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annotate rust/hg-core/examples/nodemap/index.rs @ 47385:f6bb181c75f8

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rust: Parse "subinclude"d files along the way, not later When parsing a `.hgignore` file and encountering an `include:` line, the included file is parsed recursively right then in a depth-first fashion. With `subinclude:` however included files were parsed (recursively) much later. This changes it to be expanded during parsing, like `.hgignore`. The motivation for this is an upcoming changeset that needs to detect changes in which files are ignored or not. The plan is to hash all ignore files while they are being read, and store that hash in the dirstate (in v2 format). In order to allow a potential alternative implementations to read that format, the algorithm to compute that hash must be documented. Having a well-defined depth-first ordering for the tree of (sub-)included files makes that easier. Differential Revision: https://phab.mercurial-scm.org/D10834
author Simon Sapin <simon.sapin@octobus.net>
date Wed, 02 Jun 2021 18:03:43 +0200
parents 8f7c6656ac79
children e834b79def74
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1 // Copyright 2019-2020 Georges Racinet <georges.racinet@octobus.net>
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2 //
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3 // This software may be used and distributed according to the terms of the
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4 // GNU General Public License version 2 or any later version.
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5
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6 //! Minimal `RevlogIndex`, readable from standard Mercurial file format
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7 use hg::*;
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8 use memmap::*;
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9 use std::fs::File;
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10 use std::ops::Deref;
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11 use std::path::Path;
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12 use std::slice;
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13
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14 pub struct Index {
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15 data: Box<dyn Deref<Target = [IndexEntry]> + Send>,
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16 }
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17
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18 /// A fixed sized index entry. All numbers are big endian
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19 #[repr(C)]
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20 pub struct IndexEntry {
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21 not_used_yet: [u8; 24],
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22 p1: Revision,
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23 p2: Revision,
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24 node: Node,
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25 unused_node: [u8; 12],
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26 }
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27
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28 pub const INDEX_ENTRY_SIZE: usize = 64;
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29
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30 impl IndexEntry {
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31 fn parents(&self) -> [Revision; 2] {
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32 [Revision::from_be(self.p1), Revision::from_be(self.p1)]
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33 }
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34 }
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35
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36 impl RevlogIndex for Index {
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37 fn len(&self) -> usize {
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38 self.data.len()
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39 }
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40
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41 fn node(&self, rev: Revision) -> Option<&Node> {
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42 if rev == NULL_REVISION {
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43 return None;
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44 }
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45 let i = rev as usize;
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46 if i >= self.len() {
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47 None
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48 } else {
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49 Some(&self.data[i].node)
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50 }
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51 }
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52 }
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53
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54 impl Graph for &Index {
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55 fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {
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56 let [p1, p2] = (*self).data[rev as usize].parents();
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57 let len = (*self).len();
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58 if p1 < NULL_REVISION
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59 || p2 < NULL_REVISION
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60 || p1 as usize >= len
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61 || p2 as usize >= len
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62 {
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63 return Err(GraphError::ParentOutOfRange(rev));
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64 }
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65 Ok([p1, p2])
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66 }
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67 }
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68
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69 struct IndexMmap(Mmap);
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70
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71 impl Deref for IndexMmap {
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72 type Target = [IndexEntry];
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73
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74 fn deref(&self) -> &[IndexEntry] {
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75 let ptr = self.0.as_ptr() as *const IndexEntry;
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76 // Any misaligned data will be ignored.
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77 debug_assert_eq!(
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78 self.0.len() % std::mem::align_of::<IndexEntry>(),
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79 0,
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80 "Misaligned data in mmap"
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81 );
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82 unsafe { slice::from_raw_parts(ptr, self.0.len() / INDEX_ENTRY_SIZE) }
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83 }
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84 }
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85
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86 impl Index {
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87 pub fn load_mmap(path: impl AsRef<Path>) -> Self {
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88 let file = File::open(path).unwrap();
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89 let msg = "Index file is missing, or missing permission";
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90 let mmap = unsafe { MmapOptions::new().map(&file) }.expect(msg);
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91 Self {
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92 data: Box::new(IndexMmap(mmap)),
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93 }
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94 }
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95 }