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annotate rust/hg-core/examples/nodemap/index.rs @ 51599:9b51a4fb0f96

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bundlespec: type the _bundlespeccontentopts dictionary If only we had a tool to detect the kind of stupid error we just fixed? ho wait.
author Pierre-Yves David <pierre-yves.david@octobus.net>
date Tue, 09 Apr 2024 14:37:24 +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 }