// consuming and closing the Request's Body. RoundTrip may
	// read fields of the request in a separate goroutine. Callers
	// should not mutate or reuse the request until the Response's
	// Body has been closed.
	//
	// RoundTrip must always close the body, including on errors,
	// but depending on the implementation may do so in a separate
	// goroutine even after RoundTrip returns. This means that
	// callers wanting to reuse the body for subsequent requests
	// must arrange to wait for the Close call before doing so.
	//
	// The Request's URL and Header fields must be initialized.
	RoundTrip(*Request) (*Response, error)
}

// refererForURL returns a referer without any authentication info or
// an empty string if lastReq scheme is https and newReq scheme is http.
func refererForURL(,  *url.URL) string {
	// https://tools.ietf.org/html/rfc7231#section-5.5.2
	//   "Clients SHOULD NOT include a Referer header field in a
	//    (non-secure) HTTP request if the referring page was
	//    transferred with a secure protocol."
	if .Scheme == "https" && .Scheme == "http" {
		return ""
	}
	 := .String()
	if .User != nil {
		// This is not very efficient, but is the best we can
		// do without:
		// - introducing a new method on URL
		// - creating a race condition
		// - copying the URL struct manually, which would cause
		//   maintenance problems down the line
		 := .User.String() + "@"
		 = strings.Replace(, , "", 1)
	}
	return 
}

// didTimeout is non-nil only if err != nil.
func ( *Client) ( *Request,  time.Time) ( *Response,  func() bool,  error) {
	if .Jar != nil {
		for ,  := range .Jar.Cookies(.URL) {
			.AddCookie()
		}
	}
	, ,  = send(, .transport(), )
	if  != nil {
		return nil, , 
	}
	if .Jar != nil {
		if  := .Cookies(); len() > 0 {
			.Jar.SetCookies(.URL, )
		}
	}
	return , nil, nil
}

func ( *Client) () time.Time {
	if .Timeout > 0 {
		return time.Now().Add(.Timeout)
	}
	return time.Time{}
}

func ( *Client) () RoundTripper {
	if .Transport != nil {
		return .Transport
	}
	return DefaultTransport
}

// send issues an HTTP request.
// Caller should close resp.Body when done reading from it.
func send( *Request,  RoundTripper,  time.Time) ( *Response,  func() bool,  error) {
	 :=  // req is either the original request, or a modified fork

	if  == nil {
		.closeBody()
		return nil, alwaysFalse, errors.New("http: no Client.Transport or DefaultTransport")
	}

	if .URL == nil {
		.closeBody()
		return nil, alwaysFalse, errors.New("http: nil Request.URL")
	}

	if .RequestURI != "" {
		.closeBody()
		return nil, alwaysFalse, errors.New("http: Request.RequestURI can't be set in client requests")
	}

	// forkReq forks req into a shallow clone of ireq the first
	// time it's called.
	 := func() {
		if  ==  {
			 = new(Request)
			* = * // shallow clone
		}
	}

	// Most the callers of send (Get, Post, et al) don't need
	// Headers, leaving it uninitialized. We guarantee to the
	// Transport that this has been initialized, though.
	if .Header == nil {
		()
		.Header = make(Header)
	}

	if  := .URL.User;  != nil && .Header.Get("Authorization") == "" {
		 := .Username()
		,  := .Password()
		()
		.Header = cloneOrMakeHeader(.Header)
		.Header.Set("Authorization", "Basic "+basicAuth(, ))
	}

	if !.IsZero() {
		()
	}
	,  := setRequestCancel(, , )

