gix_ref/store/packed/
buffer.rs

1use crate::store_impl::packed;
2
3impl AsRef<[u8]> for packed::Buffer {
4    fn as_ref(&self) -> &[u8] {
5        &self.data.as_ref()[self.offset..]
6    }
7}
8
9impl AsRef<[u8]> for packed::Backing {
10    fn as_ref(&self) -> &[u8] {
11        match self {
12            packed::Backing::InMemory(data) => data,
13            packed::Backing::Mapped(map) => map,
14        }
15    }
16}
17
18///
19pub mod open {
20    use std::path::PathBuf;
21
22    use crate::store_impl::packed;
23
24    /// Initialization
25    impl packed::Buffer {
26        fn open_with_backing(
27            backing: packed::Backing,
28            path: PathBuf,
29            hash_kind: gix_hash::Kind,
30        ) -> Result<Self, Error> {
31            let (backing, offset) = {
32                let (offset, sorted) = {
33                    let mut input = backing.as_ref();
34                    if *input.first().unwrap_or(&b' ') == b'#' {
35                        let header = packed::decode::header(&mut input).map_err(|_| Error::HeaderParsing)?;
36                        let offset = backing.as_ref().len() - input.len();
37                        (offset, header.sorted)
38                    } else {
39                        (0, false)
40                    }
41                };
42
43                if !sorted {
44                    // this implementation is likely slower than what git does, but it's less code, too.
45                    let mut entries =
46                        packed::Iter::new(&backing.as_ref()[offset..], hash_kind)?.collect::<Result<Vec<_>, _>>()?;
47                    entries.sort_by_key(|e| e.name.as_bstr());
48                    let mut serialized = Vec::<u8>::new();
49                    for entry in entries {
50                        serialized.extend_from_slice(entry.target);
51                        serialized.push(b' ');
52                        serialized.extend_from_slice(entry.name.as_bstr());
53                        serialized.push(b'\n');
54                        if let Some(object) = entry.object {
55                            serialized.push(b'^');
56                            serialized.extend_from_slice(object);
57                            serialized.push(b'\n');
58                        }
59                    }
60                    (Backing::InMemory(serialized), 0)
61                } else {
62                    (backing, offset)
63                }
64            };
65            Ok(packed::Buffer {
66                offset,
67                data: backing,
68                path,
69                hash_kind,
70            })
71        }
72
73        /// Open the file at `path`, parsing object ids as `hash_kind`, and map it into memory if the file size is larger
74        /// than `use_memory_map_if_larger_than_bytes`.
75        ///
76        /// In order to allow fast lookups and optimizations, the contents of the packed refs must be sorted.
77        /// If that's not the case, they will be sorted on the fly with the data being written into a memory buffer.
78        pub fn open(
79            path: PathBuf,
80            use_memory_map_if_larger_than_bytes: u64,
81            hash_kind: gix_hash::Kind,
82        ) -> Result<Self, Error> {
83            let backing = if std::fs::metadata(&path)?.len() <= use_memory_map_if_larger_than_bytes {
84                packed::Backing::InMemory(std::fs::read(&path)?)
85            } else {
86                packed::Backing::Mapped(
87                    // SAFETY: we have to take the risk of somebody changing the file underneath. Git never writes into the same file.
88                    #[allow(unsafe_code)]
89                    unsafe {
90                        memmap2::MmapOptions::new().map_copy_read_only(&std::fs::File::open(&path)?)?
91                    },
92                )
93            };
94            Self::open_with_backing(backing, path, hash_kind)
95        }
96
97        /// Open a buffer from `bytes`, which is the content of a typical `packed-refs` file, parsing object ids as
98        /// `hash_kind`.
99        ///
100        /// In order to allow fast lookups and optimizations, the contents of the packed refs must be sorted.
101        /// If that's not the case, they will be sorted on the fly.
102        pub fn from_bytes(bytes: &[u8], hash_kind: gix_hash::Kind) -> Result<Self, Error> {
103            let backing = packed::Backing::InMemory(bytes.into());
104            Self::open_with_backing(backing, PathBuf::from("<memory>"), hash_kind)
105        }
106    }
107
108    mod error {
109        use crate::packed;
110
111        /// The error returned by [`open()`][super::packed::Buffer::open()].
112        #[derive(Debug, thiserror::Error)]
113        #[allow(missing_docs)]
114        pub enum Error {
115            #[error("The packed-refs file did not have a header or wasn't sorted and could not be iterated")]
116            Iter(#[from] packed::iter::Error),
117            #[error("The header could not be parsed, even though first line started with '#'")]
118            HeaderParsing,
119            #[error("The buffer could not be opened or read")]
120            Io(#[from] std::io::Error),
121        }
122    }
123    pub use error::Error;
124
125    use crate::packed::Backing;
126}
gix_ref/store/packed/buffer.rs

gix_ref/store/packed/
buffer.rs
