http: ServeFile to handle Range header for partial requests

and send Content-Length.

Also includes some testing of the server code.

R=rsc
CC=golang-dev
https://golang.org/cl/2831041

src/pkg/http/fs.go

@@ -12,6 +12,7 @@ import (
 	"mime"
 	"os"
 	"path"
+	"strconv"
 	"strings"
 	"time"
 	"utf8"
@@ -130,6 +131,9 @@ func serveFile(w ResponseWriter, r *Request, name string, redirect bool) {
 	}
 
 	// serve file
+	size := d.Size
+	code := StatusOK
+
 	// use extension to find content type.
 	ext := path.Ext(name)
 	if ctype := mime.TypeByExtension(ext); ctype != "" {
@@ -137,16 +141,40 @@ func serveFile(w ResponseWriter, r *Request, name string, redirect bool) {
 	} else {
 		// read first chunk to decide between utf-8 text and binary
 		var buf [1024]byte
-		n, _ := io.ReadFull(f, buf[0:])
-		b := buf[0:n]
+		n, _ := io.ReadFull(f, buf[:])
+		b := buf[:n]
 		if isText(b) {
 			w.SetHeader("Content-Type", "text-plain; charset=utf-8")
 		} else {
 			w.SetHeader("Content-Type", "application/octet-stream") // generic binary
 		}
-		w.Write(b)
+		f.Seek(0, 0) // rewind to output whole file
 	}
-	io.Copy(w, f)
+
+	// handle Content-Range header.
+	// TODO(adg): handle multiple ranges
+	ranges, err := parseRange(r.Header["Range"], size)
+	if err != nil || len(ranges) > 1 {
+		Error(w, err.String(), StatusRequestedRangeNotSatisfiable)
+		return
+	}
+	if len(ranges) == 1 {
+		ra := ranges[0]
+		if _, err := f.Seek(ra.start, 0); err != nil {
+			Error(w, err.String(), StatusRequestedRangeNotSatisfiable)
+			return
+		}
+		size = ra.length
+		code = StatusPartialContent
+		w.SetHeader("Content-Range", fmt.Sprintf("%d-%d/%d", ra.start, ra.start+ra.length, d.Size))
+	}
+
+	w.SetHeader("Accept-Ranges", "bytes")
+	w.SetHeader("Content-Length", strconv.Itoa64(size))
+
+	w.WriteHeader(code)
+
+	io.Copyn(w, f, size)
 }
 
 // ServeFile replies to the request with the contents of the named file or directory.
@@ -174,3 +202,62 @@ func (f *fileHandler) ServeHTTP(w ResponseWriter, r *Request) {
 	path = path[len(f.prefix):]
 	serveFile(w, r, f.root+"/"+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
+}

