Source file src/pkg/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.

// Primitive HTTP client. See RFC 2616.

package http

import (
    "bufio"
    "encoding/base64"
    "fmt"
    "io"
    "net"
    "os"
    "strings"
)

// 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
// io.BufReader through which we read the response, and the underlying
// network connection.
type readClose struct {
    io.Reader
    io.Closer
}

// Send issues an HTTP request.  Caller should close resp.Body when done reading it.
//
// TODO: support persistent connections (multiple requests on a single connection).
// send() method is nonpublic because, when we refactor the code for persistent
// connections, it may no longer make sense to have a method with this signature.
func send(req *Request) (resp *Response, err os.Error) {
    if req.URL.Scheme != "http" {
        return nil, &badStringError{"unsupported protocol scheme", req.URL.Scheme}
    }

    addr := req.URL.Host
    if !hasPort(addr) {
        addr += ":http"
    }
    info := req.URL.Userinfo
    if len(info) > 0 {
        enc := base64.URLEncoding
        encoded := make([]byte, enc.EncodedLen(len(info)))
        enc.Encode(encoded, []byte(info))
        if req.Header == nil {
            req.Header = make(map[string]string)
        }
        req.Header["Authorization"] = "Basic " + string(encoded)
    }
    conn, err := net.Dial("tcp", "", addr)
    if err != nil {
        return nil, err
    }

    err = req.Write(conn)
    if err != nil {
        conn.Close()
        return nil, err
    }

    reader := bufio.NewReader(conn)
    resp, err = ReadResponse(reader, req.Method)
    if err != nil {
        conn.Close()
        return nil, err
    }

    resp.Body = readClose{resp.Body, conn}

    return
}

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

// Get issues a GET to the specified URL.  If the response is one of the following
// redirect codes, it follows the redirect, up to a maximum of 10 redirects:
//
//    301 (Moved Permanently)
//    302 (Found)
//    303 (See Other)
//    307 (Temporary Redirect)
//
// finalURL is the URL from which the response was fetched -- identical to the
// input URL unless redirects were followed.
//
// Caller should close r.Body when done reading it.
func Get(url string) (r *Response, finalURL string, err os.Error) {
    // TODO: if/when we add cookie support, the redirected request shouldn't
    // necessarily supply the same cookies as the original.
    // TODO: set referrer header on redirects.
    for redirect := 0; ; redirect++ {
        if redirect >= 10 {
            err = os.ErrorString("stopped after 10 redirects")
            break
        }

        var req Request
        if req.URL, err = ParseURL(url); err != nil {
            break
        }
        if r, err = send(&req); err != nil {
            break
        }
        if shouldRedirect(r.StatusCode) {
            r.Body.Close()
            if url = r.GetHeader("Location"); url == "" {
                err = os.ErrorString(fmt.Sprintf("%d response missing Location header", r.StatusCode))
                break
            }
            continue
        }
        finalURL = url
        return
    }

    err = &URLError{"Get", url, err}
    return
}

// Post issues a POST to the specified URL.
//
// Caller should close r.Body when done reading it.
func Post(url string, bodyType string, body io.Reader) (r *Response, err os.Error) {
    var req Request
    req.Method = "POST"
    req.ProtoMajor = 1
    req.ProtoMinor = 1
    req.Close = true
    req.Body = nopCloser{body}
    req.Header = map[string]string{
        "Content-Type": bodyType,
    }
    req.TransferEncoding = []string{"chunked"}

    req.URL, err = ParseURL(url)
    if err != nil {
        return nil, err
    }

    return send(&req)
}

// Head issues a HEAD to the specified URL.
func Head(url string) (r *Response, err os.Error) {
    var req Request
    req.Method = "HEAD"
    if req.URL, err = ParseURL(url); err != nil {
        return
    }
    if r, err = send(&req); err != nil {
        return
    }
    return
}

type nopCloser struct {
    io.Reader
}

func (nopCloser) Close() os.Error { return nil }