Source file src/pkg/net/http/fs.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	// HTTP file system request handler
     6	
     7	package http
     8	
     9	import (
    10		"errors"
    11		"fmt"
    12		"io"
    13		"mime"
    14		"os"
    15		"path"
    16		"path/filepath"
    17		"strconv"
    18		"strings"
    19		"time"
    20	)
    21	
    22	// A Dir implements http.FileSystem using the native file
    23	// system restricted to a specific directory tree.
    24	//
    25	// An empty Dir is treated as ".".
    26	type Dir string
    27	
    28	func (d Dir) Open(name string) (File, error) {
    29		if filepath.Separator != '/' && strings.IndexRune(name, filepath.Separator) >= 0 {
    30			return nil, errors.New("http: invalid character in file path")
    31		}
    32		dir := string(d)
    33		if dir == "" {
    34			dir = "."
    35		}
    36		f, err := os.Open(filepath.Join(dir, filepath.FromSlash(path.Clean("/"+name))))
    37		if err != nil {
    38			return nil, err
    39		}
    40		return f, nil
    41	}
    42	
    43	// A FileSystem implements access to a collection of named files.
    44	// The elements in a file path are separated by slash ('/', U+002F)
    45	// characters, regardless of host operating system convention.
    46	type FileSystem interface {
    47		Open(name string) (File, error)
    48	}
    49	
    50	// A File is returned by a FileSystem's Open method and can be
    51	// served by the FileServer implementation.
    52	type File interface {
    53		Close() error
    54		Stat() (os.FileInfo, error)
    55		Readdir(count int) ([]os.FileInfo, error)
    56		Read([]byte) (int, error)
    57		Seek(offset int64, whence int) (int64, error)
    58	}
    59	
    60	func dirList(w ResponseWriter, f File) {
    61		w.Header().Set("Content-Type", "text/html; charset=utf-8")
    62		fmt.Fprintf(w, "<pre>\n")
    63		for {
    64			dirs, err := f.Readdir(100)
    65			if err != nil || len(dirs) == 0 {
    66				break
    67			}
    68			for _, d := range dirs {
    69				name := d.Name()
    70				if d.IsDir() {
    71					name += "/"
    72				}
    73				// TODO htmlescape
    74				fmt.Fprintf(w, "<a href=\"%s\">%s</a>\n", name, name)
    75			}
    76		}
    77		fmt.Fprintf(w, "</pre>\n")
    78	}
    79	
    80	// ServeContent replies to the request using the content in the
    81	// provided ReadSeeker.  The main benefit of ServeContent over io.Copy
    82	// is that it handles Range requests properly, sets the MIME type, and
    83	// handles If-Modified-Since requests.
    84	//
    85	// If the response's Content-Type header is not set, ServeContent
    86	// first tries to deduce the type from name's file extension and,
    87	// if that fails, falls back to reading the first block of the content
    88	// and passing it to DetectContentType.
    89	// The name is otherwise unused; in particular it can be empty and is
    90	// never sent in the response.
    91	//
    92	// If modtime is not the zero time, ServeContent includes it in a
    93	// Last-Modified header in the response.  If the request includes an
    94	// If-Modified-Since header, ServeContent uses modtime to decide
    95	// whether the content needs to be sent at all.
    96	//
    97	// The content's Seek method must work: ServeContent uses
    98	// a seek to the end of the content to determine its size.
    99	//
   100	// Note that *os.File implements the io.ReadSeeker interface.
   101	func ServeContent(w ResponseWriter, req *Request, name string, modtime time.Time, content io.ReadSeeker) {
   102		size, err := content.Seek(0, os.SEEK_END)
   103		if err != nil {
   104			Error(w, "seeker can't seek", StatusInternalServerError)
   105			return
   106		}
   107		_, err = content.Seek(0, os.SEEK_SET)
   108		if err != nil {
   109			Error(w, "seeker can't seek", StatusInternalServerError)
   110			return
   111		}
   112		serveContent(w, req, name, modtime, size, content)
   113	}
   114	
   115	// if name is empty, filename is unknown. (used for mime type, before sniffing)
   116	// if modtime.IsZero(), modtime is unknown.
   117	// content must be seeked to the beginning of the file.
