D11096: dirstate-v2: Reuse existing paths when appending to a data file
SimonSapin
phabricator at mercurial-scm.org
Thu Jul 15 15:28:45 UTC 2021
SimonSapin created this revision.
Herald added a reviewer: hg-reviewers.
Herald added a subscriber: mercurial-patches.
REVISION SUMMARY
When writing a dirstate in v2 format by appending to an existing data file,
filenames / paths that are borrowed from the previous on-disk representation
can be reused.
REPOSITORY
rHG Mercurial
BRANCH
default
REVISION DETAIL
https://phab.mercurial-scm.org/D11096
AFFECTED FILES
rust/hg-core/src/dirstate_tree/on_disk.rs
CHANGE DETAILS
diff --git a/rust/hg-core/src/dirstate_tree/on_disk.rs b/rust/hg-core/src/dirstate_tree/on_disk.rs
--- a/rust/hg-core/src/dirstate_tree/on_disk.rs
+++ b/rust/hg-core/src/dirstate_tree/on_disk.rs
@@ -590,9 +590,12 @@
&mut self,
nodes: dirstate_map::ChildNodesRef,
) -> Result<ChildNodes, DirstateError> {
+ // Reuse already-written nodes if possible
if self.append {
if let dirstate_map::ChildNodesRef::OnDisk(nodes_slice) = nodes {
- let start = self.offset_of(nodes_slice);
+ let start = self.on_disk_offset_of(nodes_slice).expect(
+ "dirstate-v2 OnDisk nodes not found within on_disk",
+ );
let len = child_nodes_len_from_usize(nodes_slice.len());
return Ok(ChildNodes { start, len });
}
@@ -678,11 +681,9 @@
Ok(ChildNodes { start, len })
}
- /// Takes a slice of items within `on_disk` and returns its offset for the
- /// start of `on_disk`.
- ///
- /// Panics if the given slice is not within `on_disk`.
- fn offset_of<T>(&self, slice: &[T]) -> Offset
+ /// If the given slice of items is within `on_disk`, returns its offset
+ /// from the start of `on_disk`.
+ fn on_disk_offset_of<T>(&self, slice: &[T]) -> Option<Offset>
where
T: BytesCast,
{
@@ -693,10 +694,14 @@
}
let slice_addresses = address_range(slice.as_bytes());
let on_disk_addresses = address_range(self.dirstate_map.on_disk);
- assert!(on_disk_addresses.contains(slice_addresses.start()));
- assert!(on_disk_addresses.contains(slice_addresses.end()));
- let offset = slice_addresses.start() - on_disk_addresses.start();
- offset_from_usize(offset)
+ if on_disk_addresses.contains(slice_addresses.start())
+ && on_disk_addresses.contains(slice_addresses.end())
+ {
+ let offset = slice_addresses.start() - on_disk_addresses.start();
+ Some(offset_from_usize(offset))
+ } else {
+ None
+ }
}
fn curent_offset(&mut self) -> Offset {
@@ -708,8 +713,14 @@
}
fn write_path(&mut self, slice: &[u8]) -> PathSlice {
+ let len = path_len_from_usize(slice.len());
+ // Reuse an already-written path if possible
+ if self.append {
+ if let Some(start) = self.on_disk_offset_of(slice) {
+ return PathSlice { start, len };
+ }
+ }
let start = self.curent_offset();
- let len = path_len_from_usize(slice.len());
self.out.extend(slice.as_bytes());
PathSlice { start, len }
}
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