Mercurial > public > mercurial-scm > hg
annotate rust/hg-cpython/src/pybytes_deref.rs @ 51199:16d477bb0078
rust-index: return variables systematic naming convention
To help knowing at a glance when a method is ready, making
us more comofortable when we are close to the final removal of
scaffolding, we introduce the systematic variable names `rust_res` and
`c_res`. The goal of this series is to always return the formet.
We take again the case of `pack_header` as example.
Our personal opinion is to usually avoid such poor semantics as `res`, but
usually accept it when it close to the actual return, which will be the
case in most methods of this series. Also, the name can simply be dropped
when we remove the scaffolding. To follow on the example, the body of
`pack_header()` should become this in the final version:
```
let index = self.index(py).borrow();
let packed = index.pack_header(args.get_item(py, 0).extract(py)?);
Ok(PyBytes::new(py, &packed).into_object());
```
in these cases it is close to the actual return and will be removed
at the end entirely.
author | Georges Racinet <georges.racinet@octobus.net> |
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date | Sat, 30 Sep 2023 16:15:56 +0200 |
parents | be3b545c5cff |
children | 7346f93be7a4 |
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1 use cpython::{PyBytes, Python}; |
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2 use stable_deref_trait::StableDeref; |
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3 |
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4 /// Safe abstraction over a `PyBytes` together with the `&[u8]` slice |
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5 /// that borrows it. Implements `Deref<Target = [u8]>`. |
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6 /// |
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7 /// Calling `PyBytes::data` requires a GIL marker but we want to access the |
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8 /// data in a thread that (ideally) does not need to acquire the GIL. |
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9 /// This type allows separating the call an the use. |
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10 /// |
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11 /// It also enables using a (wrapped) `PyBytes` in GIL-unaware generic code. |
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12 pub struct PyBytesDeref { |
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13 #[allow(unused)] |
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14 keep_alive: PyBytes, |
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15 |
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16 /// Borrows the buffer inside `self.keep_alive`, |
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17 /// but the borrow-checker cannot express self-referential structs. |
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18 data: *const [u8], |
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19 } |
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20 |
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21 impl PyBytesDeref { |
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22 pub fn new(py: Python, bytes: PyBytes) -> Self { |
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23 Self { |
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24 data: bytes.data(py), |
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25 keep_alive: bytes, |
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26 } |
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27 } |
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28 |
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29 pub fn unwrap(self) -> PyBytes { |
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30 self.keep_alive |
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31 } |
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32 } |
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33 |
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34 impl std::ops::Deref for PyBytesDeref { |
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35 type Target = [u8]; |
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36 |
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37 fn deref(&self) -> &[u8] { |
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38 // Safety: the raw pointer is valid as long as the PyBytes is still |
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39 // alive, and the returned slice borrows `self`. |
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40 unsafe { &*self.data } |
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41 } |
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42 } |
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43 |
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44 unsafe impl StableDeref for PyBytesDeref {} |
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45 |
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46 fn require_send<T: Send>() {} |
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47 |
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48 #[allow(unused)] |
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49 fn static_assert_pybytes_is_send() { |
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50 #[allow(clippy::no_effect)] |
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51 require_send::<PyBytes>; |
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52 } |
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53 |
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54 // Safety: PyBytes is Send. Raw pointers are not by default, |
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55 // but here sending one to another thread is fine since we ensure it stays |
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56 // valid. |
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57 unsafe impl Send for PyBytesDeref {} |