fletchr-uintn 0.0.1rc3

PyArrow extension array of unsigned integers with arbitrary fixed bit width N in [1, 64].

fletchr-uintn

A PyArrow extension type for unsigned integers of arbitrary fixed bit width N ∈ [1, 64]. The bit width lives in the Arrow type rather than as sidecar schema metadata, so mismatched widths fail loudly on concat, the width survives slice / cast / IPC / Parquet round-trips, and any column-level operation that wants to know "how many bits does this hold" reads it off column.type.bits.

Why?

PyArrow's built-in uint8 / uint16 / uint32 / uint64 cover only the four power-of-two widths native to most CPUs. Protocol and binary formats routinely use other widths (10, 12, 14, 24, 48), and the usual workarounds — over-allocating (uint16 for a 12-bit field) or passing the width out-of-band in schema metadata — either lose the constraint on bitwise ops or drop it on the next slice. fletchr.uintn(bits=N) puts the width in the type and ships bit-width-safe kernels that keep padding bits zero across every operation.

Features

• Storage in the smallest native uint8 / uint16 / uint32 / uint64 container that fits N; padding bits above N are kept zero across construction and every operation.
• Lossless round-trip through Arrow IPC, Arrow Flight, and Parquet. Readers that don't have the extension registered see the raw uintN storage transparently — no exotic types in the wire format.
• Full Arrow null support via the standard validity bitmap.
• Bit-width-safe bitwise operators (~, &, |, ^, shifts, popcount, bit-reversal) — padding bits never leak.
• Cross-language wire format pinned in SPEC.md so Arrow readers in Java, C++, Go, R, JavaScript, etc. can implement compatible deserializers.

Install

uv add fletchr-uintn        # or: pip install fletchr-uintn

Requires Python 3.9+, NumPy 2.0+, and PyArrow 17+.

Quickstart

import pyarrow as pa
import pyarrow.parquet as pq
from fletchr_uintn import uintn_array

# 12-bit values — fit in a uint16 container, but the type knows it's 12 bits.
a = uintn_array([0, 1, 4095, None, 100], bits=12)
a.type            # UIntNType(bits=12)
a.to_pylist()     # [0, 1, 4095, None, 100]

# Bitwise ops respect the declared width: ~0 is 4095, not 65535.
(~a).to_pylist()  # [4095, 4094, 0, None, 3995]

# Composes as a column inside any pa.Table; round-trips through Parquet.
pq.write_table(pa.table({"x": a}), "out.parquet")
back = pq.read_table("out.parquet").column("x")
assert back.type.bits == 12

# Mismatched bit widths fail at the Arrow type system, not silently:
pa.concat_arrays([a, uintn_array([0, 1], bits=10)])  # raises ArrowInvalid

Public API

from fletchr_uintn import (
    UIntNType,        # the pa.ExtensionType
    UIntNArray,       # the pa.ExtensionArray (with bitwise methods)
    uintn_array,      # validated factory; dispatches on input type
    pack_bits,        # inverse of UIntNArray.unpack_bits
)

The extension type registers itself on import, so any pa.Table deserialized after import fletchr_uintn will surface UIntNArray columns instead of raw uintN storage.

Links

• Source: https://github.com/fletchr-labs/fletchr
• Issues: https://github.com/fletchr-labs/fletchr/issues
• Wire format spec: SPEC.md

License

MIT.