X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/9ccff2073a124639eec457e4fb47d9cbf2527d04..bcf8d387aaed911d955e1f26142caba785cd4e07:/sdk/go/keepclient/hashcheck.go

diff --git a/sdk/go/keepclient/hashcheck.go b/sdk/go/keepclient/hashcheck.go
index 1f696d95b6..9295c14cc2 100644
--- a/sdk/go/keepclient/hashcheck.go
+++ b/sdk/go/keepclient/hashcheck.go
@@ -1,8 +1,7 @@
-// Lightweight implementation of io.ReadCloser that checks the contents read
-// from the underlying io.Reader a against checksum hash.  To avoid reading the
-// entire contents into a buffer up front, the hash is updated with each read,
-// and the actual checksum is not checked until the underlying reader returns
-// EOF.
+// Copyright (C) The Arvados Authors. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package keepclient
 
 import (
@@ -14,27 +13,29 @@ import (
 
 var BadChecksum = errors.New("Reader failed checksum")
 
+// HashCheckingReader is an io.ReadCloser that checks the contents
+// read from the underlying io.Reader against the provided hash.
 type HashCheckingReader struct {
 	// The underlying data source
 	io.Reader
 
-	// The hashing function to use
+	// The hash function to use
 	hash.Hash
 
 	// The hash value to check against.  Must be a hex-encoded lowercase string.
 	Check string
 }
 
-// Read from the underlying reader, update the hashing function, and pass the
-// results through.  Will return BadChecksum on the last read instead of EOF if
-// the checksum doesn't match.
+// Reads from the underlying reader, update the hashing function, and
+// pass the results through. Returns BadChecksum (instead of EOF) on
+// the last read if the checksum doesn't match.
 func (this HashCheckingReader) Read(p []byte) (n int, err error) {
 	n, err = this.Reader.Read(p)
 	if n > 0 {
 		this.Hash.Write(p[:n])
 	}
 	if err == io.EOF {
-		sum := this.Hash.Sum(make([]byte, 0, this.Hash.Size()))
+		sum := this.Hash.Sum(nil)
 		if fmt.Sprintf("%x", sum) != this.Check {
 			err = BadChecksum
 		}
@@ -42,8 +43,9 @@ func (this HashCheckingReader) Read(p []byte) (n int, err error) {
 	return n, err
 }
 
-// Write entire contents of this.Reader to 'dest'.  Returns BadChecksum if the
-// data written to 'dest' doesn't match the hash code of this.Check.
+// WriteTo writes the entire contents of this.Reader to dest. Returns
+// BadChecksum if writing is successful but the checksum doesn't
+// match.
 func (this HashCheckingReader) WriteTo(dest io.Writer) (written int64, err error) {
 	if writeto, ok := this.Reader.(io.WriterTo); ok {
 		written, err = writeto.WriteTo(io.MultiWriter(dest, this.Hash))
@@ -51,28 +53,35 @@ func (this HashCheckingReader) WriteTo(dest io.Writer) (written int64, err error
 		written, err = io.Copy(io.MultiWriter(dest, this.Hash), this.Reader)
 	}
 
-	sum := this.Hash.Sum(make([]byte, 0, this.Hash.Size()))
+	if err != nil {
+		return written, err
+	}
 
+	sum := this.Hash.Sum(nil)
 	if fmt.Sprintf("%x", sum) != this.Check {
-		err = BadChecksum
+		return written, BadChecksum
 	}
 
-	return written, err
+	return written, nil
 }
 
-// Close() the underlying Reader if it is castable to io.ReadCloser.  This will
-// drain the underlying reader of any remaining data and check the checksum.
+// Close reads all remaining data from the underlying Reader and
+// returns BadChecksum if the checksum doesn't match. It also closes
+// the underlying Reader if it implements io.ReadCloser.
 func (this HashCheckingReader) Close() (err error) {
 	_, err = io.Copy(this.Hash, this.Reader)
 
-	if closer, ok := this.Reader.(io.ReadCloser); ok {
-		err = closer.Close()
+	if closer, ok := this.Reader.(io.Closer); ok {
+		closeErr := closer.Close()
+		if err == nil {
+			err = closeErr
+		}
 	}
-
-	sum := this.Hash.Sum(make([]byte, 0, this.Hash.Size()))
-	if fmt.Sprintf("%x", sum) != this.Check {
-		err = BadChecksum
+	if err != nil {
+		return err
 	}
-
-	return err
+	if fmt.Sprintf("%x", this.Hash.Sum(nil)) != this.Check {
+		return BadChecksum
+	}
+	return nil
 }