   118	func serveContent(w ResponseWriter, r *Request, name string, modtime time.Time, size int64, content io.ReadSeeker) {
   119		if checkLastModified(w, r, modtime) {
   120			return
   121		}
   122	
   123		code := StatusOK
   124	
   125		// If Content-Type isn't set, use the file's extension to find it.
   126		if w.Header().Get("Content-Type") == "" {
   127			ctype := mime.TypeByExtension(filepath.Ext(name))
   128			if ctype == "" {
   129				// read a chunk to decide between utf-8 text and binary
   130				var buf [1024]byte
   131				n, _ := io.ReadFull(content, buf[:])
   132				b := buf[:n]
   133				ctype = DetectContentType(b)
   134				_, err := content.Seek(0, os.SEEK_SET) // rewind to output whole file
   135				if err != nil {
   136					Error(w, "seeker can't seek", StatusInternalServerError)
   137					return
   138				}
   139			}
   140			w.Header().Set("Content-Type", ctype)
   141		}
   142	
   143		// handle Content-Range header.
   144		// TODO(adg): handle multiple ranges
   145		sendSize := size
   146		if size >= 0 {
   147			ranges, err := parseRange(r.Header.Get("Range"), size)
   148			if err == nil && len(ranges) > 1 {
   149				err = errors.New("multiple ranges not supported")
   150			}
   151			if err != nil {
   152				Error(w, err.Error(), StatusRequestedRangeNotSatisfiable)
   153				return
   154			}
   155			if len(ranges) == 1 {
   156				ra := ranges[0]
   157				if _, err := content.Seek(ra.start, os.SEEK_SET); err != nil {
   158					Error(w, err.Error(), StatusRequestedRangeNotSatisfiable)
   159					return
   160				}
   161				sendSize = ra.length
   162				code = StatusPartialContent
   163				w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", ra.start, ra.start+ra.length-1, size))
   164			}
   165	
   166			w.Header().Set("Accept-Ranges", "bytes")
   167			if w.Header().Get("Content-Encoding") == "" {
   168				w.Header().Set("Content-Length", strconv.FormatInt(sendSize, 10))
   169			}
   170		}
   171	
   172		w.WriteHeader(code)
   173	
   174		if r.Method != "HEAD" {
   175			if sendSize == -1 {
   176				io.Copy(w, content)
   177			} else {
   178				io.CopyN(w, content, sendSize)
   179			}
   180		}
   181	}
   182	
   183	// modtime is the modification time of the resource to be served, or IsZero().
   184	// return value is whether this request is now complete.
   185	func checkLastModified(w ResponseWriter, r *Request, modtime time.Time) bool {
   186		if modtime.IsZero() {
   187			return false
   188		}
   189	
   190		// The Date-Modified header truncates sub-second precision, so
   191		// use mtime < t+1s instead of mtime <= t to check for unmodified.
   192		if t, err := time.Parse(TimeFormat, r.Header.Get("If-Modified-Since")); err == nil && modtime.Before(t.Add(1*time.Second)) {
   193			w.WriteHeader(StatusNotModified)
   194			return true
   195		}
   196		w.Header().Set("Last-Modified", modtime.UTC().Format(TimeFormat))
   197		return false
   198	}
   199	
   200	// name is '/'-separated, not filepath.Separator.
   201	func serveFile(w ResponseWriter, r *Request, fs FileSystem, name string, redirect bool) {
   202		const indexPage = "/index.html"
   203	
   204		// redirect .../index.html to .../
   205		// can't use Redirect() because that would make the path absolute,
   206		// which would be a problem running under StripPrefix
   207		if strings.HasSuffix(r.URL.Path, indexPage) {
   208			localRedirect(w, r, "./")
   209			return
   210		}
   211	
   212		f, err := fs.Open(name)
   213		if err != nil {
   214			// TODO expose actual error?
   215			NotFound(w, r)
   216			return
   217		}
   218		defer f.Close()
   219	
   220		d, err1 := f.Stat()
   221		if err1 != nil {
   222			// TODO expose actual error?
