Merge branch '10700-dispatch'

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

diff --git a/sdk/go/keepclient/hashcheck.go b/sdk/go/keepclient/hashcheck.go
index a585d0088833d08994b3891361623b3bfeabe78e..1706134757fae14a6cc0f0ccecc1a7b6a46a3002 100644 (file)
--- a/sdk/go/keepclient/hashcheck.go
+++ b/sdk/go/keepclient/hashcheck.go
@@ -1,8 +1,3 @@
-// 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.
 package keepclient
 
 import (
@@ -14,25 +9,28 @@ 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 err == nil {
+       if n > 0 {
                this.Hash.Write(p[:n])
-       } else if err == io.EOF {
+       }
+       if err == io.EOF {
                sum := this.Hash.Sum(make([]byte, 0, this.Hash.Size()))
                if fmt.Sprintf("%x", sum) != this.Check {
                        err = BadChecksum
@@ -41,8 +39,8 @@ 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 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))
@@ -59,8 +57,9 @@ func (this HashCheckingReader) WriteTo(dest io.Writer) (written int64, err error
        return written, err
 }
 
-// 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)