libgo: Update to Go 1.3 release.

[official-gcc.git] / libgo / go / net / http / fs.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 file system request handler

package http

import (
        "errors"
        "fmt"
        "io"
        "mime"
        "mime/multipart"
        "net/textproto"
        "net/url"
        "os"
        "path"
        "path/filepath"
        "strconv"
        "strings"
        "time"
)

// A Dir implements http.FileSystem using the native file
// system restricted to a specific directory tree.
//
// An empty Dir is treated as ".".
type Dir string

func (d Dir) Open(name string) (File, error) {
        if filepath.Separator != '/' && strings.IndexRune(name, filepath.Separator) >= 0 ||
                strings.Contains(name, "\x00") {
                return nil, errors.New("http: invalid character in file path")
        }
        dir := string(d)
        if dir == "" {
                dir = "."
        }
        f, err := os.Open(filepath.Join(dir, filepath.FromSlash(path.Clean("/"+name))))
        if err != nil {
                return nil, err
        }
        return f, nil
}

// A FileSystem implements access to a collection of named files.
// The elements in a file path are separated by slash ('/', U+002F)
// characters, regardless of host operating system convention.
type FileSystem interface {
        Open(name string) (File, error)
}

// A File is returned by a FileSystem's Open method and can be
// served by the FileServer implementation.
//
// The methods should behave the same as those on an *os.File.
type File interface {
        io.Closer
        io.Reader
        Readdir(count int) ([]os.FileInfo, error)
        Seek(offset int64, whence int) (int64, error)
        Stat() (os.FileInfo, error)
}

func dirList(w ResponseWriter, f File) {
        w.Header().Set("Content-Type", "text/html; charset=utf-8")
        fmt.Fprintf(w, "<pre>\n")
        for {
                dirs, err := f.Readdir(100)
                if err != nil || len(dirs) == 0 {
                        break
                }
                for _, d := range dirs {
                        name := d.Name()
                        if d.IsDir() {
                                name += "/"
                        }
                        // name may contain '?' or '#', which must be escaped to remain
                        // part of the URL path, and not indicate the start of a query
                        // string or fragment.
                        url := url.URL{Path: name}
                        fmt.Fprintf(w, "<a href=\"%s\">%s</a>\n", url.String(), htmlReplacer.Replace(name))
                }
        }
        fmt.Fprintf(w, "</pre>\n")
}

// ServeContent replies to the request using the content in the
// provided ReadSeeker.  The main benefit of ServeContent over io.Copy
// is that it handles Range requests properly, sets the MIME type, and
// handles If-Modified-Since requests.
//
// If the response's Content-Type header is not set, ServeContent
// first tries to deduce the type from name's file extension and,
// if that fails, falls back to reading the first block of the content
// and passing it to DetectContentType.
// The name is otherwise unused; in particular it can be empty and is
// never sent in the response.
//
// If modtime is not the zero time, ServeContent includes it in a
// Last-Modified header in the response.  If the request includes an
// If-Modified-Since header, ServeContent uses modtime to decide
// whether the content needs to be sent at all.
//
// The content's Seek method must work: ServeContent uses
// a seek to the end of the content to determine its size.
//
// If the caller has set w's ETag header, ServeContent uses it to
// handle requests using If-Range and If-None-Match.
//
// Note that *os.File implements the io.ReadSeeker interface.
func ServeContent(w ResponseWriter, req *Request, name string, modtime time.Time, content io.ReadSeeker) {
        sizeFunc := func() (int64, error) {
                size, err := content.Seek(0, os.SEEK_END)
                if err != nil {
                        return 0, errSeeker
                }
                _, err = content.Seek(0, os.SEEK_SET)
                if err != nil {
                        return 0, errSeeker
                }
                return size, nil
        }
        serveContent(w, req, name, modtime, sizeFunc, content)
}

// errSeeker is returned by ServeContent's sizeFunc when the content
// doesn't seek properly. The underlying Seeker's error text isn't
// included in the sizeFunc reply so it's not sent over HTTP to end
// users.
var errSeeker = errors.New("seeker can't seek")

