http: add MultipartForm, FormFile, and ParseMultipartForm to Request

R=rsc, bradfitz
CC=golang-dev
https://golang.org/cl/4431068

src/pkg/http/request.go

@@ -28,8 +28,13 @@ const (
 	maxValueLength   = 4096
 	maxHeaderLines   = 1024
 	chunkSize        = 4 << 10  // 4 KB chunks
+	defaultMaxMemory = 32 << 20 // 32 MB
 )
 
+// ErrMissingFile is returned by FormFile when the provided file field name
+// is either not present in the request or not a file field.
+var ErrMissingFile = os.ErrorString("http: no such file")
+
 // HTTP request parsing errors.
 type ProtocolError struct {
 	os.ErrorString
@@ -136,6 +141,10 @@ type Request struct {
 	// The parsed form. Only available after ParseForm is called.
 	Form map[string][]string
 
+	// The parsed multipart form, including file uploads.
+	// Only available after ParseMultipartForm is called.
+	MultipartForm *multipart.Form
+
 	// Trailer maps trailer keys to values.  Like for Header, if the
 	// response has multiple trailer lines with the same key, they will be
 	// concatenated, delimited by commas.
@@ -165,9 +174,30 @@ func (r *Request) ProtoAtLeast(major, minor int) bool {
 		r.ProtoMajor == major && r.ProtoMinor >= minor
 }
 
+// multipartByReader is a sentinel value.
+// Its presence in Request.MultipartForm indicates that parsing of the request
+// body has been handed off to a MultipartReader instead of ParseMultipartFrom.
+var multipartByReader = &multipart.Form{
+	Value: make(map[string][]string),
+	File:  make(map[string][]*multipart.FileHeader),
+}
+
 // MultipartReader returns a MIME multipart reader if this is a
 // multipart/form-data POST request, else returns nil and an error.
+// Use this function instead of ParseMultipartForm to
+// process the request body as a stream.
 func (r *Request) MultipartReader() (multipart.Reader, os.Error) {
+	if r.MultipartForm == multipartByReader {
+		return nil, os.NewError("http: MultipartReader called twice")
+	}
+	if r.MultipartForm != nil {
+		return nil, os.NewError("http: multipart handled by ParseMultipartForm")
+	}
+	r.MultipartForm = multipartByReader
+	return r.multipartReader()
+}
+
+func (r *Request) multipartReader() (multipart.Reader, os.Error) {
 	v := r.Header.Get("Content-Type")
 	if v == "" {
 		return nil, ErrNotMultipart
@@ -578,7 +608,9 @@ func parseQuery(m map[string][]string, query string) (err os.Error) {
 	return err
 }
 
-// ParseForm parses the request body as a form for POST requests, or the raw query for GET requests.
+// ParseForm parses the raw query.
+// For POST requests, it also parses the request body as a form.
+// ParseMultipartForm calls ParseForm automatically.
 // It is idempotent.
 func (r *Request) ParseForm() (err os.Error) {
 	if r.Form != nil {
@@ -611,7 +643,8 @@ func (r *Request) ParseForm() (err os.Error) {
 			if err == nil {
 				err = e
 			}
-		// TODO(dsymonds): Handle multipart/form-data
+		case "multipart/form-data":
+			// handled by ParseMultipartForm
 		default:
 			return &badStringError{"unknown Content-Type", ct}
 		}
@@ -619,11 +652,50 @@ func (r *Request) ParseForm() (err os.Error) {
 	return err
 }
 
