What causes "Invalid data type: %s" in HelloZeroNet/ZeroNet?

Convert the value first: data = data.encode() if isinstance(data, str) else bytes(data).

HelloZeroNet/ZeroNet · error · Exception

Invalid data type: %s

Error message

Invalid data type: %s

What it means

packPiecefield in BigfilePiecefield.py compresses a piecefield (bytes of b'\x00'/b'\x01' flags describing downloaded big-file pieces) into run-length encoded 16-bit words. It raises Exception("Invalid data type: %s") when the input is neither bytes nor bytearray — the compressor refuses to guess how to encode other types.

Source

Thrown at plugins/Bigfile/BigfilePiecefield.py:6

import array


def packPiecefield(data):
    if not isinstance(data, bytes) and not isinstance(data, bytearray):
        raise Exception("Invalid data type: %s" % type(data))

    res = []
    if not data:
        return array.array("H", b"")

    if data[0] == b"\x00":
        res.append(0)
        find = b"\x01"
    else:
        find = b"\x00"
    last_pos = 0
    pos = 0
    while 1:
        pos = data.find(find, pos)
        if find == b"\x00":
            find = b"\x01"
        else:
            find = b"\x00"

View on GitHub (pinned to 454c0b2e7e)

Solutions

Convert the value first: data = data.encode() if isinstance(data, str) else bytes(data).
Check where the piecefield is stored/loaded (json/DB) and preserve it as bytes (e.g. store base64).
Fix the API caller to pass the raw bytes from Piecefield.tobytes().
Add an isinstance check at the boundary before packing.

Example fix

// before
packed = packPiecefield(piecefield_data)  # piecefield_data is str from JSON
// after
if isinstance(piecefield_data, str):
    piecefield_data = piecefield_data.encode("latin1")
packed = packPiecefield(piecefield_data)

Defensive patterns

Strategy: type-guard

Validate before calling

if not isinstance(data, (bytes, bytearray)):
    data = data.encode("latin1") if isinstance(data, str) else bytes(data)

Type guard

def is_piecefield_bytes(data):
    return isinstance(data, (bytes, bytearray))

Try / catch

try:
    packed = packPiecefield(data)
except Exception as e:
    if "Invalid data type" in str(e):
        packed = packPiecefield(data.encode("latin1"))
    else:
        raise

Prevention

Store piecefields in bytes-safe formats (base64) across JSON/DB round-trips
Never let JSON decoding turn piecefield bytes into str
Convert with encode('latin1') at load boundaries
Unit-test save/load round-trips of piecefields

When it happens

Trigger: Calling packPiecefield (directly or via Piecefield.pack()/frombytes->pack chains) with a str, list, array, or None instead of bytes/bytearray — typically a piecefield stored/loaded through a channel that decoded it (e.g. JSON turning bytes into str).

Common situations: Piecefields persisted to sites.json/SQLite as text and read back as str; receiving piecefield data over the ZeroNet protocol where decoding changed the type; passing memoryview or array('H') directly.

Related errors

AI-assisted analysis of HelloZeroNet/ZeroNet@454c0b2e7e (2026-09-02). Data as JSON: /api/errors/2fb148fc35fbb3c4. Report an issue: GitHub.