Rebase.

[official-gcc.git] / libgo / go / net / http / client.go

// 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 2616.
//
// This is the high-level Client interface.
// The low-level implementation is in transport.go.

package http

import (
        "encoding/base64"
        "errors"
        "fmt"
        "io"
        "io/ioutil"
        "log"
        "net/url"
        "strings"
        "sync"
        "time"
)

// 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.
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 and
        // CheckRedirect's error (wrapped in a url.Error) instead of
        // issuing the Request req.
        //
        // 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.
        // If Jar is nil, cookies are not sent in requests and ignored
        // in responses.
        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's Transport must support the CancelRequest
        // method or Client will return errors when attempting to make
        // a request with Get, Head, Post, or Do. Client's default
        // Transport (DefaultTransport) supports 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
        // the Response for the request req.  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 Body, including on errors. The
        // request's URL and Header fields are guaranteed to be
        // initialized.
        RoundTrip(*Request) (*Response, error)
}

// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
// return true if the string includes a port.
func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }

// Used in Send to implement io.ReadCloser by bundling together the
// bufio.Reader through which we read the response, and the underlying
// network connection.
type readClose struct {
        io.Reader
        io.Closer
}

func (c *Client) send(req *Request) (*Response, error) {
        if c.Jar != nil {
                for _, cookie := range c.Jar.Cookies(req.URL) {
                        req.AddCookie(cookie)
                }
        }
        resp, err := send(req, c.transport())
        if err != nil {
                return nil, err
        }
        if c.Jar != nil {
                if rc := resp.Cookies(); len(rc) > 0 {
                        c.Jar.SetCookies(req.URL, rc)
                }
        }
        return resp, err
}

// Do sends an HTTP request and returns an HTTP response, following
// policy (e.g. redirects, cookies, auth) as configured on the client.
//
// An error is returned if caused by client policy (such as
// CheckRedirect), or if there was an HTTP protocol error.
// A non-2xx response doesn't cause an error.
//
// When err is nil, resp always contains a non-nil resp.Body.
//
// Callers should close resp.Body when done reading from it. If
// resp.Body is not 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.
//
// Generally Get, Post, or PostForm will be used instead of Do.
func (c *Client) Do(req *Request) (resp *Response, err error) {
        if req.Method == "GET" || req.Method == "HEAD" {
                return c.doFollowingRedirects(req, shouldRedirectGet)
        }
        if req.Method == "POST" || req.Method == "PUT" {
                return c.doFollowingRedirects(req, shouldRedirectPost)
        }
        return c.send(req)
}

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

// send issues an HTTP request.
// Caller should close resp.Body when done reading from it.
func send(req *Request, t RoundTripper) (resp *Response, err error) {
        if t == nil {
                req.closeBody()
                return nil, errors.New("http: no Client.Transport or DefaultTransport")
        }

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

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

        // 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 req.Header == nil {
                req.Header = make(Header)
        }

        if u := req.URL.User; u != nil {
                username := u.Username()
                password, _ := u.Password()
                req.Header.Set("Authorization", "Basic "+basicAuth(username, password))
        }
        resp, err = t.RoundTrip(req)
        if err != nil {
                if resp != nil {
                        log.Printf("RoundTripper returned a response & error; ignoring response")
                }
                return nil, err
        }
        return resp, nil
}

// See 2 (end of page 4) http://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(username, password string) string {
        auth := username + ":" + password
        return base64.StdEncoding.EncodeToString([]byte(auth))
}

// True if the specified HTTP status code is one for which the Get utility should
// automatically redirect.
func shouldRedirectGet(statusCode int) bool {
        switch statusCode {
        case StatusMovedPermanently, StatusFound, StatusSeeOther, StatusTemporaryRedirect:
                return true
        }
        return false
}

// True if the specified HTTP status code is one for which the Post utility should
// automatically redirect.
func shouldRedirectPost(statusCode int) bool {
        switch statusCode {
        case StatusFound, StatusSeeOther:
                return true
        }
        return false
}

// 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)
//
// 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.
//
// 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.
func Get(url string) (resp *Response, err error) {
        return DefaultClient.Get(url)
}

// 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)
//
// 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.
//
// When err is nil, resp always contains a non-nil resp.Body.
// Caller should close resp.Body when done reading from it.
func (c *Client) Get(url string) (resp *Response, err error) {
        req, err := NewRequest("GET", url, nil)
        if err != nil {
                return nil, err
        }
        return c.doFollowingRedirects(req, shouldRedirectGet)
}

func (c *Client) doFollowingRedirects(ireq *Request, shouldRedirect func(int) bool) (resp *Response, err error) {
        var base *url.URL
        redirectChecker := c.CheckRedirect
        if redirectChecker == nil {
                redirectChecker = defaultCheckRedirect
        }
        var via []*Request

