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move Cow[u8] conversions into conversions::std::slice module #3799

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Feb 5, 2024
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63 changes: 61 additions & 2 deletions src/conversions/std/slice.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,11 @@
use std::borrow::Cow;

#[cfg(feature = "experimental-inspect")]
use crate::inspect::types::TypeInfo;
use crate::{types::PyBytes, FromPyObject, IntoPy, PyAny, PyObject, PyResult, Python};
use crate::{
types::{PyByteArray, PyBytes},
FromPyObject, IntoPy, Py, PyAny, PyObject, PyResult, Python, ToPyObject,
};

impl<'a> IntoPy<PyObject> for &'a [u8] {
fn into_py(self, py: Python<'_>) -> PyObject {
Expand All @@ -24,9 +29,39 @@ impl<'py> FromPyObject<'py> for &'py [u8] {
}
}

/// Special-purpose trait impl to efficiently handle both `bytes` and `bytearray`
///
/// If the source object is a `bytes` object, the `Cow` will be borrowed and
/// pointing into the source object, and no copying or heap allocations will happen.
/// If it is a `bytearray`, its contents will be copied to an owned `Cow`.
impl<'py> FromPyObject<'py> for Cow<'py, [u8]> {
fn extract(ob: &'py PyAny) -> PyResult<Self> {
if let Ok(bytes) = ob.downcast::<PyBytes>() {
return Ok(Cow::Borrowed(bytes.as_bytes()));
}

let byte_array = ob.downcast::<PyByteArray>()?;
Ok(Cow::Owned(byte_array.to_vec()))
}
}

impl ToPyObject for Cow<'_, [u8]> {
fn to_object(&self, py: Python<'_>) -> Py<PyAny> {
PyBytes::new_bound(py, self.as_ref()).into()
}
}

impl IntoPy<Py<PyAny>> for Cow<'_, [u8]> {
fn into_py(self, py: Python<'_>) -> Py<PyAny> {
self.to_object(py)
}
}

#[cfg(test)]
mod tests {
use crate::Python;
use std::borrow::Cow;

use crate::{types::PyBytes, Python, ToPyObject};

#[test]
fn test_extract_bytes() {
Expand All @@ -36,4 +71,28 @@ mod tests {
assert_eq!(bytes, b"Hello Python");
});
}

#[test]
fn test_cow_impl() {
Python::with_gil(|py| {
let bytes = py.eval(r#"b"foobar""#, None, None).unwrap();
let cow = bytes.extract::<Cow<'_, [u8]>>().unwrap();
assert_eq!(cow, Cow::<[u8]>::Borrowed(b"foobar"));

let byte_array = py.eval(r#"bytearray(b"foobar")"#, None, None).unwrap();
let cow = byte_array.extract::<Cow<'_, [u8]>>().unwrap();
assert_eq!(cow, Cow::<[u8]>::Owned(b"foobar".to_vec()));

let something_else_entirely = py.eval("42", None, None).unwrap();
something_else_entirely
.extract::<Cow<'_, [u8]>>()
.unwrap_err();

let cow = Cow::<[u8]>::Borrowed(b"foobar").to_object(py);
assert!(cow.as_ref(py).is_instance_of::<PyBytes>());

let cow = Cow::<[u8]>::Owned(b"foobar".to_vec()).to_object(py);
assert!(cow.as_ref(py).is_instance_of::<PyBytes>());
});
}
}
61 changes: 3 additions & 58 deletions src/types/bytes.rs
Original file line number Diff line number Diff line change
@@ -1,15 +1,12 @@
use crate::ffi_ptr_ext::FfiPtrExt;
use crate::instance::{Borrowed, Bound};
use crate::types::any::PyAnyMethods;
use crate::{ffi, FromPyObject, IntoPy, Py, PyAny, PyNativeType, PyResult, Python, ToPyObject};
use std::borrow::Cow;
use crate::{ffi, Py, PyAny, PyNativeType, PyResult, Python};
use std::ops::Index;
use std::os::raw::c_char;
use std::slice::SliceIndex;
use std::str;

use super::bytearray::PyByteArray;

/// Represents a Python `bytes` object.
///
/// This type is immutable.
Expand Down Expand Up @@ -198,34 +195,6 @@ impl<I: SliceIndex<[u8]>> Index<I> for Bound<'_, PyBytes> {
}
}

/// Special-purpose trait impl to efficiently handle both `bytes` and `bytearray`
///
/// If the source object is a `bytes` object, the `Cow` will be borrowed and
/// pointing into the source object, and no copying or heap allocations will happen.
/// If it is a `bytearray`, its contents will be copied to an owned `Cow`.
impl<'py> FromPyObject<'py> for Cow<'py, [u8]> {
fn extract(ob: &'py PyAny) -> PyResult<Self> {
if let Ok(bytes) = ob.downcast::<PyBytes>() {
return Ok(Cow::Borrowed(bytes.as_bytes()));
}

let byte_array = ob.downcast::<PyByteArray>()?;
Ok(Cow::Owned(byte_array.to_vec()))
}
}

impl ToPyObject for Cow<'_, [u8]> {
fn to_object(&self, py: Python<'_>) -> Py<PyAny> {
PyBytes::new_bound(py, self.as_ref()).into()
}
}

impl IntoPy<Py<PyAny>> for Cow<'_, [u8]> {
fn into_py(self, py: Python<'_>) -> Py<PyAny> {
self.to_object(py)
}
}

#[cfg(test)]
#[cfg_attr(not(feature = "gil-refs"), allow(deprecated))]
mod tests {
Expand Down Expand Up @@ -257,7 +226,7 @@ mod tests {
b.copy_from_slice(b"Hello Rust");
Ok(())
})?;
let bytes: &[u8] = FromPyObject::extract(py_bytes)?;
let bytes: &[u8] = py_bytes.extract()?;
assert_eq!(bytes, b"Hello Rust");
Ok(())
})
Expand All @@ -267,7 +236,7 @@ mod tests {
fn test_bytes_new_with_zero_initialised() -> super::PyResult<()> {
Python::with_gil(|py| -> super::PyResult<()> {
let py_bytes = PyBytes::new_with(py, 10, |_b: &mut [u8]| Ok(()))?;
let bytes: &[u8] = FromPyObject::extract(py_bytes)?;
let bytes: &[u8] = py_bytes.extract()?;
assert_eq!(bytes, &[0; 10]);
Ok(())
})
Expand All @@ -287,28 +256,4 @@ mod tests {
.is_instance_of::<PyValueError>(py));
});
}

#[test]
fn test_cow_impl() {
Python::with_gil(|py| {
let bytes = py.eval(r#"b"foobar""#, None, None).unwrap();
let cow = bytes.extract::<Cow<'_, [u8]>>().unwrap();
assert_eq!(cow, Cow::<[u8]>::Borrowed(b"foobar"));

let byte_array = py.eval(r#"bytearray(b"foobar")"#, None, None).unwrap();
let cow = byte_array.extract::<Cow<'_, [u8]>>().unwrap();
assert_eq!(cow, Cow::<[u8]>::Owned(b"foobar".to_vec()));

let something_else_entirely = py.eval("42", None, None).unwrap();
something_else_entirely
.extract::<Cow<'_, [u8]>>()
.unwrap_err();

let cow = Cow::<[u8]>::Borrowed(b"foobar").to_object(py);
assert!(cow.as_ref(py).is_instance_of::<PyBytes>());

let cow = Cow::<[u8]>::Owned(b"foobar".to_vec()).to_object(py);
assert!(cow.as_ref(py).is_instance_of::<PyBytes>());
});
}
}
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