refactor(tvix/nar-bridge): combine writers/readers r/6695

We can drop most of Hasher if we use a MultiWriter writing to the hash
function and a minimal CountingWriter.

This should make things a bit more understandable.

Change-Id: I37ee72d9a5c73f253aecc1ad761cb723389b89fc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9529
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

1 files changed, 0 insertions, 66 deletions

diff --git a/tvix/nar-bridge/pkg/hashers/hashers.go b/tvix/nar-bridge/pkg/hashers/hashers.go
deleted file mode 100644
index 0c9e611799e3..000000000000
--- a/tvix/nar-bridge/pkg/hashers/hashers.go
+++ /dev/null
@@ -1,66 +0,0 @@
-package hashers
-
-import (
-	"errors"
-	"fmt"
-	"hash"
-	"io"
-)
-
-var _ io.Reader = &Hasher{}
-
-// Hasher wraps io.Reader.
-// You can ask it for the digest of the hash function used internally, and the
-// number of bytes written.
-type Hasher struct {
-	r         io.Reader
-	h         hash.Hash
-	bytesRead uint32
-}
-
-func NewHasher(r io.Reader, h hash.Hash) *Hasher {
-	return &Hasher{
-		r:         r,
-		h:         h,
-		bytesRead: 0,
-	}
-}
-
-func (h *Hasher) Read(p []byte) (int, error) {
-	nRead, rdErr := h.r.Read(p)
-
-	// write the number of bytes read from the reader to the hash.
-	// We need to do this independently on whether there's been error.
-	// n always describes the number of successfully written bytes.
-	nHash, hashErr := h.h.Write(p[0:nRead])
-	if hashErr != nil {
-		return nRead, fmt.Errorf("unable to write to hash: %w", hashErr)
-	}
-
-	// We assume here the hash function accepts the whole p in one Go,
-	// and doesn't early-return on the Write.
-	// We compare it with nRead and bail out if that was not the case.
-	if nHash != nRead {
-		return nRead, fmt.Errorf("hash didn't accept the full write")
-	}
-
-	// update bytesWritten
-	h.bytesRead += uint32(nRead)
-
-	if rdErr != nil {
-		if errors.Is(rdErr, io.EOF) {
-			return nRead, rdErr
-		}
-		return nRead, fmt.Errorf("error from underlying reader: %w", rdErr)
-	}
-
-	return nRead, hashErr
-}
-
-func (h *Hasher) BytesWritten() uint32 {
-	return h.bytesRead
-}
-
-func (h *Hasher) Sum(b []byte) []byte {
-	return h.h.Sum(b)
-}