1 files changed, 81 insertions, 0 deletions
diff --git a/vendor/gix-index/src/file/init.rs b/vendor/gix-index/src/file/init.rs
new file mode 100644
index 000000000..534f1f08b
--- /dev/null
+++ b/vendor/gix-index/src/file/init.rs
@@ -0,0 +1,81 @@
+#![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.
+    ///
+    /// 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,
+        options: decode::Options,
+    ) -> Result<Self, Error> {
+        let path = path.into();
+        Ok(match Self::at(&path, object_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.
+    pub fn at(path: impl Into<PathBuf>, object_hash: gix_hash::Kind, options: decode::Options) -> Result<Self, Error> {
+        let path = path.into();
+        let (data, mtime) = {
+            // SAFETY: we have to take the risk of somebody changing the file underneath. Git never writes into the same file.
+            let file = std::fs::File::open(&path)?;
+            #[allow(unsafe_code)]
+            let data = unsafe { Mmap::map(&file)? };
+            (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: Some(checksum),
+        };
+        if let Some(mut link) = file.link.take() {
+            link.dissolve_into(&mut file, object_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: crate::State, path: impl Into<PathBuf>) -> Self {
+        File {
+            state,
+            path: path.into(),
+            checksum: None,
+        }
+    }
+}