comparison rust/hg-cpython/src/revlog.rs @ 51246:41e19e8a6133

rust-index: stop using C index

We still keep its wrapper implementation in `hg-cpython::cindex`,
because we might want to recreate ancestors handling objects using
it for the case of REVLOGV2.

Also, we still instantiate it (from Python code) and store it as
attribute, for the likes of `get_cindex` and the caller that
relies on it, but that is soon to be removed, too.

51245:0b81440e2a73

    PyRevision,
};
use cpython::{
    buffer::{Element, PyBuffer},
    exc::{IndexError, ValueError},
    ObjectProtocol, PyBool, PyBytes, PyClone, PyDict, PyErr, PyInt, PyList,
    PyModule, PyObject, PyResult, PySet, PyString, PyTuple, Python,
    PythonObject, ToPyObject, UnsafePyLeaked,
};
use hg::{
    errors::HgError,
    index::{
        IndexHeader, Phase, RevisionDataParams, SnapshotsCache,

    /// Return Revision if found, raises a bare `error.RevlogError`
    /// in case of ambiguity, same as C version does
    def get_rev(&self, node: PyBytes) -> PyResult<Option<PyRevision>> {
        let opt = self.get_nodetree(py)?.borrow();
        let nt = opt.as_ref().unwrap();
        let idx = &*self.cindex(py).borrow();
        let ridx = &*self.index(py).borrow();
        let node = node_from_py_bytes(py, &node)?;
        let rust_rev =
            nt.find_bin(ridx, node.into()).map_err(|e| nodemap_error(py, e))?;
        let c_rev =
            nt.find_bin(idx, node.into()).map_err(|e| nodemap_error(py, e))?;
        assert_eq!(rust_rev, c_rev);
        Ok(rust_rev.map(Into::into))

    }

    /// same as `get_rev()` but raises a bare `error.RevlogError` if node

        }
        let node_bytes = tup.get_item(py, 7).extract(py)?;
        let node = node_from_py_object(py, &node_bytes)?;

        let rev = self.len(py)? as BaseRevision;
        let mut idx = self.cindex(py).borrow_mut();

        // This is ok since we will just add the revision to the index
        let rev = Revision(rev);
        idx.append(py, tup.clone_ref(py))?;
        self.index(py)
            .borrow_mut()
            .append(py_tuple_to_revision_data_params(py, tup)?)
            .unwrap();
        self.get_nodetree(py)?.borrow_mut().as_mut().unwrap()
            .insert(&*idx, &node, rev)
            .map_err(|e| nodemap_error(py, e))?;
        Ok(py.None())
    }

    def __delitem__(&self, key: PyObject) -> PyResult<()> {
        // __delitem__ is both for `del idx[r]` and `del idx[r1:r2]`
        self.cindex(py).borrow().inner().del_item(py, &key)?;
        let start = key.getattr(py, "start")?;
        let start = UncheckedRevision(start.extract(py)?);
        let start = self.index(py)
            .borrow()
            .check_revision(start)

        self.fill_nodemap(py, nt)?;
        Ok(())
    }

    //
    // Reforwarded C index API
    //

    // index_methods (tp_methods). Same ordering as in revlog.c

    /// return the gca set of the given revs
    def ancestors(&self, *args, **kw) -> PyResult<PyObject> {
        let rust_res = self.inner_ancestors(py, args)?;

        let c_res = self.call_cindex(py, "ancestors", args, kw)?;
        // the algorithm should always provide the results in reverse ordering
        assert_py_eq(py, "ancestors", &rust_res, &c_res)?;

        Ok(rust_res)
    }

    /// return the heads of the common ancestors of the given revs
    def commonancestorsheads(&self, *args, **kw) -> PyResult<PyObject> {
        let rust_res = self.inner_commonancestorsheads(py, args)?;

        let c_res = self.call_cindex(py, "commonancestorsheads", args, kw)?;
        // the algorithm should always provide the results in reverse ordering
        assert_py_eq(py, "commonancestorsheads", &rust_res, &c_res)?;

