Merging upstream version 1.72.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 258 insertions, 0 deletions

diff --git a/vendor/gix-commitgraph/src/file/commit.rs b/vendor/gix-commitgraph/src/file/commit.rs
new file mode 100644
index 000000000..14fe15e84
--- /dev/null
+++ b/vendor/gix-commitgraph/src/file/commit.rs
@@ -0,0 +1,258 @@
+//! Low-level operations on individual commits.
+use std::{
+    convert::TryInto,
+    fmt::{Debug, Formatter},
+    slice::Chunks,
+};
+
+use crate::{
+    file::{self, EXTENDED_EDGES_MASK, LAST_EXTENDED_EDGE_MASK, NO_PARENT},
+    File, Position,
+};
+
+/// The error used in the [`file::commit`][self] module.
+#[derive(thiserror::Error, Debug)]
+#[allow(missing_docs)]
+pub enum Error {
+    #[error("commit {0}'s extra edges overflows the commit-graph file's extra edges list")]
+    ExtraEdgesListOverflow(gix_hash::ObjectId),
+    #[error("commit {0}'s first parent is an extra edge index, which is invalid")]
+    FirstParentIsExtraEdgeIndex(gix_hash::ObjectId),
+    #[error("commit {0} has extra edges, but commit-graph file has no extra edges list")]
+    MissingExtraEdgesList(gix_hash::ObjectId),
+    #[error("commit {0} has a second parent but not a first parent")]
+    SecondParentWithoutFirstParent(gix_hash::ObjectId),
+}
+
+/// A commit as stored in a [`File`].
+#[derive(Copy, Clone)]
+pub struct Commit<'a> {
+    file: &'a File,
+    pos: file::Position,
+    // We can parse the below fields lazily if needed.
+    commit_timestamp: u64,
+    generation: u32,
+    parent1: ParentEdge,
+    parent2: ParentEdge,
+    root_tree_id: &'a gix_hash::oid,
+}
+
+#[inline]
+fn read_u32(b: &[u8]) -> u32 {
+    u32::from_be_bytes(b.try_into().unwrap())
+}
+
+impl<'a> Commit<'a> {
+    pub(crate) fn new(file: &'a File, pos: file::Position) -> Self {
+        let bytes = file.commit_data_bytes(pos);
+        Commit {
+            file,
+            pos,
+            root_tree_id: gix_hash::oid::from_bytes_unchecked(&bytes[..file.hash_len]),
+            parent1: ParentEdge::from_raw(read_u32(&bytes[file.hash_len..][..4])),
+            parent2: ParentEdge::from_raw(read_u32(&bytes[file.hash_len + 4..][..4])),
+            // TODO: Add support for corrected commit date offset overflow.
+            //      See https://github.com/git/git/commit/e8b63005c48696a26f976f5f9b0ccaf1983e439d and
+            //          https://github.com/git/git/commit/f90fca638e99a031dce8e3aca72427b2f9b4bb38 for more details and hints at a test.
+            generation: read_u32(&bytes[file.hash_len + 8..][..4]) >> 2,
+            commit_timestamp: u64::from_be_bytes(bytes[file.hash_len + 8..][..8].try_into().unwrap())
+                & 0x0003_ffff_ffff,
+        }
+    }
+
+    /// Returns the committer timestamp of this commit.
+    ///
+    /// The value is the number of seconds since 1970-01-01 00:00:00 UTC.
+    pub fn committer_timestamp(&self) -> u64 {
+        self.commit_timestamp
+    }
+
+    /// Returns the generation number of this commit.
+    ///
+    /// Commits without parents have generation number 1. Commits with parents have a generation
+    /// number that is the max of their parents' generation numbers + 1.
+    pub fn generation(&self) -> u32 {
+        self.generation
+    }
+
+    /// Returns an iterator over the parent positions for lookup in the owning [Graph][crate::Graph].
+    pub fn iter_parents(self) -> Parents<'a> {
+        // I didn't find a combinator approach that a) was as strict as ParentIterator, b) supported
+        // fuse-after-first-error behavior, and b) was significantly shorter or more understandable
+        // than ParentIterator. So here we are.
+        Parents {
+            commit_data: self,
+            state: ParentIteratorState::First,
+        }
+    }
+
+    /// Returns the hash of this commit.
+    pub fn id(&self) -> &'a gix_hash::oid {
+        self.file.id_at(self.pos)
+    }
+
+    /// Returns the first parent of this commit.
+    pub fn parent1(&self) -> Result<Option<Position>, Error> {
+        self.iter_parents().next().transpose()
+    }
+
+    /// Returns the position at which this commit is stored in the parent [File].
+    pub fn position(&self) -> file::Position {
+        self.pos
+    }
+
+    /// Return the hash of the tree this commit points to.
+    pub fn root_tree_id(&self) -> &gix_hash::oid {
+        self.root_tree_id
+    }
+}
+
+impl<'a> Debug for Commit<'a> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "Commit {{ id: {}, lex_pos: {}, generation: {}, root_tree_id: {}, parent1: {:?}, parent2: {:?} }}",
+            self.id(),
+            self.pos,
+            self.generation(),
+            self.root_tree_id(),
+            self.parent1,
+            self.parent2,
+        )
+    }
+}
+
+impl<'a> Eq for Commit<'a> {}
+
+impl<'a> PartialEq for Commit<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        std::ptr::eq(self.file, other.file) && self.pos == other.pos
+    }
+}
+
+/// An iterator over parents of a [`Commit`].
