datadir: Add open_read() method to Datadir context

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/subplotlib/src/steplibrary/datadir.rs b/subplotlib/src/steplibrary/datadir.rs
index 8aa6f00..88e6375 100644
--- a/subplotlib/src/steplibrary/datadir.rs
+++ b/subplotlib/src/steplibrary/datadir.rs
@@ -91,6 +91,17 @@ impl Datadir {
             .open(full_path)?
     }
 
+    /// Open a file for reading
+    #[throws(StepError)]
+    pub fn open_read<S: AsRef<Path>>(&self, subpath: S) -> File {
+        let full_path = self.canonicalise_filename(subpath)?;
+        OpenOptions::new()
+            .create(false)
+            .write(false)
+            .read(true)
+            .open(full_path)?
+    }
+
     #[throws(StepError)]
     pub fn create_dir_all<S: AsRef<Path>>(&self, subpath: S) {
         let full_path = self.canonicalise_filename(subpath)?;