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#![allow(unused)]
use std::path::{Path, PathBuf};
use memmap2::Mmap;
use crate::{decode, extension, File, State};
mod error {
/// The error returned by [File::at()][super::File::at()].
#[derive(Debug, thiserror::Error)]
#[allow(missing_docs)]
pub enum Error {
#[error("An IO error occurred while opening the index")]
Io(#[from] std::io::Error),
#[error(transparent)]
Decode(#[from] crate::decode::Error),
#[error(transparent)]
LinkExtension(#[from] crate::extension::link::decode::Error),
}
}
pub use error::Error;
/// Initialization
impl File {
/// Try to open the index file at `path` with `options`, assuming `object_hash` is used throughout the file, or create a new
/// index that merely exists in memory and is empty. `skip_hash` will increase the performance by a factor of 2, at the cost of
/// possibly not detecting corruption.
///
/// Note that the `path` will not be written if it doesn't exist.
pub fn at_or_default(
path: impl Into<PathBuf>,
object_hash: gix_hash::Kind,
skip_hash: bool,
options: decode::Options,
) -> Result<Self, Error> {
let path = path.into();
Ok(match Self::at(&path, object_hash, skip_hash, options) {
Ok(f) => f,
Err(Error::Io(err)) if err.kind() == std::io::ErrorKind::NotFound => {
File::from_state(State::new(object_hash), path)
}
Err(err) => return Err(err),
})
}
/// Open an index file at `path` with `options`, assuming `object_hash` is used throughout the file. If `skip_hash` is `true`,
/// we will not get or compare the checksum of the index at all, which generally increases performance of this method by a factor
/// of 2 or more.
///
/// Note that the verification of the file hash depends on `options`, and even then it's performed after the file was read and not
/// before it is read. That way, invalid files would see a more descriptive error message as we try to parse them.
pub fn at(
path: impl Into<PathBuf>,
object_hash: gix_hash::Kind,
skip_hash: bool,
options: decode::Options,
) -> Result<Self, Error> {
let _span = gix_features::trace::detail!("gix_index::File::at()");
let path = path.into();
let (data, mtime) = {
let mut file = std::fs::File::open(&path)?;
// SAFETY: we have to take the risk of somebody changing the file underneath. Git never writes into the same file.
#[allow(unsafe_code)]
let data = unsafe { Mmap::map(&file)? };
if !skip_hash {
// Note that even though it's trivial to offload this into a thread, which is worth it for all but the smallest
// index files, we choose more safety here just like git does and don't even try to decode the index if the hashes
// don't match.
// Thanks to `skip_hash`, we can get performance and it's under caller control, at the cost of some safety.
let expected = gix_hash::ObjectId::from(&data[data.len() - object_hash.len_in_bytes()..]);
if !expected.is_null() {
let _span = gix_features::trace::detail!("gix::open_index::hash_index", path = ?path);
let meta = file.metadata()?;
let num_bytes_to_hash = meta.len() - object_hash.len_in_bytes() as u64;
let actual_hash = gix_features::hash::bytes(
&mut file,
num_bytes_to_hash as usize,
object_hash,
&mut gix_features::progress::Discard,
&Default::default(),
)?;
if actual_hash != expected {
return Err(Error::Decode(decode::Error::ChecksumMismatch {
actual_checksum: actual_hash,
expected_checksum: expected,
}));
}
}
}
(data, filetime::FileTime::from_last_modification_time(&file.metadata()?))
};
let (state, checksum) = State::from_bytes(&data, mtime, object_hash, options)?;
let mut file = File { state, path, checksum };
if let Some(mut link) = file.link.take() {
link.dissolve_into(&mut file, object_hash, skip_hash, options)?;
}
Ok(file)
}
/// Consume `state` and pretend it was read from `path`, setting our checksum to `null`.
///
/// `File` instances created like that should be written to disk to set the correct checksum via `[File::write()]`.
pub fn from_state(state: State, path: impl Into<PathBuf>) -> Self {
File {
state,
path: path.into(),
checksum: None,
}
}
}
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