   223			NotFound(w, r)
   224			return
   225		}
   226	
   227		if redirect {
   228			// redirect to canonical path: / at end of directory url
   229			// r.URL.Path always begins with /
   230			url := r.URL.Path
   231			if d.IsDir() {
   232				if url[len(url)-1] != '/' {
   233					localRedirect(w, r, path.Base(url)+"/")
   234					return
   235				}
   236			} else {
   237				if url[len(url)-1] == '/' {
   238					localRedirect(w, r, "../"+path.Base(url))
   239					return
   240				}
   241			}
   242		}
   243	
   244		// use contents of index.html for directory, if present
   245		if d.IsDir() {
   246			if checkLastModified(w, r, d.ModTime()) {
   247				return
   248			}
   249			index := name + indexPage
   250			ff, err := fs.Open(index)
   251			if err == nil {
   252				defer ff.Close()
   253				dd, err := ff.Stat()
   254				if err == nil {
   255					name = index
   256					d = dd
   257					f = ff
   258				}
   259			}
   260		}
   261	
   262		if d.IsDir() {
   263			dirList(w, f)
   264			return
   265		}
   266	
   267		serveContent(w, r, d.Name(), d.ModTime(), d.Size(), f)
   268	}
   269	
   270	// localRedirect gives a Moved Permanently response.
   271	// It does not convert relative paths to absolute paths like Redirect does.
   272	func localRedirect(w ResponseWriter, r *Request, newPath string) {
   273		if q := r.URL.RawQuery; q != "" {
   274			newPath += "?" + q
   275		}
   276		w.Header().Set("Location", newPath)
   277		w.WriteHeader(StatusMovedPermanently)
   278	}
   279	
   280	// ServeFile replies to the request with the contents of the named file or directory.
   281	func ServeFile(w ResponseWriter, r *Request, name string) {
   282		dir, file := filepath.Split(name)
   283		serveFile(w, r, Dir(dir), file, false)
   284	}
   285	
   286	type fileHandler struct {
   287		root FileSystem
   288	}
   289	
   290	// FileServer returns a handler that serves HTTP requests
   291	// with the contents of the file system rooted at root.
   292	//
   293	// To use the operating system's file system implementation,
   294	// use http.Dir:
   295	//
   296	//     http.Handle("/", http.FileServer(http.Dir("/tmp")))
   297	func FileServer(root FileSystem) Handler {
   298		return &fileHandler{root}
   299	}
   300	
   301	func (f *fileHandler) ServeHTTP(w ResponseWriter, r *Request) {
   302		upath := r.URL.Path
   303		if !strings.HasPrefix(upath, "/") {
   304			upath = "/" + upath
   305			r.URL.Path = upath
   306		}
   307		serveFile(w, r, f.root, path.Clean(upath), true)
   308	}
   309	
   310	// httpRange specifies the byte range to be sent to the client.
   311	type httpRange struct {
   312		start, length int64
   313	}
   314	
   315	// parseRange parses a Range header string as per RFC 2616.
   316	func parseRange(s string, size int64) ([]httpRange, error) {
   317		if s == "" {
   318			return nil, nil // header not present
   319		}
   320		const b = "bytes="
   321		if !strings.HasPrefix(s, b) {
   322			return nil, errors.New("invalid range")
   323		}
   324		var ranges []httpRange
   325		for _, ra := range strings.Split(s[len(b):], ",") {
   326			i := strings.Index(ra, "-")
   327			if i < 0 {
   328				return nil, errors.New("invalid range")
   329			}
   330			start, end := ra[:i], ra[i+1:]
   331			var r httpRange
   332			if start == "" {
   333				// If no start is specified, end specifies the
   334				// range start relative to the end of the file.
   335				i, err := strconv.ParseInt(end, 10, 64)
   336				if err != nil {
   337					return nil, errors.New("invalid range")
   338				}
   339				if i > size {
   340					i = size
   341				}
   342				r.start = size - i
   343				r.length = size - r.start
   344			} else {
   345				i, err := strconv.ParseInt(start, 10, 64)
   346				if err != nil || i > size || i < 0 {
   347					return nil, errors.New("invalid range")
   348				}
   349				r.start = i
   350				if end == "" {
   351					// If no end is specified, range extends to end of the file.
   352					r.length = size - r.start
   353				} else {
   354					i, err := strconv.ParseInt(end, 10, 64)
   355					if err != nil || r.start > i {
   356						return nil, errors.New("invalid range")
   357					}
   358					if i >= size {
   359						i = size - 1
   360					}
   361					r.length = i - r.start + 1
   362				}
   363			}
   364			ranges = append(ranges, r)
   365		}
   366		return ranges, nil
   367	}