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|
//! Auxiliary types used by graph verification methods.
use std::{
cmp::{max, min},
collections::BTreeMap,
convert::TryInto,
path::PathBuf,
};
use crate::{
file::{self, commit},
Graph, Position, GENERATION_NUMBER_MAX,
};
/// The error used in [`verify_integrity()`][Graph::verify_integrity].
#[derive(thiserror::Error, Debug)]
#[allow(missing_docs)]
pub enum Error<E: std::error::Error + 'static> {
#[error("'{}' should have {expected} base graphs, but claims {actual} base graphs", .path.display())]
BaseGraphCount { actual: u8, expected: u8, path: PathBuf },
#[error("'{}' base graph at index {index} should have ID {expected} but is {actual}", .path.display())]
BaseGraphId {
actual: gix_hash::ObjectId,
expected: gix_hash::ObjectId,
index: u8,
path: PathBuf,
},
#[error(transparent)]
Commit(#[from] commit::Error),
#[error("{}: {err}", .path.display())]
File {
// Use zero-size error type. We will never return
// `graph::verify::Error::File(file::verify::Error::Processor(...))`, because we are the
// file's processor, and we convert`file::verify::Error::Processor<graph::verify::Error>`
// variants into direct `graph::verify::Error` values.
err: file::verify::Error<std::convert::Infallible>,
path: PathBuf,
},
#[error("Commit {id}'s generation should be {expected} but is {actual}")]
Generation {
actual: u32,
expected: u32,
id: gix_hash::ObjectId,
},
#[error(
"Commit {id} has parent position {parent_pos} that is out of range (should be in range 0-{max_valid_pos})"
)]
ParentOutOfRange {
id: gix_hash::ObjectId,
max_valid_pos: Position,
parent_pos: Position,
},
#[error("{0}")]
Processor(#[source] E),
#[error("Commit-graph should be composed of at most 256 files but actually contains {0} files")]
TooManyFiles(usize),
}
/// Statistics gathered while verifying the integrity of the graph as returned by [`Graph::verify_integrity()`].
#[derive(Clone, Debug, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
pub struct Outcome {
/// The length of the longest path between any two commits in this graph.
///
/// For example, this will be `Some(9)` for a commit graph containing 10 linear commits.
/// This will be `Some(0)` for a commit graph containing 0 or 1 commits.
/// If the longest path length is too large to fit in a [u32], then this will be [None].
pub longest_path_length: Option<u32>,
/// The total number of commits traversed.
pub num_commits: u32,
/// A mapping of `N -> number of commits with N parents`.
pub parent_counts: BTreeMap<u32, u32>,
}
impl Graph {
/// Traverse all commits in the graph and call `processor(&commit) -> Result<(), E>` on it while verifying checksums.
///
/// When `processor` returns an error, the entire verification is stopped and the error returned.
pub fn verify_integrity<E>(
&self,
mut processor: impl FnMut(&file::Commit<'_>) -> Result<(), E>,
) -> Result<Outcome, Error<E>>
where
E: std::error::Error + 'static,
{
if self.files.len() > 256 {
// A file in a split chain can only have up to 255 base files.
return Err(Error::TooManyFiles(self.files.len()));
}
let mut stats = Outcome {
longest_path_length: None,
num_commits: 0,
parent_counts: BTreeMap::new(),
};
let mut max_generation = 0u32;
// TODO: Detect duplicate commit IDs across different files. Not sure how to do this without
// a separate loop, e.g. self.iter_sorted_ids().
let mut file_start_pos = Position(0);
for (file_index, file) in self.files.iter().enumerate() {
if usize::from(file.base_graph_count()) != file_index {
return Err(Error::BaseGraphCount {
actual: file.base_graph_count(),
expected: file_index
.try_into()
.expect("files.len() check to protect against this"),
path: file.path().to_owned(),
});
}
for (base_graph_index, (expected, actual)) in self.files[..file_index]
.iter()
.map(|base_file| base_file.checksum())
.zip(file.iter_base_graph_ids())
.enumerate()
{
if actual != expected {
return Err(Error::BaseGraphId {
actual: actual.into(),
expected: expected.into(),
index: base_graph_index
.try_into()
.expect("files.len() check to protect against this"),
path: file.path().to_owned(),
});
}
}
let next_file_start_pos = Position(file_start_pos.0 + file.num_commits());
let file_stats = file
.traverse(|commit| {
let mut max_parent_generation = 0u32;
for parent_pos in commit.iter_parents() {
let parent_pos = parent_pos.map_err(Error::Commit)?;
if parent_pos >= next_file_start_pos {
return Err(Error::ParentOutOfRange {
parent_pos,
id: commit.id().into(),
max_valid_pos: Position(next_file_start_pos.0 - 1),
});
}
let parent = self.commit_at(parent_pos);
max_parent_generation = max(max_parent_generation, parent.generation());
}
// If the max parent generation is GENERATION_NUMBER_MAX, then this commit's
// generation should be GENERATION_NUMBER_MAX too.
let expected_generation = min(max_parent_generation + 1, GENERATION_NUMBER_MAX);
if commit.generation() != expected_generation {
return Err(Error::Generation {
actual: commit.generation(),
expected: expected_generation,
id: commit.id().into(),
});
}
processor(commit).map_err(Error::Processor)?;
Ok(())
})
.map_err(|err| Error::File {
err: match err {
file::verify::Error::Processor(e) => return e,
file::verify::Error::RootTreeId { id, root_tree_id } => {
file::verify::Error::RootTreeId { id, root_tree_id }
}
file::verify::Error::Mismatch { actual, expected } => {
file::verify::Error::Mismatch { actual, expected }
}
file::verify::Error::Generation { generation, id } => {
file::verify::Error::Generation { generation, id }
}
file::verify::Error::Filename(expected) => file::verify::Error::Filename(expected),
file::verify::Error::Commit(err) => file::verify::Error::Commit(err),
file::verify::Error::CommitId { id, pos } => file::verify::Error::CommitId { id, pos },
file::verify::Error::CommitsOutOfOrder {
id,
pos,
predecessor_id,
} => file::verify::Error::CommitsOutOfOrder {
id,
pos,
predecessor_id,
},
},
path: file.path().to_owned(),
})?;
max_generation = max(max_generation, file_stats.max_generation);
stats.num_commits += file_stats.num_commits;
for (key, value) in file_stats.parent_counts.into_iter() {
*stats.parent_counts.entry(key).or_insert(0) += value;
}
file_start_pos = next_file_start_pos;
}
stats.longest_path_length = if max_generation < GENERATION_NUMBER_MAX {
Some(max_generation.saturating_sub(1))
} else {
None
};
Ok(stats)
}
}
|
