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|
use std::{
borrow::Cow,
fmt::{Display, Formatter},
};
use bstr::BStr;
use gix_hashtable::HashMap;
/// The positive result produced by [describe()][function::describe()].
#[derive(Debug, Clone)]
pub struct Outcome<'name> {
/// The name of the tag or branch that is closest to the commit `id`.
///
/// If `None`, no name was found but it was requested to provide the `id` itself as fallback.
pub name: Option<Cow<'name, BStr>>,
/// The input commit object id that we describe.
pub id: gix_hash::ObjectId,
/// The number of commits that are between the tag or branch with `name` and `id`.
/// These commits are all in the future of the named tag or branch.
pub depth: u32,
/// The mapping between object ids and their names initially provided by the describe call.
pub name_by_oid: HashMap<gix_hash::ObjectId, Cow<'name, BStr>>,
/// The amount of commits we traversed.
pub commits_seen: u32,
}
impl<'a> Outcome<'a> {
/// Turn this outcome into a structure that can display itself in the typical `git describe` format.
pub fn into_format(self, hex_len: usize) -> Format<'a> {
Format {
name: self.name,
id: self.id,
hex_len,
depth: self.depth,
long: false,
dirty_suffix: None,
}
}
}
/// A structure implementing `Display`, producing a `git describe` like string.
#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone)]
pub struct Format<'a> {
/// The name of the branch or tag to display, as is.
///
/// If `None`, the `id` will be displayed as a fallback.
pub name: Option<Cow<'a, BStr>>,
/// The `id` of the commit to describe.
pub id: gix_hash::ObjectId,
/// The amount of hex characters to use to display `id`.
pub hex_len: usize,
/// The amount of commits between `name` and `id`, where `id` is in the future of `name`.
pub depth: u32,
/// If true, the long form of the describe string will be produced even if `id` lies directly on `name`,
/// hence has a depth of 0.
pub long: bool,
/// If `Some(suffix)`, it will be appended to the describe string.
/// This should be set if the working tree was determined to be dirty.
pub dirty_suffix: Option<String>,
}
impl<'a> Format<'a> {
/// Return true if the `name` is directly associated with `id`, i.e. there are no commits between them.
pub fn is_exact_match(&self) -> bool {
self.depth == 0
}
/// Set this instance to print in long mode, that is if `depth` is 0, it will still print the whole
/// long form even though it's not quite necessary.
///
/// Otherwise, it is allowed to shorten itself.
pub fn long(&mut self, long: bool) -> &mut Self {
self.long = long;
self
}
}
impl<'a> Display for Format<'a> {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
if let Some(name) = self.name.as_deref() {
if !self.long && self.is_exact_match() {
name.fmt(f)?;
} else {
write!(f, "{}-{}-g{}", name, self.depth, self.id.to_hex_with_len(self.hex_len))?;
}
} else {
self.id.to_hex_with_len(self.hex_len).fmt(f)?;
}
if let Some(suffix) = &self.dirty_suffix {
write!(f, "-{suffix}")?;
}
Ok(())
}
}
type Flags = u32;
const MAX_CANDIDATES: usize = std::mem::size_of::<Flags>() * 8;
/// The options required to call [`describe()`][function::describe()].
#[derive(Clone, Debug)]
pub struct Options<'name> {
/// The candidate names from which to determine the `name` to use for the describe string,
/// as a mapping from a commit id and the name associated with it.
pub name_by_oid: HashMap<gix_hash::ObjectId, Cow<'name, BStr>>,
/// The amount of names we will keep track of. Defaults to the maximum of 32.
///
/// If the number is exceeded, it will be capped at 32 and defaults to 10.
pub max_candidates: usize,
/// If no candidate for naming, always show the abbreviated hash. Default: false.
pub fallback_to_oid: bool,
/// Only follow the first parent during graph traversal. Default: false.
///
/// This may speed up the traversal at the cost of accuracy.
pub first_parent: bool,
}
impl<'name> Default for Options<'name> {
fn default() -> Self {
Options {
max_candidates: 10, // the same number as git uses, otherwise we perform worse by default on big repos
name_by_oid: Default::default(),
fallback_to_oid: false,
first_parent: false,
}
}
}
/// The error returned by the [`describe()`][function::describe()] function.
