Add ByteRange::offset

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
    - Includes `DefaultStoreLocks` and `DisabledStoreLocks` implementations
  - Readable and writable stores include a `new_with_locks` method to choose the store lock implementation
  - Added `ArraySubset::new_with_ranges`
+ - Added `ByteRange::offset`
 
 ### Changed
  - **Breaking**  `ReadableStorageTraits` is no longer a supertrait of `WritableStorageTraits`

src/byte_range.rs

@@ -56,6 +56,13 @@ impl ByteRange {
         }
     }
 
+    /// Return the internal offset of the byte range (which can be at its start or end).
+    #[must_use]
+    pub fn offset(&self) -> u64 {
+        let (Self::FromStart(offset, _) | Self::FromEnd(offset, _)) = self;
+        *offset
+    }
+
     /// Return the length of a byte range. `size` is the size of the entire bytes.
     #[must_use]
     pub fn length(&self, size: u64) -> u64 {