cache read performance improvements

pkg/provider/crypto/reader.go

@@ -10,7 +10,11 @@ import (
 
 type cryptoReader interface {
 	io.Reader
-	io.ReaderAt
+}
+
+type nonce struct {
+	N [NonceSize]byte
+	C int
 }
 
 type reader struct {
@@ -21,9 +25,10 @@ type reader struct {
 	buf    [FullSize]byte
 	off    int64
 
-	err   error
-	nonce [NonceSize]byte
-	cn    int64
+	err    error
+	nonce  [NonceSize]byte
+	cn     int64
+	outBuf []byte
 }
 
 func newReader(key []byte, src cryptoReader) (*reader, error) {
@@ -32,9 +37,10 @@ func newReader(key []byte, src cryptoReader) (*reader, error) {
 		return nil, err
 	}
 	return &reader{
-		a:   aead,
-		src: src,
-		cn:  -1,
+		a:      aead,
+		src:    src,
+		cn:     -1,
+		outBuf: make([]byte, 0, FullSize),
 	}, nil
 }
 
@@ -91,19 +97,24 @@ func (r *reader) readChunk() (last bool, err error) {
 		return false, err
 	}
 
-	outBuf := make([]byte, 0, ChunkSize)
-	out, err := r.a.Open(outBuf, r.nonce[:], in, nil)
+	//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.
 		last = true
 		setLastChunkFlag(&r.nonce)
-		out, err = r.a.Open(outBuf, r.nonce[:], in, nil)
+		out, err = r.a.Open(r.outBuf, r.nonce[:], in, nil)
 	}
 	if err != nil {
 		return false, errors.New("failed to decrypt and authenticate payload chunk")
 	}
 
 	incNonce(&r.nonce)
-	r.unread = r.buf[:copy(r.buf[:], out)]
+	//r.unread = r.buf[:copy(r.buf[:], out)]
+	size := FullSize
+	if len(out) < FullSize {
+		size = len(out)
+	}
+	r.unread = out[:size]
 	return last, nil
 }