+pub struct Parents<'a> {
+    commit_data: Commit<'a>,
+    state: ParentIteratorState<'a>,
+}
+
+impl<'a> Iterator for Parents<'a> {
+    type Item = Result<Position, Error>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let state = std::mem::replace(&mut self.state, ParentIteratorState::Exhausted);
+        match state {
+            ParentIteratorState::First => match self.commit_data.parent1 {
+                ParentEdge::None => match self.commit_data.parent2 {
+                    ParentEdge::None => None,
+                    _ => Some(Err(Error::SecondParentWithoutFirstParent(self.commit_data.id().into()))),
+                },
+                ParentEdge::GraphPosition(pos) => {
+                    self.state = ParentIteratorState::Second;
+                    Some(Ok(pos))
+                }
+                ParentEdge::ExtraEdgeIndex(_) => {
+                    Some(Err(Error::FirstParentIsExtraEdgeIndex(self.commit_data.id().into())))
+                }
+            },
+            ParentIteratorState::Second => match self.commit_data.parent2 {
+                ParentEdge::None => None,
+                ParentEdge::GraphPosition(pos) => Some(Ok(pos)),
+                ParentEdge::ExtraEdgeIndex(extra_edge_index) => {
+                    if let Some(extra_edges_list) = self.commit_data.file.extra_edges_data() {
+                        let start_offset: usize = extra_edge_index
+                            .try_into()
+                            .expect("an architecture able to hold 32 bits of integer");
+                        let start_offset = start_offset
+                            .checked_mul(4)
+                            .expect("an extended edge index small enough to fit in usize");
+                        if let Some(tail) = extra_edges_list.get(start_offset..) {
+                            self.state = ParentIteratorState::Extra(tail.chunks(4));
+                            // This recursive call is what blocks me from replacing ParentIterator
+                            // with a std::iter::from_fn closure.
+                            self.next()
+                        } else {
+                            Some(Err(Error::ExtraEdgesListOverflow(self.commit_data.id().into())))
+                        }
+                    } else {
+                        Some(Err(Error::MissingExtraEdgesList(self.commit_data.id().into())))
+                    }
+                }
+            },
+            ParentIteratorState::Extra(mut chunks) => {
+                if let Some(chunk) = chunks.next() {
+                    let extra_edge = read_u32(chunk);
+                    match ExtraEdge::from_raw(extra_edge) {
+                        ExtraEdge::Internal(pos) => {
+                            self.state = ParentIteratorState::Extra(chunks);
+                            Some(Ok(pos))
+                        }
+                        ExtraEdge::Last(pos) => Some(Ok(pos)),
+                    }
+                } else {
+                    Some(Err(Error::ExtraEdgesListOverflow(self.commit_data.id().into())))
+                }
+            }
+            ParentIteratorState::Exhausted => None,
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        match (&self.state, self.commit_data.parent1, self.commit_data.parent2) {
+            (ParentIteratorState::First, ParentEdge::None, ParentEdge::None) => (0, Some(0)),
+            (ParentIteratorState::First, ParentEdge::None, _) => (1, Some(1)),
+            (ParentIteratorState::First, ParentEdge::GraphPosition(_), ParentEdge::None) => (1, Some(1)),
+            (ParentIteratorState::First, ParentEdge::GraphPosition(_), ParentEdge::GraphPosition(_)) => (2, Some(2)),
+            (ParentIteratorState::First, ParentEdge::GraphPosition(_), ParentEdge::ExtraEdgeIndex(_)) => (3, None),
+            (ParentIteratorState::First, ParentEdge::ExtraEdgeIndex(_), _) => (1, Some(1)),
+            (ParentIteratorState::Second, _, ParentEdge::None) => (0, Some(0)),
+            (ParentIteratorState::Second, _, ParentEdge::GraphPosition(_)) => (1, Some(1)),
+            (ParentIteratorState::Second, _, ParentEdge::ExtraEdgeIndex(_)) => (2, None),
+            (ParentIteratorState::Extra(_), _, _) => (1, None),
+            (ParentIteratorState::Exhausted, _, _) => (0, Some(0)),
+        }
+    }
+}
+
+#[derive(Debug)]
+enum ParentIteratorState<'a> {
+    First,
+    Second,
+    Extra(Chunks<'a, u8>),
+    Exhausted,
+}
+
+#[derive(Clone, Copy, Debug)]
+enum ParentEdge {
+    None,
+    GraphPosition(Position),
+    ExtraEdgeIndex(u32),
+}
+
+impl ParentEdge {
+    pub fn from_raw(raw: u32) -> ParentEdge {
+        if raw == NO_PARENT {
+            return ParentEdge::None;
+        }
+        if raw & EXTENDED_EDGES_MASK != 0 {
+            ParentEdge::ExtraEdgeIndex(raw & !EXTENDED_EDGES_MASK)
+        } else {
+            ParentEdge::GraphPosition(Position(raw))
+        }
+    }
+}
+
+enum ExtraEdge {
+    Internal(Position),
+    Last(Position),
+}
+
+impl ExtraEdge {
+    pub fn from_raw(raw: u32) -> Self {
+        if raw & LAST_EXTENDED_EDGE_MASK != 0 {
+            Self::Last(Position(raw & !LAST_EXTENDED_EDGE_MASK))
+        } else {
+            Self::Internal(Position(raw))
+        }
+    }
+}