        Ok(rust_res)
    }

    /// Clear the index caches and inner py_class data.
    /// It is Python's responsibility to call `update_nodemap_data` again.
    def clearcaches(&self, *args, **kw) -> PyResult<PyObject> {
        self.nt(py).borrow_mut().take();
        self.docket(py).borrow_mut().take();
        self.nodemap_mmap(py).borrow_mut().take();
        self.index(py).borrow().clear_caches();
        self.call_cindex(py, "clearcaches", args, kw)
    }

    /// return the raw binary string representing a revision
    def entry_binary(&self, *args, **kw) -> PyResult<PyObject> {
        let rindex = self.index(py).borrow();
        let rev = UncheckedRevision(args.get_item(py, 0).extract(py)?);
        let rust_bytes = rindex.check_revision(rev).and_then(
            |r| rindex.entry_binary(r))
            .ok_or_else(|| rev_not_in_index(py, rev))?;
        let rust_res = PyBytes::new(py, rust_bytes).into_object();

        let c_res = self.call_cindex(py, "entry_binary", args, kw)?;
        assert_py_eq(py, "entry_binary", &rust_res, &c_res)?;
        Ok(rust_res)
    }

    /// return a binary packed version of the header
    def pack_header(&self, *args, **kw) -> PyResult<PyObject> {
        let rindex = self.index(py).borrow();
        let packed = rindex.pack_header(args.get_item(py, 0).extract(py)?);
        let rust_res = PyBytes::new(py, &packed).into_object();

        let c_res = self.call_cindex(py, "pack_header", args, kw)?;
        assert_py_eq(py, "pack_header", &rust_res, &c_res)?;
        Ok(rust_res)
    }

    /// compute phases
    def computephasesmapsets(&self, *args, **kw) -> PyResult<PyObject> {
        let py_roots = args.get_item(py, 0).extract::<PyDict>(py)?;
        let rust_res = self.inner_computephasesmapsets(py, py_roots)?;

        let c_res = self.call_cindex(py, "computephasesmapsets", args, kw)?;
        assert_py_eq(py, "computephasesmapsets", &rust_res, &c_res)?;
        Ok(rust_res)
    }

    /// reachableroots
    def reachableroots2(&self, *args, **kw) -> PyResult<PyObject> {
        let rust_res = self.inner_reachableroots2(
            py,
            UncheckedRevision(args.get_item(py, 0).extract(py)?),
            args.get_item(py, 1),
            args.get_item(py, 2),
            args.get_item(py, 3).extract(py)?,
        )?;

        let c_res = self.call_cindex(py, "reachableroots2", args, kw)?;
        // ordering of C result depends on how the computation went, and
        // Rust result ordering is arbitrary. Hence we compare after
        // sorting the results (in Python to avoid reconverting everything
        // back to Rust structs).
        assert_py_eq_normalized(py, "reachableroots2", &rust_res, &c_res,
                                |v| format!("sorted({})", v))?;

        Ok(rust_res)
    }

    /// get head revisions
    def headrevs(&self, *args, **kw) -> PyResult<PyObject> {
        let rust_res = self.inner_headrevs(py)?;

        let c_res = self.call_cindex(py, "headrevs", args, kw)?;
        assert_py_eq(py, "headrevs", &rust_res, &c_res)?;
        Ok(rust_res)
    }

    /// get filtered head revisions
    def headrevsfiltered(&self, *args, **kw) -> PyResult<PyObject> {
        let rust_res = self.inner_headrevsfiltered(py, &args.get_item(py, 0))?;
        let c_res = self.call_cindex(py, "headrevsfiltered", args, kw)?;

        assert_py_eq(py, "headrevsfiltered", &rust_res, &c_res)?;
        Ok(rust_res)
    }