#[derive(Debug, thiserror::Error)]
#[allow(missing_docs)]
pub enum Error<E>
where
E: std::error::Error + Send + Sync + 'static,
{
#[error("Commit {} could not be found during graph traversal", .oid.to_hex())]
Find {
#[source]
err: Option<E>,
oid: gix_hash::ObjectId,
},
#[error("A commit could not be decoded during traversal")]
Decode(#[from] gix_object::decode::Error),
}
pub(crate) mod function {
use std::{borrow::Cow, cmp::Ordering, collections::VecDeque, iter::FromIterator};
use bstr::BStr;
use gix_hash::oid;
use gix_hashtable::{hash_map, HashMap};
use gix_object::CommitRefIter;
use super::{Error, Outcome};
use crate::describe::{Flags, Options, MAX_CANDIDATES};
/// Given a `commit` id, traverse the commit graph and collect candidate names from the `name_by_oid` mapping to produce
/// an `Outcome`, which converted [`into_format()`][Outcome::into_format()] will produce a typical `git describe` string.
///
/// Note that the `name_by_oid` map is returned in the [`Outcome`], which can be forcefully returned even if there was no matching
/// candidate by setting `fallback_to_oid` to true.
pub fn describe<'name, Find, E>(
commit: &oid,
mut find: Find,
Options {
name_by_oid,
mut max_candidates,
fallback_to_oid,
first_parent,
}: Options<'name>,
) -> Result<Option<Outcome<'name>>, Error<E>>
where
Find: for<'b> FnMut(&oid, &'b mut Vec<u8>) -> Result<Option<CommitRefIter<'b>>, E>,
E: std::error::Error + Send + Sync + 'static,
{
max_candidates = max_candidates.min(MAX_CANDIDATES);
if let Some(name) = name_by_oid.get(commit) {
return Ok(Some(Outcome {
name: name.clone().into(),
id: commit.to_owned(),
depth: 0,
name_by_oid,
commits_seen: 0,
}));
}
if max_candidates == 0 || name_by_oid.is_empty() {
return if fallback_to_oid {
Ok(Some(Outcome {
id: commit.to_owned(),
name: None,
name_by_oid,
depth: 0,
commits_seen: 0,
}))
} else {
Ok(None)
};
}
let mut buf = Vec::new();
let mut parent_buf = Vec::new();
let mut queue = VecDeque::from_iter(Some((commit.to_owned(), u32::MAX)));
let mut candidates = Vec::new();
let mut commits_seen = 0;
let mut gave_up_on_commit = None;
let mut seen = HashMap::<gix_hash::ObjectId, Flags>::default();
seen.insert(commit.to_owned(), 0u32);
while let Some((commit, _commit_time)) = queue.pop_front() {
commits_seen += 1;
if let Some(name) = name_by_oid.get(&commit) {
if candidates.len() < max_candidates {
let identity_bit = 1 << candidates.len();
candidates.push(Candidate {
name: name.clone(),
commits_in_its_future: commits_seen - 1,
identity_bit,
order: candidates.len(),
});
*seen.get_mut(&commit).expect("inserted") |= identity_bit;
} else {
gave_up_on_commit = Some(commit);
break;
}
}
let flags = seen[&commit];
for candidate in candidates
.iter_mut()
.filter(|c| (flags & c.identity_bit) != c.identity_bit)
{
candidate.commits_in_its_future += 1;
}
if queue.is_empty() && !candidates.is_empty() {
// single-trunk history that waits to be replenished.
// Abort early if the best-candidate is in the current commits past.
