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annotate rust/hg-core/src/revlog.rs @ 47123:d8ac62374943

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dirstate-tree: Make `DirstateMap` borrow from a bytes buffer ? that has the contents of the `.hg/dirstate` file. This only applies to the tree-based flavor of `DirstateMap`. For now only the entire `&[u8]` slice is stored, so this is not useful yet. Adding a lifetime parameter to the `DirstateMap` struct (in hg-core) makes Python bindings non-trivial because we keep that struct in a Python object that has a dynamic lifetime tied to Python?s reference-counting and GC. As long as we keep the `PyBytes` that owns the borrowed bytes buffer next to the borrowing struct, the buffer will live long enough for the borrows to stay valid. However this relationship cannot be expressed in safe Rust code in a way that would statisfy they borrow-checker. We use `unsafe` code to erase that lifetime parameter, and encapsulate it in a safe abstraction similar to the owning-ref crate: https://docs.rs/owning_ref/ Differential Revision: https://phab.mercurial-scm.org/D10557
author Simon Sapin <simon.sapin@octobus.net>
date Fri, 30 Apr 2021 18:24:54 +0200
parents e8ae91b1a63d
children 4d2a5ca060e3
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1 // Copyright 2018-2020 Georges Racinet <georges.racinet@octobus.net>
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2 // and Mercurial contributors
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3 //
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4 // This software may be used and distributed according to the terms of the
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5 // GNU General Public License version 2 or any later version.
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6 //! Mercurial concepts for handling revision history
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7
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8 pub mod node;
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9 pub mod nodemap;
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10 mod nodemap_docket;
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11 pub mod path_encode;
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12 pub use node::{FromHexError, Node, NodePrefix};
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13 pub mod changelog;
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14 pub mod index;
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15 pub mod manifest;
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16 pub mod patch;
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17 pub mod revlog;
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18
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19 /// Mercurial revision numbers
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20 ///
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21 /// As noted in revlog.c, revision numbers are actually encoded in
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22 /// 4 bytes, and are liberally converted to ints, whence the i32
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23 pub type Revision = i32;
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24
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25 /// Marker expressing the absence of a parent
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26 ///
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27 /// Independently of the actual representation, `NULL_REVISION` is guaranteed
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28 /// to be smaller than all existing revisions.
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29 pub const NULL_REVISION: Revision = -1;
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30
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31 /// Same as `mercurial.node.wdirrev`
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32 ///
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33 /// This is also equal to `i32::max_value()`, but it's better to spell
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34 /// it out explicitely, same as in `mercurial.node`
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35 #[allow(clippy::unreadable_literal)]
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36 pub const WORKING_DIRECTORY_REVISION: Revision = 0x7fffffff;
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37
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38 pub const WORKING_DIRECTORY_HEX: &str =
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39 "ffffffffffffffffffffffffffffffffffffffff";
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40
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41 /// The simplest expression of what we need of Mercurial DAGs.
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42 pub trait Graph {
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43 /// Return the two parents of the given `Revision`.
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44 ///
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45 /// Each of the parents can be independently `NULL_REVISION`
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46 fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError>;
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47 }
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48
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49 #[derive(Clone, Debug, PartialEq)]
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50 pub enum GraphError {
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51 ParentOutOfRange(Revision),
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52 WorkingDirectoryUnsupported,
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53 }
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54
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55 /// The Mercurial Revlog Index
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56 ///
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57 /// This is currently limited to the minimal interface that is needed for
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58 /// the [`nodemap`](nodemap/index.html) module
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59 pub trait RevlogIndex {
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60 /// Total number of Revisions referenced in this index
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61 fn len(&self) -> usize;
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62
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63 fn is_empty(&self) -> bool {
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64 self.len() == 0
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65 }
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66
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67 /// Return a reference to the Node or `None` if rev is out of bounds
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68 ///
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69 /// `NULL_REVISION` is not considered to be out of bounds.
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70 fn node(&self, rev: Revision) -> Option<&Node>;
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71 }