    /// True if the object is a snapshot
    def issnapshot(&self, *args, **kw) -> PyResult<bool> {
        let index = self.index(py).borrow();
        let result = index
            .is_snapshot(UncheckedRevision(args.get_item(py, 0).extract(py)?))
            .map_err(|e| {
                PyErr::new::<cpython::exc::ValueError, _>(py, e.to_string())
            })?;
        let cresult = self.call_cindex(py, "issnapshot", args, kw)?;
        assert_eq!(result, cresult.extract(py)?);
        Ok(result)
    }

    /// Gather snapshot data in a cache dict
    def findsnapshots(&self, *args, **kw) -> PyResult<PyObject> {
        let index = self.index(py).borrow();
        let cache: PyDict = args.get_item(py, 0).extract(py)?;
        // this methods operates by setting new values in the cache,
        // hence we will compare results by letting the C implementation
        // operate over a deepcopy of the cache, and finally compare both

        index.find_snapshots(
            start_rev,
            end_rev,
            &mut cache_wrapper,
        ).map_err(|_| revlog_error(py))?;

        let c_args = PyTuple::new(
            py,
            &[
                c_cache.clone_ref(py).into_object(),
                args.get_item(py, 1),
                args.get_item(py, 2)
            ]
        );
        self.call_cindex(py, "findsnapshots", &c_args, kw)?;
        assert_py_eq(py, "findsnapshots cache",
                     &cache_wrapper.into_object(),
                     &c_cache.into_object())?;
        Ok(py.None())
    }

    /// determine revisions with deltas to reconstruct fulltext
    def deltachain(&self, *args, **kw) -> PyResult<PyObject> {
        let index = self.index(py).borrow();
        let rev = args.get_item(py, 0).extract::<BaseRevision>(py)?.into();
        let stop_rev =
            args.get_item(py, 1).extract::<Option<BaseRevision>>(py)?;
        let rev = index.check_revision(rev).ok_or_else(|| {

            rev, stop_rev, using_general_delta
        ).map_err(|e| {
            PyErr::new::<cpython::exc::ValueError, _>(py, e.to_string())
        })?;

        let cresult = self.call_cindex(py, "deltachain", args, kw)?;
        let cchain: Vec<BaseRevision> =
            cresult.get_item(py, 0)?.extract::<Vec<BaseRevision>>(py)?;
        let chain: Vec<_> = chain.into_iter().map(|r| r.0).collect();
        assert_eq!(chain, cchain);
        assert_eq!(stopped, cresult.get_item(py, 1)?.extract(py)?);

        Ok(
            PyTuple::new(
                py,
                &[
                    chain.into_py_object(py).into_object(),

        )

    }

    /// slice planned chunk read to reach a density threshold
    def slicechunktodensity(&self, *args, **kw) -> PyResult<PyObject> {
        let rust_res = self.inner_slicechunktodensity(
            py,
            args.get_item(py, 0),
            args.get_item(py, 1).extract(py)?,
            args.get_item(py, 2).extract(py)?
        )?;

        let c_res = self.call_cindex(py, "slicechunktodensity", args, kw)?;
        assert_py_eq(py, "slicechunktodensity", &rust_res, &c_res)?;
        Ok(rust_res)
    }

    // index_sequence_methods and index_mapping_methods.
    //

        self.len(py)
    }

    def __getitem__(&self, key: PyObject) -> PyResult<PyObject> {
        let rust_res = self.inner_getitem(py, key.clone_ref(py))?;

