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# Arrow + PyArrow integration testing

This is a Rust crate that tests compatibility between Rust's Arrow implementation and PyArrow.

Note that this crate uses two languages and an external ABI:
* `Rust`
* `Python`
* C ABI privately exposed by `Pyarrow`.
* PyCapsule ABI publicly exposed by `pyarrow`

## Basic idea

Pyarrow exposes a C ABI to convert arrow arrays from and to its C implementation, see [here](https://arrow.apache.org/docs/format/CDataInterface.html).

This package uses the equivalent struct in Rust (`arrow::array::ArrowArray`), and verifies that
we can use pyarrow's interface to move pointers from and to Rust.

## Relevant literature

* [Arrow's CDataInterface](https://arrow.apache.org/docs/format/CDataInterface.html)
* [Arrow PyCapsule Interface](https://arrow.apache.org/docs/format/CDataInterface/PyCapsuleInterface.html)
* [Rust's FFI](https://doc.rust-lang.org/nomicon/ffi.html)
* [Pyarrow private binds](https://github.com/apache/arrow/blob/ae1d24efcc3f1ac2a876d8d9f544a34eb04ae874/python/pyarrow/array.pxi#L1226)
* [PyO3](https://docs.rs/pyo3/0.12.1/pyo3/index.html)

## How to develop

```bash
# prepare development environment (used to build wheel / install in development)
python -m venv venv
venv/bin/pip install maturin toml pytest pytz pyarrow>=5.0
```

Whenever rust code changes (your changes or via git pull):

```bash
source venv/bin/activate
maturin develop
pytest -v .
```
