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// cindex.rs
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//
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// Copyright 2018 Georges Racinet <gracinet@anybox.fr>
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//
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// This software may be used and distributed according to the terms of the
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// GNU General Public License version 2 or any later version.
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//! Bindings to use the Index defined by the parsers C extension
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//!
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//! Ideally, we should use an Index entirely implemented in Rust,
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//! but this will take some time to get there.
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#![allow(dead_code)]
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use cpython::{
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exc::ImportError, exc::TypeError, ObjectProtocol, PyClone, PyErr,
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PyObject, PyResult, PyTuple, Python, PythonObject,
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};
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use hg::revlog::{Node, RevlogIndex};
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use hg::{BaseRevision, Graph, GraphError, Revision};
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use libc::{c_int, ssize_t};
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const REVLOG_CABI_VERSION: c_int = 3;
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#[repr(C)]
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pub struct Revlog_CAPI {
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abi_version: c_int,
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index_length:
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unsafe extern "C" fn(index: *mut revlog_capi::RawPyObject) -> ssize_t,
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index_node: unsafe extern "C" fn(
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index: *mut revlog_capi::RawPyObject,
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rev: ssize_t,
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) -> *const Node,
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fast_rank: unsafe extern "C" fn(
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index: *mut revlog_capi::RawPyObject,
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rev: ssize_t,
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) -> ssize_t,
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index_parents: unsafe extern "C" fn(
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index: *mut revlog_capi::RawPyObject,
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rev: c_int,
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ps: *mut [c_int; 2],
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) -> c_int,
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}
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py_capsule!(
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from mercurial.cext.parsers import revlog_CAPI
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as revlog_capi for Revlog_CAPI);
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/// A `Graph` backed up by objects and functions from revlog.c
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///
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/// This implementation of the `Graph` trait, relies on (pointers to)
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/// - the C index object (`index` member)
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/// - the `index_get_parents()` function (`parents` member)
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///
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/// # Safety
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///
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/// The C index itself is mutable, and this Rust exposition is **not
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/// protected by the GIL**, meaning that this construct isn't safe with respect
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/// to Python threads.
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///
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/// All callers of this `Index` must acquire the GIL and must not release it
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/// while working.
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///
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/// # TODO find a solution to make it GIL safe again.
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///
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/// This is non trivial, and can wait until we have a clearer picture with
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/// more Rust Mercurial constructs.
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///
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/// One possibility would be to a `GILProtectedIndex` wrapper enclosing
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/// a `Python<'p>` marker and have it be the one implementing the
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/// `Graph` trait, but this would mean the `Graph` implementor would become
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/// likely to change between subsequent method invocations of the `hg-core`
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/// objects (a serious change of the `hg-core` API):
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/// either exposing ways to mutate the `Graph`, or making it a non persistent
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/// parameter in the relevant methods that need one.
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///
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/// Another possibility would be to introduce an abstract lock handle into
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/// the core API, that would be tied to `GILGuard` / `Python<'p>`
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/// in the case of the `cpython` crate bindings yet could leave room for other
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/// mechanisms in other contexts.
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pub struct Index {
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index: PyObject,
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capi: &'static Revlog_CAPI,
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}
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impl Index {
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pub fn new(py: Python, index: PyObject) -> PyResult<Self> {
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let capi = unsafe { revlog_capi::retrieve(py)? };
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if capi.abi_version != REVLOG_CABI_VERSION {
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return Err(PyErr::new::<ImportError, _>(
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py,
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format!(
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"ABI version mismatch: the C ABI revlog version {} \
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does not match the {} expected by Rust hg-cpython",
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capi.abi_version, REVLOG_CABI_VERSION
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),
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));
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}
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let compat: u64 = index.getattr(py, "rust_ext_compat")?.extract(py)?;
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if compat == 0 {
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return Err(PyErr::new::<TypeError, _>(
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py,
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"index object not compatible with Rust",
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));
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}
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Ok(Index { index, capi })
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}
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/// return a reference to the CPython Index object in this Struct
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pub fn inner(&self) -> &PyObject {
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&self.index
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}
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pub fn append(&mut self, py: Python, tup: PyTuple) -> PyResult<PyObject> {
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self.index.call_method(
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py,
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"append",
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PyTuple::new(py, &[tup.into_object()]),
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None,
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)
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}
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}
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impl Clone for Index {
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fn clone(&self) -> Self {
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let guard = Python::acquire_gil();
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Index {
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index: self.index.clone_ref(guard.python()),
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capi: self.capi,
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}
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}
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}
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impl PyClone for Index {
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fn clone_ref(&self, py: Python) -> Self {
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Index {
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index: self.index.clone_ref(py),
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capi: self.capi,
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}
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}
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}
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impl Graph for Index {
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/// wrap a call to the C extern parents function
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fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {
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let mut res: [c_int; 2] = [0; 2];
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let code = unsafe {
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(self.capi.index_parents)(
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self.index.as_ptr(),
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rev.0 as c_int,
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&mut res as *mut [c_int; 2],
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)
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};
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match code {
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0 => Ok([Revision(res[0]), Revision(res[1])]),
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_ => Err(GraphError::ParentOutOfRange(rev)),
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}
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}
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}
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impl vcsgraph::graph::Graph for Index {
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fn parents(
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&self,
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rev: BaseRevision,
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) -> Result<vcsgraph::graph::Parents, vcsgraph::graph::GraphReadError>
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{
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// FIXME This trait should be reworked to decide between Revision
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// and UncheckedRevision, get better errors names, etc.
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match Graph::parents(self, Revision(rev)) {
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Ok(parents) => {
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Ok(vcsgraph::graph::Parents([parents[0].0, parents[1].0]))
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}
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Err(GraphError::ParentOutOfRange(rev)) => {
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Err(vcsgraph::graph::GraphReadError::KeyedInvalidKey(rev.0))
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}
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}
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}
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}
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impl vcsgraph::graph::RankedGraph for Index {
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fn rank(
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&self,
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rev: BaseRevision,
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) -> Result<vcsgraph::graph::Rank, vcsgraph::graph::GraphReadError> {
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match unsafe {
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(self.capi.fast_rank)(self.index.as_ptr(), rev as ssize_t)
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} {
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-1 => Err(vcsgraph::graph::GraphReadError::InconsistentGraphData),
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rank => Ok(rank as usize),
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}
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}
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}
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impl RevlogIndex for Index {
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/// Note C return type is Py_ssize_t (hence signed), but we shall
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/// force it to unsigned, because it's a length
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fn len(&self) -> usize {
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unsafe { (self.capi.index_length)(self.index.as_ptr()) as usize }
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}
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fn node(&self, rev: Revision) -> Option<&Node> {
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let raw = unsafe {
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(self.capi.index_node)(self.index.as_ptr(), rev.0 as ssize_t)
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};
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if raw.is_null() {
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None
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} else {
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// TODO it would be much better for the C layer to give us
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// a length, since the hash length will change in the near
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// future, but that's probably out of scope for the nodemap
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// patch series.
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//
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// The root of that unsafety relies in the signature of
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// `capi.index_node()` itself: returning a `Node` pointer
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// whereas it's a `char *` in the C counterpart.
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Some(unsafe { &*raw })
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}
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}
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}
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