No `NewReader()`/`NewWriter()` stream wrapper classes

[sumanjeet0012]

Go provides NewReader(r io.Reader) Reader and NewWriter(w io.Writer) Writer wrapper classes with ReadMultihash() and WriteMultihash() methods. Python has Multihash.read()/write() static/instance methods but no dedicated wrapper classes.

Problem

Go's io.go:

type Reader interface {
    io.Reader
    ReadMultihash() (Multihash, error)
}

type Writer interface {
    io.Writer
    WriteMultihash(Multihash) error
}

func NewReader(r io.Reader) Reader { return &mhReader{r} }
func NewWriter(w io.Writer) Writer { return &mhWriter{w} }

The mhReader.ReadMultihash() method reads varints directly from the stream (not buffering the entire input), handles io.ByteReader for efficiency, and validates the result with Cast().

Python's Multihash.read() is a classmethod that works similarly but there's no MultihashReader class that wraps a stream and provides a clean interface for reading multiple multihashes.

Proposed Solution

Add wrapper classes:

class MultihashReader:
    """Wraps a binary stream with ReadMultihash() capability."""

    def __init__(self, stream: BinaryIO):
        self._stream = stream

    def read(self, buf: bytearray) -> int:
        """Standard read interface."""
        return self._stream.readinto(buf)

    def read_multihash(self) -> Multihash:
        """Read one multihash from the stream."""
        return Multihash.read(self._stream)


class MultihashWriter:
    """Wraps a binary stream with WriteMultihash() capability."""

    def __init__(self, stream: BinaryIO):
        self._stream = stream

    def write(self, buf: bytes) -> int:
        """Standard write interface."""
        return self._stream.write(buf)

    def write_multihash(self, mh: Multihash) -> int:
        """Write one multihash to the stream."""
        return mh.write(self._stream)

Export from __init__.py and add tests.

Related

• Go implementation: go-multihash io.go