        // this conversion seems needless, but that's actually because
        // `index_getitem` does not handle conversion from PyLong,
        // which expressions such as [e for e in index] internally use.
        // Note that we don't seem to have a direct way to call
        // PySequence_GetItem (does the job), which would possibly be better
        // for performance
        // gracinet 2023: the above comment can be removed when we use
        // the pure Rust impl only. Note also that `key` can be a binary
        // node id.
        let c_key = match key.extract::<BaseRevision>(py) {
            Ok(rev) => rev.to_py_object(py).into_object(),
            Err(_) => key,
        };
        let c_res = self.cindex(py).borrow().inner().get_item(py, c_key)?;

        assert_py_eq(py, "__getitem__", &rust_res, &c_res)?;
        Ok(rust_res)
    }

    def __contains__(&self, item: PyObject) -> PyResult<bool> {
        // ObjectProtocol does not seem to provide contains(), so
        // this is an equivalent implementation of the index_contains()
        // defined in revlog.c
        let cindex = self.cindex(py).borrow();
        match item.extract::<i32>(py) {
            Ok(rev) => {
                Ok(rev >= -1 && rev < self.len(py)? as BaseRevision)
            }
            Err(_) => {
                let item_bytes: PyBytes = item.extract(py)?;
                let rust_res = self.has_node(py, item_bytes)?;

                let c_res = cindex.inner().call_method(
                    py,
                    "has_node",
                    PyTuple::new(py, &[item.clone_ref(py)]),
                    None)?
                .extract(py)?;

                assert_eq!(rust_res, c_res);
                Ok(rust_res)
            }
        }
    }

    }

    @property
    def entry_size(&self) -> PyResult<PyInt> {
        let rust_res: PyInt = INDEX_ENTRY_SIZE.to_py_object(py);

        let c_res = self.cindex(py).borrow().inner()
            .getattr(py, "entry_size")?;
        assert_py_eq(py, "entry_size", rust_res.as_object(), &c_res)?;

        Ok(rust_res)
    }

    @property
    def rust_ext_compat(&self) -> PyResult<PyInt> {
        // will be entirely removed when the Rust index yet useful to
        // implement in Rust to detangle things when removing `self.cindex`
        let rust_res: PyInt = 1.to_py_object(py);

        let c_res = self.cindex(py).borrow().inner()
            .getattr(py, "rust_ext_compat")?;
        assert_py_eq(py, "rust_ext_compat", rust_res.as_object(), &c_res)?;

        Ok(rust_res)
    }

});

struct PySnapshotsCache<'p> {
    py: Python<'p>,
    dict: PyDict,
}

impl<'p> PySnapshotsCache<'p> {
    fn into_object(self) -> PyObject {
        self.dict.into_object()
    }
}

impl<'p> SnapshotsCache for PySnapshotsCache<'p> {
    fn insert_for(
        &mut self,
        rev: BaseRevision,
        value: BaseRevision,

        )
    }

    fn len(&self, py: Python) -> PyResult<usize> {
        let rust_index_len = self.index(py).borrow().len();
        let cindex_len = self.cindex(py).borrow().inner().len(py)?;
        assert_eq!(rust_index_len, cindex_len);
        Ok(rust_index_len)
    }

    /// This is scaffolding at this point, but it could also become
    /// a way to start a persistent nodemap or perform a

            let mut nt = NodeTree::load_bytes(readonly, 0);
            self.fill_nodemap(py, &mut nt)?;
            self.nt(py).borrow_mut().replace(nt);
        }
        Ok(self.nt(py))
    }

    /// forward a method call to the underlying C index
    fn call_cindex(
        &self,
        py: Python,
        name: &str,
        args: &PyTuple,
        kwargs: Option<&PyDict>,
    ) -> PyResult<PyObject> {
        self.cindex(py)
            .borrow()
            .inner()
            .call_method(py, name, args, kwargs)
    }

    pub fn clone_cindex(&self, py: Python) -> cindex::Index {
        self.cindex(py).borrow().clone_ref(py)
    }

        NodeMapError::MultipleResults => revlog_error(py),
        NodeMapError::RevisionNotInIndex(r) => nodemap_rev_not_in_index(py, r),
    }
}