// if name is empty, filename is unknown. (used for mime type, before sniffing)
// if modtime.IsZero(), modtime is unknown.
// content must be seeked to the beginning of the file.
// The sizeFunc is called at most once. Its error, if any, is sent in the HTTP response.
func serveContent(w ResponseWriter, r *Request, name string, modtime time.Time, sizeFunc func() (int64, error), content io.ReadSeeker) {
        if checkLastModified(w, r, modtime) {
                return
        }
        rangeReq, done := checkETag(w, r)
        if done {
                return
        }

        code := StatusOK

        // If Content-Type isn't set, use the file's extension to find it, but
        // if the Content-Type is unset explicitly, do not sniff the type.
        ctypes, haveType := w.Header()["Content-Type"]
        var ctype string
        if !haveType {
                ctype = mime.TypeByExtension(filepath.Ext(name))
                if ctype == "" {
                        // read a chunk to decide between utf-8 text and binary
                        var buf [sniffLen]byte
                        n, _ := io.ReadFull(content, buf[:])
                        ctype = DetectContentType(buf[:n])
                        _, err := content.Seek(0, os.SEEK_SET) // rewind to output whole file
                        if err != nil {
                                Error(w, "seeker can't seek", StatusInternalServerError)
                                return
                        }
                }
                w.Header().Set("Content-Type", ctype)
        } else if len(ctypes) > 0 {
                ctype = ctypes[0]
        }

        size, err := sizeFunc()
        if err != nil {
                Error(w, err.Error(), StatusInternalServerError)
                return
        }

        // handle Content-Range header.
        sendSize := size
        var sendContent io.Reader = content
        if size >= 0 {
                ranges, err := parseRange(rangeReq, size)
                if err != nil {
                        Error(w, err.Error(), StatusRequestedRangeNotSatisfiable)
                        return
                }
                if sumRangesSize(ranges) > size {
                        // The total number of bytes in all the ranges
                        // is larger than the size of the file by
                        // itself, so this is probably an attack, or a
                        // dumb client.  Ignore the range request.
                        ranges = nil
                }
                switch {
                case len(ranges) == 1:
                        // RFC 2616, Section 14.16:
                        // "When an HTTP message includes the content of a single
                        // range (for example, a response to a request for a
                        // single range, or to a request for a set of ranges
                        // that overlap without any holes), this content is
                        // transmitted with a Content-Range header, and a
                        // Content-Length header showing the number of bytes
                        // actually transferred.
                        // ...
                        // A response to a request for a single range MUST NOT
                        // be sent using the multipart/byteranges media type."
                        ra := ranges[0]
                        if _, err := content.Seek(ra.start, os.SEEK_SET); err != nil {
                                Error(w, err.Error(), StatusRequestedRangeNotSatisfiable)
                                return
                        }
                        sendSize = ra.length
                        code = StatusPartialContent
                        w.Header().Set("Content-Range", ra.contentRange(size))
                case len(ranges) > 1:
                        for _, ra := range ranges {
                                if ra.start > size {
                                        Error(w, err.Error(), StatusRequestedRangeNotSatisfiable)
                                        return
                                }
                        }
                        sendSize = rangesMIMESize(ranges, ctype, size)
                        code = StatusPartialContent

                        pr, pw := io.Pipe()
                        mw := multipart.NewWriter(pw)
                        w.Header().Set("Content-Type", "multipart/byteranges; boundary="+mw.Boundary())
                        sendContent = pr
                        defer pr.Close() // cause writing goroutine to fail and exit if CopyN doesn't finish.
                        go func() {
                                for _, ra := range ranges {
                                        part, err := mw.CreatePart(ra.mimeHeader(ctype, size))
                                        if err != nil {
                                                pw.CloseWithError(err)
                                                return
                                        }
                                        if _, err := content.Seek(ra.start, os.SEEK_SET); err != nil {
                                                pw.CloseWithError(err)
                                                return
                                        }
                                        if _, err := io.CopyN(part, content, ra.length); err != nil {
                                                pw.CloseWithError(err)
                                                return
                                        }
                                }
                                mw.Close()
                                pw.Close()
                        }()
                }

                w.Header().Set("Accept-Ranges", "bytes")
                if w.Header().Get("Content-Encoding") == "" {
                        w.Header().Set("Content-Length", strconv.FormatInt(sendSize, 10))
                }
        }

        w.WriteHeader(code)

        if r.Method != "HEAD" {
                io.CopyN(w, sendContent, sendSize)
        }
}

