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index: precompute base data offsets

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These offsets are getting messier, so let's calculate them in one place. This
will probably help compiler optimization.
This commit is contained in:
Yuya Nishihara 2024-02-18 16:58:42 +09:00
parent 3c7aa75b9b
commit d5c75da4f5
1 changed files with 39 additions and 41 deletions
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80
lib/src/default_index/readonly.rs
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@ -219,8 +219,13 @@ pub(super) struct ReadonlyIndexSegment {
// Number of commits not counting the parent file
num_local_commits: u32,
num_local_change_ids: u32,
num_parent_overflow_entries: u32,
num_change_overflow_entries: u32,
// Base data offsets in bytes:
commit_lookup_base: usize,
change_id_table_base: usize,
change_pos_table_base: usize,
parent_overflow_base: usize,
change_overflow_base: usize,
data: Vec<u8>,
}
@ -318,6 +323,7 @@ impl ReadonlyIndexSegment {
let num_change_overflow_entries = read_u32(file)?;
let mut data = vec![];
file.read_to_end(&mut data).map_err(from_io_err)?;
let commit_graph_entry_size = CommitGraphEntry::size(commit_id_length);
let graph_size = (num_local_commits as usize) * commit_graph_entry_size;
let commit_lookup_entry_size = CommitLookupEntry::size(commit_id_length);
@ -326,18 +332,22 @@ impl ReadonlyIndexSegment {
let change_pos_table_size = (num_local_change_ids as usize) * 4;
let parent_overflow_size = (num_parent_overflow_entries as usize) * 4;
let change_overflow_size = (num_change_overflow_entries as usize) * 4;
let expected_size = graph_size
+ commit_lookup_size
+ change_id_table_size
+ change_pos_table_size
+ parent_overflow_size
+ change_overflow_size;
let graph_base = 0;
let commit_lookup_base = graph_base + graph_size;
let change_id_table_base = commit_lookup_base + commit_lookup_size;
let change_pos_table_base = change_id_table_base + change_id_table_size;
let parent_overflow_base = change_pos_table_base + change_pos_table_size;
let change_overflow_base = parent_overflow_base + parent_overflow_size;
let expected_size = change_overflow_base + change_overflow_size;
if data.len() != expected_size {
return Err(ReadonlyIndexLoadError::invalid_data(
name,
"unexpected data length",
));
}
Ok(Arc::new(ReadonlyIndexSegment {
parent_file,
num_parent_commits,
@ -348,8 +358,12 @@ impl ReadonlyIndexSegment {
commit_lookup_entry_size,
num_local_commits,
num_local_change_ids,
num_parent_overflow_entries,
num_change_overflow_entries,
commit_lookup_base,
change_id_table_base,
change_pos_table_base,
parent_overflow_base,
change_overflow_base,
data,
}))
}
@ -371,19 +385,18 @@ impl ReadonlyIndexSegment {
}
fn graph_entry(&self, local_pos: LocalPosition) -> CommitGraphEntry {
assert!(local_pos.0 < self.num_local_commits);
let table = &self.data[..self.commit_lookup_base];
let offset = (local_pos.0 as usize) * self.commit_graph_entry_size;
CommitGraphEntry {
data: &self.data[offset..][..self.commit_graph_entry_size],
data: &table[offset..][..self.commit_graph_entry_size],
}
}
fn commit_lookup_entry(&self, lookup_pos: u32) -> CommitLookupEntry {
assert!(lookup_pos < self.num_local_commits);
let offset = (lookup_pos as usize) * self.commit_lookup_entry_size
+ (self.num_local_commits as usize) * self.commit_graph_entry_size;
let table = &self.data[self.commit_lookup_base..self.change_id_table_base];
let offset = (lookup_pos as usize) * self.commit_lookup_entry_size;
CommitLookupEntry {
data: &self.data[offset..][..self.commit_lookup_entry_size],
data: &table[offset..][..self.commit_lookup_entry_size],
commit_id_length: self.commit_id_length,
}
}
@ -394,32 +407,22 @@ impl ReadonlyIndexSegment {
// might be better to add borrowed version of ChangeId
fn change_lookup_id_bytes(&self, lookup_pos: u32) -> &[u8] {
assert!(lookup_pos < self.num_local_change_ids);
let offset = (lookup_pos as usize) * self.change_id_length
+ (self.num_local_commits as usize) * self.commit_graph_entry_size
+ (self.num_local_commits as usize) * self.commit_lookup_entry_size;
&self.data[offset..][..self.change_id_length]
let table = &self.data[self.change_id_table_base..self.change_pos_table_base];
let offset = (lookup_pos as usize) * self.change_id_length;
&table[offset..][..self.change_id_length]
}
fn change_lookup_pos(&self, lookup_pos: u32) -> ChangeLocalPosition {
assert!(lookup_pos < self.num_local_change_ids);
let offset = (lookup_pos as usize) * 4
+ (self.num_local_commits as usize) * self.commit_graph_entry_size
+ (self.num_local_commits as usize) * self.commit_lookup_entry_size
+ (self.num_local_change_ids as usize) * self.change_id_length;
ChangeLocalPosition(u32::from_le_bytes(
self.data[offset..][..4].try_into().unwrap(),
))
let table = &self.data[self.change_pos_table_base..self.parent_overflow_base];
let offset = (lookup_pos as usize) * 4;
ChangeLocalPosition(u32::from_le_bytes(table[offset..][..4].try_into().unwrap()))
}
fn overflow_parents(&self, overflow_pos: u32, num_parents: u32) -> SmallIndexPositionsVec {
assert!(overflow_pos + num_parents <= self.num_parent_overflow_entries);
let offset = (overflow_pos as usize) * 4
+ (self.num_local_commits as usize) * self.commit_graph_entry_size
+ (self.num_local_commits as usize) * self.commit_lookup_entry_size
+ (self.num_local_change_ids as usize) * self.change_id_length
+ (self.num_local_change_ids as usize) * 4;
self.data[offset..][..(num_parents as usize) * 4]
let table = &self.data[self.parent_overflow_base..self.change_overflow_base];
let offset = (overflow_pos as usize) * 4;
let size = (num_parents as usize) * 4;
table[offset..][..size]
.chunks_exact(4)
.map(|chunk| IndexPosition(u32::from_le_bytes(chunk.try_into().unwrap())))
.collect()
@ -427,14 +430,9 @@ impl ReadonlyIndexSegment {
/// Scans graph entry positions stored in the overflow change ids table.
fn overflow_changes_from(&self, overflow_pos: u32) -> impl Iterator<Item = LocalPosition> + '_ {
let base = (self.num_local_commits as usize) * self.commit_graph_entry_size
+ (self.num_local_commits as usize) * self.commit_lookup_entry_size
+ (self.num_local_change_ids as usize) * self.change_id_length
+ (self.num_local_change_ids as usize) * 4
+ (self.num_parent_overflow_entries as usize) * 4;
let size = (self.num_change_overflow_entries as usize) * 4;
let table = &self.data[self.change_overflow_base..];
let offset = (overflow_pos as usize) * 4;
self.data[base..][..size][offset..]
table[offset..]
.chunks_exact(4)
.map(|chunk| LocalPosition(u32::from_le_bytes(chunk.try_into().unwrap())))
}