gix_pack/data/file/
init.rs

1use std::path::{Path, PathBuf};
2
3use crate::data;
4
5/// Instantiation
6impl data::File<crate::MMap> {
7    /// Try opening a data file at the given `path`.
8    ///
9    /// The `object_hash` is a way to read (and write) the same file format with different hashes, as the hash kind
10    /// isn't stored within the file format itself.
11    ///
12    /// This constructor leaves allocation limiting disabled, allowing allocations of any size dictated by pack data.
13    /// Use [`Self::from_data()`] together with [`File::with_alloc_limit_bytes()`][crate::data::File::with_alloc_limit_bytes()]
14    /// when working with untrusted input.
15    pub fn at(path: impl AsRef<Path>, object_hash: gix_hash::Kind) -> Result<Self, data::header::decode::Error> {
16        Self::at_inner(path.as_ref(), object_hash)
17    }
18
19    fn at_inner(path: &Path, object_hash: gix_hash::Kind) -> Result<Self, data::header::decode::Error> {
20        let data = crate::mmap::read_only(path).map_err(|e| data::header::decode::Error::Io {
21            source: e,
22            path: path.to_owned(),
23        })?;
24        Self::from_data(data, path.to_owned(), object_hash)
25    }
26}
27
28impl<T> data::File<T>
29where
30    T: crate::FileData,
31{
32    /// Instantiate a data file from `data` as assumed to be read or memory-mapped from `path`.
33    ///
34    /// This constructor leaves allocation limiting disabled, allowing allocations of any size dictated by pack data.
35    /// Call [`File::with_alloc_limit_bytes()`][crate::data::File::with_alloc_limit_bytes()] before decoding entries from untrusted input.
36    pub fn from_data(data: T, path: PathBuf, object_hash: gix_hash::Kind) -> Result<Self, data::header::decode::Error> {
37        use crate::data::header::N32_SIZE;
38        let hash_len = object_hash.len_in_bytes();
39        let pack_len = data.len();
40        let id = gix_features::hash::crc32(path.as_os_str().to_string_lossy().as_bytes());
41        if pack_len < N32_SIZE * 3 + hash_len {
42            return Err(data::header::decode::Error::Corrupt(format!(
43                "Pack data of size {pack_len} is too small for even an empty pack with shortest hash"
44            )));
45        }
46        let (kind, num_objects) =
47            data::header::decode(&data[..12].try_into().expect("enough data after previous check"))?;
48        Ok(Self {
49            data,
50            path,
51            id,
52            version: kind,
53            num_objects,
54            hash_len,
55            object_hash,
56            alloc_limit_bytes: None,
57        })
58    }
59
60    /// Configure the maximum size of a single allocation caused by user-controlled on-disk pack data.
61    ///
62    /// Use `None` to disable the limit, which is also the default.
63    ///
64    /// This is currently enforced when decoding pack entries and resolving delta chains.
65    /// Callers that allocate from pack metadata directly should consult [`File::alloc_limit_bytes()`][crate::data::File::alloc_limit_bytes()]
66    /// and apply the same limit themselves.
67    pub fn with_alloc_limit_bytes(mut self, alloc_limit_bytes: Option<usize>) -> Self {
68        self.alloc_limit_bytes = alloc_limit_bytes;
69        self
70    }
71}
gix_pack/data/file/init.rs

gix_pack/data/file/
init.rs
