annotate rust/hg-core/src/dirstate_tree/dirstate_map.rs @ 47123:d8ac62374943

dirstate-tree: Make `DirstateMap` borrow from a bytes buffer

… that has the contents of the `.hg/dirstate` file.
This only applies to the tree-based flavor of `DirstateMap`.

For now only the entire `&[u8]` slice is stored, so this is not useful yet.

Adding a lifetime parameter to the `DirstateMap` struct (in hg-core) makes
Python bindings non-trivial because we keep that struct in a Python object
that has a dynamic lifetime tied to Python’s reference-counting and GC.
As long as we keep the `PyBytes` that owns the borrowed bytes buffer next to
the borrowing struct, the buffer will live long enough for the borrows to stay
valid. However this relationship cannot be expressed in safe Rust code in a
way that would statisfy they borrow-checker. We use `unsafe` code to erase
that lifetime parameter, and encapsulate it in a safe abstraction similar to
the owning-ref crate: https://docs.rs/owning_ref/

Differential Revision: https://phab.mercurial-scm.org/D10557

use bytes_cast::BytesCast;
use micro_timer::timed;
use std::convert::TryInto;
use std::path::PathBuf;

use super::path_with_basename::WithBasename;
use crate::dirstate::parsers::clear_ambiguous_mtime;
use crate::dirstate::parsers::pack_entry;
use crate::dirstate::parsers::packed_entry_size;
use crate::dirstate::parsers::parse_dirstate_entries;
use crate::dirstate::parsers::Timestamp;
use crate::matchers::Matcher;
use crate::utils::hg_path::{HgPath, HgPathBuf};
use crate::CopyMapIter;
use crate::DirstateEntry;
use crate::DirstateError;
use crate::DirstateMapError;
use crate::DirstateParents;
use crate::DirstateStatus;
use crate::EntryState;
use crate::FastHashMap;
use crate::PatternFileWarning;
use crate::StateMapIter;
use crate::StatusError;
use crate::StatusOptions;

pub struct DirstateMap<'on_disk> {
    /// Contents of the `.hg/dirstate` file
    on_disk: &'on_disk [u8],

    pub(super) root: ChildNodes,

    /// Number of nodes anywhere in the tree that have `.entry.is_some()`.
    nodes_with_entry_count: usize,

    /// Number of nodes anywhere in the tree that have
    /// `.copy_source.is_some()`.
    nodes_with_copy_source_count: usize,
}

/// Using a plain `HgPathBuf` of the full path from the repository root as a
/// map key would also work: all paths in a given map have the same parent
/// path, so comparing full paths gives the same result as comparing base
/// names. However `BTreeMap` would waste time always re-comparing the same
/// string prefix.
pub(super) type ChildNodes = FastHashMap<WithBasename<HgPathBuf>, Node>;

/// Represents a file or a directory
#[derive(Default)]
pub(super) struct Node {
    /// `None` for directories
    pub(super) entry: Option<DirstateEntry>,

    pub(super) copy_source: Option<HgPathBuf>,

    pub(super) children: ChildNodes,

    /// How many (non-inclusive) descendants of this node are tracked files
    tracked_descendants_count: usize,
}

impl Node {
    pub(super) fn state(&self) -> Option<EntryState> {
        self.entry.as_ref().map(|entry| entry.state)
    }
}

/// `(full_path, entry, copy_source)`
type NodeDataMut<'a> = (
    &'a WithBasename<HgPathBuf>,
    &'a mut Option<DirstateEntry>,
    &'a mut Option<HgPathBuf>,
);

impl<'on_disk> DirstateMap<'on_disk> {
    pub fn new(
        on_disk: &'on_disk [u8],
    ) -> Result<(Self, Option<DirstateParents>), DirstateError> {
        let mut map = Self {
            on_disk,
            root: ChildNodes::default(),
            nodes_with_entry_count: 0,
            nodes_with_copy_source_count: 0,
        };
        let parents = map.read()?;
        Ok((map, parents))
    }

