pyo3 0.27.2

Bindings to Python interpreter
Documentation 
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#![cfg(feature = "macros")]
#![cfg(any(not(Py_LIMITED_API), Py_3_11))]
#![warn(unsafe_op_in_unsafe_fn)]

use pyo3::{buffer::PyBuffer, exceptions::PyBufferError, ffi, prelude::*};
use std::{
    os::raw::{c_int, c_void},
    ptr,
};

#[macro_use]
mod test_utils;

enum TestGetBufferError {
    NullShape,
    NullStrides,
    IncorrectItemSize,
    IncorrectFormat,
    IncorrectAlignment,
}

#[pyclass]
struct TestBufferErrors {
    buf: Vec<u32>,
    error: Option<TestGetBufferError>,
}

#[pymethods]
impl TestBufferErrors {
    unsafe fn __getbuffer__(
        slf: PyRefMut<'_, Self>,
        view: *mut ffi::Py_buffer,
        flags: c_int,
    ) -> PyResult<()> {
        if view.is_null() {
            return Err(PyBufferError::new_err("View is null"));
        }

        if (flags & ffi::PyBUF_WRITABLE) == ffi::PyBUF_WRITABLE {
            return Err(PyBufferError::new_err("Object is not writable"));
        }

        let bytes = &slf.buf;

        unsafe {
            (*view).buf = bytes.as_ptr() as *mut c_void;
            (*view).len = bytes.len() as isize;
            (*view).readonly = 1;
            (*view).itemsize = std::mem::size_of::<u32>() as isize;

            let msg = ffi::c_str!("I");
            (*view).format = msg.as_ptr() as *mut _;

            (*view).ndim = 1;
            (*view).shape = &mut (*view).len;

            (*view).strides = &mut (*view).itemsize;

            (*view).suboffsets = ptr::null_mut();
            (*view).internal = ptr::null_mut();

            if let Some(err) = &slf.error {
                use TestGetBufferError::*;
                match err {
                    NullShape => {
                        (*view).shape = std::ptr::null_mut();
                    }
                    NullStrides => {
                        (*view).strides = std::ptr::null_mut();
                    }
                    IncorrectItemSize => {
                        (*view).itemsize += 1;
                    }
                    IncorrectFormat => {
                        (*view).format = ffi::c_str!("B").as_ptr() as _;
                    }
                    IncorrectAlignment => (*view).buf = (*view).buf.add(1),
                }
            }

            (*view).obj = slf.into_ptr();
        }

        Ok(())
    }
}

#[test]
fn test_get_buffer_errors() {
    Python::attach(|py| {
        let instance = Py::new(
            py,
            TestBufferErrors {
                buf: vec![0, 1, 2, 3],
                error: None,
            },
        )
        .unwrap();

        assert!(PyBuffer::<u32>::get(instance.bind(py)).is_ok());

        instance.borrow_mut(py).error = Some(TestGetBufferError::NullShape);
        assert_eq!(
            PyBuffer::<u32>::get(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: shape is null"
        );

        instance.borrow_mut(py).error = Some(TestGetBufferError::NullStrides);
        assert_eq!(
            PyBuffer::<u32>::get(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: strides is null"
        );

        instance.borrow_mut(py).error = Some(TestGetBufferError::IncorrectItemSize);
        assert_eq!(
            PyBuffer::<u32>::get(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: buffer contents are not compatible with u32"
        );

        instance.borrow_mut(py).error = Some(TestGetBufferError::IncorrectFormat);
        assert_eq!(
            PyBuffer::<u32>::get(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: buffer contents are not compatible with u32"
        );

        instance.borrow_mut(py).error = Some(TestGetBufferError::IncorrectAlignment);
        assert_eq!(
            PyBuffer::<u32>::get(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: buffer contents are insufficiently aligned for u32"
        );
    });
}