/// assert two Python objects to be equal from a Python point of view
///
/// `method` is a label for the assertion error message, intended to be the
/// name of the caller.
/// `normalizer` is a function that takes a Python variable name and returns
/// an expression that the conparison will actually use.
/// Foe example: `|v| format!("sorted({})", v)`
fn assert_py_eq_normalized(
    py: Python,
    method: &str,
    rust: &PyObject,
    c: &PyObject,
    normalizer: impl FnOnce(&str) -> String + Copy,
) -> PyResult<()> {
    let locals = PyDict::new(py);
    locals.set_item(py, "rust".into_py_object(py).into_object(), rust)?;
    locals.set_item(py, "c".into_py_object(py).into_object(), c)?;
    //    let lhs = format!(normalizer_fmt, "rust");
    //    let rhs = format!(normalizer_fmt, "c");
    let is_eq: PyBool = py
        .eval(
            &format!("{} == {}", &normalizer("rust"), &normalizer("c")),
            None,
            Some(&locals),
        )?
        .extract(py)?;
    assert!(
        is_eq.is_true(),
        "{} results differ. Rust: {:?} C: {:?} (before any normalization)",
        method,
        rust,
        c
    );
    Ok(())
}

fn assert_py_eq(
    py: Python,
    method: &str,
    rust: &PyObject,
    c: &PyObject,
) -> PyResult<()> {
    assert_py_eq_normalized(py, method, rust, c, |v| v.to_owned())
}

/// Create the module, with __package__ given from parent
pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
    let dotted_name = &format!("{}.revlog", package);
    let m = PyModule::new(py, dotted_name)?;
    m.add(py, "__package__", package)?;

51246:41e19e8a6133

    PyRevision,
};
use cpython::{
    buffer::{Element, PyBuffer},
    exc::{IndexError, ValueError},
    ObjectProtocol, PyBytes, PyClone, PyDict, PyErr, PyInt, PyList, PyModule,
    PyObject, PyResult, PySet, PyString, PyTuple, Python, PythonObject,
    ToPyObject, UnsafePyLeaked,
};
use hg::{
    errors::HgError,
    index::{
        IndexHeader, Phase, RevisionDataParams, SnapshotsCache,

    /// Return Revision if found, raises a bare `error.RevlogError`
    /// in case of ambiguity, same as C version does
    def get_rev(&self, node: PyBytes) -> PyResult<Option<PyRevision>> {
        let opt = self.get_nodetree(py)?.borrow();
        let nt = opt.as_ref().unwrap();
        let ridx = &*self.index(py).borrow();
        let node = node_from_py_bytes(py, &node)?;
        let rust_rev =
            nt.find_bin(ridx, node.into()).map_err(|e| nodemap_error(py, e))?;
        Ok(rust_rev.map(Into::into))

    }

    /// same as `get_rev()` but raises a bare `error.RevlogError` if node

        }
        let node_bytes = tup.get_item(py, 7).extract(py)?;
        let node = node_from_py_object(py, &node_bytes)?;

        let rev = self.len(py)? as BaseRevision;

        // This is ok since we will just add the revision to the index
        let rev = Revision(rev);
        self.index(py)
            .borrow_mut()
            .append(py_tuple_to_revision_data_params(py, tup)?)
            .unwrap();
        let idx = &*self.index(py).borrow();
        self.get_nodetree(py)?.borrow_mut().as_mut().unwrap()
            .insert(idx, &node, rev)
            .map_err(|e| nodemap_error(py, e))?;
        Ok(py.None())
    }

    def __delitem__(&self, key: PyObject) -> PyResult<()> {
        // __delitem__ is both for `del idx[r]` and `del idx[r1:r2]`
        let start = key.getattr(py, "start")?;
        let start = UncheckedRevision(start.extract(py)?);
        let start = self.index(py)
            .borrow()
            .check_revision(start)

        self.fill_nodemap(py, nt)?;
        Ok(())
    }

    //
    // Index methods previously reforwarded to C index (tp_methods)
    // Same ordering as in revlog.c
    //

