Mercurial > hg
view rust/hg-core/src/copy_tracing.rs @ 45944:595979dc924e
copies: introduce a basic Rust function for `combine_changeset_copies`
This new function mirror the python code. This first implementation does a lot
of data copies and is therefore quite slow. However my goal here is to create a
simple "frame" from where to start adding optimization.
This patch focus on the `hg-core` part of this work. Coming patches will do the
necessary `hg-cpython` work to be able to use this from Python.
Differential Revision: https://phab.mercurial-scm.org/D9297
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
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date | Thu, 01 Oct 2020 18:51:06 +0200 |
parents | |
children | 0d99778af68a |
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use crate::utils::hg_path::HgPathBuf; use crate::Revision; use std::collections::HashMap; use std::collections::HashSet; pub type PathCopies = HashMap<HgPathBuf, HgPathBuf>; #[derive(Clone, Debug)] struct TimeStampedPathCopy { /// revision at which the copy information was added rev: Revision, /// the copy source, (Set to None in case of deletion of the associated /// key) path: Option<HgPathBuf>, } /// maps CopyDestination to Copy Source (+ a "timestamp" for the operation) type TimeStampedPathCopies = HashMap<HgPathBuf, TimeStampedPathCopy>; /// hold parent 1, parent 2 and relevant files actions. pub type RevInfo = (Revision, Revision, ChangedFiles); /// represent the files affected by a changesets /// /// This hold a subset of mercurial.metadata.ChangingFiles as we do not need /// all the data categories tracked by it. pub struct ChangedFiles { removed: HashSet<HgPathBuf>, merged: HashSet<HgPathBuf>, salvaged: HashSet<HgPathBuf>, copied_from_p1: PathCopies, copied_from_p2: PathCopies, } impl ChangedFiles { pub fn new( removed: HashSet<HgPathBuf>, merged: HashSet<HgPathBuf>, salvaged: HashSet<HgPathBuf>, copied_from_p1: PathCopies, copied_from_p2: PathCopies, ) -> Self { ChangedFiles { removed, merged, salvaged, copied_from_p1, copied_from_p2, } } pub fn new_empty() -> Self { ChangedFiles { removed: HashSet::new(), merged: HashSet::new(), salvaged: HashSet::new(), copied_from_p1: PathCopies::new(), copied_from_p2: PathCopies::new(), } } } /// Same as mercurial.copies._combine_changeset_copies, but in Rust. /// /// Arguments are: /// /// revs: all revisions to be considered /// children: a {parent ? [childrens]} mapping /// target_rev: the final revision we are combining copies to /// rev_info(rev): callback to get revision information: /// * first parent /// * second parent /// * ChangedFiles /// isancestors(low_rev, high_rev): callback to check if a revision is an /// ancestor of another pub fn combine_changeset_copies( revs: Vec<Revision>, children: HashMap<Revision, Vec<Revision>>, target_rev: Revision, rev_info: &impl Fn(Revision) -> RevInfo, is_ancestor: &impl Fn(Revision, Revision) -> bool, ) -> PathCopies { let mut all_copies = HashMap::new(); for rev in revs { // Retrieve data computed in a previous iteration let copies = all_copies.remove(&rev); let copies = match copies { Some(c) => c, None => TimeStampedPathCopies::default(), // root of the walked set }; let current_children = match children.get(&rev) { Some(c) => c, None => panic!("inconsistent `revs` and `children`"), }; for child in current_children { // We will chain the copies information accumulated for `rev` with // the individual copies information for each of its children. // Creating a new PathCopies for each `rev` ? `children` vertex. let (p1, p2, changes) = rev_info(*child); let (parent, child_copies) = if rev == p1 { (1, &changes.copied_from_p1) } else { assert_eq!