webdav: add an ownCloud Infinite Scale vendor that enables tus chunked upload support

This change adds a new vendor called "infinitescale" to the webdav
backend. It enables the ownCloud Infinite Scale
https://github.com/owncloud/ocis project and implements its specific
chunked uploader following the tus protocol https://tus.io

Signed-off-by: Christian Richter <crichter@owncloud.com>
Co-authored-by: Klaas Freitag <klaas.freitag@kiteworks.com>
Co-authored-by: Christian Richter <crichter@owncloud.com>
Co-authored-by: Christian Richter <1058116+dragonchaser@users.noreply.github.com>
Co-authored-by: Ralf Haferkamp <r.haferkamp@opencloud.eu>

backend/webdav/tus-upload.go

@@ -0,0 +1,88 @@
+package webdav
+
+import (
+	"bytes"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// Metadata is a typedef for a string to string map to hold metadata
+type Metadata map[string]string
+
+// Upload is a struct containing the file status during upload
+type Upload struct {
+	stream io.ReadSeeker
+	size   int64
+	offset int64
+
+	Fingerprint string
+	Metadata    Metadata
+}
+
+// Updates the Upload information based on offset.
+func (u *Upload) updateProgress(offset int64) {
+	u.offset = offset
+}
+
+// Finished returns whether this upload is finished or not.
+func (u *Upload) Finished() bool {
+	return u.offset >= u.size
+}
+
+// Progress returns the progress in a percentage.
+func (u *Upload) Progress() int64 {
+	return (u.offset * 100) / u.size
+}
+
+// Offset returns the current upload offset.
+func (u *Upload) Offset() int64 {
+	return u.offset
+}
+
+// Size returns the size of the upload body.
+func (u *Upload) Size() int64 {
+	return u.size
+}
+
+// EncodedMetadata encodes the upload metadata.
+func (u *Upload) EncodedMetadata() string {
+	var encoded []string
+
+	for k, v := range u.Metadata {
+		encoded = append(encoded, fmt.Sprintf("%s %s", k, b64encode(v)))
+	}
+
+	return strings.Join(encoded, ",")
+}
+
+func b64encode(s string) string {
+	return base64.StdEncoding.EncodeToString([]byte(s))
+}
+
+// NewUpload creates a new upload from an io.Reader.
+func NewUpload(reader io.Reader, size int64, metadata Metadata, fingerprint string) *Upload {
+	stream, ok := reader.(io.ReadSeeker)
+
+	if !ok {
+		buf := new(bytes.Buffer)
+		_, err := buf.ReadFrom(reader)
+		if err != nil {
+			return nil
+		}
+		stream = bytes.NewReader(buf.Bytes())
+	}
+
+	if metadata == nil {
+		metadata = make(Metadata)
+	}
+
+	return &Upload{
+		stream: stream,
+		size:   size,
+
+		Fingerprint: fingerprint,
+		Metadata:    metadata,
+	}
+}