dirstate-v2: Separate Rust structs for Timestamp and PackedTimestamp
PackedTimestamp is now exclusively for dirstate-v2 serialization purpose.
It contains unaligned big-endian integers. Timestamp is used everywhere else
and contains native Rust integers.
Differential Revision: https://phab.mercurial-scm.org/D11632
--- a/rust/hg-core/src/dirstate/entry.rs Mon Oct 11 22:19:42 2021 +0200
+++ b/rust/hg-core/src/dirstate/entry.rs Tue Oct 12 16:20:05 2021 +0200
@@ -1,6 +1,7 @@
use crate::errors::HgError;
use bitflags::bitflags;
use std::convert::TryFrom;
+use std::time::{SystemTime, UNIX_EPOCH};
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum EntryState {
@@ -28,6 +29,73 @@
}
}
+#[derive(Copy, Clone, PartialEq)]
+pub struct Timestamp {
+ seconds: i64,
+
+ /// In `0 .. 1_000_000_000`.
+ ///
+ /// This timestamp is after `(seconds, 0)` by this many nanoseconds.
+ nanoseconds: u32,
+}
+
+impl Timestamp {
+ pub fn new(seconds: i64, nanoseconds: u32) -> Self {
+ Self {
+ seconds,
+ nanoseconds,
+ }
+ }
+
+ pub fn seconds(&self) -> i64 {
+ self.seconds
+ }
+
+ pub fn nanoseconds(&self) -> u32 {
+ self.nanoseconds
+ }
+}
+
+impl From<SystemTime> for Timestamp {
+ fn from(system_time: SystemTime) -> Self {
+ // On Unix, `SystemTime` is a wrapper for the `timespec` C struct:
+ // https://www.gnu.org/software/libc/manual/html_node/Time-Types.html#index-struct-timespec
+ // We want to effectively access its fields, but the Rust standard
+ // library does not expose them. The best we can do is:
+ let seconds;
+ let nanoseconds;
+ match system_time.duration_since(UNIX_EPOCH) {
+ Ok(duration) => {
+ seconds = duration.as_secs() as i64;
+ nanoseconds = duration.subsec_nanos();
+ }
+ Err(error) => {
+ // `system_time` is before `UNIX_EPOCH`.
+ // We need to undo this algorithm:
+ // https://github.com/rust-lang/rust/blob/6bed1f0bc3cc50c10aab26d5f94b16a00776b8a5/library/std/src/sys/unix/time.rs#L40-L41
+ let negative = error.duration();
+ let negative_secs = negative.as_secs() as i64;
+ let negative_nanos = negative.subsec_nanos();
+ if negative_nanos == 0 {
+ seconds = -negative_secs;
+ nanoseconds = 0;
+ } else {
+ // For example if `system_time` was 4.3 seconds before
+ // the Unix epoch we get a Duration that represents
+ // `(-4, -0.3)` but we want `(-5, +0.7)`:
+ const NSEC_PER_SEC: u32 = 1_000_000_000;
+ seconds = -1 - negative_secs;
+ nanoseconds = NSEC_PER_SEC - negative_nanos;
+ }
+ }
+ };
+ Self {
+ seconds,
+ nanoseconds,
+ }
+ }
+}
+
pub const V1_RANGEMASK: i32 = 0x7FFFFFFF;
pub const MTIME_UNSET: i32 = -1;
--- a/rust/hg-core/src/dirstate_tree/dirstate_map.rs Mon Oct 11 22:19:42 2021 +0200
+++ b/rust/hg-core/src/dirstate_tree/dirstate_map.rs Tue Oct 12 16:20:05 2021 +0200
@@ -330,9 +330,9 @@
pub(super) fn cached_directory_mtime(
&self,
- ) -> Option<&'tree on_disk::Timestamp> {
+ ) -> Option<crate::dirstate::Timestamp> {
match self {
- NodeRef::InMemory(_path, node) => match &node.data {
+ NodeRef::InMemory(_path, node) => match node.data {
NodeData::CachedDirectory { mtime } => Some(mtime),
_ => None,
},
@@ -376,7 +376,7 @@
pub(super) enum NodeData {
Entry(DirstateEntry),
- CachedDirectory { mtime: on_disk::Timestamp },
+ CachedDirectory { mtime: crate::dirstate::Timestamp },
None,
}
--- a/rust/hg-core/src/dirstate_tree/on_disk.rs Mon Oct 11 22:19:42 2021 +0200
+++ b/rust/hg-core/src/dirstate_tree/on_disk.rs Tue Oct 12 16:20:05 2021 +0200
@@ -2,6 +2,7 @@
//!