+// ParseMultipartForm parses a request body as multipart/form-data.
+// The whole request body is parsed and up to a total of maxMemory bytes of
+// its file parts are stored in memory, with the remainder stored on
+// disk in temporary files.
+// ParseMultipartForm calls ParseForm if necessary.
+// After one call to ParseMultipartForm, subsequent calls have no effect.
+func (r *Request) ParseMultipartForm(maxMemory int64) os.Error {
+	if r.Form == nil {
+		err := r.ParseForm()
+		if err != nil {
+			return err
+		}
+	}
+	if r.MultipartForm != nil {
+		return nil
+	}
+	if r.MultipartForm == multipartByReader {
+		return os.NewError("http: multipart handled by MultipartReader")
+	}
+
+	mr, err := r.multipartReader()
+	if err == ErrNotMultipart {
+		return nil
+	} else if err != nil {
+		return err
+	}
+
+	f, err := mr.ReadForm(maxMemory)
+	if err != nil {
+		return err
+	}
+	for k, v := range f.Value {
+		r.Form[k] = append(r.Form[k], v...)
+	}
+	r.MultipartForm = f
+
+	return nil
+}
+
 // FormValue returns the first value for the named component of the query.
-// FormValue calls ParseForm if necessary.
+// FormValue calls ParseMultipartForm and ParseForm if necessary.
 func (r *Request) FormValue(key string) string {
 	if r.Form == nil {
-		r.ParseForm()
+		r.ParseMultipartForm(defaultMaxMemory)
 	}
 	if vs := r.Form[key]; len(vs) > 0 {
 		return vs[0]
@@ -631,6 +703,25 @@ func (r *Request) FormValue(key string) string {
 	return ""
 }
 
+// FormFile returns the first file for the provided form key.
+// FormFile calls ParseMultipartForm and ParseForm if necessary.
+func (r *Request) FormFile(key string) (multipart.File, *multipart.FileHeader, os.Error) {
+	if r.MultipartForm == multipartByReader {
+		return nil, nil, os.NewError("http: multipart handled by MultipartReader")
+	}
+	if r.MultipartForm == nil {
+		err := r.ParseMultipartForm(defaultMaxMemory)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+	if fhs := r.MultipartForm.File[key]; len(fhs) > 0 {
+		f, err := fhs[0].Open()
+		return f, fhs[0], err
+	}
+	return nil, nil, ErrMissingFile
+}
+
 func (r *Request) expectsContinue() bool {
 	return strings.ToLower(r.Header.Get("Expect")) == "100-continue"
 }

src/pkg/http/request_test.go

@@ -10,6 +10,8 @@ import (
 	. "http"
 	"http/httptest"
 	"io"
+	"io/ioutil"
+	"mime/multipart"
 	"os"
 	"reflect"
 	"regexp"
@@ -82,7 +84,7 @@ func TestPostQuery(t *testing.T) {
 	req.Header = Header{
 		"Content-Type": {"application/x-www-form-urlencoded; boo!"},
 	}
-	req.Body = nopCloser{strings.NewReader("z=post&both=y")}
+	req.Body = ioutil.NopCloser(strings.NewReader("z=post&both=y"))
 	if q := req.FormValue("q"); q != "foo" {
 		t.Errorf(`req.FormValue("q") = %q, want "foo"`, q)
 	}
@@ -115,7 +117,7 @@ func TestPostContentTypeParsing(t *testing.T) {
 		req := &Request{
 			Method: "POST",
 			Header: Header(test.contentType),
-			Body:   nopCloser{bytes.NewBufferString("body")},
+			Body:   ioutil.NopCloser(bytes.NewBufferString("body")),
 		}
 		err := req.ParseForm()
 		if !test.error && err != nil {
@@ -131,7 +133,7 @@ func TestMultipartReader(t *testing.T) {
 	req := &Request{
 		Method: "POST",
 		Header: Header{"Content-Type": {`multipart/form-data; boundary="foo123"`}},
-		Body:   nopCloser{new(bytes.Buffer)},
+		Body:   ioutil.NopCloser(new(bytes.Buffer)),
 	}
 	multipart, err := req.MultipartReader()
 	if multipart == nil {
@@ -170,9 +172,115 @@ func TestRedirect(t *testing.T) {
 	}
 }
 