    /// Should only be called in `new`
    #[timed]
    fn read(&mut self) -> Result<Option<DirstateParents>, DirstateError> {
        if self.on_disk.is_empty() {
            return Ok(None);
        }

        let parents = parse_dirstate_entries(
            self.on_disk,
            |path, entry, copy_source| {
                let tracked = entry.state.is_tracked();
                let node = Self::get_or_insert_node_tracing_ancestors(
                    &mut self.root,
                    path,
                    |ancestor| {
                        if tracked {
                            ancestor.tracked_descendants_count += 1
                        }
                    },
                );
                assert!(
                    node.entry.is_none(),
                    "duplicate dirstate entry in read"
                );
                assert!(
                    node.copy_source.is_none(),
                    "duplicate dirstate entry in read"
                );
                node.entry = Some(*entry);
                node.copy_source = copy_source.map(HgPath::to_owned);
                self.nodes_with_entry_count += 1;
                if copy_source.is_some() {
                    self.nodes_with_copy_source_count += 1
                }
            },
        )?;

        Ok(Some(parents.clone()))
    }

    fn get_node(&self, path: &HgPath) -> Option<&Node> {
        let mut children = &self.root;
        let mut components = path.components();
        let mut component =
            components.next().expect("expected at least one components");
        loop {
            let child = children.get(component)?;
            if let Some(next_component) = components.next() {
                component = next_component;
                children = &child.children;
            } else {
                return Some(child);
            }
        }
    }

    /// Returns a mutable reference to the node at `path` if it exists
    ///
    /// This takes `root` instead of `&mut self` so that callers can mutate
    /// other fields while the returned borrow is still valid
    fn get_node_mut<'tree>(
        root: &'tree mut ChildNodes,
        path: &HgPath,
    ) -> Option<&'tree mut Node> {
        Self::get_node_mut_tracing_ancestors(root, path, |_| {})
    }

    /// Same as `get_node_mut`, and calls `each_ancestor` for each ancestor of
    /// the node.
    ///
    /// Note that `each_ancestor` may be called (with what would be ancestors)
    /// even if it turns out there is no node at `path`.
    fn get_node_mut_tracing_ancestors<'tree>(
        root: &'tree mut ChildNodes,
        path: &HgPath,
        mut each_ancestor: impl FnMut(&mut Node),
    ) -> Option<&'tree mut Node> {
        let mut children = root;
        let mut components = path.components();
        let mut component =
            components.next().expect("expected at least one components");
        loop {
            let child = children.get_mut(component)?;
            if let Some(next_component) = components.next() {
                each_ancestor(child);
                component = next_component;
                children = &mut child.children;
            } else {
                return Some(child);
            }
        }
    }

    fn get_or_insert_node<'tree>(
        root: &'tree mut ChildNodes,
        path: &HgPath,
    ) -> &'tree mut Node {
        Self::get_or_insert_node_tracing_ancestors(root, path, |_| {})
    }

    fn get_or_insert_node_tracing_ancestors<'tree>(
        root: &'tree mut ChildNodes,
        path: &HgPath,
        mut each_ancestor: impl FnMut(&mut Node),
    ) -> &'tree mut Node {
        let mut child_nodes = root;
        let mut inclusive_ancestor_paths =
            WithBasename::inclusive_ancestors_of(path);
        let mut ancestor_path = inclusive_ancestor_paths
            .next()
            .expect("expected at least one inclusive ancestor");
        loop {
            // TODO: can we avoid allocating an owned key in cases where the
            // map already contains that key, without introducing double
            // lookup?
            let child_node =
                child_nodes.entry(ancestor_path.to_owned()).or_default();
            if let Some(next) = inclusive_ancestor_paths.next() {
                each_ancestor(child_node);
                ancestor_path = next;
                child_nodes = &mut child_node.children;
            } else {
                return child_node;
            }
        }
    }

    fn add_or_remove_file(
        &mut self,
        path: &HgPath,
        old_state: EntryState,
        new_entry: DirstateEntry,
    ) {
        let tracked_count_increment =
            match (old_state.is_tracked(), new_entry.state.is_tracked()) {
                (false, true) => 1,
                (true, false) => -1,
                _ => 0,
            };