    /// return the gca set of the given revs
    def ancestors(&self, *args, **_kw) -> PyResult<PyObject> {
        let rust_res = self.inner_ancestors(py, args)?;
        Ok(rust_res)
    }

    /// return the heads of the common ancestors of the given revs
    def commonancestorsheads(&self, *args, **_kw) -> PyResult<PyObject> {
        let rust_res = self.inner_commonancestorsheads(py, args)?;
        Ok(rust_res)
    }

    /// Clear the index caches and inner py_class data.
    /// It is Python's responsibility to call `update_nodemap_data` again.
    def clearcaches(&self) -> PyResult<PyObject> {
        self.nt(py).borrow_mut().take();
        self.docket(py).borrow_mut().take();
        self.nodemap_mmap(py).borrow_mut().take();
        self.index(py).borrow().clear_caches();
        Ok(py.None())
    }

    /// return the raw binary string representing a revision
    def entry_binary(&self, *args, **_kw) -> PyResult<PyObject> {
        let rindex = self.index(py).borrow();
        let rev = UncheckedRevision(args.get_item(py, 0).extract(py)?);
        let rust_bytes = rindex.check_revision(rev).and_then(
            |r| rindex.entry_binary(r))
            .ok_or_else(|| rev_not_in_index(py, rev))?;
        let rust_res = PyBytes::new(py, rust_bytes).into_object();
        Ok(rust_res)
    }

    /// return a binary packed version of the header
    def pack_header(&self, *args, **_kw) -> PyResult<PyObject> {
        let rindex = self.index(py).borrow();
        let packed = rindex.pack_header(args.get_item(py, 0).extract(py)?);
        let rust_res = PyBytes::new(py, &packed).into_object();
        Ok(rust_res)
    }

    /// compute phases
    def computephasesmapsets(&self, *args, **_kw) -> PyResult<PyObject> {
        let py_roots = args.get_item(py, 0).extract::<PyDict>(py)?;
        let rust_res = self.inner_computephasesmapsets(py, py_roots)?;
        Ok(rust_res)
    }

    /// reachableroots
    def reachableroots2(&self, *args, **_kw) -> PyResult<PyObject> {
        let rust_res = self.inner_reachableroots2(
            py,
            UncheckedRevision(args.get_item(py, 0).extract(py)?),
            args.get_item(py, 1),
            args.get_item(py, 2),
            args.get_item(py, 3).extract(py)?,
        )?;
        Ok(rust_res)
    }

    /// get head revisions
    def headrevs(&self) -> PyResult<PyObject> {
        let rust_res = self.inner_headrevs(py)?;
        Ok(rust_res)
    }

    /// get filtered head revisions
    def headrevsfiltered(&self, *args, **_kw) -> PyResult<PyObject> {
        let rust_res = self.inner_headrevsfiltered(py, &args.get_item(py, 0))?;
        Ok(rust_res)
    }

    /// True if the object is a snapshot
    def issnapshot(&self, *args, **_kw) -> PyResult<bool> {
        let index = self.index(py).borrow();
        let result = index
            .is_snapshot(UncheckedRevision(args.get_item(py, 0).extract(py)?))
            .map_err(|e| {
                PyErr::new::<cpython::exc::ValueError, _>(py, e.to_string())
            })?;
        Ok(result)
    }

    /// Gather snapshot data in a cache dict
    def findsnapshots(&self, *args, **_kw) -> PyResult<PyObject> {
        let index = self.index(py).borrow();
        let cache: PyDict = args.get_item(py, 0).extract(py)?;
        // this methods operates by setting new values in the cache,
        // hence we will compare results by letting the C implementation
        // operate over a deepcopy of the cache, and finally compare both

        index.find_snapshots(
            start_rev,
            end_rev,
            &mut cache_wrapper,
        ).map_err(|_| revlog_error(py))?;
        Ok(py.None())
    }

