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use std::{
ops::Range,
path::{Path, PathBuf},
};
use crate::{
data,
index::PrefixLookupResult,
multi_index::{EntryIndex, File, PackIndex, Version},
};
/// Represents an entry within a multi index file, effectively mapping object [`IDs`][git_hash::ObjectId] to pack data
/// files and the offset within.
#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone)]
#[cfg_attr(feature = "serde1", derive(serde::Serialize, serde::Deserialize))]
pub struct Entry {
/// The ID of the object.
pub oid: git_hash::ObjectId,
/// The offset to the object's header in the pack data file.
pub pack_offset: data::Offset,
/// The index of the pack matching our [`File::index_names()`] slice.
pub pack_index: PackIndex,
}
/// Access methods
impl File {
/// Returns the version of the multi-index file.
pub fn version(&self) -> Version {
self.version
}
/// Returns the path from which the multi-index file was loaded.
///
/// Note that it might have changed in the mean time, or might have been removed as well.
pub fn path(&self) -> &Path {
&self.path
}
/// Returns the amount of indices stored in this multi-index file. It's the same as [File::index_names().len()][File::index_names()],
/// and returned as one past the highest known index.
pub fn num_indices(&self) -> PackIndex {
self.num_indices
}
/// Returns the total amount of objects available for lookup, and returned as one past the highest known entry index
pub fn num_objects(&self) -> EntryIndex {
self.num_objects
}
/// Returns the kind of hash function used for object ids available in this index.
pub fn object_hash(&self) -> git_hash::Kind {
self.object_hash
}
/// Returns the checksum over the entire content of the file (excluding the checksum itself).
///
/// It can be used to validate it didn't change after creation.
pub fn checksum(&self) -> git_hash::ObjectId {
git_hash::ObjectId::from(&self.data[self.data.len() - self.hash_len..])
}
/// Return all names of index files (`*.idx`) whose objects we contain.
///
/// The corresponding pack can be found by replacing the `.idx` extension with `.pack`.
pub fn index_names(&self) -> &[PathBuf] {
&self.index_names
}
}
impl File {
/// Return the object id at the given `index`, which ranges from 0 to [File::num_objects()].
pub fn oid_at_index(&self, index: EntryIndex) -> &git_hash::oid {
debug_assert!(index < self.num_objects, "index out of bounds");
let index: usize = index as usize;
let start = self.lookup_ofs + index * self.hash_len;
git_hash::oid::from_bytes_unchecked(&self.data[start..][..self.hash_len])
}
/// Given a `prefix`, find an object that matches it uniquely within this index and return `Some(Ok(entry_index))`.
/// If there is more than one object matching the object `Some(Err(())` is returned.
///
/// Finally, if no object matches the index, the return value is `None`.
///
/// Pass `candidates` to obtain the set of entry-indices matching `prefix`, with the same return value as
/// one would have received if it remained `None`. It will be empty if no object matched the `prefix`.
///
// NOTE: pretty much the same things as in `index::File::lookup`, change things there
// as well.
pub fn lookup_prefix(
&self,
prefix: git_hash::Prefix,
candidates: Option<&mut Range<EntryIndex>>,
) -> Option<PrefixLookupResult> {
crate::index::access::lookup_prefix(
prefix,
candidates,
&self.fan,
|idx| self.oid_at_index(idx),
self.num_objects,
)
}
/// Find the index ranging from 0 to [File::num_objects()] that belongs to data associated with `id`, or `None` if it wasn't found.
///
/// Use this index for finding additional information via [`File::pack_id_and_pack_offset_at_index()`].
pub fn lookup(&self, id: impl AsRef<git_hash::oid>) -> Option<EntryIndex> {
crate::index::access::lookup(id, &self.fan, |idx| self.oid_at_index(idx))
}
/// Given the `index` ranging from 0 to [File::num_objects()], return the pack index and its absolute offset into the pack.
///
/// The pack-index refers to an entry in the [`index_names`][File::index_names()] list, from which the pack can be derived.
pub fn pack_id_and_pack_offset_at_index(&self, index: EntryIndex) -> (PackIndex, data::Offset) {
const OFFSET_ENTRY_SIZE: usize = 4 + 4;
let index = index as usize;
let start = self.offsets_ofs + index * OFFSET_ENTRY_SIZE;
const HIGH_BIT: u32 = 1 << 31;
let pack_index = crate::read_u32(&self.data[start..][..4]);
let offset = &self.data[start + 4..][..4];
let ofs32 = crate::read_u32(offset);
let pack_offset = if (ofs32 & HIGH_BIT) == HIGH_BIT {
// We determine if large offsets are actually larger than 4GB and if not, we don't use the high-bit to signal anything
// but allow the presence of the large-offset chunk to signal what's happening.
if let Some(offsets_64) = self.large_offsets_ofs {
let from = offsets_64 + (ofs32 ^ HIGH_BIT) as usize * 8;
crate::read_u64(&self.data[from..][..8])
} else {
ofs32 as u64
}
} else {
ofs32 as u64
};
(pack_index, pack_offset)
}
/// Return an iterator over all entries within this file.
pub fn iter(&self) -> impl Iterator<Item = Entry> + '_ {
(0..self.num_objects).map(move |idx| {
let (pack_index, pack_offset) = self.pack_id_and_pack_offset_at_index(idx);
Entry {
oid: self.oid_at_index(idx).to_owned(),
pack_offset,
pack_index,
}
})
}
}