# slice.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/pyo3-0.13.2/src/types/slice.rs`.
Keywords: rust, rustlang, rust-lang

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    // Copyright (c) 2017-present PyO3 Project and Contributors

    use crate::err::{PyErr, PyResult};
    use crate::ffi::{self, Py_ssize_t};
    use crate::instance::PyNativeType;
    use crate::{AsPyPointer, PyAny, PyObject, Python, ToPyObject};
    use std::os::raw::c_long;

    /// Represents a Python `slice`.
    ///
    /// Only `c_long` indices supported at the moment by the `PySlice` object.
    #[repr(transparent)]
    pub struct PySlice(PyAny);

    pyobject_native_type!(
        PySlice,
        ffi::PySliceObject,
        ffi::PySlice_Type,
        ffi::PySlice_Check
    );

    /// Represents Python `slice` indices.
    pub struct PySliceIndices {
        pub start: isize,
        pub stop: isize,
        pub step: isize,
        pub slicelength: isize,
    }

    impl PySliceIndices {
        pub fn new(start: isize, stop: isize, step: isize) -> PySliceIndices {
            PySliceIndices {
                start,
                stop,
                step,
                slicelength: 0,
            }
        }
    }

    impl PySlice {
        /// Constructs a new slice with the given elements.
        pub fn new(py: Python, start: isize, stop: isize, step: isize) -> &PySlice {
            unsafe {
                let ptr = ffi::PySlice_New(
                    ffi::PyLong_FromLong(start as c_long),
                    ffi::PyLong_FromLong(stop as c_long),
                    ffi::PyLong_FromLong(step as c_long),
                );
                py.from_owned_ptr(ptr)
            }
        }

        /// Retrieves the start, stop, and step indices from the slice object,
        /// assuming a sequence of length `length`, and stores the length of the
        /// slice in its `slicelength` member.
        #[inline]
        pub fn indices(&self, length: c_long) -> PyResult<PySliceIndices> {
            // non-negative Py_ssize_t should always fit into Rust usize
            unsafe {
                let slicelength: isize = 0;
                let start: isize = 0;
                let stop: isize = 0;
                let step: isize = 0;
                let r = ffi::PySlice_GetIndicesEx(
                    self.as_ptr(),
                    length as Py_ssize_t,
                    &start as *const _ as *mut _,
                    &stop as *const _ as *mut _,
                    &step as *const _ as *mut _,
                    &slicelength as *const _ as *mut _,
                );
                if r == 0 {
                    Ok(PySliceIndices {
                        start,
                        stop,
                        step,
                        slicelength,
                    })
                } else {
                    Err(PyErr::fetch(self.py()))
                }
            }
        }
    }

    impl ToPyObject for PySliceIndices {
        fn to_object(&self, py: Python) -> PyObject {
            PySlice::new(py, self.start, self.stop, self.step).into()
        }
    }