rust-index: add a struct wrapping the C index

Implementing the full index logic in one go is journey larger than we would
like.

To achieve a smoother transition, we start with a simple Rust wrapper that delegates
allwork to the current C implementation. Once we will have a fully working index
object in Rust, we can easily start using more and more Rust Code with it.

The object in this patch is functional and tested. However, multiple of the
currently existing rust (in the `hg-cpython` crate) requires a `Graph`. Right
now we build this `Graph` (as cindex::Index) using the C index passed as
a PyObject. They will have to be updated to be made compatible.

Differential Revision: https://phab.mercurial-scm.org/D7655

tests/test-rust-revlog.py

@@ -0,0 +1,34 b''
+from __future__ import absolute_import
+import unittest
+
+try:
+    from mercurial import rustext
+
+    rustext.__name__  # trigger immediate actual import
+except ImportError:
+    rustext = None
+else:
+    from mercurial.rustext import revlog
+
+from mercurial.testing import revlog as revlogtesting
+
+
[e-mail](
+    rustext is None, "rustext module revlog relies on is not available",
+)
+class RustRevlogIndexTest(revlogtesting.RevlogBasedTestBase):
+    def test_heads(self):
+        idx = self.parseindex()
+        rustidx = revlog.MixedIndex(idx)
+        self.assertEqual(rustidx.headrevs(), idx.headrevs())
+
+    def test_len(self):
+        idx = self.parseindex()
+        rustidx = revlog.MixedIndex(idx)
+        self.assertEqual(len(rustidx), len(idx))
+
+
+if __name__ == '__main__':
+    import silenttestrunner
+
+    silenttestrunner.main(__name__)

rust/hg-cpython/src/lib.rs

@@ -50,6 +50,7 b' py_module_initializer!(rustext, initrust'
     m.add(py, "dagop", dagops::init_module(py, &dotted_name)?)?;
     m.add(py, "discovery", discovery::init_module(py, &dotted_name)?)?;
     m.add(py, "dirstate", dirstate::init_module(py, &dotted_name)?)?;
+    m.add(py, "revlog", revlog::init_module(py, &dotted_name)?)?;
     m.add(
         py,
         "filepatterns",

rust/hg-cpython/src/revlog.rs

@@ -6,7 +6,12 b''
 // GNU General Public License version 2 or any later version.
 
 use crate::cindex;
-use cpython::{PyObject, PyResult, Python};
+use cpython::{
+    ObjectProtocol, PyDict, PyModule, PyObject, PyResult, PyTuple, Python,
+    PythonObject, ToPyObject,
+};
+use hg::Revision;
+use std::cell::RefCell;
 
 /// Return a Struct implementing the Graph trait
 pub(crate) fn pyindex_to_graph(
@@ -15,3 +20,198 b' pub(crate) fn pyindex_to_graph('
 ) -> PyResult<cindex::Index> {
     cindex::Index::new(py, index)
 }
+
+py_class!(pub class MixedIndex |py| {
+    data cindex: RefCell<cindex::Index>;
+
+    def __new__(_cls, cindex: PyObject) -> PyResult<MixedIndex> {
+        Self::create_instance(py, RefCell::new(
+            cindex::Index::new(py, cindex)?))
+    }
+
+
+    // 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> {
+        self.call_cindex(py, "ancestors", args, kw)
+    }
+
+    /// return the heads of the common ancestors of the given revs
+    def commonancestorsheads(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "commonancestorsheads", args, kw)
+    }
+
+    /// clear the index caches
+    def clearcaches(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "clearcaches", args, kw)
+    }
+
+    /// get an index entry
+    def get(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "get", args, kw)
+    }
+
+    /// return `rev` associated with a node or None
+    def get_rev(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "get_rev", args, kw)
+    }
+
+    /// return True if the node exist in the index
+    def has_node(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "has_node", args, kw)
+    }
+
+    /// return `rev` associated with a node or raise RevlogError
+    def rev(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "rev", args, kw)
+    }
+
+    /// compute phases
+    def computephasesmapsets(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "computephasesmapsets", args, kw)
+    }
+
+    /// reachableroots
+    def reachableroots2(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "reachableroots2", args, kw)
+    }
+
+    /// get head revisions
+    def headrevs(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "headrevs", args, kw)
+    }
+
+    /// get filtered head revisions
+    def headrevsfiltered(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "headrevsfiltered", args, kw)
+    }
+
+    /// True if the object is a snapshot
+    def issnapshot(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "issnapshot", args, kw)
+    }
+
+    /// Gather snapshot data in a cache dict
+    def findsnapshots(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "findsnapshots", args, kw)
+    }
+
+    /// determine revisions with deltas to reconstruct fulltext
+    def deltachain(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "deltachain", args, kw)
+    }
+
+    /// slice planned chunk read to reach a density threshold
+    def slicechunktodensity(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "slicechunktodensity", args, kw)
+    }
+
+    /// append an index entry
+    def append(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "append", args, kw)
+    }
+
+    /// match a potentially ambiguous node ID
+    def partialmatch(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "partialmatch", args, kw)
+    }
+
+    /// find length of shortest hex nodeid of a binary ID
+    def shortest(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "shortest", args, kw)
+    }
+
+    /// stats for the index
+    def stats(&self, *args, **kw) -> PyResult<PyObject> {
+        self.call_cindex(py, "stats", args, kw)
+    }
+
+    // index_sequence_methods and index_mapping_methods.
+    //
+    // Since we call back through the high level Python API,
+    // there's no point making a distinction between index_get
+    // and index_getitem.
+
+    def __len__(&self) -> PyResult<usize> {
+        self.cindex(py).borrow().inner().len(py)
+    }
+
+    def __getitem__(&self, key: PyObject) -> PyResult<PyObject> {
+        // 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 be better for
+        // for performance
+        let key = match key.extract::<Revision>(py) {
+            Ok(rev) => rev.to_py_object(py).into_object(),
+            Err(_) => key,
+        };
+        self.cindex(py).borrow().inner().get_item(py, key)
+    }
+
+    def __setitem__(&self, key: PyObject, value: PyObject) -> PyResult<()> {
+        self.cindex(py).borrow().inner().set_item(py, key, value)
+    }
+
+    def __delitem__(&self, key: PyObject) -> PyResult<()> {
+        self.cindex(py).borrow().inner().del_item(py, key)
+    }
+
+    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::<Revision>(py) {
+            Ok(rev) => {
+                Ok(rev >= -1 && rev < cindex.inner().len(py)? as Revision)
+            }
+            Err(_) => {
+                cindex.inner().call_method(
+                    py,
+                    "has_node",
+                    PyTuple::new(py, &[item]),
+                    None)?
+                .extract(py)
+            }
+        }
+    }
+
+
+});
+
+impl MixedIndex {
+    /// 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)
+    }
+}
+
+/// 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)?;
+    m.add(py, "__doc__", "RevLog - Rust implementations")?;
+
+    m.add_class::<MixedIndex>(py)?;
+
+    let sys = PyModule::import(py, "sys")?;
+    let sys_modules: PyDict = sys.get(py, "modules")?.extract(py)?;
+    sys_modules.set_item(py, dotted_name, &m)?;
+
+    Ok(m)
+}