let mut shortest_depth = Flags::MAX;
let mut best_candidates_at_same_depth = 0_u32;
for candidate in &candidates {
match candidate.commits_in_its_future.cmp(&shortest_depth) {
Ordering::Less => {
shortest_depth = candidate.commits_in_its_future;
best_candidates_at_same_depth = candidate.identity_bit;
}
Ordering::Equal => {
best_candidates_at_same_depth |= candidate.identity_bit;
}
Ordering::Greater => {}
}
}
if (flags & best_candidates_at_same_depth) == best_candidates_at_same_depth {
break;
}
}
parents_by_date_onto_queue_and_track_names(
&mut find,
&mut buf,
&mut parent_buf,
&mut queue,
&mut seen,
&commit,
flags,
first_parent,
)?;
}
if candidates.is_empty() {
return if fallback_to_oid {
Ok(Some(Outcome {
id: commit.to_owned(),
name: None,
name_by_oid,
depth: 0,
commits_seen,
}))
} else {
Ok(None)
};
}
candidates.sort_by(|a, b| {
a.commits_in_its_future
.cmp(&b.commits_in_its_future)
.then_with(|| a.order.cmp(&b.order))
});
if let Some(commit_id) = gave_up_on_commit {
queue.push_front((commit_id, u32::MAX));
commits_seen -= 1;
}
commits_seen += finish_depth_computation(
queue,
find,
candidates.first_mut().expect("at least one candidate"),
seen,
buf,
parent_buf,
first_parent,
)?;
Ok(candidates.into_iter().next().map(|c| Outcome {
name: c.name.into(),
id: commit.to_owned(),
depth: c.commits_in_its_future,
name_by_oid,
commits_seen,
}))
}
#[allow(clippy::too_many_arguments)]
fn parents_by_date_onto_queue_and_track_names<Find, E>(
find: &mut Find,
buf: &mut Vec<u8>,
parent_buf: &mut Vec<u8>,
queue: &mut VecDeque<(gix_hash::ObjectId, u32)>,
seen: &mut HashMap<gix_hash::ObjectId, Flags>,
commit: &gix_hash::oid,
commit_flags: Flags,
first_parent: bool,
) -> Result<(), Error<E>>
where
Find: for<'b> FnMut(&oid, &'b mut Vec<u8>) -> Result<Option<CommitRefIter<'b>>, E>,
E: std::error::Error + Send + Sync + 'static,
{
let commit_iter = find(commit, buf)
.map_err(|err| Error::Find {
err: Some(err),
oid: commit.to_owned(),
})?
.ok_or_else(|| Error::Find {
err: None,
oid: commit.to_owned(),
})?;
for token in commit_iter {
match token {
Ok(gix_object::commit::ref_iter::Token::Tree { .. }) => continue,
Ok(gix_object::commit::ref_iter::Token::Parent { id: parent_id }) => match seen.entry(parent_id) {
hash_map::Entry::Vacant(entry) => {
let parent = match find(&parent_id, parent_buf).map_err(|err| Error::Find {
err: Some(err),
oid: commit.to_owned(),
})? {
Some(p) => p,
None => continue, // skip missing objects, they don't exist.
};
let parent_commit_date = parent
.committer()
.map(|committer| committer.time.seconds_since_unix_epoch)
.unwrap_or_default();
entry.insert(commit_flags);
match queue.binary_search_by(|c| c.1.cmp(&parent_commit_date).reverse()) {
Ok(_) => queue.push_back((parent_id, parent_commit_date)),
Err(pos) => queue.insert(pos, (parent_id, parent_commit_date)),
};
}
hash_map::Entry::Occupied(mut entry) => {
*entry.get_mut() |= commit_flags;
}
},
Ok(_unused_token) => break,
Err(err) => return Err(err.into()),
}
if first_parent {
break;
}
}
Ok(())
}
#[allow(clippy::too_many_arguments)]
fn finish_depth_computation<'name, Find, E>(
mut queue: VecDeque<(gix_hash::ObjectId, u32)>,
mut find: Find,
best_candidate: &mut Candidate<'name>,
mut seen: HashMap<gix_hash::ObjectId, Flags>,
mut buf: Vec<u8>,
mut parent_buf: Vec<u8>,
first_parent: bool,
) -> Result<u32, Error<E>>
where
Find: for<'b> FnMut(&oid, &'b mut Vec<u8>) -> Result<Option<CommitRefIter<'b>>, E>,
E: std::error::Error + Send + Sync + 'static,
{
let mut commits_seen = 0;
while let Some((commit, _commit_time)) = queue.pop_front() {
commits_seen += 1;
let flags = seen[&commit];
if (flags & best_candidate.identity_bit) == best_candidate.identity_bit {
if queue
.iter()
.all(|(id, _)| (seen[id] & best_candidate.identity_bit) == best_candidate.identity_bit)
{
break;
}
} else {
best_candidate.commits_in_its_future += 1;
}
parents_by_date_onto_queue_and_track_names(
&mut find,
&mut buf,
&mut parent_buf,
&mut queue,
&mut seen,
&commit,
flags,
first_parent,
)?;
}
Ok(commits_seen)
}
#[derive(Debug)]
struct Candidate<'a> {
name: Cow<'a, BStr>,
commits_in_its_future: Flags,
/// A single bit identifying this candidate uniquely in a bitset
identity_bit: Flags,
/// The order at which we found the candidate, first one has order = 0
order: usize,
}
}
|