fix: OpenFile::read_at no longer errors on invalid offset or length (#…

…331)

This is needed if weired access to the `OpenFile` is made. This is e.g.
the case for the `mount` command.

Also the docu of the affected methods has been clarified.

---------

Co-authored-by: simonsan <[email protected]>

crates/core/src/repository.rs

@@ -1615,6 +1615,12 @@ impl<P, S: IndexedFull> Repository<P, S> {
     /// * `offset` - The offset to start reading
     /// * `length` - The length to read
     ///
+    /// # Returns
+    ///
+    /// The read bytes from the given offset and length.
+    /// If offset is behind the end of the file, an empty `Bytes` is returned.
+    /// If length is too large, the result up to the end of the file is returned.
+    ///
     /// # Errors
     ///
     // TODO: Document errors

crates/core/src/vfs.rs

@@ -476,15 +476,17 @@ impl OpenFile {
     ///
     /// * `repo` - The repository to read the `OpenFile` from
     /// * `offset` - The offset to read the `OpenFile` from
-    /// * `length` - The length until to read the `OpenFile`
+    /// * `length` - The length of the content to read from the `OpenFile`
     ///
     /// # Errors
     ///
     // TODO: Document errors
     ///
     /// # Returns
     ///
-    /// The read bytes from the given offset and length
+    /// The read bytes from the given offset and length.
+    /// If offset is behind the end of the file, an empty `Bytes` is returned.
+    /// If length is too large, the result up to the end of the file is returned.
     pub fn read_at<P, S: IndexedFull>(
         &self,
         repo: &Repository<P, S>,
@@ -497,7 +499,7 @@ impl OpenFile {
         offset -= self.content[i].starts_at;
         let mut result = BytesMut::with_capacity(length);
 
-        while length > 0 && i < self.content.len() {
+        while length > 0 && i < self.content.len() - 1 {
             let data = repo.get_blob_cached(&BlobId::from(*self.content[i].id), BlobType::Data)?;
             if offset > data.len() {
                 // we cannot read behind the blob. This only happens if offset is too large to fit in the last blob

crates/core/tests/integration.rs

@@ -24,6 +24,7 @@
 //! The fixtures are passed as arguments to the test functions.
 
 use anyhow::Result;
+use bytes::Bytes;
 use flate2::read::GzDecoder;
 use globset::Glob;
 use insta::{
@@ -414,7 +415,7 @@ fn test_backup_stdin_command(
 }
 
 #[rstest]
-fn test_ls(
+fn test_ls_and_read(
     tar_gz_testdata: Result<TestSource>,
     set_up_repo: Result<RepoOpen>,
     insta_node_redaction: Settings,
@@ -444,8 +445,22 @@ fn test_ls(
         .collect::<RusticResult<_>>()?;
 
     insta_node_redaction.bind(|| {
-        assert_with_win("ls", entries);
+        assert_with_win("ls", &entries);
     });
+
+    // test reading a file from the repository
+    let repo = repo.to_indexed()?;
+    let path: PathBuf = ["test", "0", "tests", "testfile"].iter().collect();
+    let node = entries.get(&path).unwrap();
+    let file = repo.open_file(node)?;
+
+    let data = repo.read_file_at(&file, 0, 21)?; // read full content
+    assert_eq!(Bytes::from("This is a test file.\n"), &data);
+    let data2 = repo.read_file_at(&file, 0, 4096)?; // read beyond file end
+    assert_eq!(data2, &data);
+    assert_eq!(Bytes::new(), repo.read_file_at(&file, 25, 1)?); // offset beyond file end
+    assert_eq!(Bytes::from("test"), repo.read_file_at(&file, 10, 4)?); // read partial content
+
     Ok(())
 }