    /// determine revisions with deltas to reconstruct fulltext
    def deltachain(&self, *args, **_kw) -> PyResult<PyObject> {
        let index = self.index(py).borrow();
        let rev = args.get_item(py, 0).extract::<BaseRevision>(py)?.into();
        let stop_rev =
            args.get_item(py, 1).extract::<Option<BaseRevision>>(py)?;
        let rev = index.check_revision(rev).ok_or_else(|| {

            rev, stop_rev, using_general_delta
        ).map_err(|e| {
            PyErr::new::<cpython::exc::ValueError, _>(py, e.to_string())
        })?;

        let chain: Vec<_> = chain.into_iter().map(|r| r.0).collect();
        Ok(
            PyTuple::new(
                py,
                &[
                    chain.into_py_object(py).into_object(),

        )

    }

    /// slice planned chunk read to reach a density threshold
    def slicechunktodensity(&self, *args, **_kw) -> PyResult<PyObject> {
        let rust_res = self.inner_slicechunktodensity(
            py,
            args.get_item(py, 0),
            args.get_item(py, 1).extract(py)?,
            args.get_item(py, 2).extract(py)?
        )?;
        Ok(rust_res)
    }

    // index_sequence_methods and index_mapping_methods.
    //

        self.len(py)
    }

    def __getitem__(&self, key: PyObject) -> PyResult<PyObject> {
        let rust_res = self.inner_getitem(py, key.clone_ref(py))?;
        Ok(rust_res)
    }

    def __contains__(&self, item: PyObject) -> PyResult<bool> {
        // ObjectProtocol does not seem to provide contains(), so
        // this is an equivalent implementation of the index_contains()
        // defined in revlog.c
        match item.extract::<i32>(py) {
            Ok(rev) => {
                Ok(rev >= -1 && rev < self.len(py)? as BaseRevision)
            }
            Err(_) => {
                let item_bytes: PyBytes = item.extract(py)?;
                let rust_res = self.has_node(py, item_bytes)?;
                Ok(rust_res)
            }
        }
    }

    }

    @property
    def entry_size(&self) -> PyResult<PyInt> {
        let rust_res: PyInt = INDEX_ENTRY_SIZE.to_py_object(py);
        Ok(rust_res)
    }

    @property
    def rust_ext_compat(&self) -> PyResult<PyInt> {
        // will be entirely removed when the Rust index yet useful to
        // implement in Rust to detangle things when removing `self.cindex`
        let rust_res: PyInt = 1.to_py_object(py);
        Ok(rust_res)
    }

});

struct PySnapshotsCache<'p> {
    py: Python<'p>,
    dict: PyDict,
}

impl<'p> SnapshotsCache for PySnapshotsCache<'p> {
    fn insert_for(
        &mut self,
        rev: BaseRevision,
        value: BaseRevision,

        )
    }

    fn len(&self, py: Python) -> PyResult<usize> {
        let rust_index_len = self.index(py).borrow().len();
        Ok(rust_index_len)
    }

    /// This is scaffolding at this point, but it could also become
    /// a way to start a persistent nodemap or perform a

            let mut nt = NodeTree::load_bytes(readonly, 0);
            self.fill_nodemap(py, &mut nt)?;
            self.nt(py).borrow_mut().replace(nt);
        }
        Ok(self.nt(py))
    }

    pub fn clone_cindex(&self, py: Python) -> cindex::Index {
        self.cindex(py).borrow().clone_ref(py)
    }

        NodeMapError::MultipleResults => revlog_error(py),
        NodeMapError::RevisionNotInIndex(r) => nodemap_rev_not_in_index(py, r),
    }
}

/// Create the module, with __package__ given from parent
pub fn init_module(py: Python, package: &str) -> PyResult<PyModule> {
    let dotted_name = &format!("{}.revlog", package);
    let m = PyModule::new(py, dotted_name)?;
    m.add(py, "__package__", package)?;