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annotate rust/hg-core/examples/nodemap/index.rs @ 51864:db7dbe6f7bb2

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rust: add Vfs trait This will allow for the use of multiple vfs like in the Python implementation, as well as hiding the details of the upcoming Python vfs wrapper to hg-core.
author Rapha?l Gom?s <rgomes@octobus.net>
date Wed, 19 Jun 2024 14:49:35 +0200
parents 4c5f6e95df84
children bd8081e9fd62
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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 memmap2::*;
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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 [self.p1, self.p2]
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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 Some(&self.data[rev.0 as usize].node)
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46 }
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47 }
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48
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49 impl Graph for &Index {
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50 fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {
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51 let [p1, p2] = self.data[rev.0 as usize].parents();
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52 let len = (*self).len();
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53 if p1 < NULL_REVISION
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54 || p2 < NULL_REVISION
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55 || p1.0 as usize >= len
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56 || p2.0 as usize >= len
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57 {
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58 return Err(GraphError::ParentOutOfRange(rev));
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59 }
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60 Ok([p1, p2])
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61 }
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62 }
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63
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64 struct IndexMmap(Mmap);
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65
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66 impl Deref for IndexMmap {
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67 type Target = [IndexEntry];
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68
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69 fn deref(&self) -> &[IndexEntry] {
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70 let ptr = self.0.as_ptr() as *const IndexEntry;
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71 // Any misaligned data will be ignored.
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72 debug_assert_eq!(
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73 self.0.len() % std::mem::align_of::<IndexEntry>(),
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74 0,
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75 "Misaligned data in mmap"
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76 );
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77 unsafe { slice::from_raw_parts(ptr, self.0.len() / INDEX_ENTRY_SIZE) }
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78 }
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79 }
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80
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81 impl Index {
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82 pub fn load_mmap(path: impl AsRef<Path>) -> Self {
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83 let file = File::open(path).unwrap();
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84 let msg = "Index file is missing, or missing permission";
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85 let mmap = unsafe { MmapOptions::new().map(&file) }.expect(msg);
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86 Self {
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87 data: Box::new(IndexMmap(mmap)),
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88 }
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89 }
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90 }