-// TODO: stop copy/pasting this around.  move to io/ioutil?
-type nopCloser struct {
-	io.Reader
+func TestMultipartRequest(t *testing.T) {
+	// Test that we can read the values and files of a 
+	// multipart request with FormValue and FormFile,
+	// and that ParseMultipartForm can be called multiple times.
+	req := newTestMultipartRequest(t)
+	if err := req.ParseMultipartForm(25); err != nil {
+		t.Fatal("ParseMultipartForm first call:", err)
+	}
+	defer req.MultipartForm.RemoveAll()
+	validateTestMultipartContents(t, req, false)
+	if err := req.ParseMultipartForm(25); err != nil {
+		t.Fatal("ParseMultipartForm second call:", err)
+	}
+	validateTestMultipartContents(t, req, false)
+}
+
+func TestMultipartRequestAuto(t *testing.T) {
+	// Test that FormValue and FormFile automatically invoke
+	// ParseMultipartForm and return the right values.
+	req := newTestMultipartRequest(t)
+	defer func() {
+		if req.MultipartForm != nil {
+			req.MultipartForm.RemoveAll()
+		}
+	}()
+	validateTestMultipartContents(t, req, true)
+}
+
+func newTestMultipartRequest(t *testing.T) *Request {
+	b := bytes.NewBufferString(strings.Replace(message, "\n", "\r\n", -1))
+	req, err := NewRequest("POST", "/", b)
+	if err != nil {
+		t.Fatalf("NewRequest:", err)
+	}
+	ctype := fmt.Sprintf(`multipart/form-data; boundary="%s"`, boundary)
+	req.Header.Set("Content-type", ctype)
+	return req
+}
+
+func validateTestMultipartContents(t *testing.T, req *Request, allMem bool) {
+	if g, e := req.FormValue("texta"), textaValue; g != e {
+		t.Errorf("texta value = %q, want %q", g, e)
+	}
+	if g, e := req.FormValue("texta"), textaValue; g != e {
+		t.Errorf("texta value = %q, want %q", g, e)
+	}
+
+	assertMem := func(n string, fd multipart.File) {
+		if _, ok := fd.(*os.File); ok {
+			t.Error(n, " is *os.File, should not be")
+		}
+	}
+	fd := testMultipartFile(t, req, "filea", "filea.txt", fileaContents)
+	assertMem("filea", fd)
+	fd = testMultipartFile(t, req, "fileb", "fileb.txt", filebContents)
+	if allMem {
+		assertMem("fileb", fd)
+	} else {
+		if _, ok := fd.(*os.File); !ok {
+			t.Errorf("fileb has unexpected underlying type %T", fd)
+		}
+	}
+}
+
+func testMultipartFile(t *testing.T, req *Request, key, expectFilename, expectContent string) multipart.File {
+	f, fh, err := req.FormFile(key)
+	if err != nil {
+		t.Fatalf("FormFile(%q):", key, err)
+	}
+	if fh.Filename != expectFilename {
+		t.Errorf("filename = %q, want %q", fh.Filename, expectFilename)
+	}
+	var b bytes.Buffer
+	_, err = io.Copy(&b, f)
+	if err != nil {
+		t.Fatal("copying contents:", err)
+	}
+	if g := b.String(); g != expectContent {
+		t.Errorf("contents = %q, want %q", g, expectContent)
+	}
+	return f
 }
 
-func (nopCloser) Close() os.Error { return nil }
+const (
+	fileaContents = "This is a test file."
+	filebContents = "Another test file."
+	textaValue    = "foo"
+	textbValue    = "bar"
+	boundary      = `MyBoundary`
+)
+
+const message = `
+--MyBoundary
+Content-Disposition: form-data; name="filea"; filename="filea.txt"
+Content-Type: text/plain
+
+` + fileaContents + `
+--MyBoundary
+Content-Disposition: form-data; name="fileb"; filename="fileb.txt"
+Content-Type: text/plain
+
+` + filebContents + `
+--MyBoundary
+Content-Disposition: form-data; name="texta"
+
+` + textaValue + `
+--MyBoundary
+Content-Disposition: form-data; name="textb"
+
+` + textbValue + `
+--MyBoundary--
+`

src/pkg/http/server.go

@@ -423,6 +423,9 @@ func (w *response) finishRequest() {
 	}
 	w.conn.buf.Flush()
 	w.req.Body.Close()
+	if w.req.MultipartForm != nil {
+		w.req.MultipartForm.RemoveAll()
+	}
 
 	if w.contentLength != -1 && w.contentLength != w.written {
 		// Did not write enough. Avoid getting out of sync.