	,  = .RoundTrip()
	if  != nil {
		()
		if  != nil {
			log.Printf("RoundTripper returned a response & error; ignoring response")
		}
		if ,  := .(tls.RecordHeaderError);  {
			// If we get a bad TLS record header, check to see if the
			// response looks like HTTP and give a more helpful error.
			// See golang.org/issue/11111.
			if string(.RecordHeader[:]) == "HTTP/" {
				 = errors.New("http: server gave HTTP response to HTTPS client")
			}
		}
		return nil, , 
	}
	if  == nil {
		return nil, , fmt.Errorf("http: RoundTripper implementation (%T) returned a nil *Response with a nil error", )
	}
	if .Body == nil {
		// The documentation on the Body field says “The http Client and Transport
		// guarantee that Body is always non-nil, even on responses without a body
		// or responses with a zero-length body.” Unfortunately, we didn't document
		// that same constraint for arbitrary RoundTripper implementations, and
		// RoundTripper implementations in the wild (mostly in tests) assume that
		// they can use a nil Body to mean an empty one (similar to Request.Body).
		// (See https://golang.org/issue/38095.)
		//
		// If the ContentLength allows the Body to be empty, fill in an empty one
		// here to ensure that it is non-nil.
		if .ContentLength > 0 && .Method != "HEAD" {
			return nil, , fmt.Errorf("http: RoundTripper implementation (%T) returned a *Response with content length %d but a nil Body", , .ContentLength)
		}
		.Body = io.NopCloser(strings.NewReader(""))
	}
	if !.IsZero() {
		.Body = &cancelTimerBody{
			stop:          ,
			rc:            .Body,
			reqDidTimeout: ,
		}
	}
	return , nil, nil
}

// timeBeforeContextDeadline reports whether the non-zero Time t is
// before ctx's deadline, if any. If ctx does not have a deadline, it
// always reports true (the deadline is considered infinite).
func timeBeforeContextDeadline( time.Time,  context.Context) bool {
	,  := .Deadline()
	if ! {
		return true
	}
	return .Before()
}

// knownRoundTripperImpl reports whether rt is a RoundTripper that's
// maintained by the Go team and known to implement the latest
// optional semantics (notably contexts). The Request is used
// to check whether this particular request is using an alternate protocol,
// in which case we need to check the RoundTripper for that protocol.
func knownRoundTripperImpl( RoundTripper,  *Request) bool {
	switch t := .(type) {
	case *Transport:
		if  := .alternateRoundTripper();  != nil {
			return (, )
		}
		return true
	case *http2Transport, http2noDialH2RoundTripper:
		return true
	}
	// There's a very minor chance of a false positive with this.
	// Instead of detecting our golang.org/x/net/http2.Transport,
	// it might detect a Transport type in a different http2
	// package. But I know of none, and the only problem would be
	// some temporarily leaked goroutines if the transport didn't
	// support contexts. So this is a good enough heuristic:
	if reflect.TypeOf().String() == "*http2.Transport" {
		return true
	}
	return false
}

// setRequestCancel sets req.Cancel and adds a deadline context to req
// if deadline is non-zero. The RoundTripper's type is used to
// determine whether the legacy CancelRequest behavior should be used.
//
// As background, there are three ways to cancel a request:
// First was Transport.CancelRequest. (deprecated)
// Second was Request.Cancel.
// Third was Request.Context.
// This function populates the second and third, and uses the first if it really needs to.
func setRequestCancel( *Request,  RoundTripper,  time.Time) ( func(),  func() bool) {
	if .IsZero() {
		return nop, alwaysFalse
	}
	 := knownRoundTripperImpl(, )
	 := .Context()

	if .Cancel == nil &&  {
		// If they already had a Request.Context that's
		// expiring sooner, do nothing:
		if !timeBeforeContextDeadline(, ) {
			return nop, alwaysFalse
		}

		var  func()
		.ctx,  = context.WithDeadline(, )
		return , func() bool { return time.Now().After() }
	}
	 := .Cancel // the user's original Request.Cancel, if any

	var  func()
	if  := .Context(); timeBeforeContextDeadline(, ) {
		.ctx,  = context.WithDeadline(, )
	}

	 := make(chan struct{})
	.Cancel = 

	 := func() {
		// The second way in the func comment above:
		close()
		// The first way, used only for RoundTripper
		// implementations written before Go 1.5 or Go 1.6.
		type  interface{ (*Request) }
		if ,  := .();  {
			.()
		}
	}

	 := make(chan struct{})
	var  sync.Once
	 = func() {
		.Do(func() {
			close()
			if  != nil {
				()
			}
		})
	}

	 := time.NewTimer(time.Until())
	var  atomicBool

	go func() {
		select {
		case <-:
			()
			.Stop()
		case <-.C:
			.setTrue()
			()
		case <-:
			.Stop()
		}
	}()

	return , .isSet
}

// See 2 (end of page 4) https://www.ietf.org/rfc/rfc2617.txt
// "To receive authorization, the client sends the userid and password,
// separated by a single colon (":") character, within a base64
// encoded string in the credentials."
// It is not meant to be urlencoded.
func basicAuth(,  string) string {
	 :=  + ":" + 
	return base64.StdEncoding.EncodeToString([]byte())
}