src/pkg/http/fs_test.go

@@ -0,0 +1,172 @@
+// Copyright 2010 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.
+
+package http
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os"
+	"sync"
+	"testing"
+)
+
+var ParseRangeTests = []struct {
+	s      string
+	length int64
+	r      []httpRange
+}{
+	{"", 0, nil},
+	{"foo", 0, nil},
+	{"bytes=", 0, nil},
+	{"bytes=5-4", 10, nil},
+	{"bytes=0-2,5-4", 10, nil},
+	{"bytes=0-9", 10, []httpRange{{0, 10}}},
+	{"bytes=0-", 10, []httpRange{{0, 10}}},
+	{"bytes=5-", 10, []httpRange{{5, 5}}},
+	{"bytes=0-20", 10, []httpRange{{0, 10}}},
+	{"bytes=15-,0-5", 10, nil},
+	{"bytes=-5", 10, []httpRange{{5, 5}}},
+	{"bytes=-15", 10, []httpRange{{0, 10}}},
+	{"bytes=0-499", 10000, []httpRange{{0, 500}}},
+	{"bytes=500-999", 10000, []httpRange{{500, 500}}},
+	{"bytes=-500", 10000, []httpRange{{9500, 500}}},
+	{"bytes=9500-", 10000, []httpRange{{9500, 500}}},
+	{"bytes=0-0,-1", 10000, []httpRange{{0, 1}, {9999, 1}}},
+	{"bytes=500-600,601-999", 10000, []httpRange{{500, 101}, {601, 399}}},
+	{"bytes=500-700,601-999", 10000, []httpRange{{500, 201}, {601, 399}}},
+}
+
+func TestParseRange(t *testing.T) {
+	for _, test := range ParseRangeTests {
+		r := test.r
+		ranges, err := parseRange(test.s, test.length)
+		if err != nil && r != nil {
+			t.Errorf("parseRange(%q) returned error %q", test.s, err)
+		}
+		if len(ranges) != len(r) {
+			t.Errorf("len(parseRange(%q)) = %d, want %d", test.s, len(ranges), len(r))
+			continue
+		}
+		for i := range r {
+			if ranges[i].start != r[i].start {
+				t.Errorf("parseRange(%q)[%d].start = %d, want %d", test.s, i, ranges[i].start, r[i].start)
+			}
+			if ranges[i].length != r[i].length {
+				t.Errorf("parseRange(%q)[%d].length = %d, want %d", test.s, i, ranges[i].length, r[i].length)
+			}
+		}
+	}
+}
+
+const (
+	testFile       = "testdata/file"
+	testFileLength = 11
+)
+
+var (
+	serverOnce sync.Once
+	serverAddr string
+)
+
+func startServer(t *testing.T) {
+	serverOnce.Do(func() {
+		HandleFunc("/ServeFile", func(w ResponseWriter, r *Request) {
+			ServeFile(w, r, "testdata/file")
+		})
+		l, err := net.Listen("tcp", "127.0.0.1:0")
+		if err != nil {
+			t.Fatal("listen:", err)
+		}
+		serverAddr = l.Addr().String()
+		go Serve(l, nil)
+	})
+}
+
+var ServeFileRangeTests = []struct {
+	start, end int
+	r          string
+	code       int
+}{
+	{0, testFileLength, "", StatusOK},
+	{0, 5, "0-4", StatusPartialContent},
+	{2, testFileLength, "2-", StatusPartialContent},
+	{testFileLength - 5, testFileLength, "-5", StatusPartialContent},
+	{3, 8, "3-7", StatusPartialContent},
+	{0, 0, "20-", StatusRequestedRangeNotSatisfiable},
+}
+
+func TestServeFile(t *testing.T) {
+	startServer(t)
+	var err os.Error
+
+	file, err := ioutil.ReadFile(testFile)
+	if err != nil {
+		t.Fatal("reading file:", err)
+	}
+
+	// set up the Request (re-used for all tests)
+	var req Request
+	req.Header = make(map[string]string)
+	if req.URL, err = ParseURL("http://" + serverAddr + "/ServeFile"); err != nil {
+		t.Fatal("ParseURL:", err)
+	}
+	req.Method = "GET"
+
+	// straight GET
+	_, body := getBody(t, req)
+	if !equal(body, file) {
+		t.Fatalf("body mismatch: got %q, want %q", body, file)
+	}
+
+	// Range tests
+	for _, rt := range ServeFileRangeTests {
+		req.Header["Range"] = "bytes=" + rt.r
+		if rt.r == "" {
+			req.Header["Range"] = ""
+		}
+		r, body := getBody(t, req)
+		if r.StatusCode != rt.code {
+			t.Errorf("range=%q: StatusCode=%d, want %d", rt.r, r.StatusCode, rt.code)
+		}
+		if rt.code == StatusRequestedRangeNotSatisfiable {
+			continue
+		}
+		h := fmt.Sprintf("%d-%d/%d", rt.start, rt.end, testFileLength)
+		if rt.r == "" {
+			h = ""
+		}
+		if r.Header["Content-Range"] != h {
+			t.Errorf("header mismatch: range=%q: got %q, want %q", rt.r, r.Header["Content-Range"], h)
+		}
+		if !equal(body, file[rt.start:rt.end]) {
+			t.Errorf("body mismatch: range=%q: got %q, want %q", rt.r, body, file[rt.start:rt.end])
+		}
+	}
+}
+
+func getBody(t *testing.T, req Request) (*Response, []byte) {
+	r, err := send(&req)
+	if err != nil {
+		t.Fatal(req.URL.String(), "send:", err)
+	}
+	b, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		t.Fatal("reading Body:", err)
+	}
+	return r, b
+}
+
+func equal(a, b []byte) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}

src/pkg/http/testdata/file

@@ -0,0 +1 @@
+0123456789