add function to read blob from worktree

Author: pascalkuthe

gix-worktree/src/lib.rs

@@ -13,3 +13,5 @@ pub mod fs;
 pub mod index;
 
 pub(crate) mod os;
+///
+pub mod read;

gix-worktree/src/read.rs

@@ -0,0 +1,79 @@
+use crate::fs;
+use gix_object::Blob;
+use gix_path as path;
+use std::borrow::Cow;
+use std::fs::{read_link, File};
+use std::io;
+use std::io::Read;
+use std::path::Path;
+
+/// Error returned by [`Blob::read`] and related functions
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    ///
+    #[error("Could not convert symlink path to UTF8")]
+    IllformedUtf8,
+    ///
+    #[error("IO error while reading blob")]
+    Io(#[from] io::Error),
+}
+
+// TODO: what to do about precompose unicode and ignore case_here?
+
+/// Create a blob from a file/symlink
+pub fn read_blob(path: &Path, capabilities: &fs::Capabilities) -> Result<Blob, Error> {
+    let mut buf = Vec::new();
+    let res = read_blob_to_buf(path, &mut buf, capabilities)?;
+    match res {
+        Cow::Borrowed(_) => Ok(Blob { data: buf }),
+        Cow::Owned(data) => Ok(Blob { data }),
+    }
+}
+
+/// Create a blob from a file/symlink
+pub fn read_blob_with_meta(path: &Path, is_symlink: bool, capabilities: &fs::Capabilities) -> Result<Blob, Error> {
+    let mut buf = Vec::new();
+    let res = read_blob_to_buf_with_meta(path, is_symlink, &mut buf, capabilities)?;
+    match res {
+        Cow::Borrowed(_) => Ok(Blob { data: buf }),
+        Cow::Owned(data) => Ok(Blob { data }),
+    }
+}
+
+// TODO: there is no reason this should be a Cow
+// std isn't great about allowing users to avoid allocations but we could
+// simply write our own wrapper around libc::readlink which reuses the
+// buffer. This would require unsafe code tough (obviously)
+
+/// Create blob data from a file/symlink
+pub fn read_blob_to_buf<'a>(
+    path: &Path,
+    buf: &'a mut Vec<u8>,
+    capabilities: &fs::Capabilities,
+) -> Result<Cow<'a, [u8]>, Error> {
+    read_blob_to_buf_with_meta(path, path.symlink_metadata()?.is_symlink(), buf, capabilities)
+}
+
+/// Create a blob from a file/symlink
+pub fn read_blob_to_buf_with_meta<'a>(
+    path: &Path,
+    is_symlink: bool,
+    buf: &'a mut Vec<u8>,
+    capabilities: &fs::Capabilities,
+) -> Result<Cow<'a, [u8]>, Error> {
+    // symlinks are only stored as actual symlinks if the FS supports it otherwise they are just
+    // normal files with their content equal to the linked path (so can be read normally)
+    //
+    if is_symlink && capabilities.symlink {
+        let symlink_path = path::try_into_bstr(read_link(path)?).map_err(|_| Error::IllformedUtf8)?;
+        match path::to_unix_separators_on_windows(symlink_path) {
+            Cow::Borrowed(path) => Ok(Cow::Borrowed(path.as_ref())),
+            Cow::Owned(path) => Ok(Cow::Owned(path.into())),
+        }
+    } else {
+        buf.clear();
+        File::open(path)?.read_to_end(buf)?;
+        // TODO apply filters
+        Ok(buf.as_slice().into())
+    }
+}