more async improvements and crypto bugfix

pkg/provider/crypto/file.go

@@ -139,7 +139,6 @@ func (f *file) Seek(offset int64, whence int) (n int64, err error) {
 		return
 	}
 	f.nonce = [NonceSize]byte{}
-	//inc(&f.nonce, cn)
 	put(&f.nonce, cn)
 	f.r.nonce = f.nonce
 	f.w.nonce = f.nonce
@@ -184,26 +183,32 @@ func (f *file) ReadAt(p []byte, pos int64) (n int, err error) {
 func (f *file) WriteAt(data []byte, pos int64) (n int, err error) {
 	f.wmu.Lock()
 	defer f.wmu.Unlock()
-	cn, off, woff := align(pos)
-	c, ok := f.w.cm[cn]
-	if !ok {
-		c = &chunkWriter{offset: off + KDFNonceSize, w: f.w, cn: cn}
-		//inc(&c.nonce, cn)
-		put(&c.nonce, cn)
-		f.w.cm[cn] = c
-		if f.w.last == nil {
-			f.w.last = c
-		} else if cn > f.w.last.cn {
-			f.w.last = c
+	for n != len(data) {
+		cn, off, woff := align(pos + int64(n))
+		c, ok := f.w.cm[cn]
+		if !ok {
+			c = &chunkWriter{offset: off + KDFNonceSize, w: f.w, cn: cn}
+			put(&c.nonce, cn)
+			f.w.cm[cn] = c
+			if f.w.last == nil {
+				f.w.last = c
+			} else if cn > f.w.last.cn {
+				f.w.last = c
+			}
+		}
+		w, e := c.writeAt(data[n:], woff)
+		n += w
+		if c.full() {
+			// async flush
+			go func() {
+				c.flush(notLastChunk)
+			}()
+			delete(f.w.cm, cn)
+		}
+		if e != nil {
+			err = e
+			return
 		}
-	}
-	n, err = c.writeAt(data, woff)
-	if c.full() {
-		// async flush
-		go func() {
-			c.flush(notLastChunk)
-		}()
-		delete(f.w.cm, cn)
 	}
 	return
 }

pkg/provider/crypto/reader.go

@@ -97,7 +97,6 @@ func (r *reader) readChunk() (last bool, err error) {
 		return false, err
 	}
 
-	//outBuf := make([]byte, 0, ChunkSize)
 	out, err := r.a.Open(r.outBuf, r.nonce[:], in, nil)
 	if err != nil && !last {
 		// Check if this was a full-length final chunk.
@@ -110,7 +109,6 @@ func (r *reader) readChunk() (last bool, err error) {
 	}
 
 	incNonce(&r.nonce)
-	//r.unread = r.buf[:copy(r.buf[:], out)]
 	size := FullSize
 	if len(out) < FullSize {
 		size = len(out)