// modtime is the modification time of the resource to be served, or IsZero().
// return value is whether this request is now complete.
func checkLastModified(w ResponseWriter, r *Request, modtime time.Time) bool {
        if modtime.IsZero() {
                return false
        }

        // The Date-Modified header truncates sub-second precision, so
        // use mtime < t+1s instead of mtime <= t to check for unmodified.
        if t, err := time.Parse(TimeFormat, r.Header.Get("If-Modified-Since")); err == nil && modtime.Before(t.Add(1*time.Second)) {
                h := w.Header()
                delete(h, "Content-Type")
                delete(h, "Content-Length")
                w.WriteHeader(StatusNotModified)
                return true
        }
        w.Header().Set("Last-Modified", modtime.UTC().Format(TimeFormat))
        return false
}

// checkETag implements If-None-Match and If-Range checks.
// The ETag must have been previously set in the ResponseWriter's headers.
//
// The return value is the effective request "Range" header to use and
// whether this request is now considered done.
func checkETag(w ResponseWriter, r *Request) (rangeReq string, done bool) {
        etag := w.Header().get("Etag")
        rangeReq = r.Header.get("Range")

        // Invalidate the range request if the entity doesn't match the one
        // the client was expecting.
        // "If-Range: version" means "ignore the Range: header unless version matches the
        // current file."
        // We only support ETag versions.
        // The caller must have set the ETag on the response already.
        if ir := r.Header.get("If-Range"); ir != "" && ir != etag {
                // TODO(bradfitz): handle If-Range requests with Last-Modified
                // times instead of ETags? I'd rather not, at least for
                // now. That seems like a bug/compromise in the RFC 2616, and
                // I've never heard of anybody caring about that (yet).
                rangeReq = ""
        }

        if inm := r.Header.get("If-None-Match"); inm != "" {
                // Must know ETag.
                if etag == "" {
                        return rangeReq, false
                }

                // TODO(bradfitz): non-GET/HEAD requests require more work:
                // sending a different status code on matches, and
                // also can't use weak cache validators (those with a "W/
                // prefix).  But most users of ServeContent will be using
                // it on GET or HEAD, so only support those for now.
                if r.Method != "GET" && r.Method != "HEAD" {
                        return rangeReq, false
                }

                // TODO(bradfitz): deal with comma-separated or multiple-valued
                // list of If-None-match values.  For now just handle the common
                // case of a single item.
                if inm == etag || inm == "*" {
                        h := w.Header()
                        delete(h, "Content-Type")
                        delete(h, "Content-Length")
                        w.WriteHeader(StatusNotModified)
                        return "", true
                }
        }
        return rangeReq, false
}

// name is '/'-separated, not filepath.Separator.
func serveFile(w ResponseWriter, r *Request, fs FileSystem, name string, redirect bool) {
        const indexPage = "/index.html"

        // redirect .../index.html to .../
        // can't use Redirect() because that would make the path absolute,
        // which would be a problem running under StripPrefix
        if strings.HasSuffix(r.URL.Path, indexPage) {
                localRedirect(w, r, "./")
                return
        }

        f, err := fs.Open(name)
        if err != nil {
                // TODO expose actual error?
                NotFound(w, r)
                return
        }
        defer f.Close()

        d, err1 := f.Stat()
        if err1 != nil {
                // TODO expose actual error?
                NotFound(w, r)
                return
        }

        if redirect {
                // redirect to canonical path: / at end of directory url
                // r.URL.Path always begins with /
                url := r.URL.Path
                if d.IsDir() {
                        if url[len(url)-1] != '/' {
                                localRedirect(w, r, path.Base(url)+"/")
                                return
                        }
                } else {
                        if url[len(url)-1] == '/' {
                                localRedirect(w, r, "../"+path.Base(url))
                                return
                        }
                }
        }

        // use contents of index.html for directory, if present
        if d.IsDir() {
                index := name + indexPage
                ff, err := fs.Open(index)
                if err == nil {
                        defer ff.Close()
                        dd, err := ff.Stat()
                        if err == nil {
                                name = index
                                d = dd
                                f = ff
                        }
                }
        }

        // Still a directory? (we didn't find an index.html file)
        if d.IsDir() {
                if checkLastModified(w, r, d.ModTime()) {
                        return
                }
                dirList(w, f)
                return
        }

        // serverContent will check modification time
        sizeFunc := func() (int64, error) { return d.Size(), nil }
        serveContent(w, r, d.Name(), d.ModTime(), sizeFunc, f)
}

