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

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    use crate::{
        ffi, AsPyPointer, FromPyObject, IntoPy, Py, PyAny, PyObject, PyResult, PyTryFrom, Python,
        ToPyObject,
    };
    use std::ops::Index;
    use std::os::raw::c_char;
    use std::slice::SliceIndex;
    use std::str;

    /// Represents a Python `bytes` object.
    ///
    /// This type is immutable.
    #[repr(transparent)]
    pub struct PyBytes(PyAny);

    pyobject_native_var_type!(PyBytes, ffi::PyBytes_Type, ffi::PyBytes_Check);

    impl PyBytes {
        /// Creates a new Python bytestring object.
        /// The bytestring is initialized by copying the data from the `&[u8]`.
        ///
        /// Panics if out of memory.
        pub fn new<'p>(py: Python<'p>, s: &[u8]) -> &'p PyBytes {
            let ptr = s.as_ptr() as *const c_char;
            let len = s.len() as ffi::Py_ssize_t;
            unsafe { py.from_owned_ptr(ffi::PyBytes_FromStringAndSize(ptr, len)) }
        }

        /// Creates a new Python `bytes` object with an `init` closure to write its contents.
        /// Before calling `init` the bytes' contents are zero-initialised.
        /// * If Python raises a MemoryError on the allocation, `new_with` will return
        ///   it inside `Err`.
        /// * If `init` returns `Err(e)`, `new_with` will return `Err(e)`.
        /// * If `init` returns `Ok(())`, `new_with` will return `Ok(&PyBytes)`.
        ///
        /// # Example
        /// ```
        /// use pyo3::{prelude::*, types::PyBytes};
        /// Python::with_gil(|py| -> PyResult<()> {
        ///     let py_bytes = PyBytes::new_with(py, 10, |bytes: &mut [u8]| {
        ///         bytes.copy_from_slice(b"Hello Rust");
        ///         Ok(())
        ///     })?;
        ///     let bytes: &[u8] = FromPyObject::extract(py_bytes)?;
        ///     assert_eq!(bytes, b"Hello Rust");
        ///     Ok(())
        /// });
        /// ```
        pub fn new_with<F>(py: Python, len: usize, init: F) -> PyResult<&PyBytes>
        where
            F: FnOnce(&mut [u8]) -> PyResult<()>,
        {
            unsafe {
                let pyptr = ffi::PyBytes_FromStringAndSize(std::ptr::null(), len as ffi::Py_ssize_t);
                // Check for an allocation error and return it
                let pypybytes: Py<PyBytes> = Py::from_owned_ptr_or_err(py, pyptr)?;
                let buffer = ffi::PyBytes_AsString(pyptr) as *mut u8;
                debug_assert!(!buffer.is_null());
                // Zero-initialise the uninitialised bytestring
                std::ptr::write_bytes(buffer, 0u8, len);
                // (Further) Initialise the bytestring in init
                // If init returns an Err, pypybytearray will automatically deallocate the buffer
                init(std::slice::from_raw_parts_mut(buffer, len)).map(|_| pypybytes.into_ref(py))
            }
        }

        /// Creates a new Python byte string object from a raw pointer and length.
        ///
        /// Panics if out of memory.
        ///
        /// # Safety
        ///
        /// This function dereferences the raw pointer `ptr` as the
        /// leading pointer of a slice of length `len`. [As with
        /// `std::slice::from_raw_parts`, this is
        /// unsafe](https://doc.rust-lang.org/std/slice/fn.from_raw_parts.html#safety).
        pub unsafe fn from_ptr(py: Python<'_>, ptr: *const u8, len: usize) -> &PyBytes {
            py.from_owned_ptr(ffi::PyBytes_FromStringAndSize(
                ptr as *const _,
                len as isize,
            ))
        }

        /// Gets the Python string as a byte slice.
        #[inline]
        pub fn as_bytes(&self) -> &[u8] {
            unsafe {
                let buffer = ffi::PyBytes_AsString(self.as_ptr()) as *const u8;
                let length = ffi::PyBytes_Size(self.as_ptr()) as usize;
                debug_assert!(!buffer.is_null());
                std::slice::from_raw_parts(buffer, length)
            }
        }
    }

    /// This is the same way [Vec] is indexed.
    impl<I: SliceIndex<[u8]>> Index<I> for PyBytes {
        type Output = I::Output;

        fn index(&self, index: I) -> &Self::Output {
            &self.as_bytes()[index]
        }
    }

    impl<'a> IntoPy<PyObject> for &'a [u8] {
        fn into_py(self, py: Python) -> PyObject {
            PyBytes::new(py, self).to_object(py)
        }
    }

    impl<'a> FromPyObject<'a> for &'a [u8] {
        fn extract(obj: &'a PyAny) -> PyResult<Self> {
            Ok(<PyBytes as PyTryFrom>::try_from(obj)?.as_bytes())
        }
    }
    #[cfg(test)]
    mod test {
        use super::PyBytes;
        use crate::FromPyObject;
        use crate::Python;

        #[test]
        fn test_extract_bytes() {
            let gil = Python::acquire_gil();
            let py = gil.python();

            let py_bytes = py.eval("b'Hello Python'", None, None).unwrap();
            let bytes: &[u8] = FromPyObject::extract(py_bytes).unwrap();
            assert_eq!(bytes, b"Hello Python");
        }

        #[test]
        fn test_bytes_index() {
            let gil = Python::acquire_gil();
            let py = gil.python();
            let bytes = PyBytes::new(py, b"Hello World");
            assert_eq!(bytes[1], b'e');
        }

        #[test]
        fn test_bytes_new_with() -> super::PyResult<()> {
            let gil = Python::acquire_gil();
            let py = gil.python();
            let py_bytes = PyBytes::new_with(py, 10, |b: &mut [u8]| {
                b.copy_from_slice(b"Hello Rust");
                Ok(())
            })?;
            let bytes: &[u8] = FromPyObject::extract(py_bytes)?;
            assert_eq!(bytes, b"Hello Rust");
            Ok(())
        }

        #[test]
        fn test_bytes_new_with_zero_initialised() -> super::PyResult<()> {
            let gil = Python::acquire_gil();
            let py = gil.python();
            let py_bytes = PyBytes::new_with(py, 10, |_b: &mut [u8]| Ok(()))?;
            let bytes: &[u8] = FromPyObject::extract(py_bytes)?;
            assert_eq!(bytes, &[0; 10]);
            Ok(())
        }

        #[test]
        fn test_bytes_new_with_error() {
            use crate::exceptions::PyValueError;
            let gil = Python::acquire_gil();
            let py = gil.python();
            let py_bytes_result = PyBytes::new_with(py, 10, |_b: &mut [u8]| {
                Err(PyValueError::new_err("Hello Crustaceans!"))
            });
            assert!(py_bytes_result.is_err());
            assert!(py_bytes_result
                .err()
                .unwrap()
                .is_instance::<PyValueError>(py));
        }
    }