// Get issues a GET to the specified URL. If the response is one of
// the following redirect codes, Get follows the redirect, up to a
// maximum of 10 redirects:
//
//    301 (Moved Permanently)
//    302 (Found)
//    303 (See Other)
//    307 (Temporary Redirect)
//    308 (Permanent Redirect)
//
// An error is returned if there were too many redirects or if there
// was an HTTP protocol error. A non-2xx response doesn't cause an
// error. Any returned error will be of type *url.Error. The url.Error
// value's Timeout method will report true if request timed out or was
// canceled.
//
// When err is nil, resp always contains a non-nil resp.Body.
// Caller should close resp.Body when done reading from it.
//
// Get is a wrapper around DefaultClient.Get.
//
// To make a request with custom headers, use NewRequest and
// DefaultClient.Do.
func ( string) ( *Response,  error) {
	return DefaultClient.Get()
}

// Get issues a GET to the specified URL. If the response is one of the
// following redirect codes, Get follows the redirect after calling the
// Client's CheckRedirect function:
//
//    301 (Moved Permanently)
//    302 (Found)
//    303 (See Other)
//    307 (Temporary Redirect)
//    308 (Permanent Redirect)
//
// An error is returned if the Client's CheckRedirect function fails
// or if there was an HTTP protocol error. A non-2xx response doesn't
// cause an error. Any returned error will be of type *url.Error. The
// url.Error value's Timeout method will report true if the request
// timed out.
//
// When err is nil, resp always contains a non-nil resp.Body.
// Caller should close resp.Body when done reading from it.
//
// To make a request with custom headers, use NewRequest and Client.Do.
func ( *Client) ( string) ( *Response,  error) {
	,  := NewRequest("GET", , nil)
	if  != nil {
		return nil, 
	}
	return .Do()
}

func alwaysFalse() bool { return false }

// ErrUseLastResponse can be returned by Client.CheckRedirect hooks to
// control how redirects are processed. If returned, the next request
// is not sent and the most recent response is returned with its body
// unclosed.
var ErrUseLastResponse = errors.New("net/http: use last response")

// checkRedirect calls either the user's configured CheckRedirect
// function, or the default.
func ( *Client) ( *Request,  []*Request) error {
	 := .CheckRedirect
	if  == nil {
		 = defaultCheckRedirect
	}
	return (, )
}

// redirectBehavior describes what should happen when the
// client encounters a 3xx status code from the server
func redirectBehavior( string,  *Response,  *Request) ( string, ,  bool) {
	switch .StatusCode {
	case 301, 302, 303:
		 = 
		 = true
		 = false

		// RFC 2616 allowed automatic redirection only with GET and
		// HEAD requests. RFC 7231 lifts this restriction, but we still
		// restrict other methods to GET to maintain compatibility.
		// See Issue 18570.
		if  != "GET" &&  != "HEAD" {
			 = "GET"
		}
	case 307, 308:
		 = 
		 = true
		 = true

		// Treat 307 and 308 specially, since they're new in
		// Go 1.8, and they also require re-sending the request body.
		if .Header.Get("Location") == "" {
			// 308s have been observed in the wild being served
			// without Location headers. Since Go 1.7 and earlier
			// didn't follow these codes, just stop here instead
			// of returning an error.
			// See Issue 17773.
			 = false
			break
		}
		if .GetBody == nil && .outgoingLength() != 0 {
			// We had a request body, and 307/308 require
			// re-sending it, but GetBody is not defined. So just
			// return this response to the user instead of an
			// error, like we did in Go 1.7 and earlier.
			 = false
		}
	}
	return , , 
}

// urlErrorOp returns the (*url.Error).Op value to use for the
// provided (*Request).Method value.
func urlErrorOp( string) string {
	if  == "" {
		return "Get"
	}
	return [:1] + strings.ToLower([1:])
}