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

        var reqmu sync.Mutex // guards req
        req := ireq

        var timer *time.Timer
        if c.Timeout > 0 {
                type canceler interface {
                        CancelRequest(*Request)
                }
                tr, ok := c.transport().(canceler)
                if !ok {
                        return nil, fmt.Errorf("net/http: Client Transport of type %T doesn't support CancelRequest; Timeout not supported", c.transport())
                }
                timer = time.AfterFunc(c.Timeout, func() {
                        reqmu.Lock()
                        defer reqmu.Unlock()
                        tr.CancelRequest(req)
                })
        }

        urlStr := "" // next relative or absolute URL to fetch (after first request)
        redirectFailed := false
        for redirect := 0; ; redirect++ {
                if redirect != 0 {
                        nreq := new(Request)
                        nreq.Method = ireq.Method
                        if ireq.Method == "POST" || ireq.Method == "PUT" {
                                nreq.Method = "GET"
                        }
                        nreq.Header = make(Header)
                        nreq.URL, err = base.Parse(urlStr)
                        if err != nil {
                                break
                        }
                        if len(via) > 0 {
                                // Add the Referer header.
                                lastReq := via[len(via)-1]
                                if lastReq.URL.Scheme != "https" {
                                        nreq.Header.Set("Referer", lastReq.URL.String())
                                }

                                err = redirectChecker(nreq, via)
                                if err != nil {
                                        redirectFailed = true
                                        break
                                }
                        }
                        reqmu.Lock()
                        req = nreq
                        reqmu.Unlock()
                }

                urlStr = req.URL.String()
                if resp, err = c.send(req); err != nil {
                        break
                }

                if shouldRedirect(resp.StatusCode) {
                        // Read the body if small so underlying TCP connection will be re-used.
                        // No need to check for errors: if it fails, Transport won't reuse it anyway.
                        const maxBodySlurpSize = 2 << 10
                        if resp.ContentLength == -1 || resp.ContentLength <= maxBodySlurpSize {
                                io.CopyN(ioutil.Discard, resp.Body, maxBodySlurpSize)
                        }
                        resp.Body.Close()
                        if urlStr = resp.Header.Get("Location"); urlStr == "" {
                                err = errors.New(fmt.Sprintf("%d response missing Location header", resp.StatusCode))
                                break
                        }
                        base = req.URL
                        via = append(via, req)
                        continue
                }
                if timer != nil {
                        resp.Body = &cancelTimerBody{timer, resp.Body}
                }
                return resp, nil
        }

        method := ireq.Method
        urlErr := &url.Error{
                Op:  method[0:1] + strings.ToLower(method[1:]),
                URL: urlStr,
                Err: err,
        }

        if redirectFailed {
                // Special case for Go 1 compatibility: return both the response
                // and an error if the CheckRedirect function failed.
                // See http://golang.org/issue/3795
                return resp, urlErr
        }

        if resp != nil {
                resp.Body.Close()
        }
        return nil, urlErr
}

func defaultCheckRedirect(req *Request, via []*Request) error {
        if len(via) >= 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.
//
// Post is a wrapper around DefaultClient.Post
func Post(url string, bodyType string, body io.Reader) (resp *Response, err error) {
        return DefaultClient.Post(url, bodyType, body)
}

// Post issues a POST to the specified URL.
//
// Caller should close resp.Body when done reading from it.
//
// If the provided body is also an io.Closer, it is closed after the
// request.
func (c *Client) Post(url string, bodyType string, body io.Reader) (resp *Response, err error) {
        req, err := NewRequest("POST", url, body)
        if err != nil {
                return nil, err
        }
        req.Header.Set("Content-Type", bodyType)
        return c.doFollowingRedirects(req, shouldRedirectPost)
}

// PostForm issues a POST to the specified URL, with data's keys and
// values URL-encoded as the request body.
//
// 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
func PostForm(url string, data url.Values) (resp *Response, err error) {
        return DefaultClient.PostForm(url, data)
}

// PostForm issues a POST to the specified URL,
// with data's keys and values urlencoded as the request body.
//
// When err is nil, resp always contains a non-nil resp.Body.
// Caller should close resp.Body when done reading from it.
func (c *Client) PostForm(url string, data url.Values) (resp *Response, err error) {
        return c.Post(url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
}

// 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)
//
// Head is a wrapper around DefaultClient.Head
func Head(url string) (resp *Response, err error) {
        return DefaultClient.Head(url)
}

// 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)
func (c *Client) Head(url string) (resp *Response, err error) {
        req, err := NewRequest("HEAD", url, nil)
        if err != nil {
                return nil, err
        }
        return c.doFollowingRedirects(req, shouldRedirectGet)
}

type cancelTimerBody struct {
        t  *time.Timer
        rc io.ReadCloser
}

func (b *cancelTimerBody) Read(p []byte) (n int, err error) {
        n, err = b.rc.Read(p)
        if err == io.EOF {
                b.t.Stop()
        }
        return
}

func (b *cancelTimerBody) Close() error {
        err := b.rc.Close()
        b.t.Stop()
        return err
}