//! See `mercurial/helptext/internals/dirstate-v2.txt`
+use crate::dirstate::Timestamp;
use crate::dirstate_tree::dirstate_map::{self, DirstateMap, NodeRef};
use crate::dirstate_tree::path_with_basename::WithBasename;
use crate::errors::HgError;
@@ -15,7 +16,6 @@
use format_bytes::format_bytes;
use std::borrow::Cow;
use std::convert::{TryFrom, TryInto};
-use std::time::{SystemTime, UNIX_EPOCH};
/// Added at the start of `.hg/dirstate` when the "v2" format is used.
/// This a redundant sanity check more than an actual "magic number" since
@@ -119,9 +119,9 @@
}
/// Duration since the Unix epoch
-#[derive(BytesCast, Copy, Clone, PartialEq)]
+#[derive(BytesCast, Copy, Clone)]
#[repr(C)]
-pub(super) struct Timestamp {
+struct PackedTimestamp {
seconds: I64Be,
/// In `0 .. 1_000_000_000`.
@@ -316,14 +316,14 @@
) -> Result<dirstate_map::NodeData, DirstateV2ParseError> {
if self.has_entry() {
Ok(dirstate_map::NodeData::Entry(self.assume_entry()))
- } else if let Some(&mtime) = self.cached_directory_mtime() {
+ } else if let Some(mtime) = self.cached_directory_mtime() {
Ok(dirstate_map::NodeData::CachedDirectory { mtime })
} else {
Ok(dirstate_map::NodeData::None)
}
}
- pub(super) fn cached_directory_mtime(&self) -> Option<&Timestamp> {
+ pub(super) fn cached_directory_mtime(&self) -> Option<Timestamp> {
if self.flags.contains(Flags::HAS_MTIME) && !self.has_entry() {
Some(self.data.as_timestamp())
} else {
@@ -423,58 +423,23 @@
}
fn from_timestamp(timestamp: Timestamp) -> Self {
+ let packed = PackedTimestamp {
+ seconds: timestamp.seconds().into(),
+ nanoseconds: timestamp.nanoseconds().into(),
+ };
// Safety: both types implement the `ByteCast` trait, so we could
// safely use `as_bytes` and `from_bytes` to do this conversion. Using
// `transmute` instead makes the compiler check that the two types
// have the same size, which eliminates the error case of
// `from_bytes`.
- unsafe { std::mem::transmute::<Timestamp, Entry>(timestamp) }
+ unsafe { std::mem::transmute::<PackedTimestamp, Entry>(packed) }
}
- fn as_timestamp(&self) -> &Timestamp {
+ fn as_timestamp(self) -> Timestamp {
// Safety: same as above in `from_timestamp`
- unsafe { &*(self as *const Entry as *const Timestamp) }
- }
-}
-
-impl Timestamp {
- pub fn seconds(&self) -> i64 {
- self.seconds.get()
- }
-}
-
-impl From<SystemTime> for Timestamp {
- fn from(system_time: SystemTime) -> Self {
- // On Unix, `SystemTime` is a wrapper for the `timespec` C struct:
- // https://www.gnu.org/software/libc/manual/html_node/Time-Types.html#index-struct-timespec
- // We want to effectively access its fields, but the Rust standard
- // library does not expose them. The best we can do is:
- let (secs, nanos) = match system_time.duration_since(UNIX_EPOCH) {
- Ok(duration) => {
- (duration.as_secs() as i64, duration.subsec_nanos())
- }
- Err(error) => {
- // `system_time` is before `UNIX_EPOCH`.