// Do sends an HTTP request and returns an HTTP response, following
// policy (such as redirects, cookies, auth) as configured on the
// client.
//
// An error is returned if caused by client policy (such as
// CheckRedirect), or failure to speak HTTP (such as a network
// connectivity problem). A non-2xx status code doesn't cause an
// error.
//
// If the returned error is nil, the Response will contain a non-nil
// Body which the user is expected to close. If the Body is not both
// read to EOF and closed, the Client's underlying RoundTripper
// (typically Transport) may not be able to re-use a persistent TCP
// connection to the server for a subsequent "keep-alive" request.
//
// The request Body, if non-nil, will be closed by the underlying
// Transport, even on errors.
//
// On error, any Response can be ignored. A non-nil Response with a
// non-nil error only occurs when CheckRedirect fails, and even then
// the returned Response.Body is already closed.
//
// Generally Get, Post, or PostForm will be used instead of Do.
//
// If the server replies with a redirect, the Client first uses the
// CheckRedirect function to determine whether the redirect should be
// followed. If permitted, a 301, 302, or 303 redirect causes
// subsequent requests to use HTTP method GET
// (or HEAD if the original request was HEAD), with no body.
// A 307 or 308 redirect preserves the original HTTP method and body,
// provided that the Request.GetBody function is defined.
// The NewRequest function automatically sets GetBody for common
// standard library body types.
//
// Any returned error will be of type *url.Error. The url.Error
// value's Timeout method will report true if request timed out or was
// canceled.
func ( *Client) ( *Request) (*Response, error) {
	return .do()
}

var testHookClientDoResult func(retres *Response, reterr error)

func ( *Client) ( *Request) ( *Response,  error) {
	if testHookClientDoResult != nil {
		defer func() { testHookClientDoResult(, ) }()
	}
	if .URL == nil {
		.closeBody()
		return nil, &url.Error{
			Op:  urlErrorOp(.Method),
			Err: errors.New("http: nil Request.URL"),
		}
	}

	var (
		      = .deadline()
		          []*Request
		          *Response
		   = .makeHeadersCopier()
		 = false // have we closed the current req.Body?

		// Redirect behavior:
		 string
		    bool
	)
	 := func( error) error {
		// the body may have been closed already by c.send()
		if ! {
			.closeBody()
		}
		var  string
		if  != nil && .Request != nil {
			 = stripPassword(.Request.URL)
		} else {
			 = stripPassword(.URL)
		}
		return &url.Error{
			Op:  urlErrorOp([0].Method),
			URL: ,
			Err: ,
		}
	}
	for {
		// For all but the first request, create the next
		// request hop and replace req.
		if len() > 0 {
			 := .Header.Get("Location")
			if  == "" {
				.closeBody()
				return nil, (fmt.Errorf("%d response missing Location header", .StatusCode))
			}
			,  := .URL.Parse()
			if  != nil {
				.closeBody()
				return nil, (fmt.Errorf("failed to parse Location header %q: %v", , ))
			}
			 := ""
			if .Host != "" && .Host != .URL.Host {
				// If the caller specified a custom Host header and the
				// redirect location is relative, preserve the Host header
				// through the redirect. See issue #22233.
				if ,  := url.Parse();  != nil && !.IsAbs() {
					 = .Host
				}
			}
			 := [0]
			 = &Request{
				Method:   ,
				Response: ,
				URL:      ,
				Header:   make(Header),
				Host:     ,
				Cancel:   .Cancel,
				ctx:      .ctx,
			}
			if  && .GetBody != nil {
				.Body,  = .GetBody()
				if  != nil {
					.closeBody()
					return nil, ()
				}
				.ContentLength = .ContentLength
			}

			// Copy original headers before setting the Referer,
			// in case the user set Referer on their first request.
			// If they really want to override, they can do it in
			// their CheckRedirect func.
			()

			// Add the Referer header from the most recent
			// request URL to the new one, if it's not https->http:
			if  := refererForURL([len()-1].URL, .URL);  != "" {
				.Header.Set("Referer", )
			}
			 = .checkRedirect(, )

			// Sentinel error to let users select the
			// previous response, without closing its
			// body. See Issue 10069.
			if  == ErrUseLastResponse {
				return , nil
			}

			// Close the previous response's body. But
			// read at least some of the body so if it's
			// small the underlying TCP connection will be
			// re-used. No need to check for errors: if it
			// fails, the Transport won't reuse it anyway.
			const  = 2 << 10
			if .ContentLength == -1 || .ContentLength <=  {
				io.CopyN(io.Discard, .Body, )
			}
			.Body.Close()

			if  != nil {
				// Special case for Go 1 compatibility: return both the response
				// and an error if the CheckRedirect function failed.
				// See https://golang.org/issue/3795
				// The resp.Body has already been closed.
				 := ()
				.(*url.Error).URL = 
				return , 
			}
		}