// localRedirect gives a Moved Permanently response.
// It does not convert relative paths to absolute paths like Redirect does.
func localRedirect(w ResponseWriter, r *Request, newPath string) {
        if q := r.URL.RawQuery; q != "" {
                newPath += "?" + q
        }
        w.Header().Set("Location", newPath)
        w.WriteHeader(StatusMovedPermanently)
}

// ServeFile replies to the request with the contents of the named file or directory.
func ServeFile(w ResponseWriter, r *Request, name string) {
        dir, file := filepath.Split(name)
        serveFile(w, r, Dir(dir), file, false)
}

type fileHandler struct {
        root FileSystem
}

// FileServer returns a handler that serves HTTP requests
// with the contents of the file system rooted at root.
//
// To use the operating system's file system implementation,
// use http.Dir:
//
//     http.Handle("/", http.FileServer(http.Dir("/tmp")))
func FileServer(root FileSystem) Handler {
        return &fileHandler{root}
}

func (f *fileHandler) ServeHTTP(w ResponseWriter, r *Request) {
        upath := r.URL.Path
        if !strings.HasPrefix(upath, "/") {
                upath = "/" + upath
                r.URL.Path = upath
        }
        serveFile(w, r, f.root, path.Clean(upath), true)
}

// httpRange specifies the byte range to be sent to the client.
type httpRange struct {
        start, length int64
}

func (r httpRange) contentRange(size int64) string {
        return fmt.Sprintf("bytes %d-%d/%d", r.start, r.start+r.length-1, size)
}

func (r httpRange) mimeHeader(contentType string, size int64) textproto.MIMEHeader {
        return textproto.MIMEHeader{
                "Content-Range": {r.contentRange(size)},
                "Content-Type":  {contentType},
        }
}

// parseRange parses a Range header string as per RFC 2616.
func parseRange(s string, size int64) ([]httpRange, error) {
        if s == "" {
                return nil, nil // header not present
        }
        const b = "bytes="
        if !strings.HasPrefix(s, b) {
                return nil, errors.New("invalid range")
        }
        var ranges []httpRange
        for _, ra := range strings.Split(s[len(b):], ",") {
                ra = strings.TrimSpace(ra)
                if ra == "" {
                        continue
                }
                i := strings.Index(ra, "-")
                if i < 0 {
                        return nil, errors.New("invalid range")
                }
                start, end := strings.TrimSpace(ra[:i]), strings.TrimSpace(ra[i+1:])
                var r httpRange
                if start == "" {
                        // If no start is specified, end specifies the
                        // range start relative to the end of the file.
                        i, err := strconv.ParseInt(end, 10, 64)
                        if err != nil {
                                return nil, errors.New("invalid range")
                        }
                        if i > size {
                                i = size
                        }
                        r.start = size - i
                        r.length = size - r.start
                } else {
                        i, err := strconv.ParseInt(start, 10, 64)
                        if err != nil || i > size || i < 0 {
                                return nil, errors.New("invalid range")
                        }
                        r.start = i
                        if end == "" {
                                // If no end is specified, range extends to end of the file.
                                r.length = size - r.start
                        } else {
                                i, err := strconv.ParseInt(end, 10, 64)
                                if err != nil || r.start > i {
                                        return nil, errors.New("invalid range")
                                }
                                if i >= size {
                                        i = size - 1
                                }
                                r.length = i - r.start + 1
                        }
                }
                ranges = append(ranges, r)
        }
        return ranges, nil
}

// countingWriter counts how many bytes have been written to it.
type countingWriter int64

func (w *countingWriter) Write(p []byte) (n int, err error) {
        *w += countingWriter(len(p))
        return len(p), nil
}

// rangesMIMESize returns the number of bytes it takes to encode the
// provided ranges as a multipart response.
func rangesMIMESize(ranges []httpRange, contentType string, contentSize int64) (encSize int64) {
        var w countingWriter
        mw := multipart.NewWriter(&w)
        for _, ra := range ranges {
                mw.CreatePart(ra.mimeHeader(contentType, contentSize))
                encSize += ra.length
        }
        mw.Close()
        encSize += int64(w)
        return
}

func sumRangesSize(ranges []httpRange) (size int64) {
        for _, ra := range ranges {
                size += ra.length
        }
        return
}