tvl-depot/tvix/nar-bridge/pkg/reader/hashers.go
Florian Klink 0ecd10bf30 feat(tvix/nar-bridge): init
This provides a Nix HTTP Binary Cache interface in front of a tvix-store
that's reachable via gRPC.

TODOs:

 - remove import command, move serve up to toplevel. We have nix-copy-
   closure and tvix-store commands.
 - loop into CI. We should be able to fetch the protos as a third-party
   dependency.
 - Check if we can test nar-bridge slightly easier in an integration
   test.
 - Ensure we support connecting to unix sockets and grpc+http at least,
   using the same syntax as tvix-store.
 - Don't buffer the entire blob when rendering NAR

Co-Authored-By: Connor Brewster <cbrewster@hey.com>
Co-Authored-By: Márton Boros <martonboros@gmail.com>
Co-Authored-By: Vo Minh Thu <noteed@gmail.com>

Change-Id: I6064474e49dfe78cea67676957462d9f28658d4a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9339
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
2023-09-17 13:24:53 +00:00

66 lines
1.4 KiB
Go

package reader
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)
}