- // We need to undo this algorithm:
- // https://github.com/rust-lang/rust/blob/6bed1f0bc3cc50c10aab26d5f94b16a00776b8a5/library/std/src/sys/unix/time.rs#L40-L41
- let negative = error.duration();
- let negative_secs = negative.as_secs() as i64;
- let negative_nanos = negative.subsec_nanos();
- if negative_nanos == 0 {
- (-negative_secs, 0)
- } else {
- // For example if `system_time` was 4.3 seconds before
- // the Unix epoch we get a Duration that represents
- // `(-4, -0.3)` but we want `(-5, +0.7)`:
- const NSEC_PER_SEC: u32 = 1_000_000_000;
- (-1 - negative_secs, NSEC_PER_SEC - negative_nanos)
- }
- }
- };
- Timestamp {
- seconds: secs.into(),
- nanoseconds: nanos.into(),
- }
+ let packed =
+ unsafe { std::mem::transmute::<Entry, PackedTimestamp>(self) };
+ Timestamp::new(packed.seconds.get(), packed.nanoseconds.get())
}
}
--- a/rust/hg-core/src/dirstate_tree/status.rs Mon Oct 11 22:19:42 2021 +0200
+++ b/rust/hg-core/src/dirstate_tree/status.rs Tue Oct 12 16:20:05 2021 +0200
@@ -1,3 +1,4 @@
+use crate::dirstate::entry::Timestamp;
use crate::dirstate::status::IgnoreFnType;
use crate::dirstate_tree::dirstate_map::BorrowedPath;
use crate::dirstate_tree::dirstate_map::ChildNodesRef;
@@ -5,7 +6,6 @@
use crate::dirstate_tree::dirstate_map::NodeData;
use crate::dirstate_tree::dirstate_map::NodeRef;
use crate::dirstate_tree::on_disk::DirstateV2ParseError;
-use crate::dirstate_tree::on_disk::Timestamp;
use crate::matchers::get_ignore_function;
use crate::matchers::Matcher;
use crate::utils::files::get_bytes_from_os_string;
@@ -182,7 +182,7 @@
fn can_skip_fs_readdir(
&self,
directory_metadata: Option<&std::fs::Metadata>,
- cached_directory_mtime: Option<&Timestamp>,
+ cached_directory_mtime: Option<Timestamp>,
) -> bool {
if !self.options.list_unknown && !self.options.list_ignored {
// All states that we care about listing have corresponding
@@ -200,7 +200,7 @@
if let Some(meta) = directory_metadata {
if let Ok(current_mtime) = meta.modified() {
let current_mtime = Timestamp::from(current_mtime);
- if current_mtime == *cached_mtime {
+ if current_mtime == cached_mtime {
// The mtime of that directory has not changed
// since then, which means that the results of
// `read_dir` should also be unchanged.
@@ -222,7 +222,7 @@
directory_hg_path: &BorrowedPath<'tree, 'on_disk>,
directory_fs_path: &Path,
directory_metadata: Option<&std::fs::Metadata>,
- cached_directory_mtime: Option<&Timestamp>,
+ cached_directory_mtime: Option<Timestamp>,
is_at_repo_root: bool,
) -> Result<bool, DirstateV2ParseError> {
if self.can_skip_fs_readdir(directory_metadata, cached_directory_mtime)
@@ -468,7 +468,7 @@
// unlikely enough in practice.
let timestamp = directory_mtime.into();
let cached = dirstate_node.cached_directory_mtime();
- if cached != Some(×tamp) {
+ if cached != Some(timestamp) {
let hg_path = dirstate_node
.full_path_borrowed(self.dmap.on_disk)?
.detach_from_tree();