        let node = Self::get_or_insert_node_tracing_ancestors(
            &mut self.root,
            path,
            |ancestor| {
                // We can’t use `+= increment` because the counter is unsigned,
                // and we want debug builds to detect accidental underflow
                // through zero
                match tracked_count_increment {
                    1 => ancestor.tracked_descendants_count += 1,
                    -1 => ancestor.tracked_descendants_count -= 1,
                    _ => {}
                }
            },
        );
        if node.entry.is_none() {
            self.nodes_with_entry_count += 1
        }
        node.entry = Some(new_entry)
    }

    fn iter_nodes<'a>(
        &'a self,
    ) -> impl Iterator<Item = (&'a WithBasename<HgPathBuf>, &'a Node)> + 'a
    {
        // Depth first tree traversal.
        //
        // If we could afford internal iteration and recursion,
        // this would look like:
        //
        // ```
        // fn traverse_children(
        //     children: &ChildNodes,
        //     each: &mut impl FnMut(&Node),
        // ) {
        //     for child in children.values() {
        //         traverse_children(&child.children, each);
        //         each(child);
        //     }
        // }
        // ```
        //
        // However we want an external iterator and therefore can’t use the
        // call stack. Use an explicit stack instead:
        let mut stack = Vec::new();
        let mut iter = self.root.iter();
        std::iter::from_fn(move || {
            while let Some((key, child_node)) = iter.next() {
                // Pseudo-recursion
                let new_iter = child_node.children.iter();
                let old_iter = std::mem::replace(&mut iter, new_iter);
                stack.push((key, child_node, old_iter));
            }
            // Found the end of a `children.iter()` iterator.
            if let Some((key, child_node, next_iter)) = stack.pop() {
                // "Return" from pseudo-recursion by restoring state from the
                // explicit stack
                iter = next_iter;

                Some((key, child_node))
            } else {
                // Reached the bottom of the stack, we’re done
                None
            }
        })
    }

    /// Mutable iterator for the `(entry, copy source)` of each node.
    ///
    /// It would not be safe to yield mutable references to nodes themeselves
    /// with `-> impl Iterator<Item = &mut Node>` since child nodes are
    /// reachable from their ancestor nodes, potentially creating multiple
    /// `&mut` references to a given node.
    fn iter_node_data_mut<'a>(
        &'a mut self,
    ) -> impl Iterator<Item = NodeDataMut<'a>> + 'a {
        // Explict stack for pseudo-recursion, see `iter_nodes` above.
        let mut stack = Vec::new();
        let mut iter = self.root.iter_mut();
        std::iter::from_fn(move || {
            while let Some((key, child_node)) = iter.next() {
                // Pseudo-recursion
                let data =
                    (key, &mut child_node.entry, &mut child_node.copy_source);
                let new_iter = child_node.children.iter_mut();
                let old_iter = std::mem::replace(&mut iter, new_iter);
                stack.push((data, old_iter));
            }
            // Found the end of a `children.values_mut()` iterator.
            if let Some((data, next_iter)) = stack.pop() {
                // "Return" from pseudo-recursion by restoring state from the
                // explicit stack
                iter = next_iter;

                Some(data)
            } else {
                // Reached the bottom of the stack, we’re done
                None
            }
        })
    }
}

impl<'on_disk> super::dispatch::DirstateMapMethods for DirstateMap<'on_disk> {
    fn clear(&mut self) {
        self.root.clear();
        self.nodes_with_entry_count = 0;
        self.nodes_with_copy_source_count = 0;
    }

    fn add_file(
        &mut self,
        filename: &HgPath,
        old_state: EntryState,
        entry: DirstateEntry,
    ) -> Result<(), DirstateMapError> {
        self.add_or_remove_file(filename, old_state, entry);
        Ok(())
    }