(rev, p2); (2, &changes.copied_from_p2) }; let mut new_copies = copies.clone(); for (dest, source) in child_copies { let entry; if let Some(v) = copies.get(source) { entry = match &v.path { Some(path) => Some((*(path)).to_owned()), None => Some(source.to_owned()), } } else { entry = Some(source.to_owned()); } // Each new entry is introduced by the children, we record this // information as we will need it to take the right decision // when merging conflicting copy information. See // merge_copies_dict for details. let ttpc = TimeStampedPathCopy { rev: *child, path: entry, }; new_copies.insert(dest.to_owned(), ttpc); } // We must drop copy information for removed file. // // We need to explicitly record them as dropped to propagate this // information when merging two TimeStampedPathCopies object. for f in changes.removed.iter() { if new_copies.contains_key(f.as_ref()) { let ttpc = TimeStampedPathCopy { rev: *child, path: None, }; new_copies.insert(f.to_owned(), ttpc); } } // Merge has two parents needs to combines their copy information. // // If the vertex from the other parent was already processed, we // will have a value for the child ready to be used. We need to // grab it and combine it with the one we already // computed. If not we can simply store the newly // computed data. The processing happening at // the time of the second parent will take care of combining the // two TimeStampedPathCopies instance. match all_copies.remove(child) { None => { all_copies.insert(child, new_copies); } Some(other_copies) => { let (minor, major) = match parent { 1 => (other_copies, new_copies), 2 => (new_copies, other_copies), _ => unreachable!(), }; let merged_copies = merge_copies_dict(minor, major, &changes, is_ancestor); all_copies.insert(child, merged_copies); } }; } } // Drop internal information (like the timestamp) and return the final // mapping. let tt_result = all_copies .remove(&target_rev) .expect("target revision was not processed"); let mut result = PathCopies::default(); for (dest, tt_source) in tt_result { if let Some(path) = tt_source.path { result.insert(dest, path); } } result } /// merge two copies-mapping together, minor and major /// /// In case of conflict, value from "major" will be picked, unless in some /// cases. See inline documentation for details. #[allow(clippy::if_same_then_else)] fn merge_copies_dict( minor: TimeStampedPathCopies, major: TimeStampedPathCopies, changes: &ChangedFiles, is_ancestor: &impl Fn(Revision, Revision) -> bool, ) -> TimeStampedPathCopies { let mut result = minor.clone(); for (dest, src_major) in major { let overwrite; if let Some(src_minor) = minor.get(&dest) { if src_major.path == src_minor.path { // we have the same value, but from other source; if src_major.rev == src_minor.rev { // If the two entry are identical, no need to do anything overwrite = false; } else if is_ancestor(src_major.rev, src_minor.rev) { overwrite = false; } else { overwrite = true; } } else if src_major.rev == src_minor.rev { // We cannot get copy information for both p1 and p2 in the // same rev. So this is the same value. overwrite = false; } else if src_major.path.is_none() && changes.salvaged.contains(&dest) { // If the file is "deleted" in the major side but was salvaged // by the merge, we keep the minor side alive overwrite = false; } else if src_minor.path.is_none() && changes.salvaged.contains(&dest) { // If the file is "deleted" in the minor side but was salvaged // by the merge, unconditionnaly preserve the major side. overwrite = true; } else if changes.merged.contains(&dest) { // If the file was actively merged, copy information from each // side might conflict. The major side will win such conflict. overwrite = true; } else if is_ancestor(src_major.rev, src_minor.rev) { // If the minor side is strictly newer than the major side, it // should be kept. overwrite = false; } else if src_major.path.is_some() { // without any special case, the "major" value win other the // "minor" one. overwrite = true; } else if is_ancestor(src_minor.rev, src_major.rev) { // the "major" rev is a direct ancestors of "minor", any // different value should overwrite overwrite = true; } else { // major version is None (so the file was deleted on that // branch) annd that branch is independant (neither minor nor // major is an ancestors of the other one.) We preserve the new // information about the new file. overwrite = false; } } else { // minor had no value overwrite = true; } if overwrite { result.insert(dest, src_major); } } result }