Add winnow view Python example

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 - added example combining Python bindings with winnow parsing
+- added Python example demonstrating structured parsing with winnow's `view`
 - added `ByteSource` support for `VecDeque<T>` when `zerocopy` is enabled and kept the deque as owner
 - added `ByteSource` support for `Cow<'static, T>` where `T: AsRef<[u8]>`
 - added `ByteArea` for staged file writes with `Section::freeze()` to return `Bytes`

Cargo.toml

@@ -45,3 +45,11 @@ required-features = ["pyo3"]
 [[example]]
 name = "pybytes"
 required-features = ["pyo3"]
+
+[[example]]
+name = "python_winnow"
+required-features = ["pyo3", "winnow"]
+
+[[example]]
+name = "python_winnow_view"
+required-features = ["pyo3", "winnow", "zerocopy"]

INVENTORY.md

@@ -4,7 +4,7 @@
 - None at the moment.
 
 ## Desired Functionality
-- Python example using winnow::view to parse structured data.
+- Add Kani proofs for winnow view helpers.
 
 ## Discovered Issues
 - None at the moment.

README.md

@@ -148,6 +148,7 @@ needs these libraries installed; otherwise disable the feature during testing.
 - [`examples/pybytes.rs`](examples/pybytes.rs) – demonstrates the `pyo3` feature using `PyBytes`
 - [`examples/from_python.rs`](examples/from_python.rs) – wrap a Python `bytes` object into `Bytes`
 - [`examples/python_winnow.rs`](examples/python_winnow.rs) – parse Python bytes with winnow
+- [`examples/python_winnow_view.rs`](examples/python_winnow_view.rs) – parse structured data from Python bytes using winnow's `view`
 
 ## Comparison
 

examples/python_winnow_view.rs

@@ -0,0 +1,28 @@
+#![cfg(all(feature = "pyo3", feature = "winnow", feature = "zerocopy"))]
+
+use anybytes::{winnow as ab_winnow, Bytes, View};
+use pyo3::{prelude::*, types::PyBytes};
+use winnow::{error::ContextError, stream::AsBytes, Parser};
+use zerocopy::{Immutable, KnownLayout, TryFromBytes};
+
+#[derive(TryFromBytes, Immutable, KnownLayout)]
+#[repr(C)]
+struct Header {
+    magic: u16,
+    value: u16,
+}
+
+fn main() -> PyResult<()> {
+    Python::with_gil(|py| {
+        let obj = PyBytes::new(py, &[0x34, 0x12, 0x78, 0x56]);
+        let mut bytes = Bytes::from_source(obj);
+
+        let mut parser = ab_winnow::view::<Header, ContextError>;
+        let header: View<Header> = parser.parse_next(&mut bytes).expect("parse header");
+
+        assert_eq!(header.magic, 0x1234);
+        assert_eq!(header.value, 0x5678);
+        assert_eq!(bytes.as_bytes(), b"".as_ref());
+        Ok(())
+    })
+}