15370: Fix flaky test.

[arvados.git] / sdk / go / keepclient / hashcheck.go

diff --git a/sdk/go/keepclient/hashcheck.go b/sdk/go/keepclient/hashcheck.go
index 1f696d95b64d60f69c772063be7ae5b60e671cca..0966e072eae6d354ad8664d935ce290fb35f7649 100644 (file)
--- 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 (
@@ -14,65 +13,75 @@ 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.
-func (this HashCheckingReader) Read(p []byte) (n int, err error) {
-       n, err = this.Reader.Read(p)
+// 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 (hcr HashCheckingReader) Read(p []byte) (n int, err error) {
+       n, err = hcr.Reader.Read(p)
        if n > 0 {
-               this.Hash.Write(p[:n])
+               hcr.Hash.Write(p[:n])
        }
        if err == io.EOF {
-               sum := this.Hash.Sum(make([]byte, 0, this.Hash.Size()))
-               if fmt.Sprintf("%x", sum) != this.Check {
+               sum := hcr.Hash.Sum(nil)
+               if fmt.Sprintf("%x", sum) != hcr.Check {
                        err = BadChecksum
                }
        }
        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.
-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))
+// WriteTo writes the entire contents of hcr.Reader to dest. Returns
+// BadChecksum if writing is successful but the checksum doesn't
+// match.
+func (hcr HashCheckingReader) WriteTo(dest io.Writer) (written int64, err error) {
+       if writeto, ok := hcr.Reader.(io.WriterTo); ok {
+               written, err = writeto.WriteTo(io.MultiWriter(dest, hcr.Hash))
        } else {
-               written, err = io.Copy(io.MultiWriter(dest, this.Hash), this.Reader)
+               written, err = io.Copy(io.MultiWriter(dest, hcr.Hash), hcr.Reader)
        }
 
-       sum := this.Hash.Sum(make([]byte, 0, this.Hash.Size()))
+       if err != nil {
+               return written, err
+       }
 
-       if fmt.Sprintf("%x", sum) != this.Check {
-               err = BadChecksum
+       sum := hcr.Hash.Sum(nil)
+       if fmt.Sprintf("%x", sum) != hcr.Check {
+               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.
-func (this HashCheckingReader) Close() (err error) {
-       _, err = io.Copy(this.Hash, this.Reader)
+// 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 (hcr HashCheckingReader) Close() (err error) {
+       _, err = io.Copy(hcr.Hash, hcr.Reader)
 
-       if closer, ok := this.Reader.(io.ReadCloser); ok {
-               err = closer.Close()
+       if closer, ok := hcr.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", hcr.Hash.Sum(nil)) != hcr.Check {
+               return BadChecksum
+       }
+       return nil
 }