    fn remove_file(
        &mut self,
        filename: &HgPath,
        old_state: EntryState,
        size: i32,
    ) -> Result<(), DirstateMapError> {
        let entry = DirstateEntry {
            state: EntryState::Removed,
            mode: 0,
            size,
            mtime: 0,
        };
        self.add_or_remove_file(filename, old_state, entry);
        Ok(())
    }

    fn drop_file(
        &mut self,
        filename: &HgPath,
        old_state: EntryState,
    ) -> Result<bool, DirstateMapError> {
        let was_tracked = old_state.is_tracked();
        if let Some(node) = Self::get_node_mut_tracing_ancestors(
            &mut self.root,
            filename,
            |ancestor| {
                if was_tracked {
                    ancestor.tracked_descendants_count -= 1
                }
            },
        ) {
            let had_entry = node.entry.is_some();
            let had_copy_source = node.copy_source.is_some();

            // TODO: this leaves in the tree a "non-file" node. Should we
            // remove the node instead, together with ancestor nodes for
            // directories that become empty?
            node.entry = None;
            node.copy_source = None;

            if had_entry {
                self.nodes_with_entry_count -= 1
            }
            if had_copy_source {
                self.nodes_with_copy_source_count -= 1
            }
            Ok(had_entry)
        } else {
            assert!(!was_tracked);
            Ok(false)
        }
    }

    fn clear_ambiguous_times(&mut self, filenames: Vec<HgPathBuf>, now: i32) {
        for filename in filenames {
            if let Some(node) = Self::get_node_mut(&mut self.root, &filename) {
                if let Some(entry) = node.entry.as_mut() {
                    clear_ambiguous_mtime(entry, now);
                }
            }
        }
    }

    fn non_normal_entries_contains(&mut self, key: &HgPath) -> bool {
        self.get_node(key)
            .and_then(|node| node.entry.as_ref())
            .map_or(false, DirstateEntry::is_non_normal)
    }

    fn non_normal_entries_remove(&mut self, _key: &HgPath) {
        // Do nothing, this `DirstateMap` does not have a separate "non normal
        // entries" set that need to be kept up to date
    }

    fn non_normal_or_other_parent_paths(
        &mut self,
    ) -> Box<dyn Iterator<Item = &HgPathBuf> + '_> {
        Box::new(self.iter_nodes().filter_map(|(path, node)| {
            node.entry
                .as_ref()
                .filter(|entry| {
                    entry.is_non_normal() || entry.is_from_other_parent()
                })
                .map(|_| path.full_path())
        }))
    }

    fn set_non_normal_other_parent_entries(&mut self, _force: bool) {
        // Do nothing, this `DirstateMap` does not have a separate "non normal
        // entries" and "from other parent" sets that need to be recomputed
    }

    fn iter_non_normal_paths(
        &mut self,
    ) -> Box<dyn Iterator<Item = &HgPathBuf> + Send + '_> {
        self.iter_non_normal_paths_panic()
    }

    fn iter_non_normal_paths_panic(
        &self,
    ) -> Box<dyn Iterator<Item = &HgPathBuf> + Send + '_> {
        Box::new(self.iter_nodes().filter_map(|(path, node)| {
            node.entry
                .as_ref()
                .filter(|entry| entry.is_non_normal())
                .map(|_| path.full_path())
        }))
    }

    fn iter_other_parent_paths(
        &mut self,
    ) -> Box<dyn Iterator<Item = &HgPathBuf> + Send + '_> {
        Box::new(self.iter_nodes().filter_map(|(path, node)| {
            node.entry
                .as_ref()
                .filter(|entry| entry.is_from_other_parent())
                .map(|_| path.full_path())
        }))
    }

    fn has_tracked_dir(
        &mut self,
        directory: &HgPath,
    ) -> Result<bool, DirstateMapError> {
        if let Some(node) = self.get_node(directory) {
            // A node without a `DirstateEntry` was created to hold child
            // nodes, and is therefore a directory.
            Ok(node.entry.is_none() && node.tracked_descendants_count > 0)
        } else {
            Ok(false)
        }
    }

