google cloud storage: Fix memory leak - fixes #17

This was the same problem as issue #5 (which affected google drive)

drive/drive.go

@@ -21,7 +21,6 @@ import (
 	"log"
 	"mime"
 	"net/http"
-	"os"
 	"path"
 	"strings"
 	"sync"
@@ -603,30 +602,6 @@ func (f *FsDrive) ListDir() fs.DirChan {
 	return out
 }
 
-// seekWrapper wraps an io.Reader with a basic Seek for
-// code.google.com/p/google-api-go-client/googleapi
-// to detect the length (see getReaderSize function)
-type seekWrapper struct {
-	in   io.Reader
-	size int64
-}
-
-// Read bytes from the object - see io.Reader
-func (file *seekWrapper) Read(p []byte) (n int, err error) {
-	return file.in.Read(p)
-}
-
-// Seek - minimal implementation for Google Drive's length detection
-func (file *seekWrapper) Seek(offset int64, whence int) (int64, error) {
-	switch whence {
-	case os.SEEK_CUR:
-		return 0, nil
-	case os.SEEK_END:
-		return file.size, nil
-	}
-	return 0, nil
-}
-
 // Put the object
 //
 // This assumes that the object doesn't not already exists - if you
@@ -663,7 +638,7 @@ func (f *FsDrive) Put(in io.Reader, remote string, modTime time.Time, size int64
 	}
 
 	// Make the API request to upload metadata and file data.
-	in = &seekWrapper{in: in, size: size}
+	in = &fs.SeekWrapper{In: in, Size: size}
 	info, err = f.svc.Files.Insert(info).Media(in).Do()
 	if err != nil {
 		return o, fmt.Errorf("Upload failed: %s", err)
@@ -872,7 +847,7 @@ func (o *FsObjectDrive) Update(in io.Reader, modTime time.Time, size int64) erro
 	}
 
 	// Make the API request to upload metadata and file data.
-	in = &seekWrapper{in: in, size: size}
+	in = &fs.SeekWrapper{In: in, Size: size}
 	info, err := o.drive.svc.Files.Update(info.Id, info).SetModifiedDate(true).Media(in).Do()
 	if err != nil {
 		return fmt.Errorf("Update failed: %s", err)

fs/seekwrapper.go

@@ -0,0 +1,39 @@
+package fs
+
+import (
+	"io"
+	"os"
+)
+
+// SeekWrapper wraps an io.Reader with a basic Seek method which
+// returns the Size attribute.
+//
+// This is used for google.golang.org/api/googleapi/googleapi.go
+// to detect the length (see getReaderSize function)
+//
+// Without this the getReaderSize function reads the entire file into
+// memory to find its length.
+type SeekWrapper struct {
+	In   io.Reader
+	Size int64
+}
+
+// Read bytes from the object - see io.Reader
+func (file *SeekWrapper) Read(p []byte) (n int, err error) {
+	return file.In.Read(p)
+}
+
+// Seek - minimal implementation for Google API length detection
+func (file *SeekWrapper) Seek(offset int64, whence int) (int64, error) {
+	switch whence {
+	case os.SEEK_CUR:
+		return 0, nil
+	case os.SEEK_END:
+		return file.Size, nil
+	}
+	return 0, nil
+}
+
+// Interfaces that SeekWrapper implements
+var _ io.Reader = (*SeekWrapper)(nil)
+var _ io.Seeker = (*SeekWrapper)(nil)

googlecloudstorage/googlecloudstorage.go

@@ -359,8 +359,9 @@ func (f *FsStorage) ListDir() fs.DirChan {
 // The new object may have been created if an error is returned
 func (f *FsStorage) Put(in io.Reader, remote string, modTime time.Time, size int64) (fs.Object, error) {
 	// Temporary FsObject under construction
-	fs := &FsObjectStorage{storage: f, remote: remote}
-	return fs, fs.Update(in, modTime, size)
+	o := &FsObjectStorage{storage: f, remote: remote}
+	in = &fs.SeekWrapper{In: in, Size: size}
+	return o, o.Update(in, modTime, size)
 }
 
 // Mkdir creates the bucket if it doesn't exist
@@ -562,6 +563,7 @@ func (o *FsObjectStorage) Update(in io.Reader, modTime time.Time, size int64) er
 		Updated:     modTime.Format(timeFormatOut), // Doesn't get set
 		Metadata:    metadataFromModTime(modTime),
 	}
+	in = &fs.SeekWrapper{In: in, Size: size}
 	newObject, err := o.storage.svc.Objects.Insert(o.storage.bucket, &object).Media(in).Name(object.Name).PredefinedAcl(o.storage.objectAcl).Do()
 	if err != nil {
 		return err