1 files changed, 182 insertions, 0 deletions
diff --git a/src/mime/multipart/formdata.go b/src/mime/multipart/formdata.go
new file mode 100644
index 0000000..fca5f9e
--- /dev/null
+++ b/src/mime/multipart/formdata.go
@@ -0,0 +1,182 @@
+// Copyright 2011 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 multipart
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"math"
+	"net/textproto"
+	"os"
+)
+
+// ErrMessageTooLarge is returned by ReadForm if the message form
+// data is too large to be processed.
+var ErrMessageTooLarge = errors.New("multipart: message too large")
+
+// TODO(adg,bradfitz): find a way to unify the DoS-prevention strategy here
+// with that of the http package's ParseForm.
+
+// ReadForm parses an entire multipart message whose parts have
+// a Content-Disposition of "form-data".
+// It stores up to maxMemory bytes + 10MB (reserved for non-file parts)
+// in memory. File parts which can't be stored in memory will be stored on
+// disk in temporary files.
+// It returns ErrMessageTooLarge if all non-file parts can't be stored in
+// memory.
+func (r *Reader) ReadForm(maxMemory int64) (*Form, error) {
+	return r.readForm(maxMemory)
+}
+
+func (r *Reader) readForm(maxMemory int64) (_ *Form, err error) {
+	form := &Form{make(map[string][]string), make(map[string][]*FileHeader)}
+	defer func() {
+		if err != nil {
+			form.RemoveAll()
+		}
+	}()
+
+	// Reserve an additional 10 MB for non-file parts.
+	maxValueBytes := maxMemory + int64(10<<20)
+	if maxValueBytes <= 0 {
+		if maxMemory < 0 {
+			maxValueBytes = 0
+		} else {
+			maxValueBytes = math.MaxInt64
+		}
+	}
+	for {
+		p, err := r.NextPart()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		name := p.FormName()
+		if name == "" {
+			continue
+		}
+		filename := p.FileName()
+
+		var b bytes.Buffer
+
+		if filename == "" {
+			// value, store as string in memory
+			n, err := io.CopyN(&b, p, maxValueBytes+1)
+			if err != nil && err != io.EOF {
+				return nil, err
+			}
+			maxValueBytes -= n
+			if maxValueBytes < 0 {
+				return nil, ErrMessageTooLarge
+			}
+			form.Value[name] = append(form.Value[name], b.String())
+			continue
+		}
+
+		// file, store in memory or on disk
+		fh := &FileHeader{
+			Filename: filename,
+			Header:   p.Header,
+		}
+		n, err := io.CopyN(&b, p, maxMemory+1)
+		if err != nil && err != io.EOF {
+			return nil, err
+		}
+		if n > maxMemory {
+			// too big, write to disk and flush buffer
+			file, err := os.CreateTemp("", "multipart-")
+			if err != nil {
+				return nil, err
+			}
+			size, err := io.Copy(file, io.MultiReader(&b, p))
+			if cerr := file.Close(); err == nil {
+				err = cerr
+			}
+			if err != nil {
+				os.Remove(file.Name())
+				return nil, err
+			}
+			fh.tmpfile = file.Name()
+			fh.Size = size
+		} else {
+			fh.content = b.Bytes()
+			fh.Size = int64(len(fh.content))
+			maxMemory -= n
+			maxValueBytes -= n
+		}
+		form.File[name] = append(form.File[name], fh)
+	}
+
+	return form, nil
+}
+
+// Form is a parsed multipart form.
+// Its File parts are stored either in memory or on disk,
+// and are accessible via the *FileHeader's Open method.
+// Its Value parts are stored as strings.
+// Both are keyed by field name.
+type Form struct {
+	Value map[string][]string
+	File  map[string][]*FileHeader
+}
+
+// RemoveAll removes any temporary files associated with a Form.
+func (f *Form) RemoveAll() error {
+	var err error
+	for _, fhs := range f.File {
+		for _, fh := range fhs {
+			if fh.tmpfile != "" {
+				e := os.Remove(fh.tmpfile)
+				if e != nil && err == nil {
+					err = e
+				}
+			}
+		}
+	}
+	return err
+}
+
+// A FileHeader describes a file part of a multipart request.
+type FileHeader struct {
+	Filename string
+	Header   textproto.MIMEHeader
+	Size     int64
+
+	content []byte
+	tmpfile string
+}
+
+// Open opens and returns the FileHeader's associated File.
+func (fh *FileHeader) Open() (File, error) {
+	if b := fh.content; b != nil {
+		r := io.NewSectionReader(bytes.NewReader(b), 0, int64(len(b)))
+		return sectionReadCloser{r}, nil
+	}
+	return os.Open(fh.tmpfile)
+}
+
+// File is an interface to access the file part of a multipart message.
+// Its contents may be either stored in memory or on disk.
+// If stored on disk, the File's underlying concrete type will be an *os.File.
+type File interface {
+	io.Reader
+	io.ReaderAt
+	io.Seeker
+	io.Closer
+}
+
+// helper types to turn a []byte into a File
+
+type sectionReadCloser struct {
+	*io.SectionReader
+}
+
+func (rc sectionReadCloser) Close() error {
+	return nil
+}