From f21463d5f4f695332c7db27cd07e6200fd258075 Mon Sep 17 00:00:00 2001
From: Christian Schwarz <cmrs@cmrs.io>
Date: Sat, 29 Jul 2023 14:15:02 +0200
Subject: [PATCH 1/2] handle empty ranges in BitSlice::copy_within

resolves #236
---
 src/slice/api.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/slice/api.rs b/src/slice/api.rs
index 6ac0de00..00208967 100644
--- a/src/slice/api.rs
+++ b/src/slice/api.rs
@@ -2229,6 +2229,12 @@ where
 	where R: RangeExt<usize> {
 		let len = self.len();
 		let src = src.normalize(0, len);
+		// prevent the asserts below from failing for empty ranges
+		if src.start == src.end {
+			assert!(src.start <= len, "range start index {} is out of bounds for bit-slice of length {}", src.start, len);
+			assert!(dest <= len, "index {} is out of bounds for bit-slice of length {}", dest, len);
+			return;
+		}
 		self.assert_in_bounds(src.start, 0 .. len);
 		self.assert_in_bounds(src.end, 0 ..= len);
 		self.assert_in_bounds(dest, 0 .. len);

From 3da24a0b27111179f427e0106532e3a7bf598464 Mon Sep 17 00:00:00 2001
From: Christian Schwarz <cmrs@cmrs.io>
Date: Sat, 29 Jul 2023 14:15:47 +0200
Subject: [PATCH 2/2] add regression tests for #236

---
 src/slice/tests.rs | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/slice/tests.rs b/src/slice/tests.rs
index edcb7a6c..feb2584b 100644
--- a/src/slice/tests.rs
+++ b/src/slice/tests.rs
@@ -75,6 +75,31 @@ fn copying() {
 	}
 }
 
+// regression tests for #236
+#[test]
+fn copy_within_supports_empty_ranges() {
+	let empty = bits![mut u8, Lsb0; 0; 0];
+	empty.copy_within(0..0, 0);
+	assert_eq!(empty, bits![]);
+
+	let non_empty = bits![mut u8, Lsb0; 0; 3];
+	non_empty.copy_within(2..2, 0);
+	assert_eq!(non_empty, bits![0, 0, 0]);
+}
+#[test]
+#[should_panic]
+fn copy_within_panics_if_empty_range_exceeds_bounds() {
+	let empty_slice = bits![mut u8, Lsb0; 0; 0];
+	empty_slice.copy_within(2..2, 0);
+}
+#[test]
+#[should_panic]
+fn copy_within_panics_if_dest_for_empty_range_exceeds_bounds() {
+	let empty_slice = bits![mut u8, Lsb0; 0; 0];
+	empty_slice.copy_within(0..0, 1);
+}
+
+
 #[test]
 fn writing() {
 	let bits = bits![mut 0; 2];