dirstate-v2: Reserve a few bytes of space for future extensions
See doc-comment
Differential Revision: https://phab.mercurial-scm.org/D11101
--- a/mercurial/dirstateutils/docket.py Fri Jul 16 14:08:26 2021 +0200
+++ b/mercurial/dirstateutils/docket.py Fri Jul 16 16:19:31 2021 +0200
@@ -16,7 +16,7 @@
# Must match the constant of the same name in
# `rust/hg-core/src/dirstate_tree/on_disk.rs`
-TREE_METADATA_SIZE = 40
+TREE_METADATA_SIZE = 44
# * 12 bytes: format marker
# * 32 bytes: node ID of the working directory's first parent
--- a/rust/hg-core/src/dirstate_tree/on_disk.rs Fri Jul 16 14:08:26 2021 +0200
+++ b/rust/hg-core/src/dirstate_tree/on_disk.rs Fri Jul 16 16:19:31 2021 +0200
@@ -49,13 +49,13 @@
/// Must match the constant of the same name in
/// `mercurial/dirstateutils/docket.py`
-const TREE_METADATA_SIZE: usize = 40;
+const TREE_METADATA_SIZE: usize = 44;
/// Make sure that size-affecting changes are made knowingly
#[allow(unused)]
fn static_assert_size_of() {
- let _ = std::mem::transmute::<DocketHeader, [u8; 121]>;
let _ = std::mem::transmute::<TreeMetadata, [u8; TREE_METADATA_SIZE]>;
+ let _ = std::mem::transmute::<DocketHeader, [u8; TREE_METADATA_SIZE + 81]>;
let _ = std::mem::transmute::<Node, [u8; 43]>;
}
@@ -90,6 +90,12 @@
/// How many bytes of this data file are not used anymore
unreachable_bytes: Size,
+ /// Current version always sets these bytes to zero when creating or
+ /// updating a dirstate. Future versions could assign some bits to signal
+ /// for example "the version that last wrote/updated this dirstate did so
+ /// in such and such way that can be relied on by versions that know to."
+ unused: [u8; 4],
+
/// If non-zero, a hash of ignore files that were used for some previous
/// run of the `status` algorithm.
///
@@ -579,6 +585,7 @@
.nodes_with_copy_source_count
.into(),
unreachable_bytes: dirstate_map.unreachable_bytes.into(),
+ unused: [0; 4],
ignore_patterns_hash: dirstate_map.ignore_patterns_hash,
};
Ok((writer.out, meta.as_bytes().to_vec(), append))