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// 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 (
"fmt"
"io"
"mime"
"os"
"path/filepath"
"strconv"
"strings"
"time"
"utf8"
)
// Heuristic: b is text if it is valid UTF-8 and doesn't
// contain any unprintable ASCII or Unicode characters.
func isText(b []byte) bool {
for len(b) > 0 && utf8.FullRune(b) {
rune, size := utf8.DecodeRune(b)
if size == 1 && rune == utf8.RuneError {
// decoding error
return false
}
if 0x7F <= rune && rune <= 0x9F {
return false
}
if rune < ' ' {
switch rune {
case '\n', '\r', '\t':
// okay
default:
// binary garbage
return false
}
}
b = b[size:]
}
return true
}
func dirList(w ResponseWriter, f *os.File) {
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.IsDirectory() {
name += "/"
}
// TODO htmlescape
fmt.Fprintf(w, "<a href=\"%s\">%s</a>\n", name, name)
}
}
fmt.Fprintf(w, "</pre>\n")
}
func serveFile(w ResponseWriter, r *Request, name string, redirect bool) {
const indexPage = "/index.html"
// redirect .../index.html to .../
if strings.HasSuffix(r.URL.Path, indexPage) {
Redirect(w, r, r.URL.Path[0:len(r.URL.Path)-len(indexPage)+1], StatusMovedPermanently)
return
}
f, err := os.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.IsDirectory() {
if url[len(url)-1] != '/' {
Redirect(w, r, url+"/", StatusMovedPermanently)
return
}
} else {
if url[len(url)-1] == '/' {
Redirect(w, r, url[0:len(url)-1], StatusMovedPermanently)
return
}
}
}
if t, _ := time.Parse(TimeFormat, r.Header.Get("If-Modified-Since")); t != nil && d.Mtime_ns/1e9 <= t.Seconds() {
w.WriteHeader(StatusNotModified)
return
}
w.Header().Set("Last-Modified", time.SecondsToUTC(d.Mtime_ns/1e9).Format(TimeFormat))
// use contents of index.html for directory, if present
if d.IsDirectory() {
index := name + filepath.FromSlash(indexPage)
ff, err := os.Open(index)
if err == nil {
defer ff.Close()
dd, err := ff.Stat()
if err == nil {
name = index
d = dd
f = ff
}
}
}
if d.IsDirectory() {
dirList(w, f)
return
}
// serve file
size := d.Size
code := StatusOK
// If Content-Type isn't set, use the file's extension to find it.
if w.Header().Get("Content-Type") == "" {
ctype := mime.TypeByExtension(filepath.Ext(name))
if ctype == "" {
// read a chunk to decide between utf-8 text and binary
var buf [1024]byte
n, _ := io.ReadFull(f, buf[:])
b := buf[:n]
if isText(b) {
ctype = "text/plain; charset=utf-8"
} else {
// generic binary
ctype = "application/octet-stream"
}
f.Seek(0, os.SEEK_SET) // rewind to output whole file
}
w.Header().Set("Content-Type", ctype)
}
// handle Content-Range header.
// TODO(adg): handle multiple ranges
ranges, err := parseRange(r.Header.Get("Range"), size)
if err == nil && len(ranges) > 1 {
err = os.NewError("multiple ranges not supported")
}
if err != nil {
Error(w, err.String(), StatusRequestedRangeNotSatisfiable)
return
}
if len(ranges) == 1 {
ra := ranges[0]
if _, err := f.Seek(ra.start, os.SEEK_SET); err != nil {
Error(w, err.String(), StatusRequestedRangeNotSatisfiable)
return
}
size = ra.length
code = StatusPartialContent
w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", ra.start, ra.start+ra.length-1, d.Size))
}
w.Header().Set("Accept-Ranges", "bytes")
if w.Header().Get("Content-Encoding") == "" {
w.Header().Set("Content-Length", strconv.Itoa64(size))
}
w.WriteHeader(code)
if r.Method != "HEAD" {
io.Copyn(w, f, size)
}
}
// ServeFile replies to the request with the contents of the named file or directory.
func ServeFile(w ResponseWriter, r *Request, name string) {
serveFile(w, r, name, false)
}
type fileHandler struct {
root string
prefix string
}
// FileServer returns a handler that serves HTTP requests
// with the contents of the file system rooted at root.
// It strips prefix from the incoming requests before
// looking up the file name in the file system.
func FileServer(root, prefix string) Handler { return &fileHandler{root, prefix} }
func (f *fileHandler) ServeHTTP(w ResponseWriter, r *Request) {
path := r.URL.Path
if !strings.HasPrefix(path, f.prefix) {
NotFound(w, r)
return
}
path = path[len(f.prefix):]
serveFile(w, r, filepath.Join(f.root, filepath.FromSlash(path)), true)
}
// httpRange specifies the byte range to be sent to the client.
type httpRange struct {
start, length int64
}
// parseRange parses a Range header string as per RFC 2616.
func parseRange(s string, size int64) ([]httpRange, os.Error) {
if s == "" {
return nil, nil // header not present
}
const b = "bytes="
if !strings.HasPrefix(s, b) {
return nil, os.NewError("invalid range")
}
var ranges []httpRange
for _, ra := range strings.Split(s[len(b):], ",", -1) {
i := strings.Index(ra, "-")
if i < 0 {
return nil, os.NewError("invalid range")
}
start, end := ra[:i], 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.Atoi64(end)
if err != nil {
return nil, os.NewError("invalid range")
}
if i > size {
i = size
}
r.start = size - i
r.length = size - r.start
} else {
i, err := strconv.Atoi64(start)
if err != nil || i > size || i < 0 {
return nil, os.NewError("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.Atoi64(end)
if err != nil || r.start > i {
return nil, os.NewError("invalid range")
}
if i >= size {
i = size - 1
}
r.length = i - r.start + 1
}
}
ranges = append(ranges, r)
}
return ranges, nil
}