		 = append(, )
		var  error
		var  func() bool
		if , ,  = .send(, );  != nil {
			// c.send() always closes req.Body
			 = true
			if !.IsZero() && () {
				 = &httpError{
					// TODO: early in cycle: s/Client.Timeout exceeded/timeout or context cancellation/
					err:     .Error() + " (Client.Timeout exceeded while awaiting headers)",
					timeout: true,
				}
			}
			return nil, ()
		}

		var  bool
		, ,  = redirectBehavior(.Method, , [0])
		if ! {
			return , nil
		}

		.closeBody()
	}
}

// makeHeadersCopier makes a function that copies headers from the
// initial Request, ireq. For every redirect, this function must be called
// so that it can copy headers into the upcoming Request.
func ( *Client) ( *Request) func(*Request) {
	// The headers to copy are from the very initial request.
	// We use a closured callback to keep a reference to these original headers.
	var (
		  = cloneOrMakeHeader(.Header)
		 map[string][]*Cookie
	)
	if .Jar != nil && .Header.Get("Cookie") != "" {
		 = make(map[string][]*Cookie)
		for ,  := range .Cookies() {
			[.Name] = append([.Name], )
		}
	}

	 :=  // The previous request
	return func( *Request) {
		// If Jar is present and there was some initial cookies provided
		// via the request header, then we may need to alter the initial
		// cookies as we follow redirects since each redirect may end up
		// modifying a pre-existing cookie.
		//
		// Since cookies already set in the request header do not contain
		// information about the original domain and path, the logic below
		// assumes any new set cookies override the original cookie
		// regardless of domain or path.
		//
		// See https://golang.org/issue/17494
		if .Jar != nil &&  != nil {
			var  bool
			 := .Response // The response that caused the upcoming redirect
			for ,  := range .Cookies() {
				if ,  := [.Name];  {
					delete(, .Name)
					 = true
				}
			}
			if  {
				.Del("Cookie")
				var  []string
				for ,  := range  {
					for ,  := range  {
						 = append(, .Name+"="+.Value)
					}
				}
				sort.Strings() // Ensure deterministic headers
				.Set("Cookie", strings.Join(, "; "))
			}
		}

		// Copy the initial request's Header values
		// (at least the safe ones).
		for ,  := range  {
			if shouldCopyHeaderOnRedirect(, .URL, .URL) {
				.Header[] = 
			}
		}

		 =  // Update previous Request with the current request
	}
}

func defaultCheckRedirect( *Request,  []*Request) error {
	if len() >= 10 {
		return errors.New("stopped after 10 redirects")
	}
	return nil
}

// Post issues a POST to the specified URL.
//
// Caller should close resp.Body when done reading from it.
//
// If the provided body is an io.Closer, it is closed after the
// request.
//
// Post is a wrapper around DefaultClient.Post.
//
// To set custom headers, use NewRequest and DefaultClient.Do.
//
// See the Client.Do method documentation for details on how redirects
// are handled.
func (,  string,  io.Reader) ( *Response,  error) {
	return DefaultClient.Post(, , )
}

// Post issues a POST to the specified URL.
//
// Caller should close resp.Body when done reading from it.
//
// If the provided body is an io.Closer, it is closed after the
// request.
//
// To set custom headers, use NewRequest and Client.Do.
//
// See the Client.Do method documentation for details on how redirects
// are handled.
func ( *Client) (,  string,  io.Reader) ( *Response,  error) {
	,  := NewRequest("POST", , )
	if  != nil {
		return nil, 
	}
	.Header.Set("Content-Type", )
	return .Do()
}

// PostForm issues a POST to the specified URL, with data's keys and
// values URL-encoded as the request body.
//
// The Content-Type header is set to application/x-www-form-urlencoded.
// To set other headers, use NewRequest and DefaultClient.Do.
//
// When err is nil, resp always contains a non-nil resp.Body.
// Caller should close resp.Body when done reading from it.
//
// PostForm is a wrapper around DefaultClient.PostForm.
//
// See the Client.Do method documentation for details on how redirects
// are handled.
func ( string,  url.Values) ( *Response,  error) {
	return DefaultClient.PostForm(, )
}

