rust-revlog: a trait for the revlog index
As explained in the doc comment, this is the minimum needed
for our immediate concern, which is to implement a nodemap
in Rust.
The trait will be later implemented in `hg-cpython` by the
index Python object implemented in C, thanks to exposition
of the corresponding functions as a capsule.
The `None` return cases in `node()` match what the `index_node()`
C function does.
Differential Revision: https://phab.mercurial-scm.org/D7789
--- a/rust/hg-core/src/revlog.rs Fri Jan 24 17:10:45 2020 -0800
+++ b/rust/hg-core/src/revlog.rs Wed Jan 22 16:35:56 2020 +0100
@@ -40,3 +40,17 @@
ParentOutOfRange(Revision),
WorkingDirectoryUnsupported,
}
+
+/// The Mercurial Revlog Index
+///
+/// This is currently limited to the minimal interface that is needed for
+/// the [`nodemap`](nodemap/index.html) module
+pub trait RevlogIndex {
+ /// Total number of Revisions referenced in this index
+ fn len(&self) -> usize;
+
+ /// Return a reference to the Node or `None` if rev is out of bounds
+ ///
+ /// `NULL_REVISION` is not considered to be out of bounds.
+ fn node(&self, rev: Revision) -> Option<&Node>;
+}