    fn has_dir(
        &mut self,
        directory: &HgPath,
    ) -> Result<bool, DirstateMapError> {
        if let Some(node) = self.get_node(directory) {
            // A node without a `DirstateEntry` was created to hold child
            // nodes, and is therefore a directory.
            Ok(node.entry.is_none())
        } else {
            Ok(false)
        }
    }

    fn pack(
        &mut self,
        parents: DirstateParents,
        now: Timestamp,
    ) -> Result<Vec<u8>, DirstateError> {
        // Optizimation (to be measured?): pre-compute size to avoid `Vec`
        // reallocations
        let mut size = parents.as_bytes().len();
        for (path, node) in self.iter_nodes() {
            if node.entry.is_some() {
                size += packed_entry_size(
                    path.full_path(),
                    node.copy_source.as_ref(),
                )
            }
        }

        let mut packed = Vec::with_capacity(size);
        packed.extend(parents.as_bytes());

        let now: i32 = now.0.try_into().expect("time overflow");
        for (path, opt_entry, copy_source) in self.iter_node_data_mut() {
            if let Some(entry) = opt_entry {
                clear_ambiguous_mtime(entry, now);
                pack_entry(
                    path.full_path(),
                    entry,
                    copy_source.as_ref(),
                    &mut packed,
                );
            }
        }
        Ok(packed)
    }

    fn set_all_dirs(&mut self) -> Result<(), DirstateMapError> {
        // Do nothing, this `DirstateMap` does not a separate `all_dirs` that
        // needs to be recomputed
        Ok(())
    }

    fn set_dirs(&mut self) -> Result<(), DirstateMapError> {
        // Do nothing, this `DirstateMap` does not a separate `dirs` that needs
        // to be recomputed
        Ok(())
    }

    fn status<'a>(
        &'a mut self,
        matcher: &'a (dyn Matcher + Sync),
        root_dir: PathBuf,
        ignore_files: Vec<PathBuf>,
        options: StatusOptions,
    ) -> Result<(DirstateStatus<'a>, Vec<PatternFileWarning>), StatusError>
    {
        super::status::status(self, matcher, root_dir, ignore_files, options)
    }

    fn copy_map_len(&self) -> usize {
        self.nodes_with_copy_source_count
    }

    fn copy_map_iter(&self) -> CopyMapIter<'_> {
        Box::new(self.iter_nodes().filter_map(|(path, node)| {
            node.copy_source
                .as_ref()
                .map(|copy_source| (path.full_path(), copy_source))
        }))
    }

    fn copy_map_contains_key(&self, key: &HgPath) -> bool {
        if let Some(node) = self.get_node(key) {
            node.copy_source.is_some()
        } else {
            false
        }
    }

    fn copy_map_get(&self, key: &HgPath) -> Option<&HgPathBuf> {
        self.get_node(key)?.copy_source.as_ref()
    }

    fn copy_map_remove(&mut self, key: &HgPath) -> Option<HgPathBuf> {
        let count = &mut self.nodes_with_copy_source_count;
        Self::get_node_mut(&mut self.root, key).and_then(|node| {
            if node.copy_source.is_some() {
                *count -= 1
            }
            node.copy_source.take()
        })
    }

    fn copy_map_insert(
        &mut self,
        key: HgPathBuf,
        value: HgPathBuf,
    ) -> Option<HgPathBuf> {
        let node = Self::get_or_insert_node(&mut self.root, &key);
        if node.copy_source.is_none() {
            self.nodes_with_copy_source_count += 1
        }
        node.copy_source.replace(value)
    }

    fn len(&self) -> usize {
        self.nodes_with_entry_count
    }

    fn contains_key(&self, key: &HgPath) -> bool {
        self.get(key).is_some()
    }

    fn get(&self, key: &HgPath) -> Option<&DirstateEntry> {
        self.get_node(key)?.entry.as_ref()
    }

    fn iter(&self) -> StateMapIter<'_> {
        Box::new(self.iter_nodes().filter_map(|(path, node)| {
            node.entry.as_ref().map(|entry| (path.full_path(), entry))
        }))
    }
}