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Differential D11620

dirstate-v2: Swap the order of size and mtime on disk
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Authored by SimonSapin on Oct 8 2021, 8:06 AM.

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rHG6e01bcd111d2: dirstate-v2: Swap the order of size and mtime on disk

Summary

This makes the dirstate-v2 file format match dirstate-v1 for the order of
mode, size, and mtime. This order does not matter as long as these
components are handled through named fields/attributes in code, but in a few
places we still have tuples so having the same order everywhere might help
avoid a bug that might not be obvious since those components have the same type.

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rHG Mercurial

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Automatic diff as part of commit; unit tests not applicable.

Event Timeline

SimonSapin created this revision.Oct 8 2021, 8:06 AM

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SimonSapin added a child revision: D11547: dirstate-v2: Name a constant in the Rust implementation.Oct 8 2021, 8:06 AM

I’ve split this from D11547.

Because of how BytesCast is used, the struct definition defines the file format.

This makes the dirstate-v2 file format match dirstate-v2 for the order of

Should the second "v2" be "v1?

(And I assume "Change swap" can be just "Swap".)

SimonSapin retitled this revision from dirstate-v2: Change swap the order of size and mtime on disk to dirstate-v2: Swap the order of size and mtime on disk.Oct 12 2021, 7:04 AM

SimonSapin edited the summary of this revision. (Show Details)

Ah yes. Thanks!

SimonSapin added a parent revision: D11625: dirstate-v2: Document flags/mode/size/mtime fields of tree nodes.Oct 12 2021, 1:00 PM

SimonSapin added a child revision: D11631: dirstate-v2: Only convert from SystemTime to Timestamp and not back.

SimonSapin updated this revision to Diff 30717.

SimonSapin added a commit: rHG6e01bcd111d2: dirstate-v2: Swap the order of size and mtime on disk.Oct 12 2021, 2:02 PM

This revision was not accepted when it landed; it landed in state Needs Review.

Closed by commit rHG6e01bcd111d2: dirstate-v2: Swap the order of size and mtime on disk (authored by SimonSapin). · Explain Why

This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

			Path	Packages
M			mercurial/helptext/internals/dirstate-v2.txt (10 lines)
M			rust/hg-core/src/dirstate_tree/on_disk.rs (2 lines)

Diff	ID	Description	Created	Lint	Unit
Base		Base
Diff 1	30683		Oct 8 2021, 8:06 AM	★	★
Diff 2	30717		Oct 12 2021, 1:00 PM	★	★
Diff 3	30750	rHG6e01bcd111d26c4c131315888adc9d87b45a4fe4	Oct 8 2021, 6:57 AM	★	★

Status	Author	Revision
Closed	SimonSapin	D11635 dirstate-v2: Replace the 32-bit `mode` field with two bits
Closed	SimonSapin	D11634 dirstate-v2: Store unsigned integers inside DirstateEntry
Closed	SimonSapin	D11633 dirstate-v2: Truncate directory mtimes to 31 bits of seconds
Closed	SimonSapin	D11632 dirstate-v2: Separate Rust structs for Timestamp and PackedTimestamp
Closed	SimonSapin	D11629 dirstate-v2: Change the representation of negative directory mtime
Closed	SimonSapin	D11631 dirstate-v2: Only convert from SystemTime to Timestamp and not back
Abandoned	SimonSapin	D11624 dirstate-v2: Change the representation of negative directory mtime
Closed	marmoute	D11547 dirstate-v2: Name a constant in the Rust implementation
Closed	SimonSapin	D11620 dirstate-v2: Swap the order of size and mtime on disk
Closed	SimonSapin	D11625 dirstate-v2: Document flags/mode/size/mtime fields of tree nodes
Closed	SimonSapin	D11623 dirstate-v2: Use "byte sequence" in docs

Diff 30750

mercurial/helptext/internals/dirstate-v2.txt


	* Offset 31:			* Offset 31:
	If `HAS_MODE_AND_SIZE` is unset, four zero bytes.			If `HAS_MODE_AND_SIZE` is unset, four zero bytes.
	Otherwise, a 32-bit integer for the Unix mode (as in `stat_result.st_mode`)			Otherwise, a 32-bit integer for the Unix mode (as in `stat_result.st_mode`)
	expected for this file to be considered clean.			expected for this file to be considered clean.
	Only the `S_IXUSR` bit (owner has execute permission) is considered.			Only the `S_IXUSR` bit (owner has execute permission) is considered.

	* Offset 35:			* Offset 35:
	If `HAS_MTIME` is unset, four zero bytes.			If `HAS_MODE_AND_SIZE` is unset, four zero bytes.
	Otherwise, a 32-bit integer for expected modified time of the file			Otherwise, a 32-bit integer for expected size of the file
	(as in `stat_result.st_mtime`),
	truncated to its 31 least-significant bits.			truncated to its 31 least-significant bits.
	Unlike in dirstate-v1, negative values are not used.			Unlike in dirstate-v1, negative values are not used.

	* Offset 39:			* Offset 39:
	If `HAS_MODE_AND_SIZE` is unset, four zero bytes.			If `HAS_MTIME` is unset, four zero bytes.
	Otherwise, a 32-bit integer for expected size of the file			Otherwise, a 32-bit integer for expected modified time of the file
				(as in `stat_result.st_mtime`),
	truncated to its 31 least-significant bits.			truncated to its 31 least-significant bits.
	Unlike in dirstate-v1, negative values are not used.			Unlike in dirstate-v1, negative values are not used.

	If an untracked node `HAS_MTIME` unset, this space is unused:			If an untracked node `HAS_MTIME` unset, this space is unused:

	* Offset 31:			* Offset 31:
	12 bytes set to zero			12 bytes set to zero

rust/hg-core/src/dirstate_tree/on_disk.rs

	const HAS_MTIME = 1 << 4;			const HAS_MTIME = 1 << 4;
	}			}
	}			}

	#[derive(BytesCast, Copy, Clone, Debug)]			#[derive(BytesCast, Copy, Clone, Debug)]
	#[repr(C)]			#[repr(C)]
	struct Entry {			struct Entry {
	mode: I32Be,			mode: I32Be,
	mtime: I32Be,
	size: I32Be,			size: I32Be,
				mtime: I32Be,
	}			}

	/// Duration since the Unix epoch			/// Duration since the Unix epoch
	#[derive(BytesCast, Copy, Clone, PartialEq)]			#[derive(BytesCast, Copy, Clone, PartialEq)]
	#[repr(C)]			#[repr(C)]
	pub(super) struct Timestamp {			pub(super) struct Timestamp {
	seconds: I64Be,			seconds: I64Be,