// PostForm issues a POST to the specified URL,
// with data's keys and values URL-encoded as the request body.
//
// The Content-Type header is set to application/x-www-form-urlencoded.
// To set other headers, use NewRequest and Client.Do.
//
// When err is nil, resp always contains a non-nil resp.Body.
// Caller should close resp.Body when done reading from it.
//
// See the Client.Do method documentation for details on how redirects
// are handled.
func ( *Client) ( string,  url.Values) ( *Response,  error) {
	return .Post(, "application/x-www-form-urlencoded", strings.NewReader(.Encode()))
}

// Head issues a HEAD to the specified URL. If the response is one of
// the following redirect codes, Head follows the redirect, up to a
// maximum of 10 redirects:
//
//    301 (Moved Permanently)
//    302 (Found)
//    303 (See Other)
//    307 (Temporary Redirect)
//    308 (Permanent Redirect)
//
// Head is a wrapper around DefaultClient.Head
func ( string) ( *Response,  error) {
	return DefaultClient.Head()
}

// Head issues a HEAD to the specified URL. If the response is one of the
// following redirect codes, Head follows the redirect after calling the
// Client's CheckRedirect function:
//
//    301 (Moved Permanently)
//    302 (Found)
//    303 (See Other)
//    307 (Temporary Redirect)
//    308 (Permanent Redirect)
func ( *Client) ( string) ( *Response,  error) {
	,  := NewRequest("HEAD", , nil)
	if  != nil {
		return nil, 
	}
	return .Do()
}

// CloseIdleConnections closes any connections on its Transport which
// were previously connected from previous requests but are now
// sitting idle in a "keep-alive" state. It does not interrupt any
// connections currently in use.
//
// If the Client's Transport does not have a CloseIdleConnections method
// then this method does nothing.
func ( *Client) () {
	type  interface {
		()
	}
	if ,  := .transport().();  {
		.()
	}
}

// cancelTimerBody is an io.ReadCloser that wraps rc with two features:
// 1) on Read error or close, the stop func is called.
// 2) On Read failure, if reqDidTimeout is true, the error is wrapped and
//    marked as net.Error that hit its timeout.
type cancelTimerBody struct {
	stop          func() // stops the time.Timer waiting to cancel the request
	rc            io.ReadCloser
	reqDidTimeout func() bool
}

func ( *cancelTimerBody) ( []byte) ( int,  error) {
	,  = .rc.Read()
	if  == nil {
		return , nil
	}
	.stop()
	if  == io.EOF {
		return , 
	}
	if .reqDidTimeout() {
		 = &httpError{
			err:     .Error() + " (Client.Timeout or context cancellation while reading body)",
			timeout: true,
		}
	}
	return , 
}

func ( *cancelTimerBody) () error {
	 := .rc.Close()
	.stop()
	return 
}

func shouldCopyHeaderOnRedirect( string, ,  *url.URL) bool {
	switch CanonicalHeaderKey() {
	case "Authorization", "Www-Authenticate", "Cookie", "Cookie2":
		// Permit sending auth/cookie headers from "foo.com"
		// to "sub.foo.com".

		// Note that we don't send all cookies to subdomains
		// automatically. This function is only used for
		// Cookies set explicitly on the initial outgoing
		// client request. Cookies automatically added via the
		// CookieJar mechanism continue to follow each
		// cookie's scope as set by Set-Cookie. But for
		// outgoing requests with the Cookie header set
		// directly, we don't know their scope, so we assume
		// it's for *.domain.com.

		 := canonicalAddr()
		 := canonicalAddr()
		return isDomainOrSubdomain(, )
	}
	// All other headers are copied:
	return true
}

// isDomainOrSubdomain reports whether sub is a subdomain (or exact
// match) of the parent domain.
//
// Both domains must already be in canonical form.
func isDomainOrSubdomain(,  string) bool {
	if  ==  {
		return true
	}
	// If sub is "foo.example.com" and parent is "example.com",
	// that means sub must end in "."+parent.
	// Do it without allocating.
	if !strings.HasSuffix(, ) {
		return false
	}
	return [len()-len()-1] == '.'
}

func stripPassword( *url.URL) string {
	,  := .User.Password()
	if  {
		return strings.Replace(.String(), .User.String()+"@", .User.Username()+":***@", 1)
	}
	return .String()
}