fix: allow offset to be equal to the buffer length when the source or target slice is empty

Author: cdellacqua

src/lib.rs

@@ -2248,6 +2248,22 @@ mod tests {
         test_concrete!(|| AllocRingBuffer::<i32>::new(1));
     }
 
+    #[test]
+    fn test_extend_from_slice_empty_alt() {
+        macro_rules! test_concrete {
+            ($rb_init: expr) => {
+                let mut rb = $rb_init();
+                let _ = rb.enqueue(1);
+                rb.extend_from_slice(&[]);
+                assert_eq!(&rb.to_vec(), &[1]);
+            };
+        }
+
+        test_concrete!(ConstGenericRingBuffer::<i32, 1>::new);
+        test_concrete!(|| GrowableAllocRingBuffer::<i32>::with_capacity(1));
+        test_concrete!(|| AllocRingBuffer::<i32>::new(1));
+    }
+
     #[test]
     fn test_extend_from_slice_wrap_around() {
         macro_rules! test_concrete {
@@ -2369,6 +2385,23 @@ mod tests {
         test_concrete!(|| AllocRingBuffer::<i32>::new(1));
     }
 
+    #[test]
+    fn test_drain_to_slice_empty_alt() {
+        macro_rules! test_concrete {
+            ($rb_init: expr) => {
+                let mut rb = $rb_init();
+                let _ = rb.enqueue(1);
+                let mut slice = [];
+                rb.drain_to_slice(&mut slice);
+                assert_eq!(&slice, &[]);
+            };
+        }
+
+        test_concrete!(ConstGenericRingBuffer::<i32, 1>::new);
+        test_concrete!(|| GrowableAllocRingBuffer::<i32>::with_capacity(1));
+        test_concrete!(|| AllocRingBuffer::<i32>::new(1));
+    }
+
     #[test]
     fn test_drain_to_slice_wrap_around() {
         macro_rules! test_concrete {

src/ringbuffer_trait.rs

@@ -686,7 +686,7 @@ macro_rules! impl_ringbuffer_ext {
             let len = Self::ptr_len(rb);
             let dst_len = dst.len();
             assert!(
-                (offset == 0 && len == 0) || offset < len,
+                offset < len || (offset == len && dst_len == 0),
                 "offset ({offset}) is out of bounds for the current buffer length ({len})"
             );
             assert!(len - offset >= dst_len, "destination slice length ({dst_len}) greater than buffer length ({len}) when considering the specified offset ({offset})");
@@ -729,7 +729,7 @@ macro_rules! impl_ringbuffer_ext {
             let len = Self::ptr_len(rb);
             let src_len = src.len();
             assert!(
-                (offset == 0 && len == 0) || offset < len,
+                offset < len || (offset == len && src_len == 0),
                 "offset ({offset}) is out of bounds for the current buffer length ({len})"
             );
             assert!(len - offset >= src_len, "source slice length ({src_len}) greater than buffer length ({len}) when considering the specified offset ({offset})");

src/with_alloc/vecdeque.rs

@@ -263,7 +263,7 @@ unsafe impl<T> RingBuffer<T> for GrowableAllocRingBuffer<T> {
         let len = Self::ptr_len(rb);
         let dst_len = dst.len();
         assert!(
-            (offset == 0 && len == 0) || offset < len,
+            offset < len || (offset == len && dst_len == 0),
             "offset ({offset}) is out of bounds for the current buffer length ({len})"
         );
         assert!(len - offset >= dst_len, "destination slice length ({dst_len}) greater than buffer length ({len}) when considering the specified offset ({offset})");
@@ -295,7 +295,7 @@ unsafe impl<T> RingBuffer<T> for GrowableAllocRingBuffer<T> {
         let len = Self::ptr_len(rb);
         let src_len = src.len();
         assert!(
-            (offset == 0 && len == 0) || offset < len,
+            offset < len || (offset == len && src_len == 0),
             "offset ({offset}) is out of bounds for the current buffer length ({len})"
         );
         assert!(len - offset >= src_len, "source slice length ({src_len}) greater than buffer length ({len}) when considering the specified offset ({offset})");